NCERT Exemplar Solutions for Class 10 Science Chapter 15 Our Environment

These Solutions are part of NCERT Exemplar Solutions for Class 10 Science. Here we have given NCERT Exemplar Solutions for Class 10 Science Chapter 15 Our Environment

NCERT Exemplar Solutions for Class 10 Science Chapter 15 Short Answer Questions

Question 1.
Why is improper disposal of wastes a curse to environment ?
An improper disposal of wastes means addition of pollutants into environment —air, water, soil. They will harm living beings, human assets and human beings. For example, passage of sewage into water body will cause eutrophication, stink, development of sludge, killing of animals and source of water borne pathogens.

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Question 2.
Write the common food chain of a pond ecosystem.
NCERT Exemplar Solutions for Class 10 Science Chapter 15 Our Environment image - 1
Question 3.
What are the advantages of cloth bags over plastic bags during shopping ?
Advantages of Cloth Bags

  1. Cloth bags are stronger and more durable as compared to plastic bags.
  2. They are washable.
  3. They are reused time and again.
  4. Cloth bags do not pollute environment.
  5. They are made of biodegradable material which can also be recycled.

Question 4.
Why are crop fields known as artificial ecosystems ?
Crop fields are known as artificial ecosystems because they are raised, maintained, nourished and reaped by human beings.

Question 5.
Differentiate between biodegradable and non-biodegradable substances. Give examples.

Biodegradable Wastes

Non-biodegradable Wastes

1. Origin. They are biological in origin. They are commonly man-made.
2. Degradability. The wastes are degraded by microorganisms. They are not degraded by microorganisms.
3. Accumulation. They do not accumulate in nature. They pile up and accumulate in nature.
4. Biomagnification. The biodegradable wastes do not show biomagnification. The soluble non-degradable wastes enter food chains and undergo biomagnification.
5. Resource. The wastes can be converted into resource. Some wastes can be recycled.
Examples. Garbage, livestock wastes, sewage. Examples. Plastic, polythene, glass, nickel, cadmium, several pesticides.

Question 6.
Suggest one word for each of the following statements/definitions.
(a) The physical and biological world where we live in.
(b) Each level of food chain where transfer of energy takes place.
(c) The physical factors like temperature, rainfall, wind and soil of an ecosystem.
(d) Organisms which depend on the producers either directly or indirectly for food.
(a) Biosphere (also environment)
(b) Trophic level.
(c) Abiotic factors.
(d) Consumers (also heterotrophs)

Question 7.
Explain the role of decomposers in the environment. (CCE 2011)
Decomposers are saprophytes which feed on organic remains by a process of external digestion and absorption of solubilised materials, e.g., many bacteria, fungi. In the process they perform the following functions :

  1. Cleansing the earth of organic remains and continuously creating space for newer generations of organisms.
  2. Release of minerals from organic remains. The phenomenon is called mineralisation. The released minerals become available to plants for utilization in synthesis of new organic matter. Decomposers, therefore, take part in biogeochemical recycling.

Question 8.
Select the mismatched pair in the following and correct it.
(a) Biomagnification: Accumulation of chemicals at the successive trophic levels of a food chain.
(b) Ecosystem: Biotic component of environment.
(c) Aquarium: A man-made ecosystem.
(d) Parasites: Organisms which obtain food from other living organisms.
(b) Ecosystem: It is an ecological system consisting of a distinct biotic community and the physical environment (consisting of a number of abiotic factors) both interacting and exchanging materials between them.

Question 9.
We do not clean ponds or lakes but an aquarium needs to be cleaned. Why ?
An aquarium is an artificial system which is also incomplete due to absence of producers, food chains and decomposers. There is no recycling and self cleaning. However, a pond or a lake is a self sustained, natural and complete ecosystem where there is perfect recycling of nutrients.

NCERT Exemplar Solutions for Class 10 Science Chapter 15 Long Answer Questions

Question 10.
Indicate the flow of energy in an ecosystem. Why is it undirectional ? Justify. (CCE 2014)
An ecosystem does not have its own source of energy. It receives the same from sun. Green plants or producers trap the solar energy and change it into chemical form during synthesis of food. Herbivores obtain energy from the food they take. A lot of energy dissipates during transfer and utilization of food energy by herbivores (10% law). From herbivores the food energy passes to primary carnivores. However, only about 10% of herbivore energy is passed into body mass of primary carnivores.
The rest is dissipated. From primary carnivores the energy passes into secondary carnivores (10%), etc. It is ultimately lost as heat.
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Since energy available decreases at every tophic level, very little of it is available at higher trophic levels. There is dissipation of energy at every step of its transfer and transformation. Hence it cannot flow in the reverse direction i.e., energy flow is unidirectional from sun to plants, plants to animals, animals to animals, organic remains to decomposers and dissipation as heat.

Question 11.
What are decomposers ? What will be the consequences of their absence in an ecosystem ?
Definition: Decomposers or microconsumers are saprophytes which obtain their nourishment from organic remains by secreting digestive enzymes over the latter and absorbing the solubilised substances.
Absence of Decomposers:

  1. Organic remains will pile up leaving no space for new living beings,
  2. Biogeochemical cycling will stop so that raw materials will not be available to plants for manufacture of more food,
  3. In the absence of food, all living beings will die of starvation.

Question 12.
Suggest any four activities in daily life which are ecofriendly.

  1. Use of cloth bags instead of polythene or plastic bags.
  2. Separation of biodegradable and non-biodegradable in green and blue coloured bins.
  3. Use of compact fluorescent lamps instead of incandescent lamps.
  4. Harvesting of rain water and preventing wastage of resources.

Question 13.
Give two differences between food chain and food web.

Food Chain

Food Web

1. Units. It consists of a single unit of food relations. It is a complex formed by several units of food relations.
2. Sequence. It is a straight sequence of organisms. It is a network of many linkages among the connected food chains.
3. Populations. It has a maximum of 4-6 populations of different species. A food web consists of numerous populations of different species.
4. Food. Only one type of organism is used as food by a particular type of organism. An organism can use two to several types of organisms as food.
5. Disturbance. A disturbance in food chain is difficult to overcome. A disturbance is overcome after some time.
6. Endangered Species. It does not help in restoring population of endangered species. Rather it may decline further. A food web helps in increasing population of endangered species.

Question 14.
Name the wastes which are generated in your house daily. What measures would you take for their disposal ?
Wastes :

  1. Vegetable and fruit peels and rind, stale food, food leftovers, used tea leaves.
  2. Milk pouches, polythene bags, empty cartons.
  3. Waste paper (newspaper, bags, envelopes), packing paper, empty bottles, torn cloth pieces, etc.
  4. Dust and other sweepings.

Disposal :

  1. Separation into biodegradable and non-biodegradable, recyclable and non-recyclable wastes.
  2. Recyclable wastes (waste paper, cloth, polythene or plastic bags, cartons, bottles, cans, etc.) can be given to rag pickers for recycling.
  3. Preparation of compost or vetmicompost from kitchen wastes for home garden (kitchen garden).
  4. In the absence of kitchen garden, the household garbage and other wastes can be given to waste collectors for disposal.

Question 15.
Suggest suitable mechanisms for waste management in fertilizer industries.
Fertilizer industries produce mainly two types of wastes (a) Gaseous (b) Effluents. Additionally they may release heat and fuel waste if coal is being used as a source of energy.

  1. Gaseous Wastes: They are passed through wet scrubbers to dissolve the pollutant gases.
  2. Effluents: The effluents of the industry are tested for chemicals present in them. The same can be retrieved and made available to the market. Hot effluents are cooled. Acidic or alkaline nature can be corrected. Heavy metals and toxins can be separated. Only treated and harmless effluents are allowed to be discharged into surrounding environment.

Question 16.
What are the by products of fertilizer industries ? How do they affect the environment.
The most common by product of fertilizer industries are axides of nitrogen and sulphur. They pass into atmosphere and spread to all nearby places. The gases have a corrosive effect on several items besides being harmful to living beings. They also give rise to acid rain. Acid rain is highly destructive to forests, crops and aquatic biota.

Question 17.
Explain some harmful effects of agricultural practices on the environment.

  1. Soil: Fertilizer added to soil not only changes the chemistry of the soil but also kills many useful microbes.
  2. Ground Water: A part of fertilizer always leaches down into soil and reaches ground water. It raises the salt content of ground water.
  3. Eutrophication: Run-off from fields sprayed with fertilizer reaches water bodies. It results in their eutrophication.
  4. Pesticides: Pesticides sprayed over crops reach water bodies killing the biota. Persistent pesticides undergo biomagnification and prove highly harmful to higher organisms.
  5. Ground Water: Continued use of ground water in agriculture has resulted in lowering of water table at most of the places.
  6. Irrigation: It causes water-logging and salination of soils.
  7. Genetic Erosion: Use of only selected high yielding varieties has resulted in genetic erosion of the crop plants.
  8. Damage to Nature: Natural ecosystems and habitats have been damaged during clearing land for agriculture.

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