Category: CBSE Class 10

Chapter 6 Life Processes Class 10 Science Important Questions and Answers PDF will help you in scoring more marks. This consists of 1 mark Questions, 3 Mark Numericals Questions, 5 Marks Numerical Questions and previous year questions from Chemical Reactions and Equations Chapter.

Life Processes Class 10 Important Questions and Answers Science Chapter 6

Very Short Answer Questions

Question 1.
Name the term for transport of food from leaves to other parts of plants.
Answer:
Translocation of food.

More Resources

• Previous Year Question Papers for CBSE Class 10 Science
• NCERT Solutions for Class 10 Science
• NCERT Exemplar Solutions for Class 10 Science
• Value Based Questions in Science for Class 10
• HOTS Questions for Class 10 Science

Question 2.
What process in plants is known as transpiration ?
Answer:
It is loss of water in the vapour form from the exposed parts of a plant.

Question 3.
Name the tissue which transports soluble products of photosynthesis in a plant.
Answer:
Phloem.

Question 4.
Name the tissue which transports water and minerals in a plant.
Answer:
Xylem.

Question 5.
How do autotrophs obtain CO₂ and N₂ to make their food ?
Answer:
Autotrophs obtain CO₂ from air and N₂ as nitrate or ammonium ion from soil.

Question 6.
Which pancreatic enzyme is effective in digesting protein ?
Answer:
Trypsin.

Question 7.
Which enzyme present in saliva breaks down starch ?
Answer:
Ptyalin or salivary amylase.

Question 8.
What is the role of acid in our stomach ?
Answer:
HCl of gastric juice disinfects the food and acidifies it for proper functioning of proteolytic enzyme pepsin.

Question 9.
What is the role of saliva in the digestion of food ? (CBSE Delhi 2008, CCE 2014, 2016)
Answer:
Saliva moistens the ingested food with mucus, sterilises it with lysozyme and partially digests starch part of food into sugar with the help of salivary amylase or ptyalin.

Question 10.
State the function of digestive enzymes. (CBSE A.I. 2008 C)
Answer:
Digestive enzymes are hydrolytic enzymes which cause breakdown of complex and insoluble components of food into simple, soluble and absorbable substances.

Question 11.
Name the two ways in which glucose is oxidised to provide energy in various organisms.
(CBSE A.I. 2008 C)
Answer:

1. Aerobic respiration in which glucose is completely oxidised to carbon dioxide and water with the help of oxygen releasing 686 kcal of energy per mole.
2. Anaerobic respiration in which glucose is incompletely broken down in the absence of oxygen to form generally either lactic acid or ethyl alcohol and carbon dioxide releasing about 50 kcal of energy.

Question 12.
Where do plants get each of the raw materials required for photosynthesis ? (CBSE A.I. 2008 C, CCE 2015)
Answer:

1. Carbon
2. Water and Mineral Salts. From soil in terrestrial plants and liquid medium in aquatic habitat.
3. Energy. Solar radiations.

Question 13.
Where does digestion of fat take place in our body ? (CBSE A.I. 2009)
Answer:
Digestion of fat occurs in first part (duodenum and jejunum) of small intestine with the help of enzyme lipase that acts on emulsified fat to form fatty acids and glycerol.

Question 14.
Mention how organisms like Bread Mould and Mushroom obtain their food. (CBSE Foreign 2010)
Answer:
They obtain their food saprophytically from external organic matter by dissolving the same with the help of digestive enzymes.

Question 15.
Name the component of blood that helps in the formation of blood clot in the event of a cut.
(CBSE Foreign 2010)
Answer:
Blood platelets which release thromboplastin on rupturing.

Question 16.
State one difference between autotrophic and heterotrophic modes of nutrition.
(CBSE A.I. 2010, CCE 2012)
Answer:
In autotrophic nutrition, the food is self manufactured while it is obtained ready-made from outside in heterotrophic nutrition.

Question 17.
Name the process in plants where water is lost as water vapour. (CBSE A.I. 2010)
Answer:
Transpiration.

Question 18.
What is translocation in plants ? (CBSE A.I. 2010)
Answer:
Translocation is passage of food materials in solution form in plants from the region of their supply or manufacture to the region of their use or storage.

Question 19.
State basic difference in the processes of respiration and photosynthesis. (CBSE Foreign 2010)
Answer:
Respiration is a catabolic process in which glucose is broken down to release energy while photosynthesis is an anabolic process in which glucose and other organic substances are manufactured from raw materials with help of solar radiations.

Question 20.
Name the intermediate and the end products of glucose breakdown in aerobic respiration.
(CBSE Foreign 2010)
Answer:
Intermediate: Pyruvic acid (+ Energy)
End Products: CO₂ + H₂O (+ Energy)

Question 21.
What is the purpose of sending blood to the kidney for filtration ?
Answer:
For removal of nitrogenous wastes, excess salts and some toxins.

Question 22.
Name the stored food of animals. (CCE 2013)
Answer:
Glycogen and fat.

Question 23.
How does transport of water occur at night in the absence of transpiration ? (CCE 2013)
Answer:
Due to root pressure and partly to meet daytime water deficit of aerial parts.

Question 24.
Name the component of food not digested in stomach. (CCE 2013)
Answer:
Starch and other carbohydrates.

Question 25.
State the purpose of making urine. (CCE 2013)
Answer:
Extract the soluble waste products from the blood for expulsion out of the body.

Question 26.
Mention the site of complete digestion of carbohydrates, proteins and fats in humans. (CCE 2014)
Answer:
Small intestine.

Question 27.
Ventricles have thicker muscular walls than atria. ,Give reason. (CCE 2014, 2016)
Answer:
Ventricles have to pump blood forcefully so as to reach even distant capillaries, right ventricle into lungs and left ventricle to all the remaining body parts, while atria are to pump blood into adjacent ventricles.

Question 28.
How do plant cells change their shape ? (CCE 2014)
Answer:
Due to osmotic entry or exit of water and differential thickening, eg., guard cells.

Question 29.
Name two enzymes present in pancreatic juice. (CCE 2015)
Answer:
Trypsin, pancreatic amylase, pancreatic lipase.

Question 30.
State the function of alveoli in the lungs. (CCE 2015)
Answer:
Exchange of gases (CO₂ and O₂) between blood and air.

Question 31.
Name the form in which energy derived from food is stored in humans. (CCE 2015)
Answer:
Glycogen (and fat).

Question 32.
When we breathe out, the air passage does not collapse. Why ? (CCE 2015)
Answer:
Due to the presence of rings (c-shaped) of cartilage.

Question 33.
Name the process used by single celled organism for taking in food, exchange of gases or removal of wastes.
(CCE 2015)
Answer:
Diffusion.

Question 34.
Identify the category in which organisms using carbon dioxide and water as food are placed. (CCE 2015)
Answer:
Autotrophs/photoautotrophs.

Question 35.
Even when we are not doing any apparent activity, we need energy. Justify giving reason. (CCE 2016)
Answer:
A lot of metabolic activity is continuously occurring even when we are not doing any work, e.g., heart beat, breathing, digestion, absorption, blood circulation, etc. All of them require energy.

Question 36.
Name the components of blood which transport

1. Food, carbon dioxide and nitrogenous wastes
2. Oxygen. (CCE 2016)

Answer:

1. Blood Plasma. Food, CO₂ and nitrogenous wastes.
2. Erythrocytes (Haemoglobin). Oxygen.

Question 37.
Rings of cartilage are present in trachea. Why ? (CCE 2016)
Answer:
To prevent the collapse of air passage after expiration.

Short Answer Questions (2 Marks)

Question 1.
(a) Name two different ways in which glucose is oxidised to provide energy in various organisms.
(b) Write any two differences between the two ways of oxidation of glucose in organisms.
(CBSE A.I. 2008, CCE 2011)
Answer:
(a) Aerobic and anaerobic.
(b) Differences

Aerobic Respiration	Anaerobic Respiration
1. Oxygen. There is complete breakdown of respiratory substrate with the help of oxygen, the products being CO2 and H2O. 2. Energy. It forms 38 ATP molecules per glucose molecule.	There is incomplete breakdown of respiratory substrate due to non-use of oxygen with atleast one product being organic. It forms only two ATP molecules per glucose molecule.

Question 2.
What is the function of trachea ? Why do the walls not collapse even when there is less air in it ?
(CCE 2010, 2012)
Answer:
Trachea is a tube that connects pharynx with lungs for carrying air to and from lungs. Trachea is lined by ciliated mucus secreting pseudostratified epithelium for trapping dust particles and microbes.
Trachea does not collapse in reduced air pressure due to support of C-shaped cartilaginous rings.

Question 3.
Name any two digestive enzymes secreted in the human digestive system and write their function.
(CCE 2010)
Answer:

Question 4.
How do they take up carbon dioxide and perform photosynthesis ? (CCE 2010, 2012, 2013)
Answer:
Carbon dioxide is absorbed during night when stomata are open. It is fixed in malic acid from which the same is released during day time for performing Calvin cycle in light.

Question 5.
(a) What will happen to guard cells and the stomatal pore when water flows into guard cells.
(b) How do plants transmit information from cell to cell ? (CCE 2010)
Answer:
(a) Guard cells swell up and a stomatal pore is created in between them.
(b) Information is transmitted from one plant cell to another through plasmodesmata and hormones.

Question 6.
What are the different ways in which glucose is oxidised to provide energy in various organisms ?
(CCE 2010)
Answer:
(i) Aerobic. C₆H₁₂O₆ + 6O₂ —> 6 CO₂ + 6 H₂O + Energy
(it) Anaerobic,
(a) C₆H₁₂O₆ —> 2 Ethanol + 2 CO₂ + Energy.
(b) C₆H₁₂O₆ —> 2 Lactic acid + Energy

Question 7.
What is excretion ? How do unicellular organisms remove their wastes ? (CCE 2010, 2012)
Answer:
Excretion is the biological process of removal of harmful metabolic waste products from the body.
In unicellular organisms, excretion occurs through simple diffusion from the surface.

Question 8.
What is internal energy reserve in plants ? Do the animals have the same energy reserve ? Justify your answer.
(CCE 2011)
Answer:
The major internal energy reserve in plants is starch (a complex carbohydrate). Animals do not have the same energy reserve. Instead, they possess glycogen (and fat).

Question 9.
Explain the significance of peristaltic movement that occurs all along the gut during digestion.
(CCE. 2010, 2012, 2013)
Answer:
Peristaltic movement or peristalsis is a wave of alternate contraction and expansion that passes through the gut from oesophagus to large intestine. It moves the food forward in a regulated manner along the digestive tract for processing in each part properly.

Question 10.
Major amount of water is selectively reabsorbed by the tubular part of nephron in humans. What are the factors on which the amount of water reabsorbed depends ? (CCE 2011, 2012)
Answer:

1. Amount of excess water present.
2. Amount of dissolved wastes to be excreted.

Question 11.
Name two digestive glands associated with digestive system in humans. Name their secretions. (CCE 2011)
Answer:
1. Salivary glands — saliva.
2. Pancreas — pancreatic juice.

Question 12.
Which mechanism plays an important role in transportation of water in plants
(a) During daytime
(b) At night ? (CCE 2011)
Answer:
(a) Transpiration pull
(b) Water deficit of daytime and afterwards root pressure.

Question 13.
Give reasons for the following :
(a) Why is diffusion not sufficient to meet oxygen requirement of all the cells in multicellular organisms ?
(b) How desert plants perform photosynthesis if their stomata remain closed during the day ? (CCE 2011)
Answer:
(a) All living cells are not in direct contact with environment. Diffusion is a slow process and it will take very long time, days and months, to reach every living cell inside the body of a multicellular organisms.
(b) Carbon dioxide is absorbed during night when stomata are open. It is fixed in malic acid from which the same is released during day time for performing Calvin cycle in light.

Question 14.
What is translocation ? How does it take place in plants ? (CCE 2011)
Answer:
Translocation is the transport of nutrients/food in solution form inside phloem from the region of photosynthesis (or storage) to the area of consumption. For translocation, food molecules or nutrients enter phloem actively, develop an osmotic pressure and pass to the area of utilisation in a mass flow where active withdrawal occurs.

Question 15.
State two differences between arteries and veins. (CCE 2011, 2012, 2013)
Answer:

Artery	Vein
1. Direction of Flow. It carries blood from heart to an organ.	It brings blood from an organ towards the heart.
2. Speed. Blood flow is rapid in artery.	Blood flow is slow in vein.
3. Jerks. Blood flows with jerks.	Blood flows smoothly.
4. Pressure. Blood flows under pressure	There is little pressure.
5. Internal Valves. They are absent.	Internal valves are present to prevent back flow.
6. Wall. It is thick and elastic.	It is comparatively thinner and little elastic.
7. Lumen. Narrow.	Wide.
8. Type of Blood. Artery carries oxygenated blood except pulmonary arteries.	Vein carries deoxygenated blood except pulmonary veins.
9. Occurrence. It is deep seated.	It is superficial.
10. Collapsibility. Artery is not collapsible.	Vein is collapsible.
11. Blood After Death. It does not contain blood after death.	Vein is full of blood even after death.

Question 16.
Explain the process of nutrition in Amoeba. (CCE 2011, 2012)
Answer:
Amoeba ingests food particles with the help of its pseudopodia. The ingested food particle or phagosome fuses with lysosome to form food vacuole. The digested food passes out of the vacuole into cytoplasm. The undigested matter is thrown out. Fig. 1.11 B and E, if possible.

Question 17.
Explain parasitic mode of nutrition with two examples. (CCE 2011)
Answer:
Parasitic mode of nutrition is a mode of nutrition where one living being (parasite) obtains food from another living being (host) of different species.
Examples. Ascaris (in human intestine), Cuscuta (on other plants).

Question 18.
Leakage of blood from vessels reduces the efficiency of pumping system. How is leakage prevented ? (CCE 2011)
Answer:
Blood contains blood platelets. In the region of leakage, the platelets burst and release thromboplastin. It helps in coagulation of blood and seal the place of leakage or injury.

Question 19.
Draw a labelled diagram to show nutrition in Amoeba. Give one more example of unicellular organism.
(CCE 2011, 2012)
Answer:
Fig. 1.11 B and E.

Other Example. Paramoecium.

Question 20.
Leaves of a healthy potted plant were coated with vaseline. Will this plant remain healthy for long ? Give reasons for your answer. (CCE 2011, 2015)
Answer:
The plant will not remain healthy for long. Vaseline covers the cuticle and blocks the stomata.
As a result

1. It is unable to obtain oxygen from air for respiration,
2. It is unable to perform photosynthesis as no carbon dioxide diffuses from air.
3. In the absence of transpiration, the leaves get heated up and injured.

Question 21.
How is the process of transpiration useful to plant ? (CCE 2011, 2012)
Answer:

1. It helps in upward transport of sap (water and minerals)
2. Transpiration cools down the sun-exposed leaves and concentrates the minerals present in the rising water.

Question 22.
Mention the two main components of the transport system in plants.
State one function of each one of these components. (CCE 2011)
Answer:
Transport system of plants consists of two main components, xylem and phloem. Xylem (through vessels and tracheids) takes part in conduction of sap mostly in the upward direction. Phloem (through sieve tubes) transports food marterials both in upward and downward directions.

Question 23.
State the function of guard cells. What will happen to guard cells and stomatal pore when water flows to guard cells. (CCE 2011)
Answer:
Function of Guard cells : Opening, closing and regulating the stomata or stomatal pores.
Flow of Water : Passage of water into guard cells will make them turgid. The turgid guard cells bend is such a way as to open the stomatal pore.

Question 24.
Give reason :
(i) Fine hair and mucus are present in the nasal passage.
(ii) Rings of cartilage are present in the throat. (CCE 2014)
Answer:
(i) They trap fine dust particles and microbes from inhaled air.
(ii) They prevent collapsing of trachea when air pressure is low.

Question 25.
Tooth enamel is the hardest substance in our body. Name the compound of which it is made up of. At what pH of the mouth it gets corroded ? State the role of bacteria present in the mouth. Suggest a method to prevent tooth decay. (CCE 2014)
Answer:
Enamel is chemically hydroxyapetite (= calcium phosphate, 95%) alongwith proteins emamelins (5%). It gets corroded in acidic pH. The acid is produced by bacterium Streptococcus mutans that forms plaques over teeth if the teeth are not regularly cleaned as after meals.

Question 26.
Mention the site of complete digestion in our body. Name the end products formed on complete digestion of carbohydrates, proteins and fats. (CCE 2014)
Answer:
Site: Small intestine.
End Products:
Carbohydrates. Glucose.
Proteins. Amino acids.
Fats. Fatty acids and glycerol.

Question 27.
(i) Write the balanced chemical equation for the process of photosynthesis.
(ii) When do desert plants take up CO₂ and perform photosynthesis ? (CCE 2014)
Answer:

(ii) Carbon dioxide is absorbed during night when stomata are open. It is fixed in malic acid from which the same is released during day time for performing Calvin cycle in light.

Question 28.
(i) Why are cramps caused in our muscles during sudden activity ?
(ii) Name the type of respiration that takes place in Yeast during fermentation. (CCE 2014, 2015)
Answer:
(i) Cramps develop in muscles during excessive activity due to formation and accumulation of lactic acid as a result of lesser oxygen availability than required by muscles.
(ii) Anaerobic respiration.

Question 29.
In an experiment to prepare temporary mount of leaf peel, staining of leaf peel is done before putting a drop of glycerine. Explain why ?  (CCE 2014)
Answer:
Staining is required for clearer observation as it brings about differentiation of cells and cellular components.
As extra stain has to be removed, staining is carried out before mounting.

Question 30.
In the experiment to prepare temporary mount of leaf peel, which stain is preferred and how is extra stain on the slide removed. (CCE 2014)
Answer:
Stain Preferred . Safranin. Removal of Extra Stain. By blotting/filter paper.

Question 31.
Explain why only turgid leaf is selected for the preparation of temporary mount of a leaf peel. (CCE 2014)
Answer:

1. The peel can be removed easily,
2. Peel can be spread easily.
3. The cells are of normal shape and structure.

Question 32.
In an experiment to prepare temporary stained mount of a leaf epidermal peel, how can extra stain be removed ? What possible outcome would be observed if it is removed with cotton wool ? (CCE 2014)
Answer:
Extra stain is removed with the help of blotting paper. Cotton wool is not used as it has a tendency to spread the stain.

Question 33.
David observed temporary mount of leaf peel under the high power of microscope. He found two types of nucleated cells. Name the cells observed by him. (CCE 2014)
Answer:
Epidermal cells, guard cells (of stomata).

Question 34.
You have been provided with a freshly plucked leaf of Rhoeo or Lilly. What will you do to obtain a transparent leaf peel? (CCE 2015)
Answer:
Twist and tear the leaf obliquely with a jerk. A small transparent peel will be observed. The same is cut and placed in a drop of water or watch glass having water. In Rhoeo, it is the lower side which gives a good peel. Q. 35. In an experiment to prepare temporary mount of a leaf peel to show its stomata Ram was provided with a monocot leaf whereas Shyam, a dicot leaf.

Question 35.
Mention the ideal location where you would expect them to obtain the leaf peel for the experiment. (CCE 2015)
Answer:
Middle of the leaf. It is twisted and torn with a jerk. In dicot leaf, stomata occur mostly on the lower surface while in monocot leaf both the surfaces possess stomata.

Question 36.
Mention the shape of guard cells and write its constituents. (CCE 2015)
Answer:
In dicots the guard cells are bean-shaped in outline. They are two in number and joined at the ends with thick walls towards each other and thin walls towards outside. Each guard cell contains a single nucleus and a number of chlroplasts.

Question 37.
State any two functions of the cells that surround the stomata. (CCE 2015)
Answer:
Functions of Guard Cells :

1. Opening and closing of stomata.
2. Allowing exchange of gases and transpiration.

Question 38.
Explain why leaf is preferred for preparation of temporary mount to show stomata. State two functions of stomata. (CCE 2015)
Answer:
Leaf is the plant organ where maximum number of stomata are present.
Functions :

1. Absorption of CO₂
2. Release of O₂ during day time.
3. Seat of maximum transpiration.

Question 39.
Mention the materials required to prepare a temporary mount of leaf peel to show stomata. (CCE 2015)
Answer:”
Apparatus: A small potted plant, a small pot of the same size and same amount of soil as that of potted plant, a stick of the height of the plant, plastic sheets.
Observation: The internal surface of the plastic sheet belonging to the set having potted plant becomes wet. There is no such change in the second set.

Question 40.
Suresh prepared a list of materials required to prepare a temporary mount of leaf peel to show stomata but his list is not complete. Name any four materials which are not included in his list.
Leaf, petridish, coverslip, needle, forceps, brush, watch glass, safranin, microscope. (CCE 2015)
Answer:
Water, blotting paper, dilute glycerine, slide.

Question 41.
Name the observed parts of a temporary mount of a leaf peel when it is focussed under :
(a) Low power
(b) High power of a compound microscope. (CCE 2015)
Answer:
(a) Low Power : Leaf epidermal cells and a few stomata, each with two minute greenish guard cells.
(b) High Power : A stomate surrounded by colourless epidermal cells. The stomate has two bean-shaped guard cells with thicker inner walls, a number of chloroplasts and one nucleus in each.

Question 42.
Draw a labelled diagram of cross-section of a leaf. (CCE 2015)
Answer:

Question 43.
(i) Name any two substances that are selectively reabsorbed as the urine flows along the tube.
(ii) Name the part of the excretory system in which urine is stored for some time. (CCE 2015)
Answer:
(i) Glucose, amino acids.
(ii) Urinary bladder.

Question 44.
Name two enzymes secreted by pancreas. Write the function performed by these two. (CCE 2015)
Answer:

Question 45.
Give reason –
(i) The two ventricles have thicker muscular walls than the two atria in human heart.
(ii) The capillaries have walls which are one-celled thick. (CCE 2015)
Answer:
(i) Atria are to receive blood from veins and pump the same into adjacent ventricles only. They have, therefore, thin walls. Ventricles are to pump blood into arteries forcefully as it is to be sent to lungs (right ventricle) and all parts of the body (left ventricle). Therefore, walls of ventricles are thick and muscular with those of left ventricle being thicker.
(ii) Capillaries take part in exchange of materials (nutrients, wastes, gases) between blood and tissue fluid.

Question 46.
Name the cells that control the opening and closing of stomatal pore. Flow do they perform this function ?
(CCE 2016)
Answer:
Guard cells: Opening and closing of stomata is regulated by gain or loss of turgidity of their guard cells. During opening of stomata, guard cells withdraw K⁺ ions from surrounding epidermal cells, followed by absorption of water from them. As a result, guard cells swell up and become turgid. Their outer thin and elastic walls bend outwardly followed by outward movement of thicker inner walls. The latter creates a pore in between the two guard cells.
During closure movement of stomata, guard cells send out K⁺ ions. Water also passes out. Guard cells become flaccid. Their inner thick walls come to touch each other. The stomatal pore gets closed.

Question 47.
(i) Name two organisms that obtain food through parasitic nutritive strategy,
(ii) How do fungi obtain their food ? (CCE 2016)
Answer:
(i) Parasitic Nutrition. Cuscuta (a plant), Plasmodium (Malarial Parasite).
(ii) Most of the fungi are saprotrophs. They obtain their nourishment from organic matter.

Question 48.
Saprotrophs pour digestive enzymes over the organic matter in order to dissolve it. The dissolved ingredients are absorbed. David observed a temporary mount of a leaf under high power of microscope. He found two types of nucle¬ated cells. Name the cells observed by him. (CCE 2016)
Answer:
Epidermal cells, pairs of guard cells forming stomata.

Short Answer Questions (3 Marks)

Question 1.
When is blood clotting useful ? In a flow chart illustrate the four major events involved in blood clotting.
(CBSE Delhi 2006)
Answer:
Usefulness of Blood Clotting.
(i) “Plugging the place of injury.
(ii) Stoppage of blood flow from the region of injured blood vessel.
Events in Blood Clotting:

Question 2.
Give reasons for the following :
(i) Glottis is covered by epiglottis
(ii) Lung alveoli are covered with blood capillaries
(iii) The wall of trachea is supported by cartilage rings. (CBSE A.I. 2006, CCE 2012)
Answer:
(i) Epiglottis. To prevent entry of food and water during swallowing.
(ii) Lung Alveoli. Lung alveoli constitute the respiratory surface of the lungs. Their walls have rich supply of blood for gaseous exchange, i.e. passage of oxygen from alveolar air to blood and passage of carbon dioxide from blood to alveolar air.
(iii) Tracheal Rings (C-shaped). For providing support, preventing collapse of trachea and allowing for uninterrupted flow of air.

Question 3.
(a) What do you mean by double circulation of blood ? (CBSE A.I. 2007, Delhi 2008 C,CCE 2011, 2012)
(b) Why is it necessary ? (CBSE Delhi 2008 C)
Answer:
(a) Double circulation is the passage of same blood twice through heart, first from right side to lungs and back to left side for passage to rest of the body to be returned to right side. It consists of two components, pulmonary circulation (from heart to lungs and back) and systemic circulation (from heart to different parts of body and back). In pulmonary circulation deoxygenated blood is converted into oxygenated blood. In systemic circulation oxygenated blood is supplied to all parts of the body. It gets changed into deoxygenated form.
(b) Importance. Double circulation ensures supply of oxygenated blood to all body parts for efficient release of energy to ensure higher physical activity and thermoregulation of body. It also provides for direct passage of all deoxygenated blood to lungs for oxygenation.

Question 4.
What are stomata ? Draw labelled diagram of stomata. Write any two functions of stomata.
(CBSE Foreign 2008, CCE 2012)
Answer:
(a) Stomata. They are pores regualted by two chloroplast containing guard cells that occur in the epidermis of leaves and young stems for exchange of gases and transpiration.
(b) Diagram.

(c) Functions of Stomata,

1. Exchange of gases,
2. Transpiration.

Question 5.
(a) Name the process by which autotrophs prepare their own food.
(b) List three events which occur during this process. (CCE 2012)
(c) State two sources from which plants obtain nitrogen for synthesis of proteins and other compounds.
(CBSE Foreign 2008)
Answer:
(a) Process. Photosynthesis.
(b) Events,

1. Photolysis of water.
2. Production of assimitory power as ATP and NADPH₂.
3. Reduction of CO₂.

(c) Sources of Nitrogen,

1. Nitrate from soil,
2. Ammonium ion from soil.

Question 6.
What are final products produced after digestion of carbohydrates, proteins and fats ? (CCE 2010, 2011, 2013) \
Answer:
Carbohydrates. Glucose.
Proteins. Amino acids.
Fats. Fatty acids and glycerol.

Question 7.
When a sportsman runs, he gets muscle cramps. Why ?

                                                    Or

Lack of oxygen in muscles often leads to cramps among cricketers. Explain. Why ? (CCE 2010, 2011)
Answer:
Cramp is an involuntary contraction of an already contracted muscle. It occurs due to accumulation of lactic acid during anaerobic breakdown of glucose when oxygen supply is unable to match the requirement. Lactic acid acts on neuromuscular junction producing fatigue and cramps.

Question 8.
The pH of the mouth of a person is lower than 5.5. What changes will occur in his mouth ? How can these changes be controlled ? Write any two measures. (CCE 2011)
Answer:
(a) pH of the mouth becomes lower than 5.5, despite regular secretion of near neutral saliva, due to presence » of decaying food and bacteria present therein.
(b) Enamel of teeth being made of hydroxyapedte (calcium phosphate) undergoes corrosion in acidic medium. This starts tooth decay.
(c)

1. Routinely cleaning the mouth after meals,
2. Brushing the teeth with tooth paste which is generally alkaline.

Question 9.
(a) “Breathing cycle is rhythmic whereas exchange of gases is a continuous process”. Justify this statement.
(b) What happens if conducting tubes of circulatory system develops a leak ? State in brief how could this be avoided ?
(c) How opening and closing of stomata take place ? (CCE 2011)
Answer:
(a) Even after forceful exhalation, a large quantity’of air called residual volume is left in the lungs. It is helpful in continuous exchange of gases.
(b) Leakage will result in loss of blood from circulatory system, loss of efficiency of pumping system and non-supply of fresh blood to many organs. It results in death. To avoid it, blood platelets release thromboplastin in the region of leakage. It helps in sealing the place of injury through clotting of blood.
(c) Opening and closing of stomata take place by gain and loss of turgidity in the guard cells.

Question 10.
Assume you are a veterinary doctor and you had removed a good length of small intestine of a bear that was suffering from an intestinal tumour. Now, would you suggest a plant based or a meat based diet for the bear after its recovery ? Give reason for your suggestion.
Answer:
Meat based. A nonvegetarian diet requires a shorter alimentary canal while a vegetarian diet requires a longer alimentary canal for complete digestion.

Question 11.
In the human alimentary canal, name the site of complete digestion of various components of food. Explain the process of digestion. (CCE 2012)
Answer:
Site of Complete Digestion. Small intestine.
Digestion. It is the conversion of complex insoluble food ingredients into simple absorbable form. Digestion is essential as complex components of food cannot pass into body cells for nourishment. Digestion occurs with the help of digestive enzymes. In simple holozoic animals, it is intracellular. In higher animals digestion is performed in a digestive tract and is, therefore, intercellular or extracellular. The digested materials are absorbed, transported and picked up by individual cells of the body for assimilation.

Question 12.
List three kinds of blood vessels of human circulatory system and write their functions in a tabular form.
(CCE 2012)
Answer:
Capillaries, arteries and veins.

1. Capillaries,
   1. Exchange of materials between blood and tissue fluid,
   2. Filtering out tissue fluid and diapedesis
2. Arteries,
   1. Quick passage of blood from heart to different parts of body,
   2. Supply of oxygenated blood to all body parts except lungs
   3. Passage of deoxygenated blood to lungs for oxygenation.
   1. Collection and transport of deoxygenated from all body parts and passage to heart.
   2. Transport of oxygenated blood from lungs to left atrium.

Question 13.
Name three different glands associated with the digestive system in humans. Also name their secretion.
(CCE 2012)
Answer:

1. Salivary Glands: They are three pairs, a pair each of parotid, submaxillary and sublingual. Secretion is called saliva. It contains antimicrobial lysozyme and digestive enzyme ptyalin or salivary amylase.
2. Liver: It secretion is called bile. Bile takes part in alkalisation of food and emulsification of fat.
3. Pancreas: It secretion is called pancreatic juice. It contains proteolytic enzyme trypsin (secreted as trypsinogen), pancreatic lipase (steapsin) and pancreatic amylase (amylopsin).

Question 14.
List in tubular form three differences between aerobic respiration and anaerobic respiration.
(CCE 2012, 2014)
Answer:

Aerobic Respiration	Anaerobic Respiration
1.Oxygen: There is complete breakdown of respiratory substrate with the help of oxygen, the products being CO2 and H2O. 2. Energy: It forms 38 ATP molecules per glucose molecule.	There is incomplete breakdown of respiratory substrate due to non-use of oxygen with atleast one product being organic. It forms only two ATP molecules per glucose molecule.

Question 15.
With the help of a schematic flow chart, show the breakdown of glucose in a cell to provide energy :

1. In the presence of oxygen
2. In the absence of oxygen
3. When there is lack of oxygen. (CCE 2012, 2013)

Answer:

Question 16.
(a) Name the respiratory pigment in human beings and state the cell in which it is present.
(b) A product is formed is our muscles due to breakdown of glucose when there is lack of oxygen. Name the product and also mention the effect of build up of this product.
(c) Differentiate between fermentation in Yeast and aerobic respiration on the basis of end products formed.
(CCE 2012)
Answer:
(a)

1. Respiratory Pigment. Haemoglobin
2. Cell. Red blood corpuscles or erythrocytes.

(b)

1. Product. Lactic acid
2. Effect. Fatigue and cramps.

(c) In yeast, fermentation produces alcohol and CO₂ while aerobic respiration forms only CO₂ and water.

Question 17.
Mention the role of following in digestion :  (CCE 2012, 2013, 2015)

1. Pepsin
2. Saliva
3. Villi
4. Bile Juice.

Answer:

1. Pepsin: Breakdown of proteins into pepteoses and proteoses in acidic medium.
2. Saliva: Moistening of food, partial breakdown of starch and glycogen to form maltose by means of enzyme ptyalin (salivary amylase).
3. Villi: Their bases bear intestinal glands that secrete intestinal juice for completion of digestion. Villi take part in absorption of digested food.
4. Bile Juice – Juice released by liver is bile.

Functions

1. Neutralising acidity of chyme,
2. Making food alkaline for action of pancreatic enzymes,
3. Emulsification of fat.

Question 18.
List the role of each of the following in our digestive system :
(a) Muscles of stomach wall
(b) Hydrochloric acid
(c) Mucus. (CCE 2012, 2013)
Answer:
(a) Muscles of Stomach. They bring about churning movement that breaks food into small particles and mixes it with gastric juice.
(b) Hydrochloric Acid. It is gastric secretion which softens, sterilises and acidifies the food for action of enzyme pepsin.
(c) Mucus. It lubricates the food passing through alimentary canal and protects the wall of digestive tract from digestive enzymes.

Question 19.
(a) Why is transpiration important for plants ?
(b) Why plants generally wilt in the afternoon and regain their freshness in the next morning ? (CCE 2013)
Answer:
(a) Importance

1. Cooling: Evaporation of water from the aerial parts results in lowering of their temperature which will otherwise rise due to exposure to sun.
2. Concentration of Mineral:. Transpiration helps in increasing concentration of minerals present in rising water.
3. Transport: It creates a pull that helps in transport of water and minerals.

(b) Excessive transpiration and comparatively less water absorption from soil during hotter parts of day creates a water deficit in the leaf cells resulting in their loss of turgidity. As a result plants show wilting. There is little transpiration during evening and night while absorption and ascent of sap continue. As a result leaf cells become turgid and the plant regains its freshness in the morning.

Question 20.
(a) In which form, nitrogen is taken by plants ?
(b) What type of nutrition is present in Bread Mould ? (CCE 2013)
Answer:
(a) Nitrate, nitrite, ammonium ions and some organic compounds elaborated by bacteria.
(b) Bread Mould (Rhizopus) is a fungus that undertakes saprophytic type of heterotrophic nutrition. Its rhizoidal hyphae are fixed in medium having organic food/organic remains. They secrete digestive enzymes into the medium. The enzymes cause breakdown of complex compounds into simple and soluble substances. The fungus absorbs the same.

Question 21.
(a) Match the key words with their definition :
(i) Excretion
(ii) Elimination
(A) Is the removal of faeces (B) Applies to metabolic waste products that cross a plasma membrane.
(b) Name various excretory organs in vertebrates. (CCE 2013)
Answer:
(a)
(i) — B,
(ii) — A.
(b) Kidneys. Some accessory excretory organs of vertetrates are skin, lungs, liver and large intestine.

Question 22.
(a) Why is diffusion insufficient to meet the oxygen requirements of large multicellular organisms like humans ?
(b) What type of arrangement exists in the bodies of large animals to meet their oxygen requirement adequately ?
(CCE 2013)
Answer:
(a) Every living cell requires oxygen for performing cellular respiration. In unicellular organisms (e.g., Amoeba), the single cell is in direct contact with environment. Oxygen passes into it through diffusion. In simple multicellular organisms (e.g., Hydra), every cell may also get oxygen through diffusion from environment. This is not possible in complex multicellular organisms like humans. The body is covered by dead cells. The living cells are not in contact with external environment. Air containing intercellular spaces are absent. Therefore, quick diffusion cannot occur. Cell to cell diffusion is a very slow process. Passage of oxygen from lungs to toes through cell to cell diffusion will take about three years. Therefore, diffusion cannot meet the oxygen requirement of multicellular organisms like humans.
(b) Large animals have a respiratory system for meeting their oxygen requirement,

1. There is a large moist permeable membrane over a respiratory area for quick exchange of gases,
2. The respiratory surface has abundant blood supply for bringing in CO₂ and taking away O₂.
3. There is a mechanism for quick movement of fresh air over the respiratory surface and rapid disposal of foul air.

Question 23.
(a) Mohan’s friend was seriously injured and lost a lot of blood. He was advised blood transfusion immediately. But because of the rare blood group, it was not available. Immediately Mohan and his friends made efforts for the announcement to be made on TV and Radio. Soon they got many people to help them and a life was saved,
(a) What is the composition of blood ?
(b) How is oxygen and carbon dioxide transported in our body ?
(c) What values are being displayed by Mohan and his friends ? (CCE 2013)
Answer:
(a) Composition of Blood,

1. Plasma (55% of blood, 92% water, 8% solutes),
2. Red blood corpuscles (erythrocytes),
3. White blood corpuscles (leucocytes),
4. Blood platelets.

(b) Transport of O₂ and CO₂ – The two are transported by blood. Oxygen is picked up by blood from respiratory surface (97% as oxyhaemoglobin and 3% dissolved in plasma). In body tissues, oxygen separates from blood and passes into cells through tissue fluid. In return, blood picks up CO₂ from cells (70% as bicarbonates, 7% as carbonic acid and 23% as carbaminohaemoglobin) for disposal over the respiratory surface.
(c) Values Shown by Mohan and His Friends,

1. Comradeship
2. Social awakening and social service
3. Management skills.

Question 24.
(a) List the functions of juice released by the liver.
(b) Pancreas acts both as endocrine and exocrine gland. Justify giving reasons. (CCE 2013)
Answer:
(a) Juice released by liver is bile.
Functions

1. Neutralising acidity of chyme,
2. Making food alkaline for action of pancreatic enzymes,
3. Emulsification of fat.

(b) Pancreas is heterocrine gland having both exocrine and endocrine regions. Exocrine regions produce pancreatic juice while endocrine regions secrete hormones like insulin and glucagon.

Question 25.
“About 180 litre of filtrate is produced each day but only 1.5 litre of urine is excreted out.” Justify this statement. (CCE 2013)
Answer:
Glomerular filtrate contains a lot of water and useful substances while the blood passing into efferent arteriole contains a good quantity of wastes. Therefore, a long passage and hence lot of filtrate is required to correct the situation. It involves reabsorption of glucose, amino acids, ions and water in PCT and secretion of urea and other wastes from blood capillaries into urine in DCT. Urine concentration occurs in PCT, loops of Henle, DCT, collecting tubules and ducts.

Question 26.
(a) Name the site of complete digestion in human,
(b) Small intestine receives the secretions of which two organs ?
(c) Which organ secretes trypsin ? (CCE 2013)
Answer:
(a) Small intestine
(b) Pancreas and liver
(c) Pancreas as trypsinogen.

Question 27.
List three characteristics of lungs which make them an efficient respiratory surface. (CCE 2013)
Answer:

1. Large surface area of about 80 m² for exchange of respiratory gases in the form of several million alveoli.
2. Rich supply of blood capillaries over alveoli for quick exchange of gases,
3. Non-collapsible respriatory passage supported of chitinous rings in early part and surfactant in delicate part,
4. Closure in thorax where a small drop of pressure causes inhalation and a small rise in pressure produces exhalation.

Question 28.
(a) With the help of neat labelled diagram show how Amoeba captures its food ?
(b) What is the mode of nutrition in Amoeba ? (CCE 2013)
Answer:
(a) As soon as Amoeba comes in contact with a food particle, it put out pseudopodia around it, engulfs the same and forms a vesicle called phagosome. A lysosome fuses with phagosome to produce a food vacuole. Digestion occurs. The digested nutrients pass out into cytoplasm for assimilation. The food vacuole with indigestible material passes to the surface and throws out the undigested matter.Fig., 1-11 B and E.

(b) Holozoic.

Question 29.
(a) What is translocation ? Why is it essential for plants ?
(b) Where are the substances translocated by phloem delivered ? (CCE 2013)
Answer:
(a) Translocation is passage of food materials in solution form in plants from the region of their supply or manufacture to the region of their use or storage.
In plants the region of manufacture of food is only foliage while food is required by the whole plant including deep root tips and top buds and flowers. Similarly regions of storage are also away. Therefore, a translocation is always required.
(b) Delivery of Translocated Substances. The major areas where translocated substances are delivered are storage regions, growing regions, ripening fruits, etc. Of course, every living cell requires the translocates.

Question 30.
(a) Why does a piece of bread taste sweet when chewed for some time ?
(b) Cellulose acts as a roughage in man but serves as a source of nutrient in cow. Justify the statement.
(CCE 2013)
Answer:
(a) Bread contains starch which is acted upon by ptyalin (salivary amylase) to form sweet sugar maltose.
(b) Human beings have no enzymes and symbiotic bacteria for digestion of cellulose. Therefore, cellulose functions only as roughage in human beings. In cow the stomach contains cellulose digesting (fermenting) bacteria and protozoa that convert it into soluble and absorbable components including glucose.

Question 31.
Explain why is the transportation of materials necessary in animals ? (CCE 2014)
Answer:
Animals are complex multicellular organisms where there is specialisation for almost all functions like intake of food, exchange of gases and elimination of body wastes. However, every cell of the body requires nutrients and oxygen. It also eliminates CCfy and wastes. Therefore, each and every cell has to be connected to a transportation system for receiving and giving out materials. The transportation system is blood circulatory system in vertebrates. It picks up nutrients from digestive tract, oxygen from respiratory system and hormones from endocrine glands. The same are supplied to cells. Similarly, it takes carbon dioxide to respiratory surface and excretory products to kidneys for removal from’ the body.

Question 32.
Write one function each of the following components of the transport system in human beings :
(a) Blood vessels
(b) Lymph
(c) Heart. (CCE 2014)
Answer:
(a) Blood Vessels. Transport of blood to different parts of the body and exchange of materials in the region of capillaries.
(b) Lymph. To collect extra tissue fluid and materials which cannot directly enter the blood, pouring the same into blood.
(c) Heart. Pumping of bood, deoxygenated to lungs and oxygenated to all the remaining parts of the body.

Question 33.
Draw a diagram of human respiratory system and label on it
(i) Diaphragm and (ii) Larynx. (CCE 2014)
Answer:

Question 34.
Three Kinds of Blood Cells. Red blood corpuscles, white blood corpuscles and blood platelets.
Answer:

1. Red Blood Corpucles (RBCs, Erythrocytes). Transport of oxygen and smaller quantity of CO₂.
2. White Blood Corpuscles (WBCs, Leucocytes). Phagocytosis (of microbes and broken body cells) and immune response.
3. Blood Platelets (Thrombocytes). Blood clotting and plugging place of injury.

Question 35.
Draw a diagram of human excretory system and label kidneys/left kidney, ureters/urinary bladder on it.
(CCE 2014, 2015)
Answer:

Question 36.
Draw a neat diagram of sectional view of human heart and label on it
(i) Pulmonary artery
(ii) Pulmonary vein. (CCE 2014)
Answer:

Question 37.
In single celled organisms, diffusion is sufficient to meet all their requirements of food, exchange of gases or removal of wastes but it is not in case of multicellular organisms. Explain the reason for this difference.
(CCE 2014)
Answer:
Single celled organisms are in direct contact with the environment so that diffusion is helpful to them in exchange of gases, removal of wastes and even meeting their requirement of food. However, in most * multicellular organisms, the body is covered by dead cells. Cell to cell diffusion is unable to meet the requirement of all body cells. For example, in humans cell to cell diffusion will take three .years to send oxygen from lungs to toes. Multicellular organisms have developed specialised structures for performing different functions, e.g., digestive tract, respiratory surface, excretory organs. These structures are connected to all body cells through a transport system, e.g., circulatory system in animals, xylem and phloem in plants. The transport system is quite fast to bring materials to and from the cells.

Question 38.
(a) State the reason for the following :

1. Rings of cartilage are present in the trachea
2. Plants look green in colour.

(b) Write other names of the following :

1. Alveolar sac
2. Voice box.

Answer:
(a)

1. For providing support, prevent collapse under low pressure and allowing uninterrupted flow of air.
2. Presence of photosynthetic pigment chlorophyll.

(b)

1. Alveolar Sac. Sacculus alveolares, air sac.
2. Voice Box. Larynx.

Question 39.
In the experimental set up to establish that one of the atmospheric gases is essential for photosynthesis in plants
(i) Name the atmospheric gas which is essential for photosynthesis.
(ii) What is kept in watch glass in figure a and why ?
(iii) State the difference between the plants in the pots a and b after a few days. (CCE 2014, 2015)
Answer:
(i) CO₂
(ii) KOH in order to deprive the plant in a of CO₂.
(iii) After a few days the plant in pot a will turn yellow and may wither due to absence of nourishment. The plant of pot b will, however, remain healthy and green.

Question 40.
Explain how water and minerals are transported in plants. (CCE 2015)
Answer:
Water and minerals absorbed by the plant roots are passed into xylem as sap. Sap present in xylem is under tension or negative pressure as mesophyll and other cells of aerials parts lose water to the outside through transpiration.
Development of Negative Pressure. Loss of water by mesophyll and other cells of aerial parts in transpiration increases their suction pressure. They withdraw water from xylem channels. As there are billions of transpiring mesophyll cells withdrawing water from xylem channels, water present in xylem comes under negative pressure of 10-20 atmospheres. However, water column does not break due to
(a) Cohesive force amongst water molecules and
(b) Adhesion force between walls of xylem channels and water moecules.
Rise of Sap (Water and Minerals). Tension or negative pressure of water column results in upward pull just as cold-drink is sucked with the help of straw pipe. Since it develops due to transpiration, it is called transpiration pull. The mechanism of this ascent of sap was put forth by Dixon and Joly in 1894.

Question 41.
Explain why respiration through mouth is harmful. Mention the special features of nasal respiration that makes it a safer process. (CCE 2015, 2016)
Answer:
Breathing through mouth is harmful. Processing of incoming air is not carried out. Particles present in the incoming air cause irritation. Microbes present in it cause infection. Dry hot or cold air produces irritation of mucous lining.
Nasal Breathing. It has a mechanism to filter, clean, sterilise, moisten and condition the inspired air. Chances of infection, desiccation and irritation of respiratory tract are minimized. Nasal breathing is, therefore, safer.

Question 42.
Explain an activity with diagram to show that chlorophyll is essential for photosynthesis.(CCE 2015, 2016)
Answer:
Apparatus: A destarched potted plant of Croton, Pothos (Money Plant) or Coleus having variegated leaves (with green and non-green parts), Rice paper, Soft pencil, Beakers, Petridishes, Tripod stand, Wire gauze, Water bath, Blotting paper, Dropper, Box of matches, Burner or spirit lamp, spirit (or 70% alcohol), iodine solution, water, forceps.

Procedure: Destarch a potted plant of Croton or Pothos (Money Plant) having variegated leaves by keeping it in complete darkness for 2-3 days. Expose the destarched potted plant to sunlight for 2-6 hours. Pluck a variegated leaf. Place a rice paper over it. Draw the outline of green and non-green areas. The green areas contain chlorophyll. The non-green areas are pale in colour and devoid of chlorophyll. Place the leaf in boiling water for 5-10 minutes. Boiling kills the leaf. Dip the leaf in spirit or alcohol kept at 50°-60° C with the help of a water bath. After 30-45 minutes, the leaf will be decolourised completely. Take out the decolourised leaf, dip in hot water for softening the same. Spread the leaf in a petri dish. Pour dilute iodine solution over the leaf. After 4-5 minutes, rinse off excess iodine and observe.

Question 43.
Define excretion. Write two vital functions of kidney. (CCE 2015)
Answer:
Excretion. It is the elimination of metabolic waste products from the body.
Vital Functions of Kidney,

1. Elimination of metabolic waste products.
2. Maintenance of water balance or osmoregulation of body.

Question 44.
Compare alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.
(CCE 2015)
Answer:

Alveoli	Nephrons
1. Shape. They are rounded or polyhedral.	They are elongated tubules.
2. Components. Alveoli are single entities.	Each nephron has two components-Malpighian capsule and renal tubule. Renal tubule has three parts – PCT, loop of Henle and DCT.
3. Blood Capillaries. They are of one type and lie all over the alveoli.	Blood capillaries form two patches—glomerulus and peritubular capillaries.
4. Materials. They deal with respiratory gases.	They deal with body fluids.
5. Function. Alveoli perform exchange of gases between blood and inhaled air.	Nephrons bring about separation of waste products from blood.
6. Processes. Gaseous exchange occurs through diffusion.	Urine formation occurs through ultrafiltration, reabsorption, secretion and osmosis.

Question 45.
Explain the structure of bronchi with the help of neat diagram and label on it  (CCE 2015)
(i) Trachea
(ii) Bronchiole.
Answer:

Bronchi: Trachea divides into two branches called bronchi. There is short, straight right bronchus and a slightly longer oblique left bronchus. Each bronchus enters the lung of its side, branches and rebranches. Bronchi and their branches bear incomplete or C-shaped cartilaginous rings for support. They are also lined internally by ciliated and mucus secreting epithelium. Branches of bronchi ultimately produce very fine tubes called bronchioles. Bronchioles do not possess supporting cartilaginous rings. Finer bronchioles give rise to alveoli or alveolar sacs. Epithelial lining of alveoli and fine bronchioles do not possess cilia and mucus glands. They possess cells which secrete a surfactant (dipalmityl lecithin-protein complex) for preventing their collapse during exhalation. Alveoli are polyhedral to rounded sacs having extremely thin single layered wall invested closely with blood capillaries. Alveoli are actual sites of gaseous exchange.

Question 46.
Name three life processes which are essential for maintaining life and briefly explain the functioning of any one of them. (CCE 2015, 2016)
Answer:
Nutrition, respiration, exchange of materials.
Nutrition: It is the process by which living beings procure food for obtaining energy and body building materials. Body building materials are usually carbon-based. The food sources are also carbon based. They are, of course, varied. Plants manufacture their own food in the process of photosynthesis. Animals obtain food from outside. Food obtained from outside is first broken down through digestion into simpler soluble substances for absorption. Inside the cells, the simple substances are converted into various complex biochemicals to form components of protoplasm. Some biochemicals function as respiratory substfates.

Question 47.
Explain the process by which the energy requirements of the autotrophic organisms are fulfilled. In which form the unused carbohydrates get stored ? (CCE 2015)
Answer:
Photosynthesis. It occurs in the following steps :

1. Photolysis: With the help of light energy, oxygen evolving Z-complex splits up water into its components — protons (H⁺), electrons (e^–) and oxygen.
   
2. Absorption of Light Energy: Chlorophyll absorbs light energy.
3. Primary Reaction: Chlorophyll converts the absorbed light energy into chemical energy. It is called primary reaction of photosynthesis. It builds up ATP with the help of excited electrons.
4. Formation of Reducing Power: Coenzyme NADP⁺ is changed to reduced form of NADPH.
   
5. Reduction of CO₂: Carbon dioxide is reduced enzymatically with the help of NADPH and ATP to form carbohydrates.
   

Storage: Starch.

Question 48.
Explain why digestion of food is essential for all living beings. Mention the form in which energy derived from the food we eat is stored. (CCE 2015)
Answer:
(a) Food consists of complex components which cannot pass into body cells directly for nourishment. They are broken down into simpler absorbable form through the process of digestion. Digestion is intracellular in simple animals. It is intercellular inside a digestive tract in higher animals including humans. The digested materials are absorbed and transported by blood to all parts for picking up by individual cells for assimilation. The latter is then used for both release of energy and building of cellular components.
(b) Energy derived from food is stored as glycogen and fat.

Question 49.
Explain an activity with diagram to show that carbon dioxide is essential for photosynthesis. (CCE 2015)
Answer:
Apparatus: Two destarched potted plants, Two glass slabs, Two bell jars, Vaseline, Watch glass, Potassium hydroxide solution, Apparatus for starch test (water, alcohol, beakers, petri dishes, iodine solution, tripod stand, wire gauze, spirit lamp, water bath, dropper, forceps, box of matches).
Procedure: Take two potted plants which have been destarched by keeping them in dark for 2-3 days. Place them on glass slabs.
Keep a watch glass having potassium hydroxide solution on one slab. Invert bell jar over each potted plant. Seal the edges of bell jars by vaseline. Place the two sets in the sunlight. After two hours pluck one leaf from each pot and test the same for starch.
Observation: The leaf of the set B which was without potassium hydroxide solution turns blue-black while the leaf of the other set A with potassium hydroxide solution remains pale coloured.
Inference: Leaf of set B which turns blue-black has synthesised starch with the help of photosynthesis. Its bell jar contains carbon dioxide as there is no potassium hydroxide. Leaf of set A has not synthesised starch. Photosynthesis did not occur. The bell jar of this set does not contain carbon dioxide as the same is absorbed by potassium hydroxide solution. Therefore, carbon dioxide is necessary for photosynthesis.

Question 50.
Explain giving any three reasons the significance of transpiration in plants. (CCE 2016)
Answer:

1. Cooling: Evaporation of water from the aerial parts results in lowering of their temperature which will otherwise rise due to exposure to sun.
2. Concentration of Minerals: Transpiration helps in increasing concentration of minerals present in rising water.
3. Transport: It creates a pull that helps in transport of water and minerals.

Question 51.
Explain why there is need for transportation system with special tissues or organs in plants and animals ?
(CCE 2016)
Answer:
Transportation is the passage of nutrients, wastes, water and other materials from the region of their availability to the region of their use, storage or elimination. Food has to be sent to all parts of the body from the area of digestion in animal and the area of synthesis in plants. It has to be stored in special organs for supply during periods of deficiency. Plants have vascular strand for translocation while animals have blood vascular system. Animals have a pumping organ or heart for circulation of blood. Plants have distinct channels of xylem and phloem for passage of sap and nutrients.

Question 52.
Name one nitrogenous waste present in urine. What is basic unit kidney called ? How is the amount of urine produced regulated ? (CCE 2016)
Answer:
Nitrogenous Waste. Urea.
Unit. Nephron or uriniferous tubule.
Regulation. Vasopressin or antidiuretic hormone regulates the amount of urine produced. It is secreted by pituitary in amount requied to concentrate urine through bringing about reabsorption of water from the primary urine.

Question 53.
State three common features of respiratory organs of animals. (CCE 2016)
Answer:
Large surface area, thin permeable membrane, abundant blood supply.

1. Large Surface Area: There is a large respiratory surface that is either in contact with environment directly or receives air or water from outside,
2. Thin Permeable Membrane: The respiratory surface has thin permeable wall for quick diffusion and exchange of gases,
3. Abundant Blood Supply: Except in tracheal system, the respiratory surface has abundant blood supply due to presence of a network of blood capillaries.

Question 54.
Describe the structure and function of nephron with the help of diagram only. (CCE 2016)
Answer:

Long Answer Questions (5 Marks Each)

Question 1.
(a) List two differences between ‘holozoic nutrition’ and ‘saprophytic nutrition. Give two examples each of these two types of nutrition.
(b) State the roles of liver and pancreas.
(c) Name the organ which performs the following functions in humans :

1. Absorption of digested food
2. Absorption of water.

(d) Explain the statement, “Bile does not contain any enzyme but it is essential for digestion.”
(CBSE A.I. 2005, Delhi 2007, 2009)
Answer:
(a) Differences between Holozoic Nutrition and Saprophytic Nutrition

Holozoic Nutrition	Saprophytic Nutrition
1.     Type. It is ingestive type where solid food is taken in. 2.     Digestion. It is internal. Examples. Tiger, Cattle.	It is absorptive type of nutrition where simple soluble substances are taken in. Digestion is external. Examples. Rhizopus, Mushroom.

(b)

1. Role of Liver: Decomposition of haemoglobin, formation and secretion of bile for emulsification of fat. Formation of urea, heparin fibrinogen and prothrombin. Detoxification of chemicals and elimination of pathogens.
2. Role of Pancreas: Secretion of pancreatic juice having lipase, trypsin and amylase; secretion of hormones, insulin and glucagon.

(c)

1. Absorption of Digested Food. Ileum part of small intestine.
2. Absorption of Water. Large intestine.

(d) Role of Bile in Digestion.

1. Breaking of fat into fine globules or emulsification,
2. Neutralisation of acidity and making food alkaline for action of pancreatic and other enzymes.

Question 2.
(a) Draw a diagram to show the human alimentary canal and label on it the following : Gall bladder,
Stomach. Name the longest part of the alimentary canal. (CCE 2013)
(b) Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds ?
(CBSE A.I. 2009 C, CCE 2011, 2013)
Answer:
(a)

Longest Part. Small intestine (about 6 metres).
(b) Separation of Oxygenated and Deoxygenated Bloods in Birds and Mammals.
Energy needs of birds and mammals are higher due to thermoregulation of body and increased activity. They require regular and quicker supply of oxygenated blood for all body parts. This is possible only when there is complete separation of oxygenated blood and quicker oxygenation of deoxygenated blood.

Question 3.
(a) List three events that occur during the process of photosynthesis. State in brief the role of stomata in this process.
(b) Describe an experiment to show that sunlight is essential for photosynthesis.
(CBSE Delhi 2010, CCE 2010)
Answer:
(a)

1. Three Events of Photosynthesis: Information is transmitted from one plant cell to another through plasmodesmata and hormones.
2. Role of Stomata in Photosynthesis. Inward diffusion of carbon dioxide and outword diffusion of oxygen.

(b) Sunlight is Essential for Photosynthesis: It is the source of energy for photosynthesis. Light is visible part of the electromagnetic radiations. It has a wavelength of 390-760 nm. Photosynthetically active radiations or PAR are 400-700 nm. Natural source of light is sun but artificial light can also provide energy to plants for their photosynthesis. Plants absorb light mostly in violet-blue and red parts of visible light. Violet-blue light carries more energy as compared to red light. Plants growing under shade of others receive mostly green and some violet light. They have lower rates of photosynthesis.
Light has two functions, photolysis of water and excitation of chlorophyll to emit electrons. Photolysis of water produces oxygen, protons and electrons. Electrons and protons (Hydrogen ions) help in producing ATP and NADPH2, popularly called assimilatory power.

Question 4.
(a) Draw a neat diagram of alimentary canal and label the following parts :

1. The largest gland,
2. The gland that secretes digestive enzymes as well as hormones,
3. The part where digested food is absorbed.

(b) What are villi ? Mention their functions. (CCE 2010, 2012)
Answer:
(a)

1. The largest gland —Liver
2. The gland that secretes digestive enzymes as well as hormones — Pancreas
3. The part where digested food is absorbed — Small Intestine.

(b) Villi: They are transverse folds of intestine wall that not only increase surface area but also reach deep into the lumen of intestine for absorption of digested food. Villi possess blood capillaries and lacteals (lymph vessels) for quick transport of absorbed food,

Question 5.
(a) Draw the cross section of the leaf and label the following parts :

1. Upper epidermis
2. Chloroplast
3. Vascular bundle
4. Xylem
5. Phloem.

(b) Define photosynthesis.
(c) List three events which occur during this process
(d) Write the chemical equation involved in photosynthesis.
(e) How is unused energy stored in plants ?
(f) What is the site for photosynthesis ?
Answer:
(a)

(b) Photosynthesis: It is synthesis of organic food from inorganic raw materials with the help of light energy inside chlorophyll containing cells.
(c) Events: Information is transmitted from one plant cell to another through plasmodesmata and hormones.
(e) Starch, organic substances.
(f) Chloroplasts.

Question 6.
(a) Draw a diagram of human alimentary canal and label on it

1. Gall bladder
2. Liver
3. Pancreas
4. Small intestine
5. Buccal cavity
6. Large intestine.

(b) What is emulsification of fat ? Why is it necessary ?
(c) On which type of food does salivary amylase act in buccal cavity and write the name of initial product due to action of amylase.
(d) Where do carbohydrates, proteins and fats get digested in human beings ? (CCE 2010, 2012)
Answer:
(a)

(b) Emulsification of fat is the conversion of large fat pieces into very fine fat globules which can be efficiently acted upon by lipase.
(c) Salivary amylase or ptyalin acts on starch. It produces maltose and dextrins.
(d) In small intestine. Digestion of course, begins in buccal cavity (carbohydrates), stomach (proteins) and duodenum (fats).

Question 7.
(a) Draw sectional view of human heart and label

1. Pulmonary artery
2. Aorta
3. Septum
4. Ventricles.

(b) Arteries have thick walls while veins have valves. Explain.
(c) Why are valves needed in the heart ?
(d) Leakage of blood from vessels reduces the efficiency of pumping system. How is the leakage prevented ?
(CCE 2010, 2011)
Answer:
(a)

(b) In arteries, blood flows under pressure so that their walls are thick and elastic. In veins the blood is Therefore, their walls are thin. Rather, they possess semilunar valves to check back flow of blood.
(c) Valves are needed in the heart to direct the flow of blood in a particular direction.
(d) Leakage of blood from injured blood vessels is prevented by first clotting of blood at the site of injury. This seals the place of injury. Later on, the area of leakage is healed up.

Question 8.
(a) Draw human excretory system and label

1. Left kidney
2. Ureter
3. Urinary bladder
4. Vena cava.

(b) What is the main toxic waste kidney filters from blood ?
(c) Name any two substances which are selectively reabsorbed from the tubules of a nephron.(CCE 2010, 2012, 2013)
Answer:
(a)

(b) Main Toxic Waste. Urea. Selective Reabsorption, Glucose, Amino acids.

Question 9.
(a) Draw a neat diagram of human respiratory system. Label

1. Bronchioles
2. Rings of cartilage
3. Pharynx
4. Trachea
5. Larynx
6. Diaphragm.

(b) What are the factors needed for maintaining direction of diffusion in plants ?
(c) Why do aquatic animals breathe faster than terrestrial animals ? (CCE 2012, 2013)
(d) How are lungs designed in human beings to maximise the area of exchange of gases ? (CCE 2010)
Answer:
(a)

(b) Direction of Diffusion :

1. Maintenance of higher concentration in the region from which diffusion occurs,
2. Maintenance of low concentration in the region to which diffusion is to occur
3. Path of diffusion.

(c) Aquatic Animals Breathe Faster. Water contains less than 1% oxygen dissolved in it while air has 21% oxygen. Therefore, aquatic animals have to breathe faster for withdrawing higher amount of oxygen from water.
(d) Each lung has a highly branched respiratory tract called respiratory tree. A primary bronchus divides into secondary bronchi, secondary into segmental bronchi, segmental bronchus into bronchioles which divide into terminal bronchioles, respiratory bronchioles, alveolar sacs and alveoli. Alveoli are small rounded or polyhedral pouches which are extremely thin walled and possess a network of capillaries over their surface. They function as respiratory surfaces. The total area of all the alveoli is more than 80 m². It is several times more than the surface area of the whole human body.

Question 10.
Draw a neat diagram of internal structure of human heart and label the parts which do the following functions :
(a) Chamber where oxygenated blood from lungs in collected,
(b) Largest blood vessel in our body,
(c) Muscular wall separating right and left chambers.
(d) Blood vessel that carries blood from heart to lungs. (CCE 2010, 2012)
Answer:

Label
(a) Left auricle
(b) Aorta ( = systemic aorta)
(c) Septum
(d) Pulmonary artery ( = Pulmonary aorta).

Question 11.
How do the guard cells regulate opening and closing of stomatal pores ? Explain with the help of diagram. Also indicate what happens to the rate of photosynthesis if stomata get blocked due to dust. (CCE 2010)
Answer:
Regulation of Stomatal Pore:
Opening and closing of stomata is regulated by gain or loss of turgidity of their guard cells. During opening of stomata, guard cells withdraw K⁺ ions from surrounding epidermal cells, followed by absorption of water from them. As a result, guard cells swell up and become turgid. Their outer thin and elastic walls bend outwardly followed by outward movement of thicker inner walls. The latter creates a pore in between the two guard cells.
During closure movement of stomata, guard cells send out K⁺ ions. Water also passes out. Guard cells become flaccid. Their inner thick walls come to touch each other. The stomatal pore gets closed.

Blocking of Stomata:

1. Photosynthesis will be reduced,
2. There will be no gaseous exchange and transpiration. As a result leaves will burn up in hot summer sun.

Question 12.
(a) Name the enzyme present in saliva. Why is it important ?
(b) What is emulsification ?
(c) Name the substance that is oxidised in the body during respiration.
(d) Why are lungs divided into very small sac-like structures ? (CCE 2011)
Answer:
(a) Enzyme. Ptyalin or salivary amylase. It breaks down starch to form maltose sugar.
(b) Emulsification: Emulsification of fat is the conversion of large fat pieces into very fine fat globules which can be efficiently acted upon by lipase.
(c) Glucose
(d) To increase surface area for exchange of gases.

Question 13.
(a) Draw a neat diagram of human excretory system and label the part that

1. produces urine
2. releases urine to the outside

(b) What are the end products of digestion of fat and protein in human beings ? (CCE 2011)
Answer:
(a)

kidney (produces urine) and urethra (releases urine to the outside).
(b)

1. Fat—fatty acids and glycerol.
2. Protein—amino acids.

Question 14.
(a) Draw a neat diagram of excretory system of human beings and label the following : (t) Kidney (it) Ureter (iit) Urinary bladder (iv) Urethra.
(b) How is urine produced ?
(c) Name two excretory products other than 02 and C02 in plants. (CCE 2011)
Answer:
(a)

(b) A kidney has very large number of nephrons which function as filtration units. Useful substances (water, glucose, amino acids, salts) are selectively reabsorbed from primary urine. It gives rise to urine having waste products (e.g. urea, uric acid, creatine, oxalate, some salts, water soluble vitamins).
(c) Resin, Gum, Tannin.

Question 15.
(a) Draw diagram to show nutrition in Amoeba and label the part used for this purpose. Mention a purpose served by this part other than nutrition.
(b) Name the glands associated with digestion of starch in human digestive tract and mention their role.
(c) How is required pH maintained in the stomach and small intestine ? (CCE 2011)
Answer:
(a)

pseudopodia in part B. The other function of pseudopodia is locomotion.
(b)

1. Salivary glands—salivary amylase—starch to maltose sugar
2. Pancreas—pancreatic amylase—starch to maltose sugar
3. Intestine—disaccharidases—disaccharides to glucose.

(c) Stomach—acidic pH, due to secretion of HC1 by gastric glands.
Small Intestine—alkaline pH, due to bicarbonates and other bases present in bile and pancreatic juice.

Question 16.
Draw a labelled diagram of human heart. Write the function of any two chambers of human heart.
(CCE 2011)
Answer:

Functions:
Left Atrium – Receiving oxygenated blood from lungs.
Right Atrium – Receiving deoxygenated blood from the body as well as walls of the heart.

Question 17.
(a) Draw a diagram of an excretory unit of human kidney and label the following : Bowman’s capsule,
Glomerulus, collecting duct, Renal artery. ‘
(b) Write the important function of structural and functional unit of kidney.
(c) Write any one function of an artificial kidney. (CCE 2011)
Answer:
(a)

(b) Nephron. It takes part in filtration, reabsorption and selective secretion to form urine.
(c) Artificial kidney. It helps in removal of toxins, relieve uraemia, and remove wastes in patients with damaged kidneys.

Question 18.
(a) Draw a neat diagram of human respiratory system and label : Rings of cartilage, Lung, Bronchii, Alveolar sac.
(b) Name any two parasitic plants and two parasitic animals. (CCE 2011)
Answer:
(a)

(b)

1. Parasitic Plants. Cuscuta, Mistletoe
2. Parasitic Animals. Ascaris, Plasmodium.

Question 19.
“Sunlight is necessary for photosynthesis.” Explain an experiment to prove it.
Answer:
Light is Necessary for Photosynthesis.                       ,
Apparatus: Destarched potted plant, Ganong’s light screen or Black paper, Scissors and Cellotape or Clip, Water, Denatured spirit, Dropper, Forceps, Beakers, Petri dishes, Tripod stand, Wire gauze, Spirit lamp, Water bath, Iodine solution, Blotting paper, Box of matches.
Ganong’s light screen is a small metallic box with a spring handle, ventilating holes and a lid having a design cut in the centre. Alternately take a strip of black paper.
Procedure: Fix a strip of black paper in the middle on the upper surface of a leaf of destarched potted plant by means of cellotape or clips. Alternately attach a Ganong’s light screen or a black paper with a central cut design over it. Expose the plant to sunlight for 2-3 hours. Remove the black paper or Ganong’s light screen. Pluck the leaf. Test it for starch by first boiling in water for 5-10 minutes, drying in folds of blotting paper, dipping in warm denatured spirit for 30-45 minutes, washing with hot water and pouring iodine over it.
Observation: Covered part of leaf remains yellow while parts of leaf which received light turn bluish black. Bluish black colour indicates the presence of starch or photosynthesis.
Inference: Only that leaf part shows photosynthesis or positive starch test which is exposed to light. The covered part which does not receive sunlight also does not perform photosynthesis as is evident from the absence of starch. Therefore, light is necessary for photosynthesis.

Question 20.
(a) What happens to glucose, amino acids, salts and water that enter the nephron alongwith filtrate.
(b) Draw a neat labelled diagram of stomata. Write two functions of stomata.
(c) What are the basic materials used during photosynthesis ? Write chemical equation for photosyntheis.
(CCE 2011, 2012, 2013)
Answer:
(a) They are reabsorbed by the living cells of nephrons and then passed on to capillary blood.
(b)

Functions,

1. Exchange of gases,
2. Transpiration.

(c) Raw Materials. CO₂ and H₂O in the presence of solar energy and chlorophyll.

Question 21.
List and describe in brief in tabular form any five functions of blood.
Answer:

1. Transport of Respiratory Gases.	Blood transports O2 from respiratory surface to tissues and CO2 from tissues to respiratory surface.                                                                            .
2. Transport of Nutrients.	Blood picks up nutrients from digestive tract and passes the same to all parts of body for assimilation (and storage).
3. Transport of Waste Products	It transports waste products to kidneys for separation and elimination.
4. Regulation of Body Temperature	Blood distributes heat to all parts of body and dissipates the excess heat from the surface.
5. Body Defence	It contains phagocytes and immunocytes for defence against germs.

Question 22.
(a) Draw the diagram of human heart and label the following parts which

1. Receives deoxygenated blood from vena cava
2. Sends deoxygenated blood to lung through pulmonary artery
3. Receives oxygenated blood from lungs and
4. Sends oxygenated blood to all parts of the body through aorta.

(b) What does the blood consist of ?
(c) Name the respiratory pigment in human beings and discuss its role. (CCE 2011)
Answer:

1. Right atrium
2. Right ventricle
3. Left atrium
4. Left ventricle.

(b) Blood consists of blood plasma, red blood corpuscles, white blood corpuscles and blood platelets.
(c) Haemoglobin: It transports oxygen as oxyhaemoglobin and a part of CO₂ as carbaminohaemoglobin.

Question 23.
Draw diagram of human alimentary canal and label the following  (CCE 2011)

1. Part in which starch digestion starts
2. Part in which bile is stored
3. Part in which nutrients are absorbed
4. Part in which water is absorbed.

(b) Mention the role of hydrochloric acid in stomach,
(c) What function is served by

1. Gastric sphincter
2. Anal sphincter.

Answer:
(a)

1. Buccal cavity
2. Gall bladder
3. Small intestine
4. Large intestine (colon):

(b) Hydrochloric acid (HCl) is component of gastric juice. It has five functions,

1. Softening of food,
2. Conversion of pepsinogen and prorennin into active forms of pepsin and rennin
3. Acidify the food for proper action of pepsin,
4. Killing of microorganisms present in food,
5. Stoppage of action of salivary amylase.

(c)

1. Controls release of food from stomach to duçdenum.
2. Controls release of faeces through anus.

Question 24.
(a) Draw diagram of respiratory system and label the following :

1. Part through which air is taken in
2. Part which protects the lungs
3. Part which carries air into the lungs.

(b) What are alveoli ? Mention their role in respiration. (CCE 2011)
Answer:
(a)

1. Nasal passage
2. Ribs
3. Trachea and bronchi.

(b) Lung Alveoli: Lung alveoli constitute the respiratory surface of the lungs. Their walls have rich supply of blood for gaseous exchange, i.e. passage of oxygen from alveolar air to blood and passage of carbon dioxide from blood to alveolar air.

Question 25.
Draw a schematic representation of transport and exchange of 02 and C02 in human body.
(b) Draw a schematic representation of movement of water in plants during transpiration and explain it.
(c) Explain transport of food and other substances in plants.
(d) Diffusion will not be sufficient to provide raw materials in leaves and energy in roots of plants. Therefore, a proper system of transportation is essential. Explain. (CCE 2011)
Answer:
(a)

(b)

Transpiration creates a tension or negative pressure in the water column of the plant. It causes an upward transpiration pull of water and minerals (sap) which is replenished by absorption of same from the soil through the roots.
(c) Food and other nutrients pass into sieve tubes of phloem through an active process in the region of manufacture or source. An increased osmotic pressure creates a turgor gradient towards sink or region of utilisation in a mass flow. Nutrients and other organic substances are then withdrawn from the sieve tubes actively.
(d) Diffusion is a very slow process (0-05 mm/hr) while the distances are comparatively very large in plants. Therefore, raw materials absorbed by roots will take several days to reach leaves if they are to diffuse only. Similar is the case of food materials that are to travel from leaves to roots. Therefore, a proper system of rapid transportation is required.

Question 26.
(a) How many times the blood goes through the heart during one cycle in fish and why ?
(b) List the respiratory pigment present in our body. Where is it pressent ?
(c) Why are valves present in heart and viens ? (CCE 2011)
Answer:
(a) Fish has single circulation, that is, blood passes once through the heart in one cycle. It goes from heart to gills, from gills to body and back to heart.
(b) Haemoglobin. It occurs inside red blood corpuscles.
(c) Valves occur in heart and veins to prevent back flow of blood.

Question 27.
(a) Explain in brief the mechanism of circulation of blood in the human body.
(b) “Lymph is another type of fluid involved in transportation”. Justify the statement by explaining the process.
(CCE 2011)
Answer:
(a) Deoxygenated blood is collected by superior vena cava from upper part of the body, by inferior vena cava from middle and lower parts of the body and coronary sinus from the walls of heart. All the three pour their blood into right auricle. Oxygenated blood is brought by pulmonary veins from the lungs. It is poured into left auricle. On being filled, the two auricles contract simultaneously and pass their bloods into ventricles, deoxygenated in right ventricle and oxygenated in left ventricle. The distended ventricles now undergo contraction or systole forcefully. Right ventricle passes blood to pulmonary arch which divides to form pulmonary arteries. Pulmonary arteries take the deoxygenated blood to lungs. Left ventricle passes blood to systemic aorta that supplies oxygenated blood to all parts of the body.
(b) Lymph is a fluid that is specialised to collect those materials from the tissues which cannot pass directly into blood, e.g., proteins, hormones, fats (from intestine). Lymph collects the same and pass them to blood in the region of subclavian veins. For passage of lymph, the lymphatic system has lymph capillaries, lymph vessels and lymph nodes.

Question 28.
(a) Explain the excretory system in human beings. (CCE 2011)
(b) List four strategies used by plants for excretion. (CCE 2011, 2016)
Answer:
(a) In human beings, the excretory system consists of a pair of kidneys, a pair of ureters, a urinary bladder and a urethra.
Kidneys are a pair of reddish brown bean-shaped structures that lie dorsally in the abdominal cavity. A renal artery and a renal vein occur on the concave hilus region of each kidney. About a million structural and functional units called nephrons occur in each kidney. Blood is filtered in the glomerular region of a nephron. Useful substances (e.g. glucose, amino acids, salts, water) are reabsorbed and urine passes into collecting ducts. Ureters are pulsatile drainage tubes that carry urine from the kidneys to the urinary bladder. Urinary bladder is a pear-shaped distensible sac that stores urine till its volume becomes 300-800 ml. Urethra is a fine tube that carries urine from urinary bladder to the outside.
(b) Excretion Strategies in Plants,

1. Excess water is passed out through transpiration,
2. Excess O₂ formed during the day diffuses out of the leaves.
3. Alkaloids, organic acids and tannins are the common secondary metabolites. Some of these are stored in the cell vacuoles of leaves which when old fall down,
4. Resins and gums alongwith other wastes are also deposited in old non-functional xylem.

Question 29.
(a) Some finger-like projections are present in the inner wall of small intestine. Write their name. Why are they important ?
(b) What is the use of residual volume of air in lungs ? (CCE 2011, 2012, 2013)
Answer:
(a) Villi :

1. They increase surface area for absorption of digested food
2. Pass deep into lumen of intestine for increased availability of digested food.
3. Possess capillaries and lacteals for quick transport of absorbed food
4. Their epithelial cells possess microvilli for enlarging absorptive surface area.

(b) Residual volume of air is the volume of air that h left in the lungs even after maximum exhalation. The air is useful as exchange of gases continues with the blood in between exhalation and fresh inhalation.

Question 30.
Draw a diagram of sectional view of human heart and on it name and label the following parts :
(a) The chamber of heart that pumps out deoxygenated blood,
(b) The blood vessel that carries away oxygenated blood from heart
(c) The blood vessel that receives deoxygenated blood from lower part of our body. (CCE 2012)
Answer:

(a) Right ventricle (pumps deoxygenated blood)
(b) Aorta (carries away oxygenated blood from heart)
(c) Inferior vena cava.

Question 31.
(a) Draw human respiratory system and label the following — lung, bronchi, alveoli
(b) During breathing cycle what is the advantage of residual volume of air in lungs ? Explain. (CCE 2012)
Answer:
(a)

(b) Residual volume of air is the air left in the lungs after an exhalation or expiration. It is useful for continuous exchange of gases between blood and alveolar air.

Question 32.
(a) Draw a sectional view of human heart and label on it

1. Pulmonary artery
2. Right auricle
3. Vena cava
4. Pulmonary vein,

(b) Explain why ventricles have thick muscular walls than the atria ? (CCE 2012)
Answer:
(a)

(b) Atria are to receive blood from veins and pump the same into adjacent ventricles only. They have, therefore, thin walls. Ventricles are to pump blood into arteries forcefully as it is to be sent to lungs (right ventricle) and all parts of the body (left ventricle). Therefore, walls of ventricles are thick and muscular with those of left ventricle being thicker.

Question 33.
Draw a neat diagram of a section of human heart. Name and label the following on the diagram
(a) Structure/ part that divides the heart into right and left halves and prevents mixing of oxygenated and deoxygenated blood
(b) Part which prevents backflow of blood
(c) Chamber that receives deoxygenated blood from various parts of the body
(d) Chamber from where oxygenated blood is pumped out to various parts of the body.
(CCE 2012)
Answer:

(a) Septum
(b) Valves
(c) Right auricle
(d) Left ventricle.

Question 34.
(a) Draw a diagram of human respiratory system and label

1. Part where air is filtered by fine hair and mucus
2. Part which terminates in balloon-like structures
3. Balloon-like structures where exchange of gases takes place
4. Part which separates chest cavity from abdominal cavity.

(b) Draw a diagram of human excretory system and label the following

1. Part in which urine is produced
2. Part which stores the Purpose. To collect excretory products for expulsion from body.

Answer:
(a)

label

1. Nasal chamber
2. Trachea
3. Alveoli
4. Diaphragm.

(b)

label

1. Kidney
2. Urinary bladder
3. Ureter
4. Urethra.

Question 35.
(a) Explain the process of nutrition in Amoeba with the help of diagram. (CCE 2013, 2016)
(b) Explain how does Paramoecium obtain its food ? (CCE 2012)
(c) Name the form in which the following are stored :

1. Unused carbohydrates in plants
2. The energy derived from food in humans.

Answer:
(a) As soon as Amoeba comes in contact with a food particle, it put out pseudopodia around it, engulfs the same and forms a vesicle called phagosome. A lysosome fuses with phagosome to produce a food vacuole. Digestion occurs. The digested nutrients pass out into cytoplasm for assimilation. The food vacuole with indigestible material passes to the surface and throws out the undigested matter. Fig., 1-11 B and E.

(b) Paramoecium creates a current in water with the help of cilia. The food particle passes into cytostome or cell mouth for engulfment and formation of food vacuole. The indigestible material passes out through a temporary opening called cytopyge.
(c)

1. Starch
2. ATP.

Question 36.
(a) What is the mode of nutrition in

1. Fungi
2. Amarbel (Cuscuta)

(b) Name the part of alimentary canal where

1. Food is completely digested
2. Secrete juice that has trypsin
3. Secrete bile
4. Absorbs water from unabsorbed food

(c) Mention the names of any two secretions by the gastric glands and state one role played by each in our body. (CCE 2012)
Answer:
(a)

1. Fungi. Heterotrophic, commonly saprophytic
2. Amarbel (Cuscuta). Pleterotrophic, parasitic,

(b)

1. Small intestine
2. Pancreas
3. Liver
4. Large intestine,

(c)

1. Pepsin — breakdown of proteins into peptones and proteoses,
2. HCl — makes food soft, sterilised and acidified for pepsin to act upon it.

Question 37.
(a) List the major steps involved in formation of urine and state in brief their functions.
(b) State how is the process of breathing brought about in our body. (CCE 2012, 2013)
Answer:
(a) Major Steps in Urine Formation,

1. Glomerular Filtration,
2. Ultrafiltration of blood passing through urine
3. Part which connects (i) and (ii).
4. Part from which urine is passed out glomerule produces a dilute filtrate having most of the small volume solutes of plasma. It passes into Bowman’s capsule and then renal tubule,
5. Formation of Urine. Useful solutes and a major part of water are reabsorbed while some waste products left in the blood are secreted into filtrate to form urine.

(b) Breathing In (Inhalation). Thoracic cavity enlarges due to

1. Straightening of diaphragm by contraction of phrenic muscles
2. Upward and outward expansion of ribcage due to contraction of external intercostal muscles. Enlargement of thoracic cavity causes expansion of lungs and decrease in air pressure in them. Outside air rushes into lungs to equalise pressure.

Question 38.
(a) List in tubular form two ways in which transpiration is different from translocation,
(b) Why do plants have a slow transport system ?
(c) What are stomata ? What function do they perform ? With the help of diagram explain opening and closing of stomata. (CEE 2012)
Answer:
(a) Differences

Transpiration	Translocation
1.      Activity. It is loss of water in the vapour form from aerial parts of the plant. 2.       Function. It helps in cooling the sun heated aerial parts as well as create a negative pressure for ascent of sap.	1.     It is transport of materials inside the plant from one part to another. 2.     It passes nutrients from source to sink region.

(b) Plants Have Slow Transport System. Plants are fixed. Most of their body is made of dead cells. Energy requirement is less. Therefore, plants have slow transport system.
(c) Stomata: Carbon dioxide is absorbed during night when stomata are open. It is fixed in malic acid from which the same is released during day time for performing Calvin cycle in light and draw Fig. 1.4.

Question 39.
Draw a neat diagram of human excretory system and label
(a) Renal artery and
(b) Urethra on it. State the function of renal artery, kidney, ureter and urinary bladder. (CCE 2013)
Answer:

Functions:
Renal Artery: Bringing oxygenated blood laden with waste products.
Kidney: Excretion of nitrogenous and other waste products, regulation of salt content, blood pressure and water balance.
Ureter: Taking urine from kidney to urinary bladder.
Urinary Bladder: Storage of urine.

Question 40.
What is lymph ? How is composition of lymph different from blood plasma ? What is the direction of its flow ?
List two functions of lymphatic system. (CCE 2013)
Answer:
Lymph: It is a colourless or slightly yellowish viscous fluid which is derived from tissue fluid and is present inside special tubes called lymph vessels.
Difference Between Lymph and Blood Plasma

Lymph	Blood Plasma
1.  Water. It is 94% 2.   Protein. Protein content is 3.0-4.5% 3.   Fibrinogen. It is low. 4.   Albumin/Globulin Ratio. It is 1.5 5.   Food and Waste Materials. Lymph is rich in them.	1.  It is 92%. 2.   Protein content is 6-8%. 3.   Fibrinogen content is high. 4.   It is unity. 5.  The content is comparatively lower.

Direction of Flow: Lymph flows from tissues to subclavian veins—It is unidrectional.
Functions of Lymphatic System:

1. Lymph functions as a middleman that exchanges materials between blood and tissue fluid.
2. Maintenance of Blood Volume. Blood volume continues to decrease due to filtration of blood plasma from blood capillaries. Lymph collects the same and puts it back into blood.
3. They mature inside the lymph nodes and released into lymph passing through the same.
4. Tissue Secretions. Hormones, macromolecules, plasrha proteins and other secretions of the tissues are first poured into lymph for passage into blood.
5. Lymph picks up digested fat from alimentary canal for pouring into blood.
6. Wastes from tissues are first passed into lymph before they are poured into blood for separation in kidneys.
7. Lymph capillaries are specialised to attract and localise germs. The germs are taken to lymph nodes for destruction.

Question 41.
Draw a diagram of human respiratory system and label

1. Organ that is surrounded by cartilaginous rings
2. Structure where exchange of gases takes place
3. Voice box
4. Muscular structure which flattens during inhalation. (CCE 2013)

Answer:

1. Trachea
2. Alveoli
3. Larynx
4. Diaphragm.

Question 42.
(a) Bile does not contain any digestive enzyme, yet it is important for digestion of food
(b) Name the products formed after complete digestion of carbohydrates, proteins and fats in small intestine. (CCE 2013)
Answer:
(a) Role of Bile in Digestion.

1. Breaking of fat into fine globules or emulsification,
2. Neutralisation of acidity and making food alkaline for action of pancreatic and other enzymes.

(b) Carbohydrates: Glucose.
Proteins: Amino acids.
Fats: Fatty acids and glycerol.

Question 43.
(a) Draw a diagram of human respiratory system and label Trachea, Bronchi, Diaphragm.
(b) Give reasons

1. Lungs always contain residual volume,
2. Nostrils are lined with mucus. (CCE 2013)

Answer:
(a)

(b)

1. Lungs always contain residual volume due to presence of cartilaginous rings and surfactant in its components,
2. To trap dust particles and microbes.

Question 44.
(a) Draw a well labelled diagram of heart showing major arteries and veins
(b) What is selective reabsorption and how does it take place ?
Answer:
(a)

(b) Selective Reabsorption. It is reabsorption of useful substances (e.g., glucose, amino acids, vitamin C, Ca, K) from glomerular or nephric filtrate by walls of nephrons and peritubular capillaries. Selective reabsorption occurs by both active and passive processes.

Question 45.
(a) Draw a well labelled diagram of nephron
(b) Differentiate between aerobic and anaerobic respiration.
(CCE 2013)
Answer:
(a)

(b)

Aerobic Respiration	Anaerobic Respiration
1. Method: It is the common method of respiration.	It occurs permanently only in a few organisms. In others it may occur as a temporary measure to overcome shortage of oxygen.
2. Steps: It is completed in 3 steps—glycolysis, Krebs cycle and terminal oxidation.	There are two steps— glycolysis and anaerobic breakdown of pyruvic acid.
3. Oxygen: It requires oxygen.	Oxygen is not required.

Question 46.
(a) Explain the process of digestion of proteins in the stomach and small intestine.
(b) How is small intestine designated to absorb digested food. (CCE 2013)
Answer:
(a)

1. In Stomach. Pepsin of gastric juice acts on proteins in acidic medium. It converts proteins into peptones and proteoses.
   
2. In Intestine. Trypsin of pancreatic juice acts on proteins, peptones and proteoses in alkaline medium to form peptides.
   
   Erepsin or peptidases of intestinal juice acts on peptides of form amino acids. The latter are absorbed.
   

(b) Small intestine is lined by epithelium which is specialised to absorb. It has mechanisation to increase its absorbing surface area several times,

1. Villi: They are transverse folds of intestine wall that not only increase surface area but also reach deep into the lumen of intestine for absorption of digested food. Villi possess blood capillaries and lacteals (lymph vessels) for quick transport of absorbed food,
2. Microvilli: The columnar cells of the intestinal epithelium have fine microscopic outgrowths called microvilli. Microvilli increase the surface area of epithelial cells.

Question 47.
(a) What are stomata ? What function do they perform ?
(b) With the help of diagram explain opening and closing of stomata. (CCE 2013)
Answer:
(a) Stomata:
Stomata are minute pore complexes found on the surface of leaves and other soft aerial parts. Each stomate has two small specialised chloroplast containing epidermal cells called guard cells. All other epidermal cells are large and without chloroplasts. The structure of guard cells is such (kidney shaped, dumb-bell shaped) that their swelling creates a pore in between them while their contraction closes the pore. The pore is called stoma or stomatal aperture.
Function. By developing pores, stomata perform

1. Gaseous exchange
2. Transpiration.

(b) Opening and Closing: 
Opening and closing of stomata is regulated by gain or loss of turgidity of their guard cells. During opening of stomata, guard cells withdraw K⁺ ions from surrounding epidermal cells, followed by absorption of water from them. As a result, guard cells swell up and become turgid. Their outer thin and elastic walls bend outwardly followed by outward movement of thicker inner walls. The latter creates a pore in between the two guard cells.
During closure movement of stomata, guard cells send out K⁺ ions. Water also passes out. Guard cells become flaccid. Their inner thick walls come to touch each other. The stomatal pore gets closed.

Question 48.

1. Draw a neat sectional diagram of human heart and label — right ventricle, septum.
2. Name the artery which carries deoxygenated blood.
3. Name the chamber of heart which receives oxygenated blood.
4. Why are walls of the ventricles thicker than the auricles ? (CCE 2013)

Answer:

1. 
2. Pulmonary artery
3. Left atrium
4. Atria are to receive blood from veins and pump the same into adjacent ventricles only. They have, therefore, thin walls. Ventricles are to pump blood into arteries forcefully as it is to be sent to lungs (right ventricle) and all parts of the body (left ventricle). Therefore, walls of ventricles are thick and muscular with those of left ventricle being thicker.

Question 49.
Mention the location of four major glands associated with digestive system of humans and explain function of each. (CCE 2014)
Answer:

1. Salivary Glands. Three pairs — Parotid below ears, submaxillary (at the angles of lower jaw) and sublingual (below tongue). Secrete saliva which moistens the food, disinfects food by lysozyme and digests starch/glycogen partially.
2. Gastric Glands. Inside stomach. Secrete HCI (for acidification and disinfection of food) and pepsin (for partial digestion of proteins to form peptones and proteoses).
3. Liver. Right upper side of abdomen below the diaphragm. Secretes bile, which neutralises the acidity of chyme and emulsifies fat.
4. Pancreas. Lies in the loop of duodenum below the stomach. Secretes three types of digestive enzymes— proteolytic trypsin, amylolytic amylase (amylopsin) and lipolytic lipase (steapsin). All of them function in alkaline medium.

Question 50.
(a) Draw a sectional view of human heart and label the following parts on it : Pulmonary artery, right atrium, left ventricle, septum.
(b) What do the following transport :

1. Xylem
2. Phloem
3. Pulmonary vein
4. Vena cava.  (CCE 2014)

Answer:
(a)

(b)

1. Xylem. Sap (Water + mineral salts)
2. Phloem. Organic food or nutrients.
3. Pulmonary Vein. Oxygenated blood.
4. Vena Cava. Deoxygenated blood.

Question 51.
(a) Draw a diagram of human excretory system and label the following parts on it :

1. Aorta
2. Vena cava
3. Urinary bladder
4. Left kidney

(b) List two vital functions of kidney.
Answer:
(a)

(b) Vital function of kidney:

1. Elimination of metabolic waste products.
2. Maintenance of water balance or osmoregulation of body.

Question 52.
(a) In the given representation of transport and exchange of oxygen and carbon dioxide in human heart label the parts marked as a, b, c, d, e, and f.

(b) Write two points of difference between pulmonary artery and pulmonary vein. (CCE 2015)
Answer:
(a)

1. (a)—Pulmonary artery
2. (b)—Lung capillaries
3. (c) —Pulmonary vein
4. (d)—Aorta
5. (e) —Capillaries in body organs
6. (f) —Vena cava.

(b)

Pulmonary artery	Pulmonary vein
1. Distance. It operates through short distance. 2. Flow. It is from heart to lungs and back. 3. Pumping. Blood is pumped by right ventricle and received by left auricle.                         „ 4. Oxygenation-Deoxygenation. Deoxygenated blood is pumped into lungs. Oxygenated blood is received from lungs.	It operates through long distance. It is from heart to body parts (other than lungs) and back. Blood is pumped by left ventricle and received by right auricle. Oxygenated blood is pumped into different body parts (other than lungs). Deoxygenated blood is received from body organs.

Question 53.
(a) It was found that the leaves of a plant started getting wilted. Name the tissue which might have been blocked. State the role of this tissue in plants.
(b) Explain opening and closing of stomata with the help of labelled diagrams.
(c) Name the physical phenomenon by which exchange of gases occurs between plant body and atmosphere.
(CCE 2015)
Answer:
(a) Xylem. Role-

1. Conduction of sap through its tracheary elements,
2. Mechanical strength.

(b) Opening and closing of stomata is regulated by gain or loss of turgidity of their guard cells. During opening of stomata, guard cells withdraw K⁺ ions from surrounding epidermal cells, followed by absorption of water from them. As a result, guard cells swell up and become turgid. Their outer thin and elastic walls bend outwardly followed by outward movement of thicker inner walls. The latter creates a pore in between the two guard cells.
During closure movement of stomata, guard cells send out K⁺ ions. Water also passes out. Guard cells become flaccid. Their inner thick walls come to touch each other. The stomatal pore gets closed.

(c) Diffusion.

Question 54.
(a) Draw sectional view of the human heart and label the following parts on it :
Pulmonary artery, right artium, left artium, septum.
(b) What do the following transport

1. Xylem
2. Phloem
3. Pulmonary vein
4. Vena cava ?  (CCE 2015)

Answer:
(a)

(b)

1. Xylem: Transport of sap (water + minerals),
2. Phloem: Translocation of nutrients.
3. Pulmonary Vein: Oxygenated blood from lungs to heart,
4. Vena Cava: Deoxygenated blood from all parts of body to heart.

Question 55.
(a) Explain how does the exchange of gases occur in plants across the surface of stem, roots and leaves.
(b) How are water and minerals transported in plants ? (CCE 2015)
Answer:
(a)

1. Old stem and old root. By diffusion through lenticels which possess intercellular spaces amongst complementary cells for exchange of gases between atmosphere and stem interior.
2. Young root. By diffusion between root interior and soil interspaces through the epiblema root hair
   complex in young roots.
3. Young stem and leaves. Diffusion across stomata between atmosphere and intercellular spaces.

(b) Transport of water and minerals.
Water and minerals absorbed by the plant roots are passed into xylem as sap. Sap present in xylem is under tension or negative pressure as mesophyll and other cells of aerials parts lose water to the outside through transpiration.
Development of Negative Pressure. Loss of water by mesophyll and other cells of aerial parts in transpiration increases their suction pressure. They withdraw water from xylem channels. As there are billions of transpiring mesophyll cells withdrawing water from xylem channels, water present in xylem comes under negative pressure of 10-20 atmospheres. However, water column does not break due to

1. Cohesive force amongst water molecules and
2. Adhesion force between walls of xylem channels and water moecules.

Rise of Sap (Water and Minerals): Tension or negative pressure of water column results in upward pull just as cold-drink is sucked with the help of straw pipe. Since it develops due to transpiration, it is called transpiration pull. The mechanism of this ascent of sap was put forth by Dixon and Joly in 1894.

Question 56.
(a) The upward movement of water normally requires a pump in our houses, but in tall trees water rises up without any external support. Explain the mechanism.
(b) State three points of difference between the transport of materials in xylem and phloem tissues.
(CCE 2016)
Answer:
(a) Water and minerals absorbed by the plant roots are passed into xylem as sap. Sap present in xylem is under tension or negative pressure as mesophyll and other cells of aerials parts lose water to the outside through transpiration.
Development of Negative Pressure. Loss of water by mesophyll and other cells of aerial parts in transpiration increases their suction pressure. They withdraw water from xylem channels. As there are billions of transpiring mesophyll cells withdrawing water from xylem channels, water present in xylem comes under negative pressure of 10-20 atmospheres. However, water column does not break due to

1. Cohesive force amongst water molecules and
2. Adhesion force between walls of xylem channels and water moecules.

Rise of Sap (Water and Minerals). Tension or negative pressure of water column results in upward pull just as cold-drink is sucked with the help of straw pipe. Since it develops due to transpiration, it is called transpiration pull. The mechanism of this ascent of sap was put forth by Dixon and Joly in 1894.
(b)

Xylem	Phloem
1.      Direction. In xylem transport is unidirectional, mostly in the upward direction. 2.       Tension. Transport occurs due to negative pressure or tension. 3.       Cells. Nonliving cells, vessels and tracheids, take part in transport.	1.     In Phloem transport occurs both in upward and downward directions. 2.     Transport occurs due to positive pressure. 3.     Living cells, sieve tube cells, take part in transport.

Hope given Previous Year Question Papers for CBSE Class 10 Science Chapter 6 Life Processes are helpful to complete your science homework.

If you have any doubts, please comment below. Learn Insta try to provide online science tutoring for you.

Chapter 14 Sources of Energy Class 10 Science Important Questions with Answers PDF will help you in scoring more marks. This consists of 1 mark Questions, 3 Mark Numericals Questions, 5 Marks Numerical Questions and previous year questions from Chemical Reactions and Equations Chapter.

Sources of Energy Class 10 Important Questions and Answers Science Chapter 14

Very Short Answer Questions

Based on Non-renewable or conventional sources of energy

Question 1.
What is meant by non-renewable sources of energy ? (CBSE 2014)
Answer:
The sources of energy which have been formed in nature long ago under certain conditions of temperature and pressure. For example, fossil fuels like coal and petroleum.

More Resources

• Previous Year Question Papers for CBSE Class 10 Science
• NCERT Solutions for Class 10 Science
• NCERT Exemplar Solutions for Class 10 Science
• Value Based Questions in Science for Class 10
• HOTS Questions for Class 10 Science

Question 2.
Name two non-renewable or conventional sources of energy.
Answer:

1. Coal,
2. Petroleum.

Question 3.
What is a fossil fuel ? (CBSE 2011)
Answer:
The combustible substance formed from the dead remains of the animals and plants which were buried deep under the surface of the earth over millions of years is called fossil fuel.

Question 4.
Give two examples of fossil fuels.
Answer:
Coal and petroleum.

Question 5.
How is the increase in demand for energy affecting our environment adversely ? [CBSE (Delhi) 2008]
Answer:
More use of fossil fuels for fulfilling the increasing demand for energy is polluting the air, which is a great health hazard.

Question 6.
What does “LPG” stands for ?
Answer:
LPG stands for “Liquid Petroleum Gas”.

Question 7.
Write the name of the main constituent of “LPG”.
Answer:
The main constitutent of “LPG” is butane.

Question 8.
What does “CNG stand for ?
Answer:
CNG stands for “compressed Natural Gas”.

Question 9.
Write the name of the main constituent of “CNG”.
Answer:
The main constituent of CNG is methane.

Question 10.
Name the device/technique to produce electricity by burning fossil fuels.
Answer:
Thermal power plant produces electricity by burning fossil fuels.

Question 11.
What is the disadvantage of a thermal power plant ?
Answer:
Disadvantage : The burning of coal or oil in a thermal power plant causes environmental pollution and global warming.

Question 12.
Name any two gases released on burning of fossil fuels. (CBSE 2013, 2014)
Answer:
CO₂, SO₂.

Question 13.
Name two gases, other than carbon-dioxide, that are given out during burning of fossil fuel and contribute towards acid rain formation. (CBSE Sample Paper)
Answer:

1. Sulphur dioxide
2. Nitrogen dioxide.

Based on Hydro power (hydel electicity)

Question 14.
Justify in one sentence that hydro power (hydel electricity) is a renewable source of energy.
(CBSE Sample Paper)
Answer:
Since hydro power is derived from the renewable source of energy i.e., sun, so it is also a renewable source of energy.

Question 15.
Construction of dams submerges large areas of forests, how does this contribute to the greenhouse effect ?
(CBSE 2012)
Answer:
Depletion of forests means deforestation which is responsible for green house gases such as CO₂ and methane. on Biogas

Question 16.
What is bio-mass ? (CBSE 2010, 2012)
Answer:
Plants and animals waste material which can be used as fuel is called biomass.

Question 17.
How is charcoal obtained from wood ? [CBSE (All India) 2009]
Answer:
Charcoal is obtained from wood by heating the wood in the absence of air. This process is known as destructive distillation of wood.

Question 18.
Which type of micro-organisms are able to carry out the process of decomposition in a biogas plant ? (CBSE 2011)
Answer:
Anaerobic micro-organisms.

Question 19.
Name the residue obtained when wood is burnt in a limited supply of air. (CBSE 2011)
Answer:
Charcoal.

Question 20.
What is a biogas ? [CBSE (All India) 2006 (c); CBSE (Delhi) 2009, 2010]
Answer:
Biogas is a mixture of four gases namely methane, carbon dioxide, hydrogen and hydrogen sulphide.

Question 21.
Name the main constituent of a biogas and its approximate percentage content in it.
(CBSE 2010, 2012, 2013)
Answer:
Methane gas. 75% of total volume.

Question 22.
Name two main combustible components of biogas. (CBSE (Foreign) 2004, 2012, 2015)
Answer:
Methane gas and hydrogen gas.

Question 23.
Classify the two fuels-CNG and hydrogen as renewable and non-vcnewable. (CBSE (All India) 2008)
Answer:
CNG – Non-renewable
Hydrogen – Renewable.

Question 24.
Mention one feature of biogas that makes it an ideal fuel.
Answer:
It causes no air pollution and has no residue.

Question 25.
List two nutrients that the slurry left behind in the biogas plant contains. (CBSE 2011)
Answer:
Nitrogen and phosphorus, on Wind energy

Question 26.
What is meant by renewable sources of energy ?
Answer:
The sources of energy which are continuously supplied by nature. For example, the sun, the wind.

Question 27.
Name two renewable or non-conventional sources of energy.
Answer:

1. The sun,
2. The wind.

Question 28.
What is the main basic cause for winds to blow ? (CBSE 2004, 2012)
Answer:
The pressure of a region where maximum sunlight falls decreases as compared to the region where minimum sunlight falls. The air moves from a region of high pressure (i.e., cold region) to the region of low pressure (i.e., hot region). This moving air is the wind.

Question 29.
What is the minimum wind velocity required to obtain useful energy with a wind mill ? (AI CBSE 2007)
Answer:
15 km/h.

Question 30.
What is a wind energy farm ? (CBSE 2010, 2013)
Answer:
The region where large number of wind mills are erected to produce electricity is called wind energy farm.

Question 31.
Name the kind of energy possessed by wind. [AI CBSE 1992 (C)]
Answer:
Kinetic energy.

Question 32.
Name a part of India where wind energy is commercially harnessed. (CBSE 2004)
Answer:
‘Kanyakumari in Tamil Nadu.

Question 33.
Wind mill is used to produce electricity. Write the sequence of energy conversion in a wind mill.
Answer:
Wind energy —> Mechanical energy —> Electricity (i.e. electric energy).

Based on Solar Energy

Question 34.
Name two activities in our daily life in which solar energy is used.
Answer:

1. For cooking food using solar cookers.
2. For dryring clothes and food grains.

Question 35.
Name the device which directly converts solar energy into electric energy. [CBSE (Delhi) 1998, 2010, 2011]
Answer:
Solar cell.

Question 36.
What is the range of temperature attained inside a box type solar cooker when placed in the sun for two to three hours ? [CBSE (Delhi) 2001 (C)]
Answer:
From 100°C to 140°C.

Question 37.
A solar cell transforms energy of one form into another form. What are these two forms of energy ?
[CBSE (Delhi) 1995]
                                                Or
State the energy conversion taking place in solar panels. (CBSE 2012)
Answer:
Solar energy(sunlight) to electrical energy.

Question 38.
State one limitation of solar energy available from solar cells. [CBSE (All India) 2007]
Answer:
These cells do not operate during night and on a cloudy day.

Question 39.
What is solar panel ? (CBSE 2010, 2011, 2012)
Answer:
A group of solar cells connected to each other in a certain pattern forms a solar panel.

Question 40.
Name chief component of solar cells. What energy conversion takes place in a solar cell ? (CBSE 2012, 2015)
Answer:
Silicon. Solar energy is converted into electric energy by a solar cell.

Based on energy from the sea or ocean

Question 41.
Name the factor which enables the ocean to act as a store house of energy. [CBSE (Delhi) 1999 (C)]
Answer:
The high value of specific heat capacity of water enables the ocean to act as a store house of heat energy.

Question 42.
What type of energy possessed by huge waves near the sea shore ? (CBSE 2010, 2015)
Answer:
Wave possesses kinetic energy.

Question 43.
What does “OTE” stand for ?
Answer:
OTE stands for “Ocean Thermal Energy.”

Question 44.
Name the device used for obtaining ocean thermal energy.
Answer:
Ocean thermal energy conversion power plant.

Question 45.
What type of energy possessed by huge waves near the sea shore ?
Answer:
Kinetic energy.

Question 46.
Write two different ways of harnessing energy from ocean.
Answer:

1. Ocean waves,
2. Tides,
3. OTEC.

Question 47.
Name two sources of energy which are pollution free.
Answer:
The sun, wind and water.

Question 48.
Mention the minimum temperature difference required between surface water and the water at depths of upto 2km in an ocean thermal energy plant. (CBSE 2014)
Answer:
20°C.

Question 49.
What are hot spots inside earth’s crust ? (CBSE 2014)
Answer:
The hot magma rises up and is collected in the crust of the earth due to some geological changes. The regions in the crust where the hot magma is collected are called hot spots inside earth’s crust, on Nuclear Energy

Question 50.
What is nuclear energy ? (CBSE 2010)
Answer:
The energy which is obtained from the conversion of nuclear mass is called nuclear energy.

Question 51.
What is a nuclear fission ?
Answer:
The process of splitting of a heavy nucleus into lighter nuclei is known as nuclear fission.

Question 52.
Which process is carried out at a higher temperature ? Nuclear fission or nuclear fusion ? (AI CBSE 1994)
Answer:
Nuclear fusion.

Question 53.
The mass number of three elements A, B and C are 2, 180 and 235- Which one of them is suitable to make a hydrogen bomb ? [AI CBSE 1995 (C)]
Answer:
Hydrogen bomb is based on nuclear fusion reaction which occurs due to the fusion of light elements. So element A is suitable to make a hydrogen bomb.

Question 54.
What is a fusion reaction ?
Answer:
The process by which two or more light nuclei fuse together (or combine) to form a heavy nucleus along with the release of energy is called fusion reaction.

Question 55.
Name the reaction responsible for large energy production in the sun. (CBSE 2013)
Answer:
Nuclear fusion.

Question 56.
What is green house effect ? (CBSE 2012)
Answer:
The warming of earths atmosphere due to the trapping of heat radiation i.e. infirared radiation is known as green-house effect.

Short Answer Questions ( 2 & 3 Marks)

Based on Non-renewable or conventional sources of energy

Question 1.
Mention any three qualities of an ideal source of energy. (CBSE 2014)
Answer:
A good source of energy should have the following characteristics. It should

1. supply enough amount of useful energy.
2. be easily stored.
3. be easily transported.

Question 2.
Would your choice regarding choice regarding a fuel for cooking food be different if you lived
(a) in a forest,
(b) in a remote mountain or small island,
(c) in New Delhi and
(d) five centuries ago ? If yes, name the type of fuel used in different cases.
Answer:
Yes.
(a) wood would be used for cooking food in a forest.
(b) Wind energy from a wind mill or energy of flowing water would be used for cooking food in a remote mountain or small island.
(c) LPG would be used for cooking food in New Delhi.
(d) Wood and cakes of cow dung were used for cooking food five centuries ago.

Question 3.
Why are fossil fuels known as a non-renewable sources of energy ?
                                                 Or
State the reason for calling fossil fuels as non-renewable source of energy. (CBSE 2013)
Answer:
Fossil fuels like coal, petroleum and natural gases take millions of years for their forma-don. If these fuels are exhausted today, then they will not be formed very soon. Hence, they are known as non-renewable sources of energy.

Question 4.
Why are many thermal power plants set up near coal or oil fields ? (CBSE 2011, 2013, 2015)
Answer:
In a thermal power plants, fuel like coal or oil is used in large quantity to produce electricity. These plants are usually set up near coal or oil fields so that the fuel is easily available and the problem of air pollution while transporting the fuel may be minimised.

Question 5.
What steps can be taken to minimize environmental pollution caused by the burning of fossil fuels ?
(CBSE 2010)
Answer:
We can minimize environmental pollution caused by the burning of fossil fuel by

1. growing more and more trees,
2. Using smokeless chulahs and
3. smokeless chimneys in thermal power plants.

Question 6.
What are fossil fuels ? “Burning of fossil fuels leads to acid rain”, fustify this statement. (CBSE 2011)
Answer:
For fossil fuels: The combustible substance formed from the dead remains of the animals and plants which were buried deep under the surface of the earth over millions of years is called fossil fuel.
Gases produced due to the burning of fossil fuels react with water vapours in air to produce acids like carbonic acid, sulphuric acid and nitric acid. These acids come down to earth with rain known as acid rain.

Question 7.
List three energy sources that are considered to be inexhaustible. State three reasons in support your answer.
(CBSE 2012)
Answer:

1. Coal,
2. Petroleum
3. Natural gas.

These are inexhaustible energy’ source because

1. their deposit under earth is limited,
2. their continuous use will ultimate consume them and
3. they are formed in very long period of time.

Question 8.
Explain how burning of fossil fuels cause acid rain. (CBSE 2010)
Answer:
Gases produced due to burning of fossil fuels give rise to acids after reacting with water vapours in air. For example.

CO₂+ Water ———> Carbonic acid
SO₂ + Water ——–> Sulphuric acid
NO₂+ Water ———> Nitric acid

These acids come down to the earth with rain. The rain containing these acids is called acid rain.

Question 9.
List two steps of energy transformation that take place in a thermal power plant. (CBSE 2015)
Answer:
Chemical energy of fossil fuie is converted into heat energy. This heat energy is converted into mechanical energy which is then converted into electrical energy.

Based on Hydropower (hydel electricity)

Question 10.
Write any four advantages of hydroelectric power. [CBSE (Delhi) 2006]
                                           Or
List two advantages of producing hydroelectricity. (CBSE 2013)
Answer:
Advantages of Hydroelectric Power

1. Hydroelectric power is pollution free.
2. Fiydroelectric power- is dependable source of energy.
3. Lot of water is available in rivers, so the hydroelectric power is available free of cost. Money is spent only to construct dams and power stations.

Question 11.
What is the importance of hydropower plants in India ? Describe how electric energy is generated in such plants. [CBSE (Delhi) 2008, 2012, 2013]
Answer:
In India, hydropower plants fulfills l/4th or 25% demand for the total energy requirement.
Hydro Power or Hydro Electric Power Plant:
Flowing water is the major source of energy. The electricity produced by the flowing water is known as hydro-electric power. A plant used to produce hydro-electric power is known as hydro-electric power plant (For the generation of electric energy in hydropower plant).

Question 12.
Write the problems faced in construction of big dams. (CBSE 2010, 2011, 2012)
Answer:

1. A large area of fertile land is submerged in water at the site of the dam.
2. A large number of people residing near the site of dam are dislocated. Hence, lot of problems are to be faced in rehabilitating this population.
3. A large number of plants and wild life in the area of the dam is submerged in water.

Question 13.
Write any three disadvantages associated with hydro power plant. (CBSE 2015)
Answer:
Disadvantages of Hydroelectric Power :

1. Hydroelectric power is generated only near the rivers having water throughout the year. This electric power has to be carried to the sub­stations for distribution to the houses and factories situated far off from the sites of hydro electric power stations. This is done through the transmission wires, so lot of money is to be spent on this process.
2. A large area of fertile land is submerged at the site of the dam constructed for tapping energy from the flowing water.
3. A large number of people residing near the site of a dam are dislocated. So, a lot of problems are to be faced in rehabilitating this population. That is why, there is a lot of opposition by the people around the site of dam for the construction of dam.
4. A large number of plants and wild life in the area of the dam are submerged in water. So, a large variety of flora (plants) and fauna (animals) is destroyed.
5. Hydroelectric dams cannot be constructed everywhere. They are constructed mostly in hilly areas.

Question 14.
What are the advantages of constructing dams over rivers. (CBSE 2015)
Answer:
Dams are helpful to :

1. control floods over rivers.
2. generate hydro electricity.
3. irrigate agriculture land.
4. develop water sports for recreation
5. develop fishing zones.

Based on Renewable sources of energy
(Improvements in the technology for using conventional sources of energy)

Question 15.
List reasons why we need to look for alternate sources of energy. (CBSE 2011, 2012, 2013)
                                                    Or
Why is there a need to harness non-conventional sources of energy ? Give two main reasons. (CBSE Sample paper 2017-18)
Answer:

1. To fulfill the requirement of increasing demand of energy.
2. To ease out the pressure on the conventional sources of energy.
3. To reduce the pollution caused by the use of conventional sources of energy.

Question 16.
“Why is there a need to harness non-conventional sources of energy ?”
Answer:

1. Non-conventional sources of energy are pollution free, whereas fossil fuels cause lot of pollution.
2. Non-conventional sources of energy are in exhanstitle, whereas fossil fuels are limited.
3. Our demand of energy is increasing day by day.

Question 17.

1. Name four gases commonly present in biogas.
                                            Or
   List four gases generated in a biogas plant. (CBSE 2011)
2. List two advantages of using biogas over fossil fuels. [CBSE (All India) 2006]

Answer:

1. Methane, CO₂, hydrogen, Hydrogen
2. Biogas is used for cooking food and heating water. It is a good source of energy because
   1. biogas does not produce smoke during burning and hence there in no air pollution.
   2. it is a cheaper source of energy.

Question 18.
Give advantages of a biogas as fuel. (CBSE 2010)
                                                 Or
Why is biogas considered an ideal fuel for domestic use ? [CBSE (Delhi) 2009, 2012]
Answer:
Biogas is considered as an ideal fuel for domestic use because

1. it causes no air pollution and
2. it is cheaper source of energy.

Question 19.
What is biogas ? How can biogas be obtained ? Why is the use of biogas obtained from cow-dung advised in preference to burning of cow-dung cakes ? [CBSE(All India) 2006(c), 2015]
                                                 Or
Why is biogas a better fuel than animal dung cakes ? [CBSE(All India) 2005, 2013]
Answer:
Biogas is a mixture of four gases namely methane, carbon dioxide, hydrogen and hydrogen sulphide.
Biogas is obtained from anaerobic decomposition of cow dung and plants and animal wastes in a biogas plants. This is because, biogas does not produce smoke during burning and hence there is no air pollution. On the other hand, burning of animal dung cakes causes air pollution. Moreover, biogas gives more heat energy than the burning of animal dung cakes.

Question 20.
What is geothermal energy ? What are its advantages ? [CBSE (Delhi) 2007]
Answer:
The heat energy stored in the hot spots of the earth’s crust is called geo-thermal energy.
For advantages:

1. Geo-thermal energy can be converted continuously into electricity for 24 hours in a day throughout the year.
2. Geo-thermal energy causes no pollution, so it is environment friendly.
3. The cost of converting geo-thermal energy into electricity is very less.

Question 21.
Justify the statement, “Hydrogen is a cleaner and better fuel than CNG”. [CBSE (All India) 2008, 2012]
Answer:

1. Hydrogen on buring produces more heat energy than producted by the burning of CNG.
2. Burning of hydrogen produces water vapours and burning of CNG produces CO₂. So, burning of hydrogen causes less air pollution than the burning of CNG.
   Hence, hydrogen is a cleaner and better fuel than CNG.

Question 22.
Write two advantages of classifying energy sources as renewable and non-renewable. [CBSE (Delhi) 2008]
Answer:
Advantages of classifying Sources of Energy:

1. It helps us to decide which of the non-renewable sources of energy (like coal, petroleum, natural gas and fissionable materials) need to be conserved for future generations.
2. It also helps the scientists to accelerate the pace of developing new technologies and devices suitable for harnessing energy from the renewable or non-conventional sources of energy.

Question 23.
(a) Distinguish between renewable and non-renewable sources of energy with one example for each. [CBSE 2010, 2011, 2014]
(b) Choose the renewable sources of energy from the following list : coal, biogas, sun, natural gas. [CBSE (Delhi) 2008]
Answer:
(a) Renewable Sources of Energy
The sources of energy which are inexhaustible (i.e. which can never be finished) and are being continuously supplied by nature are known as renewable sources of energy. These sources of energy are also known as non-conventional sources of energy.
For example :

1. Wind
2. Hydro Power
3. The sun
4. Ocean Tidals Energy
5. Interior of the Earth
6. Biogas
7. Plants, vegetable waste etc.

Non-Renewable Sources of Energy
The sources of energy which are exhaustible (i.e. which can be finished) and have been formed in nature long ago are known as non-renewable sources of energy. These sources of energy are also known as conventional sources of energy.
For example :

1. Coal
2. Petroleum
3. Natural Gas
4. Fissionable materials like Uranium.

Non-renewable sources of energy like coal, petroleum and natural gas have a huge deposit under the earth. However, the continuous extraction of these sources for the purpose of usable energy is a matter of concern and worry because ultimately the deposit of these sources will be completely finished. It may be noted that the formation of fossil fuel take very long period. Therefore, we should use these fuels judiciously so that their deposit may last long for future.
On the other hand, renewable sources of energy will last forever. For example, it is estimated that the sun would continue to shine for another 5 billion years. Therefore, the sun as the source of energy will be available for a very long period of time. Similarly, bio-mass as the source of energy will be available for a longer period of time if we grow more and more plants periodically {i.e. at regular intervals of time). The wind energy will be at our disposal as long as the sun exists. Geo-thermal energy is another source which will be available forever.
(b) Biogas and the sun are renewable sources of energy.

Question 24.
Why is the use of wood as a fuel not advised although forests can be replenished ? [CBSE (All India) 2006]
                                               Or
The use of dry wood as domestic fuel is not considered as good. State two reasons for it.
[CBSE(Delhi) 2004 (S), 2010]
Answer:
This is because

1. Deforestation (i.e., cutting of trees in large number) causes many problems like floods, erosion of fertile land and environmental imbalance.
2. Replenishment of forests takes long time and as such wood cannot be available to supply continuous energy.

Question 25.
Charcoal is a better fuel than wood. Explain why ? (CBSE 2010)
                                              Or
Why is charcoal considered a better fuel than wood. [CBSE (All India) 2009, 2015]
Answer:
It is because

1. charcoal burns easily as compared to wood,
2. charcoal does not produce smoke on burning and hence it causes no air pollution and
3. the amount of heat produced by the burning charcoal is much more than the heat produced by the burning wood.

Question 26.
How does biogas plant help to reduce the problem of pollution ? (CBSE 2010)
Answer:

1. Biogas obtained from biogas plant does not produce smoke during burning and hence there is no air pollution.
2. Biogas plant operates with the materials like cow dung and waste of plants. These materials lying in open can cause air and water pollution.

Question 27.
Suggest two materials that can be used to produce bio-gas. Mention two tises of bio-gas and two advantages of bio-gas plant. (CBSE 2010)
Answer:

1. Animal wastes like cow-dung
2. Fruits and vegetable wastes.

Uses : Bio-gas is used to cook food and heat water.
Advantages :

1. It causes no pollution.
2. The slurry in bio-gas plant is used as manure by the farmers.

Question 28.
Biogas is considered to be a boon to the farmers. Give reasons. (CBSE 2010)
                                                   Or
List any three reasons due to which bio-gas is considered to be an excellent fuel. (CBSE 2013)
Answer:

1. Bio-gas is pollution free.
2. It is cheap as raw material {i.e., cow dung and waste of plants and vegetables) to produce biogas is available free of cost to the farmers.
3. The remains or used slurry in a bio-gas plant is used as manure by the farmers in the fields to get good yields of crops.

Question 29.
Name an efficient fuel obtained from cow dung and other animal and plant wastes. Also mention its main constituent. (CBSE 2012)
Answer:
Biogas. Methane and hydrogen gases.

Based on wind energy

Question 30.
Mention any two uses of wind energy. [CBSE (Delhi) 1997 (C), 2012]
Answer:
Wind energy is used to

1. operate water pumps to draw underground water,
2. produce electricity.

Question 31..
What are the limitations in obtaining energy from wind ? (NCERT Questions Bank, 2012)
Answer:

1. We cannot depend upon wind energy as it is available only when air is in motion. The appliances or machines operating with wind energy stop working as soon as wind stops. The minimum speed of wind to operate generator to produce electricity is about 15 km/h. As soon as the speed of the wind becomes less than 15 km/h, the generator stops working.
2. There are certain regions where wind is not available, so the use of wind energy is limited to certain places where wind is in plenty and blows most of the time.
3. Wind energy is not sufficient to operate very heavy machines.
4. Wind energy cannot be used to operate all types of machines.
5. Wind mills are usually broken during storms and hence lot of money is spent for the maintenance of a wind energy form.

Question 32.
Give

1. two limitations and
2. two advantages of wind energy. (CBSE 2015)

Answer:
Limitations:

1. Wind energy is not sufficient to operate very heavy machines.
2. Wind energy cannot be used to operate all types of machines.

Advantages:

1. Wind energy produces no smoke and no harmful gases. So this form of energy is pollution free or environment-friendly.
2. Wind energy is free of cost and hence devices operated by wind energy are economical.
3. This source of energy is a renewable source of energy and is available for all times to come under favourable conditions.

Question 33.
State in brief the process of harnessing kinetic energy of the wind to do work. Mention any four limitations of harnessing wind energy on a large scale.
Answer:
Electricity is produced when an armature of a generator rotates between two poles (North and South poles) of a strong magnet. When wind falls on the wheel of a windmill, it rotates. The axle of the armature is connected to the shaft of the wind mill. So the armature of the generator rotates between two poles of a magnet along with the rotation of the wheel of the wind mill (Figure 6).

Thus, electric current is produced. This is how, the kinetic energy of the wind is converted into electrical energy.

1. We cannot depend upon wind energy as it is available only when air is in motion. The appliances or machines operating with wind energy stop working as soon as wind stops. The minimum speed of wind to operate generator to produce electricity is about 15 km/h. As soon as the speed of the wind becomes less than 15 km/h, the generator stops working.
2. There are certain regions where wind is not available, so the use of wind energy is limited to certain places where wind is in plenty and blows most of the time.
3. Wind energy is not sufficient to operate very heavy machines.
4. Wind energy cannot be used to operate all types of machines.
5. Wind mills are usually broken during storms and hence lot of money is spent for the maintenance of a wind energy form.

Question 34.
How has the traditional use of wind and water energy been modified for our convenience 1 (CBSE 2010)
Answer:
Traditional use of wind energy was to sail boats and grinding grains. The wind energy is now used to produce electricity using wind mills.
Similarly, water energy is utilised to produce electricity on a large scale at hydroelectric power plant.

Based on solar energy

Question 35.
(a) Name the device used to convert

1. Solar energy into heat and
2. Solar energy into electricity.

(b) Explain the working of a wind will. [CBSE (All India) 2006 (C)]
Answer:
(a)

1. Solar cooker
2. Solar cell.

(b) When wind blows with a minimum speed of 15 km/h, the kinetic energy of the wind is used to rotate the blades of wind mill. The rotational energy of the blades is used to rotate the armature of the generator to produce electricity.

Question 36.
On what principle does a solar water heater operate ? (CBSE 2004)
Answer:
A black surface absorbs more heat from the sunlight. This absorbed heat is used to heat the water in a solar water heater.

Question 37.
List any four areas where solar cells are being used as a source of energy. [CBSE (All India) 2008, 2012]
                                                         Or
Mention three advantages of a solar cell. (NCERT Question Bank, CBSE 2012)
Answer:
Advantages of Solar Cells:

1. They directly convert solar energy into electrical energy.
2. They are environment-friendly i.e. they do not cause pollution.
3. They are used to operate radio sets in remote areas.

Question 38.
(a) What is the role of a plane mirror and a glass sheet in a solar cooker 1 (NCERT Question Bank)
(b) Why is energy of water flowing in a river considered to be an indirect form of solar energy ?
(c) Why is nuclear fusion reaction considered better. [CBSE (Delhi) 2007]
Answer:
(a) Plane mirror reflects solar light to fall on the glass sheet of the solar cooker. Plane glass plate does not
allow the infrared or heat radiation entered in the box to go out side the box. Thus, the box becomes hot. The phenomenon is known as green house effect.
(b) Solar energy evaporates water in rivers, lakes and oceans. These water vapours are converted into clouds (K.E. + P.E.). The clouds give rise to rain and hence water flows in rivers. Thus, energy of flowing water in the form of kinetic energy is the indirect form of solar energy.
(c) Nuclear fusion reaction gives rise to energy which is pollution-free.

Question 39.
Out of two solar cookers, one was covered by a plane glass slab and the other was left open. Which of the two
solar cookers will be more efficient and why ? (CBSE Sample Paper, CBSE 2010, Term I)
                                                          Or
You are given two solar cookers, one with a glass cover and other with top open. Which one is more efficient ? Give reason for your answer. (CBSE 2011)
                                                          Or
Why should solar cookers are to be coverted with glass plate ? (CBSE 2010, 2012)
                                                          Or
State one use of glass cover in box type solar cookers. (CBSE 2015)
Answer:
A solar cooker covered by a plane glass slab will be more efficient.
This is because glass slab does not allow the heat radiation to escape from the solar cooker and hence the temperature of the solar cooker covered with glass slab increases more than the temperature of the solar cooker which is left open.

Question 40.

1. Why are solar heating devices painted black ?
2. Name two such devices and state two limitations of these.  (CBSE 2012, 2013, 2015)

Answer:

1. It is because black surfaces are good absorber of heat.
2. Solar cooker and solar furnace.

They cannot be used

1. during night and on cloudy days
2. to cook food quickly.

Question 41.
A student constructed a box type solar cooker and covered it with a glass plate. Write the purpose served by glass plate in the cooker. (CBSE 2012)
Answer:
Glass plate covering solar cooker prevents heat radiations to escape the solar cooker. In other words, glass plate traps the heat radiation inside the cooker.

Based on energy from the sea or ocean

Question 42.
Name three forms in which energy from ocean is made available for use. What are OTEC power plants ?
How do they operate ? (CBSE (Delhi) 2005, 2015)
Answer:

1. Tidal energy,
2. Ocean waves energy
3. Ocean thermal energy.

OTEC power plants are Ocean Thermal Energy Conversion Plants. For the operation of OTEC,
The heat energy due to the temperature difference between the different layers of water in the ocean is known as ocean thermal energy (OTE). The temperature of water at the surface of the ocean is much more than the temperature of water deep into the ocean. Due to this temperature difference, heat energy can be drawn from the sea or ocean water. This heat energy is used to produce electricity.

Question 43.
The water in deeper sections of ocean is much colder than that at the surface. Discuss how this difference in temperature be exploited to obtain energy.
Answer:
The warm surface water of ocean is used to boil liquid like ammonia or chlorofluoro carbon in OTEC power plant. The vapours of this liquid at high pressure rotates the turbine of a generator to produce electricity. The dead steam is again converted into liquid by the cold water pumped up from the deep ocean. This process is repreated continuously to convert ocean thermal energy into electrical energy.

Question 44.
Explain the principle and process of converting ocean thermal energy into electricity. (CBSE 2014, 2015)
Answer:
A device used to obtain ocean thermal energy is known as Ocean Thermal Energy Conversion (OTEC) power plant (figure 12).

For operating OTEC power plant, temperature difference of 20°C or more between the surface water of ocean and water deep into the ocean is required. The warm surface water of ocean is used to boil liquid like ammonia or chlorofluo’ro carbon (CFC). The vapours of this liquid at high pressure are used to rotate the turbine of the generator to produce electricity. The unused vapours (known as dead steam) are again converted into liquid by the cold water pumped up from the deep ocean. This process is repeated time and again to convert ocean thermal energy into electric energy (i.eelectricity). The main advantage of OTEC power plant is that it can be operated for 24 hours in a day throughout the year.

Question 45.
Are geothermal energy and nuclear energy different from bio-mass energy, wind energy and ocean thermal energy ? If yes, Why ?
Answer:
Geothermal energy and nuclear energy are different from the bio-mass energy, wind energy and ocean thermal energy. This is because, bio-mass energy, wind energy and ocean thermal energy are derived from a single source of energy, that is the sun. On the other hand, geothermal and nuclear energies are not derived from the sun. Based on Nuclear energy

Question 46.
What is nuclear energy ? Give two advantages and two hazards of nuclear energy. (CBSE 2012)
Answer:
Advantages :

1. A small quantity of nuclear fuel gives a large amount of energy.
2. Nuclear fuel is inserted once in a nuclear power plant to get continuous energy over a long period of time.

Hazards : Nuclear radiation causes :

1. diseases like cancer and leukemia.
2. genetic disorder in a human body.

Question 47.
State three limitations of harnessing nuclear energy. (CBSE 2014)
Answer:
Disadvantages of Nuclear Fission Energy over the Fossil Fuel Energy

1. Nuclear fission causes more serious pollution problem than the burning of fossil fuel. The radiation emitted during nuclear fission are very harmful. They cause dangerous diseases like cancer, leukemia and sterility.
2. The biggest problem of using nuclear fission energy is the safe disposal of nuclear waste. Nuclear waste continues to emit harmful nuclear radiation. No method has been evolved for the complete elimination of the nuclear waste. But no such problem is faced in the disposal of the fossil fuel waste. For example, burning of coal give rise to ash which can be thrown in the fields. That is why, it is advised not to use nuclear fission for the production of energy on very large scale.

Long Answer Questions (5 Marks)

Question 1.
Describe the construction of a box type solar cooker or show it with the help of a diagram. How is the rise in temperature obtained in this set up ? Mention two advantages and two limitations of solar cookers.
[CBSE (Delhi) 2004 (S), 2012]
Answer:
Solar Cooker (Box Type)
Construction:
It consists of a wooden box (rectangular in shape) in which a metallic box painted black is fitted. The space between wooden box and metallic box is filled with an insulating material like thermocol. The insulating material minimizes the heat lose by conduction and radiation.
The metallic box is covered by a thick glass sheet. A plane mirror reflector is used to reflect the sun rays and attached to the box (Figure 7).

The un-cooked food placed in the black container is put inside the box.
Working:
The plane mirror reflector is adjusted in such a way that maximum sun light falls on it. The light reflected by the plane mirror falls on the thick glass sheet cover.
The heat radiation (i.e. infra-red rays coming from the sun have short wavelength and high energy) pass through the glass sheet and are absorbed by the black container or any other object placed in the box and black surface of the box. The heat radiation entered in the box are not able to come out of the box through the glass sheet. Thus, the heat radiation are trapped in the box and the inner part of the box becomes hot. The effect is known as green house effect. (For the detail of green house effect, Refer Additional Topic at the end of this chapter). The temperature inside the box increases from 100° C to 140° C. Thus, the food in the container is cooked.
Advantages of Box type Solar cooker

1. Economical : The cost of cooking food in the solar cooker is very small as money is only spent to purchase the solar cooker.
2. Pollution : No pollution is caused as there is no burning of fuel.

Disadvantages of Solar cooker

1. Food cannot be cooked at night.
2. Food cannot be cooked on a cloudy day.
3. Food cannot be cooked quickly as solar cooker takes 4 to 5 hours to cook it.

Question 2.
What are
(i) Solar concentrators and
(ii) Solar cell panels ? How are they improvement on simple devices ? Why is it that solar panels are costly ? [CBSE (Foreign) 2004)]
Answer:
(i) Solar concentrators:
Solar concentrators are the devices used to concentrate the solar energy over a small area. When a parallel beam of sunlight falls on a polished concave surface (like concave mirror), then the beam of sunlight concentrates at the focus (F) of the concave surface after reflection (Figure 8).

As a result of this concentrated beam of sunlight, the temperature at point F increases considerably. If we place a piece of paper at F, then it begins to burn after some time. A concave spherical surface which concentrates the beam of sunlight at a point is called solar concentrator.
(ii) Solar cell panels:
A group of solar cells connected to each other in a certain pattern forms a solar panel (Figure 10).

A solar panel converts sunlight into electrical energy. The efficiency of solar panel is very large as compared to the efficiency of a solar cell.

During day time, sunlight falling on the solar panel is converted into electrical energy which is stored in a battery connected to it. As soon as sunlight stops falling on it (during night and cloudy day), the battery begins to supply electric current to the appliances like electric bulbs and electric tubes connected to it.
Solar panels have limited uses. They can not be used to meet our domestic needs of electricity.
This is because of the following reasons :

1. The solar cells used in a solar panel are made of pure silicon. The production of pure silicon is very costly’ affair. These solar cells in a solar panel are joined to each other with a best conductor silver to reduce the resistance of the solar panel to get maximum electricity.
   But silver metal is also costly. Thus, we find that the cost of fabricating a solar panel is very high.
2. The storage battery connected to a solar panel can supply direct current (D.C.). So only those electric appliances can operate with the solar panel which require direct current. However, the electric appliances which require alternating current (A.C.) cannot be operated with the solar panel.
3. Solar panel can supply the electricity continuously only if the sun shines during day time.

Question 3.
Name any three forms of energy of the oceans which can be converted into usable energy forms. Describe how it is done in each case. What is the likelihood of their use on a large scale ? [CBSE (Foreign) 2004)]
Answer:
The energy from sea or ocean water is available in the following forms :

1. Energy of sea waves
2. Tidal energy
3. Ocean thermal energy

Energy of sea waves:
High winds blow across the sea. These winds produce high waves on the surface of water in the sea or ocean. Thus, the water in the sea moves as water waves’. The kinetic energy of this moving water rotates the turbine of a generator. Hence, electricity is produced.
Limitation of Energy of Sea waves: Energy of sea waves can be used only if strong winds blow all the times across the sea and there are high water waves in the sea. However, as soon as strong winds stop to blow, the electric generator stops producing electricity. Hence, we cannot depend much on the energy of sea waves.

Tidal energy:
The alternate rise and fall of water of the ocean twice in nearly 24 hours is known as tide. The tides are caused due to the gravitational force of attraction exerted by the moon and to some extent by the sun on the water of the ocean. At the time of new and full moon, when the sun and the moon are in a straight line, tides are very high. When the sun and the moon are at right angle from the earth, tides are low. The kinetic energy of water waves during tides is used to produce electricity.
Tidal power plants are constructed near narrow Bays (Figure 11).

During tides, the gates of the dam are opened. The rising water is allowed to fall on the turbine of the generator which produces electricity.
Thus, kinetic energy of the water is converted into electrical energy. During low tides, gates of the dam are closed and hence the water level behind the dam rises. 1 his raised water has potential energy. Again the gates are opened and the water is allowed to fall back into the bay. This falling water is used to rotate the turbine of the generator. Hence the electricity is produced continuously.
Ocean thermal energy:
A device used to obtain ocean thermal energy is known as Ocean Thermal Energy Conversion (OTEC) power plant (figure 12).

For operating OTEC power plant, temperature difference of 20°C or more between the surface water of ocean and water deep into the ocean is required. The warm surface water of ocean is used to boil liquid like ammonia or chlorofluo’ro carbon (CFC). The vapours of this liquid at high pressure are used to rotate the turbine of the generator to produce electricity. The unused vapours (known as dead steam) are again converted into liquid by the cold water pumped up from the deep ocean. This process is repeated time and again to convert ocean thermal energy into electric energy (i.eelectricity). The main advantage of OTEC power plant is that it can be operated for 24 hours in a day throughout the year.

Question 4.
Name the major components of biogas. What are its combustible components. Draw a simple labelled diagram of a fixed dome type biogas plant. What is the use of the residual slurry and why ?
[CBSE (Delhi) 2004)]
Answer:

Question 5.
How can solar energy be harnessed ? Mention any two limitations in using ? Solar energy. How are these limitations overcome ? (NCERT Question Bank)
Answer:
The energy emitted by the sun in the form of heat and light (i.e. radiation) is known as solar energy.
The Sun contains mainly light elements like hydrogen and helium. When the nuclei of these elements fuse together at extremely high temperature in the interior of the Sun, a large amount of energy’ is radiated in the form of heat and light continuously by the Sun. This process is known as Nuclear fusion.
All the planets of the solar system receive the energy emitted by the Sun. The energy is emitted by the Sun in the form of radiation. These radiations are visible rays, infra-red rays (i.e., heat radiation), ultraviolet rays, gamma rays, X-ray and radio waves. It may be noted that only some fraction of the total energy emitted by the Sun reach the surface of the earth.
Measurements have shown that the outer edge of the earth’s atmosphere receives solar energy equal to 1.4 kilojoule per second per square metre (1.4 kj/s m²). This amount is known as Solar constant.
Traditional Uses of Solar Energy : It is used

1. for cooking food using solar cookers.
2. for heating water using solar water heaters.
3. for producing steam by heating water to produce electricity.
4. by green plants to make their food.
5. to produce electricity using solar cells.
6. to melt metals using solar furnaces.
7. for drying clothes and food grains.

Question 6.
Name the process used to harness nuclear energy. Explain it.
                                                Or
Which is the process used to harness nuclear energy these days. Explain it briefly.
(NCERT Question Bank)
Answer:
Definition : The energy obtained from the conversion of nuclear mass is known as nuclear energy.
Units of Nuclear Energy:
Nuclear energy is expressed in electron-volt (eV). One electron-volt is the energy acquired by an electron while passing through a potential difference of one volt.
1 eV = 1.6 x 1(T^-19 C x 1 V = 1.6 x 10^-19 CV or
1 eV = 1.6 x 10^-19 J (∴ 1 CV = 1J)
Bigger unit of nuclear energy is mega electron-volt (MeV).
1 MeV = 10⁶ eV = 10⁶ x 1.6 x 10^-19 J = 1.6 x 10^-13 J
Nuclear energy is obtained by the splitting of a heavy nucleus into light nuclei and by combining light nuclei to form a large nucleus. The process of splitting of a heavy nucleus into light nuclei is known as nuclear fission. The process of combining light nuclei to form a large nucleus is known as nuclear fusion.
Hazards of using nuclear energy:
The nuclear radiation can change or damage the structure of cells in the human body.

1. They cause diseases like cancer, leukemia and blindness.
2. They cause genetic disorder in a human body.
3. They cause sterility in young generation.

Question 7.
Draw a labelled schematic diagram of a biogas plant. What use is made 6f the slurry left behind in biogas plant. (CBSE 2009)
                                                                            Or
Explain the principle and working of a biogas plant using a labelled diagram. (CBSE 2010, 2013)
Answer:
The arrangement of producing biogas from animals dung, human excreta, industrial and domestic wastes is known as biogas plant.
Fixed-dome type biogas plant:
Construction: Fixed—dome type biogas plant in shown in figure 3.

It consists of a well like underground tank made of bricks and cement. This tank is called digester and has inlet and outlet valves. The roof of the tank is dome shaped. A gas outlet pipe at the top of the dome is fitted. The dome of the digester acts as a storage tank of biogas. There is a mixing tank made above the ground level which is connected to the inlet value of the digester through a slopping inlet chamber below the ground level. On the other side of the digester, a rectangular tank called outlet chamber is constructed with bricks and cement. This outlet chamber is connected to the overflow tank which collects the used slurry.
Working: Animals-dung is mixed with water to make slurry in the mixing tank. This slurry enters the digester through the inlet chamber. The digester is filled partially with slurry so that enough space is left above it in the dome for the collection of biogas. The slurry in the digester is left for about two months for fermentation. Anaerobic micro organisms are responsible for this action. As a result of fermentation, biogas is formed which is collected in the dome. When sufficient amount of biogas is collected in the dome, it exerts a large pressure on the slurry and forced it to go into the overflow tank through the outlet chamber. The biogas is taken out from the dome through a pipe and used for cooking food or heating water whenever required.
Once the biogas plant starts functioning, more and more slurry may be fed into the digester to get the continuous supply of biogas. The used slurry collected in the overflow tank is rich in nitrogen and phosphorus which are essential for the growth of crops and plants. Hence this used slurry can be used as manure.

Question 8.
Sun is the ultimate source of energy. Explain.
                                           Or
Energy from various sources is considered to have been desired from the sun. Do you agree ? Justify your answer. (NCERT Question Bank)
Answer:

1. Renewable sources of energy or inexhaustible sources of energy.
2. Non-renewable sources of energy or exhaustible sources of energy.

1. Renewable Sources of Energy
The sources of energy which are inexhaustible (i.e. which can never be finished) and are being continuously supplied by nature are known as renewable sources of energy. These sources of energy are also known as non-conventional sources of energy.
For example :

1. Wind
2. Hydro Power
3. The sun
4. Ocean Tidals Energy
5. Interior of the Earth
6. Biogas
7. Plants, vegetable waste etc.

2. Non-Renewable Sources of Energy
The sources of energy which are exhaustible (i.e. which can be finished) and have been formed in nature long ago are known as non-renewable sources of energy. These sources of energy are also known as conventional sources of energy.
For example :

1. Coal
2. Petroleum
3. Natural Gas
4. Fissionable materials like Uranium.

Non-renewable sources of energy like coal, petroleum and natural gas have a huge deposit under the earth. However, the continuous extraction of these sources for the purpose of usable energy is a matter of concern and worry because ultimately the deposit of these sources will be completely finished. It may be noted that the formation of fossil fuel take very long period. Therefore, we should use these fuels judiciously so that their deposit may last long for future.
On the other hand, renewable sources of energy will last forever. For example, it is estimated that the sun would continue to shine for another 5 billion years. Therefore, the sun as the source of energy will be available for a very long period of time. Similarly, bio-mass as the source of energy will be available for a longer period of time if we grow more and more plants periodically {i.e. at regular intervals of time). The wind energy will be at our disposal as long as the sun exists. Geo-thermal energy is another source which will be available forever.

Hope given Previous Year Question Papers for CBSE Class 10 Science Chapter 14 Sources of Energy are helpful to complete your science homework.

If you have any doubts, please comment below. Learn Insta try to provide online science tutoring for you.

Chapter 16 Management of Natural Resources Class 10 Science Important Questions with Answers PDF will help you in scoring more marks. This consists of 1 mark Questions, 3 Mark Numericals Questions, 5 Marks Numerical Questions and previous year questions from Chemical Reactions and Equations Chapter.

Management of Natural Resources Class 10 Important Questions and Answers Science Chapter 16

Very Short Answer Questions (1 Mark Each)

Question 1.
How is the increase in demand for energy affecting air environment already ? (CBSE Delhi 2008)
Answer:
Increased consumption of fossil fuels (coal, petroleum, natural gas) is releasing a lot of polluting gases (CO₂, CO, SO₂, NO_x) some of which are causing green house effect and producing acid rain.

More Resources

• Previous Year Question Papers for CBSE Class 10 Science
• NCERT Solutions for Class 10 Science
• NCERT Exemplar Solutions for Class 10 Science
• Value Based Questions in Science for Class 10
• HOTS Questions for Class 10 Science

Question 2.
Which one of the following is a renewable resource : Natural gas, petroleum, Ground water, coal ?
Answer:
Ground water.

Question 3.
Fire wood is our conventional fuel. List any four reasons for replacing it by alternate sources of energy.
(CBSE AI. 2008)
Answer:

1. It results in deforestation,
2. Energy value is small.
3. It is bulky,
4. It causes more pollution.

Question 4.
Which one of the following gases is the major constituent of biogas : CO₂, H₂, CH₄, CO₂ ?
Answer:
CH₄ (methane).

Question 5.
State an instance where human intervention saved the forest from destruction. (CBSE Delhi 2009 C)
Answer:

1. Silent Valley (Kerala). A dam was proposed to be built up here but opposition from environmentalists and others forced to government to convert it into biosphere reserve.
2. Garwal Himalayas (Uttarakhand). ‘Chipko andolan prevented the destruction of forests and saved the environment from deterioration.
3. Kelase Forests (Karnataka). The felling of trees in the forests was opposed by ‘apiko chaluvati’ led by Pandurang Hegde

Question 6.
What is meant by renewable natural resources ? (CBSE A.I. 2009 C)
Answer:
Renewable natural resources are those resources of nature which are replenished regularly and are therefore, likely to remain available indefinitely if they are not used beyond their renewability, e.g., forests.

Question 7.
Why are coal and petroleum considered to be non-renewable sources of energy ? (CBSE A.I. 2009 C)
Answer:
Coal and petroleum are considered non-renewable sources of energy as they are not being formed continuously in nature and are, therefore, not replenished. Continuous use will result in their depletion one day.

Question 8.
A person lives near a forest. Make a list of four items which he can get from the forest to meet his daily needs. (CBSE Delhi 2010)
Answer:

1. Firewood.
2. Bamboo and thatch.
3. Food articles (edible fruits and nuts).
4. Grazing animals and fodder.

Question 9.
State any one reason for conservation of forests and wildlife. (CCE 2011)
Answer:
Forests protect soil, retain and regulate flow of rain water while wildlife maintains an ecological balance of the area.

Question 10.
Give two examples to emphasise the concept of REUSE. (CCE 2011)
Answer:
Reuse saves a lot of resources, e.g., reuse of carry bags, re-use of plastic bottles and jars.

Question 11.
Name any two stake-holders who derive benefit from forests. (CCE 2011)
Answer:

1. Forest dwellers and tribals
2. Industrialists.

Question 12.
Give one example each from your daily life where the household waste can be effectively reused and recycled •» respectively. (CCE 2013, 2014)
Answer:
Reuse: Containers of jams, pickles and other food items.
Recycle: Metal wastes, broken plastic, broken glasswares.

Question 13.
List any two measures that you suggest for better management of water resources. (CCE 2013)
Answer:
Water Resources: My major stress will be

1. Recharging of ground water through rain water harvesting, protection to wetlands and digging sponge pits or wells in the beds of rivulets,
2. Reducing spoilage of water in agriculture by helping formers to switch over to sprinkler system of irrigation, changing conventional method of rice cultivation with system of rice intensification (SRI),
3. Judicious use of water for domestic and industrial purposes.

Question 14.
Mention one negative effect of our affluent life style on the environment. (CCE 2013, 2014)
Answer:
Affluent life style wastes a lot of natural resources due to approach of convenience, attraction to well packed articles, use and throw habit.

Question 15.
Water is a valuable resource. List two ways that you’would suggest every family member to save this resource.
(CCE 2014)
Answer:

1. Closing the taps when water is not required,
2. Repair of leaky taps.
3. Preventing overflow of water during washing, bathing, cleaning teeth, etc.

Question 16.
“We need to manage our resources”. List two reasons to justify this statement. (CCE 2014)
Answer:
Management of resources is controlling the use of resources so as to
(i) Provide for their sustained availability and
(it) Equitable distribution.

Question 17.
What is meant by recycling of wastes ?
Answer:
It is the processing of waste articles to form new products.

Question 18.
List two articles that can be easily recycled but we generally throw them in the dustbin. (CCE 2015)
Answer:
Used paper, polythene, metal wastes.

Question 19.
Mention any two reasons for failure to sustain underground water. (CCE 2015)
Answer:

1. Withdrawal throughout the year while it is augmented only during rains.
2. Lack of rain water harvesting.

Question 20.
Where are coliform bacteria found in human beings ? ( CCE 2015)
Answer:
Intestinal tract.

Question 21.
Name one bio-diversity hot-spot. (CCE 2015)
Answer:
Forest.

Question 22.
Write the context in which Amrita Devi Bishnoi National award is given. (CCE 2015)
Answer:
Exceptional contribution to wildlife conservation.

Question 23.
Write one negative effect on the environment of the affluent life style of a few persons of the society. (CBSE A.I. 2015)
Answer:
Affluent life style has an approach of convenience , use and throw habit. It not only wastes a lot of natural resources but also produces a lot of wastes. 36% of solid waste consists of packing materials. Americans annually throw away about 50 billion food and drink cans and 27 billion glass botdes and jars.

Short Answer Questions (2 Marks)

Question 1.
Write two advantages of classifying energy sources as renewable and non-renewable. (CBSE Delhi 2008)
Answer:

1. A judicious use of non-renewable energy resource so as to prevent its depletion.
2. Increasing use of renewable energy source but not beyond its renewability. Stress should be laid on exploitation of inexhaustible sources of energy like solar energy.

Question 2.
What are fossil fuels ? Give two examples of fossil fuels. (CBSE Foreign 2008)
Answer:
Fossil fuels are energy yielding combustible substances that have been formed million of years ago by compression and anaerobic heating of organic matter.
Examples. Coal, Petroleum.

Question 3.
Why should we conserve forests ? Suggest any two ways to conserve forests.(CBSE A.I. 2008, CCE 2012)
Answer:
We should conserve forests because they not only provide a number of economically important products but also provide shelter to wild animals, protect soil, regulate water flow and climate.
Forests are conserved through

1. Regular sustained yield block cutting and
2. Separation of commercial forestry (production plantation) from natural forestry.

Question 4.
List four changes you would incorporate in your life style in a move towards sustainable use of available resources. (CBSE A.I. 2008 C, 2017 CCE 2011)
                                                                                                  Or
Every one of us can do something to reduce our consumption of various natural resources. List four such activities based on 3-R approach. (CCE 2013)
Answer:

1. Electricity: Reduce consumption of electricity by switching off unwanted fans and bulbs, changing incandescent bulbs to compact fluorescent lamps.
2. Water: Prevent overflow of water by closing the taps when water is not required. Leaky taps are got repaired immediately.
3. Refills: Use of refills instead of purchasing new packs, e.g., pens.
4. Cloth Bags: Using cloth bags instead of polythene, plastic or paper bags.

Question 5.
State two reasons each of conserving
(a) Forest
(b) Wildlife. (CBSE A.I. 2008 C, 2017)
Answer:
Conservation of Forests:

1. Forest provide a number of economically important products
2. They protect the soil, retain and regulate flow of rain water.

Conservation of Wildlife:

1. Wildlife is important in maintaining ecological balance of the area,
2. It is gene bank for improvement of domesticated plants and animals.

Question 6.
What are natural resources ? State two factors that work against an equitable distribution of these resources.
(CBSE Delhi 2009, A.I. 2017, CCE 2011)
Answer:
Definition: Natural resources are living and non-living components of nature which can be used by humans to meet their requirements.
Factors Against Equitable Distribution,

1. Unequal availability of resources, abundant at one place and deficient at another place,
2. Excessive use of resources by rich people and struggle for the resource in the area of deficiency by common man.

Question 7.
What is water harvesting ? Mention any two water harvesting structures. (CBSE Delhi 2009, CCE 2012)
Answer:
Definition. Water harvesting is capturing, collection and storage of rain water and surface run off for filling water bodies and recharging ground water.
Harvesting Structures,

1. Khadin
2. Kattas.

Question 8.
Why must we conserve our forests ? List any two causes for deforestation taking place.
(CBSE Delhi 2009, CCE 2012)
Answer:
(a) Why Conserve Forests: We should conserve forests because they not only provide a number of economically important products but also provide shelter to wild animals, protect soil, regulate water flow and climate.
(b) Causes of Deforestation:

1. Clearing forests for agriculture, roads, canals, human habitation.
2. Overgrazing and excessive felling of trees.

Question 9.
List any four measures for conserving forests. (CBSE A.I. 2009)
Answer:

1. Afforestation and reforestation or silviculture
2. Involving the local people in care of forests.
3. Separation of commercial forestry on waste land
4. Development of social forestry, agroforestry and urban forestry.

Question 10.
What is Chipko movement ? Why should we conserve forests ? (CBSE A.I. 2009)
Answer:
Chipko Movement: It is a non-political public movement for conservation of natural habitats, forests and wildlife by preventing their excessive exploitation.
Why Conserve Forests: We should conserve forests because they not only provide a number of economically important products but also provide shelter to wild animals, protect soil, regulate water flow and climate.

Question 11.
State any four personal choices you would like to make to reduce energy consumption without affecting the quality of life or work explaining how each one of them would help you to do so.
(CBSE Foreign 2010)
Answer:

1. Gadgets: Switching off lights, fans, T.V., radio and domestic gudgets not in use.
2. Winter: Wearing an extra sweater in winter instead of using heating devices (heater or sigri) for keeping warm.
3. CFL: Use of compact fluorescent lamps instead of incandescent bulbs as they consume only one-fifth of the power. A further improvement in use of LED (Light emitting diode).
4. School Bus or Car Pool: Use of school bus or car pool instead of personal vehicle for going to school.

Question 12.
(a) How does formation of coal and petroleum occur ?
(b) Name any two products formed when fossil fuels are burnt. (CCE 2011)
Answer:
(a) Coal and petroleum have been formed million of years ago due to burying of vegetation and other organic matter inside the earth under high pressure, heat and anaerobic conditions.
(b) Oxides of nitrogen and sulphur, CO₂.

Question 13.
How can we as individuals help in reducing the use of fossil fuels ? Mention two ways. (CCE 2011)
Answer:

1. Walking down or cycling for nearby distances.
2. Using car pool or school bus to go to school.

Question 14.
Explain with the help of two examples how the participation of local people has led to conservation of forest in the past. (CCE 2011)
Answer:

1. Chipko movement started by women under the leadership of Gaura Devi in Reni in March 1973 to prevent cutting of forest trees.
2. Regeneration of Arabari forest in Midnapore by participation of villagers under the leadership of forest officer A.K. Banerjee.

Question 15.
(a) How can development of efficient engines ensuring complete combustion of fossil fuel be useful to us ?
(b) Name the four elements that constitute fossil fuels. (CCE 2011, 2012)
Answer:
(a) Complete combustion of fossil fuel will give more run for the same amount of fuel and will reduce the degree of air pollution due to non-release of unburnt hydrocarbons.
(b) N, H, S and C

Question 16.
(a) State two disadvantages of converting forests into monocultures.
(b) Give any two advantages of water stored underground. (CCE 2011)
Answer:
(a)

1. Loss of biodiversity.
2. Non-availability of varied needs of local people for fodder, fruits, nuts and medicines.

(b)

1. Non-evaporation and noncontamination,
2. Providing soil water for vegetation and recharging wells.

Question 17.
“Burning of fossil fuels results in global warming”. Justify this statement. (CCE 2011, CBSE A.I. 2016, Foreign 2017)
Answer:
Burning of fossil fuels releases a lot of carbon dioxide. Addition of CO₂ to the atmosphere has a stronger green-house effect that is resulting in global warming. Already a rise of 0-6°C has been observed in atmospheric temperature during the 20th century.

Question 18.
How has the use of fossil fuels led to the deterioration of environment ? State any two reasons. (CCE 2011)
Answer:

1. Increased concentration of atmospheric carbon dioxide leading to global warming.
2. Release of air pollutants some of which are causing acid rain (NOx, S02).

Question 19.
With the help of an example explain how involvement of local people can lead to efficient management of forests. (CCE 2011, CBSE A.I. 2016)
Answer:
Degraded sal forest of Arabari in Midnapore could not be revived by even best efforts of the forest department. In 1972, with the permission of forest department, forest officer A.K. Banerjee invited the local people to participate and share the benefits of the forest. By 1983, there was a complete revival of Arabari forest.

Question 20.
What are fossil fuels ? How are they formed ? (CCE 2011)
Answer:
Fossil fuels are energy yielding carbon containing combustible substances that are dug out from earth. They have been formed millions of years ago due to burying of vegetation and other organic matter inside the earth under high pressure, heat and anaerobic conditions, e.g. coal, petroleum, natural gas.

Question 21.
List any four methods of conserving fossil fuels. (CCE 2011)
Answer:

1. Development of more efficient devices for combustion of fossil fuels.
2. Use of hybrid fuel and hydrogen fuel
3. Employment of alternate sources of energy like atomic energy and hydroelectric energy
4. Installation of solar panels for trapping solar energy for heating and its conversion to electricity.

Question 22.
(a) What is meant by sustainable development ?
(b) Suggest any one method to achieve it ? (CCE 2011)
Answer:
(a) Sustainable development is a strategy of development which can be sustained for a long time without undue damage to the environment.
(b) Use of smaller and more efficient devices with judicious use of natural resources.

Question 23.
(a) What is water harvesting ?
(b) Mention any two water harvesting structures. (CCE 2011, 2015)
Answer:
(a) Water harvesting is capturing, collection and storage of rain water and surface run off for filling either small water bodies or recharging ground water.
(b)

1. Crescent shaped earthen embankments or concrete and rubble check dams for collecting rain water
2. Khadins.

Question 24.
Suggest two important measures to reduce consumption of various natural resources. (CCE 2011)
Answer:

1. Controlled Exploitation: Exploitation of natural resources is limited so as to meet the just demands of the society.
2. Minimum Wastage: Technology is employed to ensure minimum wastage during processing of the resource.

Question 25.
(a) Why is LPG considered a better fuel than coal ?
(b) What is Chipko movement ? (CCE 2011)
Answer:
(a) LPG or liquefied petroleum gas is better fuel than coal as it does not produce flyash, toxic minerals and many of the air pollutants.
(b) Chipko Movement : It is a non-political public movement for conservation of natural habitats, forests and wildlife by preventing their excessive exploitation.

Question 26.
(a) What is water shed management ?
(b) How is it helpful to ecosystem ? (CCE 2011, 2012)
Answer:
(a) Watershed management is the prevention of soil erosion by planting of more trees and other vegetation in high raised areas which are the source of run off to low lying areas.
(b)

1. Flooding and soil erosion are prevented as trees in water-shed area retain more water underground.
2. More animals and other biota reach the area to form a well balanced ecosystem.

Question 27.
What harm has been caused to alpine meadows since nomadic shepherds have been stopped from grazing their cattle in such meadows ? (CCE 2011, 2012)
Answer:
The establishment of Great Himalayan National Park has prevented the nomadic shepherds to take their flocks to alpine meadows for grazing. The grass of alpine meadows now grows very tall, then falls over, stopping fresh growth.

Question 28.
We should use coal and petroleum judiciously. Why ? State any four reasons. (CCE 2011)
Answer:

1. Coal and petroleum are non-renewable exhaustible resources. They are limited in supply.
2. India spends a lot of money in importing petroleum.
3. Combustion of coal and petroleum is adding a lot of CO₂ to the atmosphere. Carbon dioxide is a green house gas which is causing global warming.
4. Burning of coal and petroleum produces a number of pollutants, some of which are causing acid rain.

Question 29.
(a) Why should coal and petroleum be used judiciously ?
(b) What ill effects can be caused if they are used non-judiciously ? (CCE 2011)
Answer:
(a) Coal and petroleum are non-renewable exhaustible resources. They are limited in supply.
(b) A non-judicious use of coal and petroleum will

1. Burn out all the reserves.
2. Give out large quantities of pollutants causing acid rain that destroys vegetation, crops, lakes and monuments alongwith many ailments.
3. Release large quantity of CO₂ that will cause global warming, melting of ice, raising sea level and submerging large parts of land.

Question 30.
Mention any two reasons for which environmentalists protested against raising height of “Sardar Sarovar Dam” on river Narmada. (CCE 2011)
Answer:

1. Submergence of additional land and destroying biota.
2. Displacement of more people from their homes and employment. .

Question 31.
List four ways in which management of fossil fuels differ from natural resources of energy. (CCE 2011)
Answer:

1. Fossil fuels were formed million of years ago due to burying of vegetation and other organic matter inside earth.
2. They are limited in supply and will not last indefinitely.
3. Their consumption has to be reduced if a vacuum in energy sector is not to be created.
4. New and renewable energy sources have to be added urgently.

Question 32.
“Industrialisation is one of the two main causes of deterioration of environment”. List any four reasons in favour of this statement. (CCE 2011, CBSE Foreign 2016)
Answer:

1. It adds to air pollution.
2. Industrial effluents cause water pollution.
3. Solid wastes generated by industries pollute soil and ground water.
4. It is also a major source of noise pollution.

Question 33.
How is the increase in demand of fossil fuels affecting the environment adversely ? Suggest two ways to minimise the problem. (CCE 2011)
Answer:
(a) Increased demand of fossil fuel due to rising requirement of energy is adversely affecting our environment by releasing large amounts of pollutants and green house gases (eg., CO₂)
(b) Minimising Problem,

1. Increasing efficiency of combustion engines and utilising fossil fuels judiciously.
2. More use of alternate sources of energy.

Question 34.
The construction of large dams lead to

1. Social and
2. Environmental problems. List two problems in each case. (CCE 2011)

Answer:
1. Social Problems :

1. Displace a large number of locals and tribals without adequate compensation.
2. The displaced persons are unable to adjust to social life of new areas. A gainful employment is also lacking.

2. Environmental Problems :

1. Large scale deforestation.
2. Large scale loss of biodiversity.

Question 35.
(a) Under what conditions is carbon monoxide released when fossil fuels are burnt ?
(b) Forests are “biodiversity hotspots”. Justify this statement. (CCE 2011)
Answer:
(a) In the presence of insufficient oxygen, carbon monoxide is produced instead of carbon dioxide.
(b) A biodiversity hotspot is an area having a large number of endemic species which are being threatened with extinction. Because of long exploitation of forest resources and pressure from industrialists, the natural biota is being replaced by commercially required trees.

Question 36.
List two reasons for conserving wildlife. (CCE 2011)
Answer:

1. Wildlife is essential for maintaining the forests.
2. It is a gene bank for improvement of domesticated plants and animals.

Question 37.
Local people around forests are referred to as “stakeholders” for conservation of forests. Give reasons.
(CCE 2012)
Answer:
Local people around forests are stakeholders in conservation of forests because they depend upon forests for

1. Firewood
2. Timber and bamboos
3. Thatch
4. Grazing of livestock and collection of fodder
5. Food articles
6. Medicines.

Question 38.
What important message is conveyed by Amrita Devi Bishnoi Award for Wildlife conservation ?(CCE 2012)
Answer:
Conservation of wildlife and forests is crucial to our own welfare as it has both economic and ecological benefits.
Economic Benefits. Source of food, fodder, timber, industrial raw materials and medicines.

Question 39.
Ecological Benefits. It regulates climate, prevents soil erosion and floods, retains rain water, supplies water to streams and springs and acts as gene bank for improvement of domesticated plants and animals. “Narmada Bachao Andolan” raised issues of how construction of big dams create environmental problems.
Discuss two such issues.(CCE 2012)
Answer:

1. Deforestation: A large area is submerged resulting in loss of forests and wildlife.
2. Environmental Changes: The impounded water raises atmospheric temperature and releases a lot of methane.

Question 40.
List two gases released on burning carbon. State their effects. (CCE 2012)
Answer:

1. Carbon Monoxide. It binds with haemoglobin and reduces its oxygen carrying capacity.
2. Carbon Dioxide. It is a green house gas, which in excess is causing global warming. Otherwise it is raw material for photosynthesis.

Question 41.
State the meaning of biodiversity hotspot. What is the criteria of measuring biodiversity of an area ?
(CCE 2012)
Answer:
Biodiversity hotspot is an area of occurrence of diverse types of organisms which is threatened with degradation and fragmentation.
The criteria for measuring biodiversity of an area is the occurrence of different types of plants and animals or species richness of the area.

Question 42.
How are fossil fuels formed in nature ? What are the products formed when combustion takes place in insufficient air ? (CCE 2012)
Answer:

1. Fossil fuels have been formed million of years ago due to burying of vegetation and other organic matter inside earth under high pressure, heat and anaerobic conditions.
2. Combustion in insufficient air releases unburnt hydrocarbons, smoke, soot and carbon monoxide.

Question 43.
“Rain water harvesting is essential”. Justify this statement giving two reasons. (CCE 2012, 2014)
Answer:
Most of our water requirements are met by pumping out ground water which has, therefore, got depleted at most of the places. Rain water harvesting is capturing, collection and storage of rain water for filling small water bodies and recharging ground water.

1. It helps in maintaining level of ground water as it is regularly recharged.
2. It ensures availability of water in nonrainy season.

Question 44.
List any two causes for the failure of sustained availability of ground water. (CCE 2012, 2015)
Answer:

1. Excessive withdrawal of ground water than its natural recharge.
2. Absence of rain water harvesting and recharge of ground water.
3. Deficient rain fall, reduced percolation and increased run off.

Question 45.
Name the fossil fuels. Why are they so called ? (CCE 2012)
Answer:
Coal, petroleum, natural gas. They are called fossil fuels because they have been formed million of years ago inside the earth from buried vegetation due to high pressure, temperature and anaerobic conditions.

Question 46.
What does chipko movement refer to ? Write its two aims. (CCE 2012, 2015 CBSE Foreign 2017)
Answer:
Chipko movement is a nonpolitical public movément for conservation of natural habitats, forests and wildlife by preventing their excessive exploitation. It started with hugging of the trees by the women under the leadership of Gaura Devi against their cutting.
Aims :

1. Allowing the local people the traditional use of forests.
2. Protection of the area from landslides, soil erosion and flash floods.

Question 47.
Mention the role of forest in conserving the environment. How do the forests get depleted ? (CCE 2012)
Answer:
Forests in Conservation of Environment. Forests protect the soil from erosion, increase rain fall, hold rain water like a sponge, lead formation of rivulets and springs, regulate climate and moderate temperature. Depletion. Excessive felling of trees, overgrazing, clearing for agriculture, roads, rails, canals, etc.

Question 48.
(a) Why are coal and petroleum called fossil fuels ?
(b) Name two elements which are present both‘is CNG and petroleum. (CCE 2012)
Answer:
(a) Coal, petroleum, natural gas. They are called fossil fuels because they have been formed million of years ago inside the earth from buried vegetation due to high pressure, temperature and anaerobic conditions.
(b) C, H.

Question 49.
Write the harmful effects of using plastic bags on the environment. Suggest alternatives to plastic bags.
(CCE 2013, CBSE Foregin 2017)
Answer:
Plastic is nonbiodegradable. Being nonbiodegradable, waste plastic articles clog drains, kill animals and pile up adversely affecting the environment. When burnt or recycled they give out toxic filmes.
An alternative to plastic bag is cloth bag. It can be reused several times. The torn cloth bag can also be recycled. It can also undergo decomposition.

Question 50.
Why is sustainable management of natural resources necessary ? Which one out of reuse and recycle would you suggest to practise and why ? (CCE 2013, 2014, 2015, CBSE Dlehi 2017)
Answer:
Sustainable management of natural resources is necessary because it will provide

1. Equitable and continuous availability of the resource to the present and future generations.
2. Little harmful impact on the environment.

Out of ‘reuse’ and recycle, I will prefer reuse:

1. There is no need to send the used article to recycling unit,
2. There is no consumption of energy as required for recycling.
3. There is no need to remarket the produce. Instead of throwing away the used one and obtaining a new one after its recycling, a container or bottle can be reused several times, of course, each time after cleaning the same. This will save a lot of money and energy.

Question 51.
List and explain any two advantages associated with water harvesting at community level.
(CCE 2013, CBSE A.I. 2017)
Answer:
Water harvesting at the community level is capturing, collection and storage of rain water and surface run off for filling either small water bodies or recharging ground water. This is carried out through water shed management, check dams, earthen dams, roof top harvesting and filter wells in flood drains.
Benefits:

1. It ensures water availability in non-rainy season,
2. It reduces the chances of flooding during rainy season,
3. Ground water level does not fall as it is regularly recharged,
4. Ground water recharge is the best form of water harvesting as the water is filtered and free from contaminations. It also does not evaporate,
5. Water becomes available for drinking as well as irrigation.

Question 52.
State the causes of Chipko movement. (CCE 2013)
Answer:
Forest resources were sold to industrialists at a rate far below the market price. They were denied to local persons even when they formed a cooperative for their purchase. The locals were also prevented from plucking leaves and lopping of branches. The contractor would fell the whole trees. This irked the villagers of Tehri-Garwal who started a movement of clasping trees when contractor will reach to fell the trees. The movement slowly got transformed into conservation of environment (forests, wildlife and natural habitats).

Question 53.
What is meant by biodiversity ? List two advantages of conserving forest and wildlife. (CCE 2014, 2015)
Answer:
Biodiversity: It is the occurrence of different types of organisms and their variants adapted to different environmental condition of the area.
Advantages of Conserving Forest and Wildlife.
Conservation of Forests:

1. Forest provide a number of economically important products
2. They protect the soil, retain and regulate flow of rain water.

Conservation of Wildlife:

1. Wildlife is important in maintaining ecological balance of the area,
2. It is gene bank for improvement of domesticated plants and animals.

Question 54.
“Affluent life style has a negative effect on the environment.” Justify this statement with the help of an example. (CCE 2014, CBSE A.I. 2016)
Answer:
Affluent life style has an approach of convenience , use and throw habit. It not only wastes a lot of natural resources but also produces a lot of wastes. 36% of solid waste consists of packing materials. Americans annually throw away about 50 billion food and drink cans and 27 billion glass botdes and jars.

Question 55.
Recycling is considered a welcome practice to deal with the environmental problems. Justify this statement with two arguments. (CCE 2014)
Answer:
Recycling or processing of waste articles to form new articles is the best practice to save the environment from piling up of wastes, contamination and pollution. It also saves the resources, e.g.,

1. Formation of new metal from metallic wastes,
2. Formation of new glass from broken glass.

Question 56.
Recycling of paper, metal, plastic and e-waste is done at most of the places. Mention the positive impact of this recycling process on environment. (CCE 2014)
Answer:
Recycling or processing of waste articles to form new articles is the best practice to save the environment from piling up of wastes, contamination and pollution. It also saves the resources.

Question 57.
From the following list, select the items that cpnstitute electronic waste : Mobile phone, T.V., Key Board, Pressure cooker, Key Ring , Pen drive and table. (CCE 2014)
Answer:
Mobile phone, T.V., Pen drive.

Question 58.
(a) What is watershed management system ?
(b) List two benefits derived by the communities that participate in the system. (CCE 2014)
Answer:
(a) Watershed management is the prevention of soil erosion by planting of more trees and other vegetation in high raised areas which are the source of run off to low lying areas.
(b)

1. There will be absence of landslides and excessive runoff during the rains.
2. Forest products become available to the communities participating in the system.

Question 59.
List two main causes of the pollution of river Ganga. State how pollution and contamination of river prove harmful for the health of the people of neighbouring areas. (CCE 2015)
Answer:
Causes :

1. Passage of raw sewage from towns and cities into it.
2. Passage of industrial effluents.
3. Immersion of ashes, bathing, washing and throwing of carcases,
4. Run off from fields.

Effect :

1. Spread of water borne diseases,
2. Contamination of fish and other animals.

Question 60.
List any two advantages associated with water stored in the ground.
Answer:

1. Ground water does not evaporate,
2. It is not contaminated easily,
3. It is available throughout the year.

Question 61.
Give four advantages of building a dam over a river. (CCE 2015)
Answer:

1. Prevention of Floods. Dams store excess water during rains and therefore prevent flooding.
2. Generation of Electricity. Dams are used for generation of electricity.
3. Irrigation. They provide irrigation water to a large area all around the year.
4. Drinking Water. Many towns and cities receive drinking water from canals originating from dams.

Question 62.
With the increasing human population demand for resources has also increased at an exponential rate.
What can be done for management of our natural resources ? (CCE 2015)
Answer:

1. Controlled exploitation,
2. Minimal wastage
3. Recycle and reuse
4. Conversion of wastes into useful products.

Question 63.
What is meant by sustainable development ? Can the change in perception of the use of natural resources by the people help it ?
Answer:
Sustainable Development: Sustainable development is a strategy of development which can be sustained for a long time without undue damage to the environment.
Change in Perception: Yes, the habit of use and throw should be curbed. Recycle and reuse should be adopted. Smaller and more effecient devices be built. Wastage at every step should be checked.

Question 64.
(a) Why do we need to manage our resources carefully ?
(b) Why management of natural resources requires a long term prespective ? (CCE 2015)
Answer:
(a) Management of resources is controlling the use of resources so as to

1. Provide for their sustained availability and
2. Equitable distribution.

(b) A long term prospective must be taken into considerations during management of natural resources so that latter continue to remain available for future generations.

Question 65.
List four measures that can be taken to conserve forests. (CCE 2015)
Answer:
Conservation is protection, augmentation and scientific management of a resource so as to maintain it at its optimum level while providing sustainable benefits for the present as well as future generations. Some approaches for conservation of forests are as follows :

1. Afforestation and Reforestation. Afforestation is developing forest over an area where none existed earlier. Reforestation is developing forest cover which has been cleared during exploitation. Degraded forests are also mended to bring them back to health. All this is done by state forest department either by themselves or with the help of joint forest management committees.
2. Separation of Commercial Forestry. Useful plants required for meeting commercial needs should be planted separately so that there is no undue pressure on natural forests. Social forestry is growing multipurpose plants on village common lands for meeting requirement of fodder, firewood and small timber. Production plantation is growing industry required plants on wastelands.
3. Controlled grazing.
4. Prevention of scraping and litter removal.
5. Practising block cutting or cutting of forest equal to its regeneration capacity.
6. Building of national parks, sanctuaries and biosphere reserves.

Question 66.
List four products of burning of coal. (CCE 2015)
Answer:
Carbon monoxide, carbon dioxide, nitrogen oxides, sulphur dioxide, fly ash.

Question 67.
List four advantages of properly managed water-shed management. (CBSE Delhi 2016)
Answer:
Definition: Watershed management is the prevention of soil erosion by planting of more trees and other vegetation in high raised areas which are the source of run off to low lying areas.
Advantages:

1. Prevents flooding,
2. Checks soil erosion.
3. Retains water underground and prevents drought,
4. Increases life of downstream reservoirs and dams,
5. Higher biomass production and income of water shed community,
6. Maintenance of ecological balance.

Question 68.
Explain giving example where active involvement of local people led to efficient management of forest. (CBSE Delhi 2016)
Answer:
Sal forest of Arabari in Midnapore district of Bengal was highly degraded and could not be revived despite best efforts of forest department. In 1972, forest officer A.K. Banerjee involved villagers in regeneration of the forest by providing them employment in silviculture and harvesting, 25% harvest and allowed collection of fuel wood and fodder at nominal charges. By 1983, the forest was fully revived.

Question 69.
What is sustainable development ? State its two main objectives. (CBSE Foreign 2016)
Answer:
Definition: Sustainable development is a strategy of development which can be sustained for a long time without undue damage to the environment.
Objectives:

1. To provide benefits of development not only to present generation but also the future generations
2. Provide healthy environment and life support system.

Question 70.
List four causes of damage to forests. (CBSE Foreign 2016)
Answer:

1. Overgrazing, scraping and excessive collection of fuel wood by the villagers and forest dwellers.
2. Clearing of forest areas by industrialists for obtaining plant products including timber and wood pulp.
3. Development project* like building of dams, roads, canals, spread of urban areas, agriculture, etc.
4. Development of facilities for tourists and nature lovers.

Question 71.
Forest are “biodiversity hot spots”. Justify this statement. (CBSE A.I. 2016)
Answer:
A biodiversity hot spot is an area having diverse types of organisms adopted to local conditions but are
threatened by degradation and fragmentation if not managed properly. Forests are called biodiversity hot . spots as their flora and fauna are threatened by high degree of exploitation and human interference.

Question 72.
List four stake holders which may be helpful in conservation of forests. (CBSEA.I. 2016)
Answer:
The four stakeholders in forests and wildlife are

1. People living in and around forests who obtain most of their requirements from forests,
2. Forest department which owns the forests.
3. Industrialists who obtain raw materials for their industries,
4. Wildlife and nature enthusiasts. Among them the persons living in and around the forests have traditional knowledge of how best the forests can be managed so that a sustainable yield can be obtained indefinitely. Therefore, authority for management of forest produce should be handed over to them. However, the forest department must monitor the same so that there is no excessive exploitation.

Question 73.
Management of forest and wildlife resources is a very challenging task. Why ? Give two reasons.
(CBSE Delhi 2017)
Answer:
Management of forest and wildlife resources is keeping them at optimum profitable level not only for the present generation but also for the furture generations. However, it is a highly challenging task as there is pressure on forests to turn monoculture for industry and providing land for roads, canals, dams, agriculture, development of industrial hubs. Similarly, management of wildlife resources is equally tedious as depletion of forests results in depletion of wildlife.

Question 74.
Why is sustainable management of natural resources necessary ? (CBSE Delhi 2017)
Answer:
Natural resources are limited in their availability. Any over-exploitation will result in their depletion and hence scarcity for future generations.

Question 75.
Explain how would the involvement of local people be useful for successful management of forests.
(CBSE Delhi 2017)
Answer:
Forest dwellers are dependent on forest produce for various aspects of life. They have developed practices to avail different resources at different times of the year. The involvement of local people in management of forests helps in sustainable availability of resources besides better care of the forests.

Question 76.
How do advantages of exploiting natural resources with short term gains in mind differ from the advantages of managing our resources with long term perspective ? (C.B.S.E’. Delhi 2017)
Answer:
Short-Term Gains: There is rapid development, industrial growth and growth of economy. However, the resources dwindle rapidly leading to slump.
Long Term Prespective: There is sustainable exploitation of resources so that development and growth of economy continues for generations.

Question 77.
What is meant by wildlife ? How is it important ? (CBSE Delhi 2017)
Answer:
Wildlife: It is living beings comprising animals, plants and microrganisms which are found in the wild. They are neither domesticated/trained nor cultivated.
Importance: 

1. Wildlife is important in maintaining ecological balance of the area,
2. It is gene bank for improvement of domesticated plants and animals.

Question 78.
Why is equitable distribution of resources essential in a society ? List two forces which are against such distribution. (CBSEA.I. 2017)
Answer:
Need for Equitable Distribution. Resources are living and non-living components of nature which are drawn upon to provide food, fodder, shelter, water, energy, articles of daily use and comforts. Every human being has the fundamental right to obtain and use the same. This is possible only when there is equitable distribution of resources.
Forces Against Equitable Distribution,

1. Restricted availability of resources,
2. Excessive consumption by the rich,
3. Profit motto by the persons exploiting resources.

Question 79.
Why are coal and petroleum categorised as natural resources ? Give a reason as to why they should be used judiciously. (CBSEA.I. 2017)
Answer:
Coal and petroleum are called natural resources because they are obtained from nature. They are nonrenewable. Hence they should be used judiciously so as to remain available for a long time to come.

Question 80.
Why are certain forests considerd “biodiversity hotspots” ? Suggest any two ways in which an individual can contribute effectively to the management of forests and wildlife. (CBSE Foreign 2017)
Answer:
Forest are called hotspots of biodiversity as they contain a number of endemic species which are threatened due to indiscriminate human exploitation and interference.
Management of Forests and Wildlife,

1. Provention of overexplistation.
2. Making people aware of ecological benefits of forests and wildlife.

Question 81.
List the products of combustion of fossil fuels. State the harmful effects of these products on envrionment.
(CBSE Foreign 2017)
Answer:
CO₂, CO, flyash, NO_x, SO₂ and hydrocarbons. They cause global warming (CO₂), acid rains (NO_x, SO₂), smog (hydrocarbons, NO_x and SO₂).

Question 82.
Suggest any two ways by which the balance between the envrionment and industrial development is maintained so as to help undisturbed survivial of the organisms on the earth. (CBSE Foreign 2017)
Answer:

1. Separation of commercial forestry or production plantation from main foresty.
2. Recycling of waste water generated by industries.
3. Treatment of industrial effluents and control of air pollution.

Short Answer Questions (3 Marks Each)

Question 1.
What is meant by exploitation of resources with short term aims ? List any four advantages.
(CBSE Delhi 2009 C)
Answer:
Short Term Aims: Exploitation of resources with short term aims is to obtain and utilise the resources to the maximum so that the benefits are available almost immediately.
Advantages,

1. It opens avenues for rapid industrial growth,
2. People get employment opportunities,
3. Commodities become available in plenty,
4. Growth in economy allows better development of public facilities.

Question 2.
What is Chipko movement ? How did this movement ultimately benefit the local population and the environment ?
(CBSE Delhi 2009 C, Foreign 2016)
Answer:
Definition: It is a non-political public movement for conservation of natural habitats, forests and wildlife by preventing their excessive exploitation.
Benefit to Local Population: Increased availability of forest products to local people and their cattle.
Benefit to Environment: Restoration of climate, protection to soil and water resources, prevention of land slides and floods.

Question 3.
What is dam ? Write two main advantages and two ill-effects of constructing a big dam.
(CBSE Delhi 2009 C)
Answer:
Dam: It is a large water reservoir built across a stream by holding back water during rainy season.
Advantages :

1. Prevention of Floods: Extra water during rainy season is used in filling the dam. This prevents floods.
2. Electricity and Canal Water: Dams are used in producing electricity by allowing water to fall on turbines. The same water is then passed into canals for supply of water to crops throughout the year.

Effects

1. Displacement. A large number of people are displaced who are unable to get gainful employment at the new place of their residence.
2. Ecological Problems. A large forest area is submerged causing deforestation, loss of biodiversity, raising atmospheres temperature and increasing emission of methane.

Question 4.
What is meant by sustainable management ? The environmentalists are insisting upon “sustainable natural resources management ?” State its four advantages. (CBSE A.I. 2009 C)
Answer:
Sustainable Management. It is controlling the use of resource in such a way as to provide for its equitable and continuous availability not only to the present generation but also for future generation without any harmful impact on the environment. Environmentalists insist on sustainable natural resources management because of the following reasons :

1. Equitable Distribution. The resources would be made available to all sections of the society instead of a few rich persons.
2. Controlled Exploitation. The exploitation is restricted so as to meet the just demands of the society.
3. Minimum Wastage. Technology is employed to ensure minimum wastage during processing of the resource.
4. Disposal of Waste. The waste of the processing units is not allowed to degrade the environment. Instead proper safety measures are taken to convert the waste into useful product.

Question 5.
State any two reasons for lauching the “Ganga Action Plan”. Which bacteria was found in Ganga water indicating contamination ? (CCE 2011)
Answer:
Ganga is a ‘sacred’ river where people take holy bath. Its ‘sacred’ water is taken to homes and temples. The river also supplies drinking water to over 50 million people. Over the years, the river has got polluted due to discharge of untreated sewage, untreated effluents, immersion of ashes and throwing of unburnt corpses. Bacteria indicating pollution are called coliform bacteria (Escherichia colt).

Question 6.
(a) What is meant by fossil fuel ?
(b) Which fossil fuel is usually conserved when we save on electricity ?
(c) At the present rate of consumption how long will the known reserves of coal and petroleum last ?
(CCE 2011)
Answer:
(a) Fossil Fuel: Fossil fuels are energy yielding combustible substances that have been formed million of years ago by compression and anaerobic heating of organic matter.
Examples: Coal, Petroleum.
(b) Coal
(c) Petroleum — 40 years.
Coal — 200 Years.

Question 7.
List three advantages of different ancient water harvesting techniques developed in various parts of India.
(CCE 2013)
Answer:

1. Management: The management of the local water harvesting technique was also local. This helped in making changes as per requirement and local condition.
2. Regulation: The use of stored water was strictly regulated. Not a drop was allowed to be wasted.
3. Cropping Pattern: It was based on water availability and experience of crop requirement.

Question 8.
Write any three problems associated with the construction of large dams which had led to public opposition in some areas. (CCE 2011)
Answer:

1. Social Problems:. A large number of tribals, peasants and other villagers are displaced. Provision of adequate compensation and rehabilitation measures are not made. The oustees of Tawa dam of M.P. built in 1970s have not yet received the promised compensation and help.
2. Economic Problems: A huge amount running into thousands of crores is spent on building large sized dams. They do not generate proportionate benefits.
3. Environmental Problems: There is enormous deforestation and loss of biodiversity.
   A number of other problems are also there which have not yet been raised by environmentalists. Every dam has a life span. What would be after the expiry of this period. Dams emit a lot of methane. They add to global warming. Water borne diseases increase in number. Impoundment of huge water can disturb the geology of the area. Seepage of water inside the earth can add to this disturbance. Hoover dam of USA has triggered a number of earthquakes. An earthquake in the area of a dam can cause deluge.

Question 9.
(a) Water is elixir of life, a very important natural resource. Your science teacher wants you to prepare a plan for a formative assessment activity. “How to save water, the vital natural resource”. Write any two ways that you will suggest to bring awareness in your neighbourhood “how to save water”.
(b) Name and explain any one way by which the underground water table does not go down further.
(CBSE A.I. 2017)
Answer:
(a) Awareness. It can be created through

1. Preparing a brochure on saving water and distributing the same among all the residents. While distributing the literature, people can be told about the requirement of saving water and how to do it.
2. Staging play about the importance of water.

(b) Water Table. Lowering of water table can be prevented through rain water harvesting by capturing, collection and storage of rain water through filling small water bodies and recharging ground water through filter wells and other means of passing rain and flood water into earth.

Long Answer Questions (5 Marks Each)

Question 1.
The nature and wildlife enthusiasts who do not depend upon forests have considerable say in their management. Initially the conservationists raised their voice for particular animals like tigers, elephants, rhinoceros. They have now recognized the need to preserve biodiversity ?
(a) Explain reason for this change of approach of wildlife enthusiasts.
(b) State two values that inspire them for this approach. (CCE 2015)
Answer:
(a) Nature and wildlife enthusiasts are highly educated, well connected and influential persons who are concerned about degradation of environment and depletion of natural resources including forests and wildlife. They were initially concerned about the dwindling population of big animals like tigers, elephants and rhinoceros. The enthusiasts soon realized that ecological balance can be maintained only by preserving the biodiversity of nautre. They have, therefore, started emphasising on creation of protected areas where exploitation is minimal and preservation is maximum.
(b)

1. Love of Nature. Nature in its entirely is a pleasure to watch. It has inspired all our poets, writers and artists besides providing recreation to all others.
2. Welfare of Tribals. Tribals have been living in and around forests for centuries. They not only meet their requirements from forests but are also traditionally conservationists with a lot of traditional knowl¬edge-of wildlife uses. By conserving biodiversity the welfare of the tribals will also be taken care of.

Question 2.
Yamuna river passing through 22Km in Delhi was once described as the life line of the city but today it has become one of the most polluted rivers in the country. According to CPCB, the water quality of Yamuna river falls under the category “E” which makes it fit for only for recreation and industrial cooling. It is completely unfit for underwater life.
(a) Give two possible causes of water pollution in Yamuna river.
(b) Suggest any one method by which pollution could be reduced in Yamuna river.
(c) Mention the values protrayed by you here ? (CCE 2015)
Answer:
(a) Causes of Water Pollution:

1. Passage of untreated and half treated sewage into river.
2. Passage of untreated industrial effluents into it.
3. Dumping of garbage, waste water and other materials by people living in slums on the bank of river.

(b) Prevention of Pollution:

1. Only properly treated and tested water should be allowed to be passed into river.
2. Industrial effluents should not be allowed to flow into river. Every industrial unit must have its own effluent treatment.
3. Slums should be shifted away from the banks and parks developed there to prevent future encroachments.

(c) Values :

1. Critical thinking
2. Problem solving
3. Control of pollution
4. Love for nature.

Hope given Previous Year Question Papers for CBSE Class 10 Science Chapter 16 Management of Natural Resources are helpful to complete your science homework.

If you have any doubts, please comment below. Learn Insta try to provide online science tutoring for you.

Chapter 11 Human Eye and Colourful World Class 10 Science Important Questions and Answers PDF will help you in scoring more marks. This consists of 1 mark Questions, 3 Mark Numericals Questions, 5 Marks Numerical Questions and previous year questions from Chemical Reactions and Equations Chapter.

Human Eye and Colourful World Class 10 Important Questions and Answers Science Chapter 11

Very Short Answer Questions ( 1 Mark)

Based on Human Eye

Question 1.
Name the following part of human eye : A thin membrane through which light enters the eye. (CBSE 2011)
Answer:
Cornea.

More Resources

• Previous Year Question Papers for CBSE Class 10 Science
• NCERT Solutions for Class 10 Science
• NCERT Exemplar Solutions for Class 10 Science
• Value Based Questions in Science for Class 10
• HOTS Questions for Class 10 Science

Question 2.
Write the function of iris in the human eye. [CBSE 2007 (Delhi), 2015, 2016]
                                                             Or
Mention the name of a structure formed in human eye that controls the size of the pupil. (CBSE 2012)
Answer:
Iris controls the size of the pupil.

Question 3.
What is the function of pupil in human eye ? (CBSE 2011, 2012)
Answer:
It controls and regulates the light entering the eye.

Question 4.
Name the following part of human eye : A dark muscular diaghram that controls the size of the pupil.
(CBSE 2011)
Answer:
Iris.

Question 5.
Name the type of lens in human eye.
Answer:
Convex lens.

Question 6.
Name the part of human eye that helps in changing the focal length of the eye lens.
                                                             Or
Name the part responsible for the power of accommodation of the human eye.
Answer:
Ciliary Muscles.

Question 7.
Name the ability of eye lens to adjust its focal length.
Answer:
Accommodation.

Question 8.
What is the nature of the image formed at the retina of human eye ?
Answer:
Real and inverted image.

Question 9.
Name the part of human eye which acts as a screen to obtain the image of an object. (CBSE 2012, 2014)
Answer:
Retina.

Question 10.
Mention the value of near point for normal eye. (CBSE 2014, 2015)
Answer:
25 cm.

Question 11.
Mention the value of far point for normal eye. (CBSE 2014, 2015)
Answer:
Infinity.

Question 12.
Mention the value of range of vision for normal eye. (CBSE 2014, 2016)
Answer:
Range of vision for normal eye is 25 cm to infinity.

Question 13.
Copy the following diagram on your answer sheet after showing the refracted rays of light from eye lens, assuming the eye is a normal human eye.

Answer:

Question 14.
Name two common defects of vision. (CBSE 2015, 2016)
Answer:

1. Myopia
2. Hypermetropia.

Question 15.
What is hypermetropia or far-sightedness ? [CBSE (Foreign) 2008]
Answer:
A human eye which can see distant objects clearly but cannot see the near objects clearly is said to be suffered with a defect called hypermetropia or far sightedness.

Question 16.
Name the type of a lens used to correct hypermetropic eye.
Answer:
Convex lens.

Question 17.
What is Myopia or near-sightedness ? (CBSE 2011)
Answer:
A human eye which can see near objects clearly but cannot see the distant objects clearly is said to be suffered with a defect called myopia or near-sightedness.

Question 18.
Name the type of a lens used to correct myopic eye.
Answer:
Concave lens.

Question 19.
Name the vision defect due to which a person can neither clearly see objects placed at the near point nor at infinity.
Answer:
Presbyopia.

Question 20.
State the type of corrective lens which is required by a person who can neither clearly see objects placed at the near point nor at infinity. (CBSE 2014)
Answer:
Bi- focal lens.

Question 21.
Make a ray diagram to show how the eye defect myopia is corrected by using a suitable lens ? (CBSE 2008, 2011)
Answer:

Question 22.
Make a ray diagram to show how the eye defect hypermetropic or far sightedness is corrected by using a suitable lens. (CBSE 2008, 2011)
Answer:

Question 23.
Draw a diagram to show the formation of image of a distant object by a myopic eye. How can such an eye defect be remedied ? (CBSE (Delhi) 2008)
Answer:
For ray diagram, see figure 5 (a).

Myopia can be remedied by using a concave lens of suitable focal length.

Question 24.
State two reasons due to which myopia may be caused.
Answer:
This defect arises due to either by

1. the elongation of the eye ball or
2. the excessive curvature of the cornea.

Question 25.
d short sighted person cannot see clearly beyond 2 m. Calculate the power of less required to correct his vision. (CBSE 2011)
Answer:
Here, d = 2 m
The concave lens of focal length f= – d is needed to correct his vision .’. f = – d = – 2 m

Question 26.
Copy the following diagram on your answer sheet showing the formation of image, assuming the given eye is a myopic eye. (CBSE 2011)

Answer:

Question 27.
Copy of following diagram on your answer sheet showing the formation of image, assuming that the given eye is hypermetropic eye.

                                                       Or
Draw ray diagram showing hypermetropic eye.
Answer:

Question 28.
A person is advised to wear spectacles with concave lenses. What type of defect of vision is he suffering from ?
(CBSE 2012)
Answer:
Myopia.

Question 29.
A person is advised to wear spectacles with convex lenses. What type of defect of vision is he suffering from ?
Answer:
Hypermetropia.

Question 30.
Draw a diagram showing refraction of a ray of light through a glass prism and mark the angle of deviation.
(CBSE 2011)
                                                             Or
Draw a ray diagram to explain the term angle of deviation. (CBSE 2017)
Answer:

The angle between the directions of incident ray and emergent ray from the prism is called angle of deviation.

Question 31.
Copy the following diagram on your answer sheet showing the different colours on the white screen.

Answer:

Based on Dispersion of light

Question 32.
What is dispersion of light ? (CBSE 2012, 2015, CBSE (Foreign) 2016)
Answer:
The phenomenon of splitting white light into seven colours when it passes through a glass prism is called dispersion of light.

Question 33.
What is the came of dispersion of light ?
                                    Or
State the came of dispersion of white light by a glass prism. (CBSE 2017)
Answer:
When white light passes through a glass prism, its constituent colours (red, orange, yellow, green, blue, indigo, violet) travel with different speeds in the prism. This causes the dispersion of light.

Question 34.
Arrange constituent colours of white light in descending order of their wavelengths.
Answer:
Red, orange, yellow, green, blue, indigo, violet. .

Question 35.
Name the component of white light that has the greatest wavelength. (CBSE Sample Paper 2016)
Answer:
Red colour.

Question 36.
Name the component of white light that has the least wavelength.
Answer:
Voilet colour.

Question 37.
Name the component of white light that deviates (i) the least and (ii) the most while passing through a glass 4 prism. (CBSE 2011, 2012, 2014, 2015, 2016)
Answer:

1. red colour,
2. violet colour.

Question 38.
Name the phenomenon occurring in nature due to dispersion of light.
Answer:
Rainbow.

Question 39.
Name the three phenomenon of light responsible for the formation of rainbow in the sky.
Answer:

1. Refraction,
2. dispersion and
3. internal reflection of light.

Question 40.
Name the colours that suffer maximum and minimum deviation respectively while passing through a prism.
(CBSE 2014)
Answer:
Red colour suffers minimum deviation and violet colour suffers maximum deviation.

Question 410.
Light of two colours A and B pass through a glass prism. A deviates more than B from its path of incidence.
Which colour has a higher speed in the prism ? (CBSE 2011)
Answer:
Colour B has higher speed than that of colour A.

Question 42.
What is meant by scattering of light ? (CBSE 2014, 2015, 2016)
Answer:
When sunlight enters the atmosphere of the earth, the atoms and molecules of different gases present in the atmosphere absorb this light. Then these atoms and molecules of the gases re-emit light in all directions. This process is known as scattering of light. The atoms or particles scattering light are known as scatterers.
The intensity of scattered light is inversely proportional to the fourth power of the wavelength of incident light, if the size of the particles (say atoms or molecules) scattering the light is less than the wavelength of the incident light.

Short Answer Questions (2 & 3 Marks)

Based on Human Eye

Question 1.
When we enter a dim-lit room from a bright light, we are not able to see the object in the room for some time.
Explain, why ? (CBSE 2011, 2016)
                                                                 Or
Why does it take some time to see objects in a cinema hall when we just enter the hall from bright sun light ? Explain. (CBSE 2011)
Answer:
In a bright light, the iris contracts the pupil of an eye to allow less light to enter the eye. When, we enter the dim-lit room, iris takes time to expand the pupil of an eye to allow more light to enter the eye so that the visible image of the object lying in the room are formed on the retina of the eye.

Question 2.
The ciliary muscles of a normal eye are in their (i) most relaxed (ii) most contracted state. In which of the two cases is the focal length of the eye-lens more ? (CBSE Sample Paper)
Answer:
The focal length of eye-lens is more when the ciliary muscles of a normal eye are in their most relaxed state.

Question 3.
Why do we have two eyes instead of one eye ?
Answer:
Two eyes are better than one eye because

1. the field of view with two eyes is more than with one eye.
2. two eyes give three dimensional picture of an object (i.e., the length, breadth and depth or height of an object) whereas one eye gives only two dimensional picture of an object.

Question 4.
A convex lens made of glass forms a sharp image on the screen for a particular position of an object with respect to the lens. A human eye lens is also a convex lens but it can form sharp images on the retina of eye for different positions of the objects. Explain, why ? (CBSE 2010)
Answer:
A convex lens made of glass has a fixed focal length and hence it forms a sharp image on the screen for a particular position of an object. However, the focal length of human eye lens can be changed by the action of ciliary muscles. In other words, human eye lens has the ability to chartge its focal length to form sharp images of objects at different positions. The process is known as accommodation of eye.

Question 5.
How is a normal eye able to see distinctly distant as well as nearer objects ? What is the distance of distinct vision ? (CBSE 2012)
Answer:
Eye has the ability known as accommodation of eye to see distant as well as nearer objects clearly. When objects is far away, the focal length of lens is increased due to the relaxed ciliary muscles. Hence sharp image of object is formed on the retina of eye. When object is nearer to the eye, the focal length of lens is decreased due to the contraction of ciliary muscles and hence sharp image of the object is formed on the retina of eye. The distance of distinct vision is 25 cm.

Based on Defects of Vision

Question 6.
What is short-sightedness ? How can this defect be corrected ? (Bihar Board 2012)
Answer:
Short-sightedness or near-sightedness or Myopia
A human eye is myopic if it can see the near objects clearly but unable to see far off objects or distant objects clearly.
Causes of Wlyopia: This defect arises due to either by

1. the elongation of the eye ball or
2. the excessive curvature of the cornea.

Question 7.
What is long-sightedness ? How can this defect be corrected ?
Answer:
A human eye which can see far off objects or distant objects clearly but can not see the near objects clearly is said to be suffered with a defect known as long sightedness or far sightedness or Hypermetropia.
Causes of Hypermetropia: This defect arises due to either by

1. the increase in the focal length of eye lens or
2. the size of the eye ball becomes too small so that the light rays from the nearby points or objects are not brought to focus on the retina of the eye.

Question 8.
What is presbyopia ? State the cause of Presbyopia. How is presbyopia of a person be corrected ?
[CBSE (All India) 2009]
Answer:
A human eye which cannot see the near objects and distant objects clearly is said to suffer from a defect known as Presbyopia. Eye suffering from Presbyopia cannot read and write comfortably.
This defect arises due to the ageing of a person. The ciliary muscles are weakened and the flexibility of the crystalline lens of the human eye decreases with age of the person. As a result, human eye is unable to focus on close as well as distant objects.
This defect can be corrected by using a bi-focal lens. A bi-focal lens consists of a concave lens which forms the upper surface of the bi-focal lens and a convex lens which forms the lower surface of the bi-focal lens. The upper surface of bi-focal lens (i.e. the concave lens) enables the person to see distant objects clearly and the lower surface of bi-focal lens {i.e. convex lens) enables the person to see the near objects.

Question 9.
An old person is unable to see clearly nearby object as well as distant objects.

1. What defect of vision is he suffering from ?
2. What kind of lens will be required to see clearly the nearby as well as distant objects ? Give reasons ?
   (CBSE 2012, 2014)

Answer:

1. Presbyopia.
2. This defect is connected by using bi-focal lens. A bi-focal lens consists of a concave lens which forms the upper surface of lens and a convex lens which form the lower surface of the lens. The upper surface enables the person to see distant objects clearly and the lower surface helps the person to see the near objects clearly.

Question 10.
A person suffering from an eye-defect uses lens of power -1D. Name the defect he is suffering from and the nature of lens used. (CBSE 2015)
Answer:
He is suffering from myopia. The lens is concave lens.

Question 11.
A person suffering from an eye-defect uses lens of power + IS D. Name the defect he is suffering from and the nature of lens used.
Answer:
He is suffering from hypermetropia. The lens is convex lens.

Question 12.
Explain why the image distance in the eye does not change when we change the distance of an object from the eye ? (CBSE 2017)
Answer:
This is because the eye lens has the ability to change its focal length to make the image always on the retina when the distance of the object from the eye is changed.

Question 13.
Due to gradual weakening of ciliary muscles and diminishing flexibility of the eye lens a certain defect of
vision arises. Write the name of this defect. Name the type of lens required by such persons to improve the vision. Explain the structure and function of such a lens. (CBSE 2017)
Answer:
Name of defet : Presbyopia
Type of lens required by persons suffering presbyopia to improve the vision is bi-focal lens.
Bi-focal lens consists of a concave lens which forms the upper surface of a bi-focal lens and a convex lens which forms the lower surface of the bi-focal lens. The upper surface of the lens enables the person to see distant objects clearly and the lower surface of the lens enables the person to see the near objects clearly.

Based on Dispersion of Light

Question 14.
What is dispersion of light ? What is the cause of dispersion ? Draw a diagram to show the dispersion of white light by a glass prism. [CBSE (All India) 2009, 2011, 2012, 2014, 2017]
Answer:
Dispersion of Light: The phenomenon of splitting white light into seven colours when it passes through a glass prism is called dispersion of light.
Cause of Dispersion: When white light passes through a glass prism, its constituent colours (red, orange, yellow, green, blue, indigo, violet) travel with different speeds in the prism. This causes the dispersion of light.

Question 15.
When white light passes through a glass prism, seven colours namely red, orange, yellow, green, blue, indigo and violet are seen on the white screen. All these colours have different angles of deviation. Explain why ?
Answer:
Speed of colour in a medium depends upon its wavelength. All the colours have different wavelength. The red colour has the longest wavelength and violet colour has the last wavelength. Therefore, red colour has the highest speed in the glass prism and the violet colour has the lowest speed in the glass prism. Hence, all colours of white light are refracted by different amounts while passing through the glass prism. Therefore, all the colours have different angles of deviations.

Question 16.
Why do different colours get separated when white light passes through prism I How can we recombine the components of white light after a prism has separated them ? Explain with the help of figure. (CBSE 2012)
Answer:
Different colours have different speeds in glass prism. Due to this fact, different colours get separated while passing through the prism.
Perform an activity to show that the colours of white light splitted by a glass prism can be recombined to get white light by another glass prism.
Apparatus required: Two glass prisms made of same kind of glass, a card board having a fine hole at its centre, a white screen.
Procedure:

1. Place a card board in front of a prism A. A ray of white light coming from the hole in the card board falls on the prism A (Figure 11).
   
2. White light splits into seven colours by prism A is made to fall on another glass prism B placed with its base upward. Since prism A disperses white light, so it is known as dispersing prism.
3. The prism B deviates colours of light towards its base. The various colours recombines at the opposite lace of glass prism B.
4. This activity was initially performed by the great scientist Issac Newton.
   The light received on the white screen placed in front of prism B is white. Since the prism B recombines the colours of light to produce white light, so glass prism B is known as recombination prism.

Question 17.
How will you use two identical glass prisms so that a narrow beam of white light incident on one prism emerges out of the second prism as a beam of white light ? Draw a labelled diagram to illustrate it. (CBSE 2015)
Answer:
Perform an activity to show that the colours of white light splitted by a glass prism can be recombined to get white light by another glass prism.
Apparatus required: Two glass prisms made of same kind of glass, a card board having a fine hole at its centre, a white screen.
Procedure:

1. Place a card board in front of a prism A. A ray of white light coming from the hole in the card board falls on the prism A (Figure 11).
   
2. White light splits into seven colours by prism A is made to fall on another glass prism B placed with its base upward. Since prism A disperses white light, so it is known as dispersing prism.
3. The prism B deviates colours of light towards its base. The various colours recombines at the opposite lace of glass prism B.
4. This activity was initially performed by the great scientist Issac Newton.
   The light received on the white screen placed in front of prism B is white. Since the prism B recombines the colours of light to produce white light, so glass prism B is known as recombination prism.

Question 18.
How did Newton, using two identical glass prisms, show that white light is made of seven colours ? (CBSE 2017)
Answer:
Investigate dispersion of white light in a glass prism

1. Place a thick card board having a small hole in it in front of a glass prism.
2. Allow sunlight to fall on the card board. The hole in the card board allows a beam of white light to fall on the prism.
3. Place a white screen at some distance away from the prism.
4. Rotate the prism slowly until a band of seven colour is figure 9 observed on the white screen.
   

Conclusion : “When a beam of white light falls on a glass prism, white light splits into its constituent colours (i.e., seven colours). This phenomenon of splitting white light into seven colours by a glass prism is known as dispersion of white light.

Question 19.
Draiv a ray diagram to show the path of a narrow beam of white light, through a combination of two identical prisms arranged together in inverted position with respect to each other, when it is allowed to fall obliquely on one of the faces of the first prism of the combination. (CBSE 2017)
Answer:

Question 20.
Why do we observe the seven colours when white light passes through a glass prism ? Which component of white light deviates the least ? (CBSE 2011, 2012)
Answer:
White light is a mixture of seven colours. The speed of different colours of white light is different in glass. So when white light passes through a glass prism, it splits into seven colours. Red colour deviates the least.

Question 21.
(i) Show formation of rainbow with the help of a ray diagram. (CBSE 2014, 2015)
(ii) What are the conditions to observe rainbow ? (CBSE 2011, 2013, 2015)
Answer:
(i)

(ii) Rainbow is observed during or after rainfall provided the sun is at the back of the observer.

Question 22.
On a sunny day, stand at a certain distance from a fountain of a water such that the position of the sun is at your back. What do you observe ? Explain the reason of your observation.
Answer:
We observe a rainbow. The droplets of water behave as glass prisms. When sun light falls on these drops, dispersion of light takes place. Hence, rainbow is seen.

Question 23.
Why do we see a rainbow in the sky only after rainfall ? [NCERT Question Bank]
Answer:
You must have seen a beautiful rainbow in the sky after rainfall. This rainbow is formed due to the dispersion of sunlight.
When sunlight falls on the water drops suspended in the atmosphere after rainfall, rainbow is formed due to the dispersion of sun light. The water drops suspended in air (or atmosphere) act as prisms.
Rainbow is the example of dispersion of sunlight. The formation of rainbow after rainfall is shown in figure 12.

Rainbow is observed during a rainfall or after the rainfall or when we look at a water fountain provided the sun is at the back of the observer.
Conditions for Observing a Rainbow
When sunlight falls on a water drop suspended in air, then the sunlight is refracted. The refracted sunlight splits (or dispersed) into its constituent colours (i.e., seven colours). Thus, water drop suspended in air behaves as a glass prism. The red colour deviates the least and the violet colour deviates the most. Different colours of refracted sunlight fall on the opposite face of the water drop.- Now, each colour suffers internal reflection. The reflected colours on reaching the lower surface of water drop are refracted again into the air. Thus, we get a spectrum of seven colours, which is known as a rainbow.

Based on Atmospheric Refraction of light

Question 24.
Describe atmospheric refraction. Explain with the help of diagram why the sun is visible to us two minutes before the actual sun-rise and two minutes even after the sunset. (CBSE 2015, CBSE (Foreign) 2017)
Answer:
The refraction of light takes place, when light travels from one medium to another medium. In other words, refraction of light takes place, when light goes from an optically rarer medium to an optical denser medium or vice-versa. The earth’s atmosphere has air all around. The air in the atmosphere is in the form of layers. The different layers of air have different densities. As we go higher and higher, the density of the layers of air goes on decreasing. Thus, the layers of air close to the surface of the earth have more density than the density of the air layers far away from the surface of the earth. Therefore, the layers of air close to the surface of the earth behave as optically denser medium and the layers of air far away from the surface of the earth behave as optically rarer medium.
When sun light enters the earth’s atmosphere, it continuously goes from rarer to the denser medium and hence refraction of light takes place. The refraction of light taking place in the atmosphere is known as atmospheric refraction.

Question 25.
We can see the sun for few minutes even after it has actually set. Explain, why ?
                                                                  Or
Explain with the help of diagram why the sun is visible to us two minutes before the actual sun-rise and two minutes after the sunset. (CBSE 2012, 2014)
Answer:
We can see the sun for few minutes even after it has actually set
Actual sun sets when it is below the horizon in the evening. The rays of light from the sun below the horizon reach our eyes because of refraction of light through atmosphere. These rays appear to come from the apparent position of the sun which is above the horizon as shown in figure 14.

Hence we can see the sun for few minutes (about 2 minutes) even after it has actually set. Similarly, the sun can be seen about 2 minutes before it actually rises. Thus, we gain about 4 minutes of additional daylight each day.

Question 26.
Why does the sun appear oval at sunset and sunrise but appears circular at noon ?
Answer:
The sun appears oval (or flattened) at sunset and sunrise but appears circular at noon
At sunset and sunrise, the sun is near the horizon. The rays of light from the upper and lower edge of the sun bend unequally while travelling through the atmosphere. As a result of this phenomenon, the sun appears oval or flattened (Figure 15).

At noon, the sun is overhead. The rays of light from the sun enter the atmosphere normally and hence they do not bend at all while passing through the atmosphere. Therefore, the sun appears circular at noon.

Question 27.
Why is the colour of clear sky blue ? Explain. (CBSE 2012, 2014, 2015, 2016)
                                            Or
Why does sky look blue on a clear day ? [CBSE (Delhi) 2008, 2011]
Answer:
When sunlight enters the earth’s atmosphere, the atoms or molecules of the gases present in the atmosphere scatter this light. Since wavelength of red colour is larger than the wavelengths of other colours in sunlight, so red colour is scattered least. Violet colour is scattered the most followed by blue, green, yellow, orange and red colours respectively. Our eye is more sensitive to the blue light than the violet light. Therefore, scattered light in the sky contains blue colour in plenty and hence the clear sky appears blue.
Note : Sky appears greyish over cities having industrial units. The smoke and dust particles in the atmosphere over such cities scatter red, orange and yellow colours more than other colours of small wavelengths. Hence, the sky appears greyish.

Question 28.
Why are stop signals on roads in red coloured light ?
[CBSE (Delhi) 2008, CBSE (All India) 2009, 2012, 2015]
Answer:
When light falls on the signal, all colours are scattered much more than that of red colour. So the red colour suffering least scattering remains confined around the signal, which in turn illuminates the signal significantly. Thus, the danger signals can be seen from very far off distances. Moreover, among all colours, red colour or red light is scattered least by smoke or fog. Hence, red signals are visible even through the smoke or fog.

Question 29.
What would have been the colour of sky if the earth had no atmosphere ? Give reason for your answer. (CBSE 2012)
Answer:
If the earth had no atmosphere, the colour of the sky would have been dark. The colour of sky depends on the scattering the sunlight due to the atmosphere. No atmosphere means no scattering of light.

Question 30.
State the difference in colours of the sun observed during sunrise/sunset and noon. Give explanation for each.
(CBSE 2013)
Answer:
The colour of the sun observed during sunrise/sunset is reddish, while its colour observed at noon is white. At sunrise/sunset, the sun is very far away from the observer. So, the sunlight travels longer distance through the atmosphere to reach the eyes of the observerer. The scattering of blue light is more than the scattering of red light. So, more red light reaches our eye and hence sun appears reddish.
During noon the sun is overhead and light from the sun travels less distance through air to reach our eye. In this case, scattering of all colours is very small. Hence, the sun appears white.

Long Answer Questions ( 5 Marks)

Question 1.
Write different parts of eye and explain their functions. Also explain, how an image of an object is formed on the retina of eye. (CBSE 2012)
Answer:
The main parts of an eye and their functions are given below :

1. Cornea is the outermost part of the eye. It is transparent part of eye and allows the light to enter in the eye.
2. Iris: It is a circular dark diaphragm having a hole in its centre. This hole is called pupil. The circular dark diaphragm has muscles and coloured pigments. The colour of an eye depends upon the colour of these pigments.
   The function of iris is to control the size of the pupil. On the other hand, pupil controls and regulates the light entering the eye. The pupil becomes small when bright light falls on the eye. However, it becomes wide when there is dim light.
3. Lens: The eye lens is a crystalline double convex lens and made of transparent and flexible tissues. It is behind the pupil and held by the muscles called ciliary muscles. It focuses the images of objects on the retina of the eye.
   
4. Ciliary muscles: These muscles hold the eye lens in position. Ciliary muscles controls the focal length of the eye lens. When these muscles contracts, then the lens becomes thick and the focal length of the lens decreases. On the other hand, when ciliary muscles are relaxed, then the lens becomes thin and the focal length of the lens increases.
5. Retina: It acts as a light-sensitive screen to obtain the image of the object. It contains number of cells in the form of rods and cones which are sensitive to light. These cells converts light energy into electrical impulses or signals.
6. Optic nerve: Optic nerve is formed by the nerve fibres coming from the retina. It carries nerve or electrical impulses or signals to the brain. The brain finally interprets the signal.

Question 2.
What is short-sightedness ? List two causes for development of short-sightedness. Describe with a ray diagram, how this defect may be corrected using spectacles. (CBSE 2011, 2012)
                                                                                       Or
What is myopia ? State the two causes of myopia with a labelled ray diagram show
(i) the eye defect myopia,
(ii) correction of myopia using lens. [CBSE (All India) 2009, 2015]
Answer:
A human eye is myopic if it can see the near objects clearly but unable to see far off objects or distant objects clearly.
Correction of short sightedness or Myopia
The image of a distant object (i.e. at infinity) is formed in front of the retina of eye suffering from myopia as shown in figure 5(a). As the image of the object lying at infinity is not formed on the retina of the eye, so such object can not be seen clearly by the Myopic eye. The far point of such an eye is near to the eye as shown in figure 5(b).

This defect can be corrected by using a concave lens of suitable focal length (or power). So, a man suffering from this defect wears spectacles having concave lens of suitable focal length. The concave lens used diverges the rays of light entering the eye from infinity. Hence this lens makes the rays of light appear to come from the far point (O’) of the defective eye as shown in figure 5(c).
Causes of Wlyopia: This defect arises due to either by

1. the elongation of the eye ball or
2. the excessive curvature of the cornea.

Question 3.
What is long-sightedness ? List two causes for development of long-sightedness. Describe with a ray diagram, how this defect may be corrected using spectacles. [CBSE (All India) 2005]
                                                                          Or
What is hypermetropia ? State the two causes of hypermetropia. With the help of a ray diagram, show (i) the eye defect hypermetropia, (ii) correction of hypermetropia by using a lens. [CBSE (Delhi) 2009, 2015]
Answer:
A human eye which can see far off objects or distant objects clearly but can not see the near objects clearly is said to be suffered with a defect known as long sightedness or far sightedness or Hypermetropia.
Correction of long-sightedness (or Hypermetropia)
The image of a normal near point (which is 25 cm from the eye lens) is formed behind the retina of eye having long-sight defect as shown in figure 4(a). Hence, the image of the normal near point formed on the retina is blurred. The near point of such eye is little far from the near point of normal eye as shown in figure 4(b).

This defect can be corrected by using a convex lens of suitable focal length. So, a man suffering from this defect wears spectacles having convex lens of suitable focal length. The convex lens of spectacles reduces the divergence of rays of light entering the eye. Hence this lens makes the rays of light appear to come from the near point of the defective eye as shown in figure 4(c).
Causes of Hypermetropia: This defect arises due to either by

1. the increase in the focal length of eye lens or
2. the size of the eye ball becomes too small so that the light rays from the nearby points or objects are not brought to focus on the retina of the eye.

Question 4.
Describe with a neat diagram how near sightedness (Myopia) can be corrected by using appropriate lenses. [CBSE (Delhi) 2006]
Answer:
A human eye is myopic if it can see the near objects clearly but unable to see far off objects or distant objects clearly.
Correction of short sightedness or Myopia
The image of a distant object (i.e. at infinity) is formed in front of the retina of eye suffering from myopia as shown in figure 5(a). As the image of the object lying at infinity is not formed on the retina of the eye, so such object can not be seen clearly by the Myopic eye. The far point of such an eye is near to the eye as shown in figure 5(b).

This defect can be corrected by using a concave lens of suitable focal length (or power). So, a man suffering from this defect wears spectacles having concave lens of suitable focal length. The concave lens used diverges the rays of light entering the eye from infinity. Hence this lens makes the rays of light appear to come from the far point (O’) of the defective eye as shown in figure 5(c).
Causes of Wlyopia: This defect arises due to either by

1. the elongation of the eye ball or
2. the excessive curvature of the cornea.

Question 5.
Explain refraction of light through a glass prism using a labelled ray diagram and hence define the angle of deviation.
Answer:
Refraction of Light Through a Prism
Prism is a homogeneous transparent refracting medium bounded by at least two non-parallel surfaces inclined at some angle.
A commonly used prism is shown in figure 6.

The two non-parallel plane surfaces participating in the refraction of light are called refracting surfaces. The angle between two non-parallel refracting surfaces is called angle of prism or refracting angle. It is denoted by A.
Find Angle of deviation of a ray of light passing through the prism Procedure

1. Place a glass prism on a sheet of white paper.
2. Mark its boundary with H.B. pencil.
3. Now fix two pins at points B and C as shown in figure 7
   
4. Look through the refracting face ac and fix two pins at H and I such that the pins H and I and the images of pins B and C line in a straight line.
5. Now remove the prism and all pins.
6. Join the points B and C and extend this line so that it touches the refracting surface ab at point E.
7. Also join the points H and I and extend this line so that it touches the refracting surface ac at point G.
8. Also join points E and G.
9. Draw perpendiculars N₁N₁‘ and N₂N₂‘ on the refracting surface ab at point E and on the refracting surface ac at point G
10. ∠N₁EC = ∠i, angle of incident and the ray BCE is the incident ray.
11. ∠N₂GH = ∠e, angle of emergence and the ray GHI is the emergent ray.
12. Produce the emergent ray GHI backward so that it intersects the incident ray produced forward at point J.
13. ∠FJG = ∠D, angle of deviation of the incident ray of light passing through the prism.

Thus, angle of deviation of a ray of light is defined as the angle between the directions of incident ray of light and the emergent ray of light.

Hope given Previous Year Question Papers for CBSE Class 10 Science Chapter 11 Human Eye and Colourful World are helpful to complete your science homework.

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ML Aggarwal Class 7 Solutions Chapter 6 Ratio and Proportion Check Your Progress for ICSE Understanding Mathematics acts as the best resource during your learning and helps you score well in your exams.

ML Aggarwal Class 7 Solutions for ICSE Maths Chapter 6 Ratio and Proportion Check Your Progress

Question 1.
A rectangular park is 120 m long and 75 m wide. Find the ratio of:
(i) breadth to its length
(ii) length to its perimeter
Solution:

Question 2.
Divide the angles of a triangle in the ratio 2 : 3 : 4.
Solution:

Question 3.
Heights of Anshul, Ankita and Dhruv are 1.04 m, 1.30 m and 91 cm respectively. Divide 100 sweets among them in the ratio of their heights.
Solution:

Question 4.
The weights of Divya and Himanshu are in the ratio 5 : 7. If Himanshu weighs 28 kg, find the weight of Divya.
Solution:

Question 5.
Which ratio is smaller- 9 : 13 or 7 : 11 ?
Solution:

Question 6.
Find the fourth proportional to
(i) 4, 7, 20
(ii) 2\(\frac { 1 }{ 2 }\), 1\(\frac { 1 }{ 4 }\), 2.2
Solution:

Question 7.
A typist types 70 pages in 3 hours 30 minutes. How long will she take to type 300 pages?
Solution:

Question 8.
12 looms weave 210 m cloth per day. How many metres of cloth will 8 looms weave per day?
Solution:

Question 9.
A journey takes 4 hours 30 minutes at a speed of 60 km/h. How long will the same journey take at a speed of 15 m/sec?
Solution: