On this page, you will find Natural Resources Class 9 Notes Science Chapter 14 Pdf free download. CBSE NCERT Class 9 Science Notes Chapter 11 Natural Resources will seemingly help them to revise the important concepts in less time.
CBSE Class 9 Science Chapter 14 Notes Natural Resources
Natural Resources Class 9 Notes Understanding the Lesson
1. Natural resource: Any substance or material derived from nature that humans can use for their benefit. The resources on the Earth are land, water and air.
2. The outer crust and the upper mantle of the Earth is called lithosphere.
3. All the water on, under and above the surface of the Earth comprises the hydrosphere.
4. The blanket of air that covers the whole of the Earth is called atmosphere.
5. The atmosphere, the hydrosphere and the lithosphere interact to constitute biosphere which is the life-supporting zone of the Earth i.e., living things are found where these three exist.
6. The two components of the biosphere are
- Biotic component: comprises of living things.
- Abiotic component: comprises of non-living things like air, water and soil.
7. Air is a mixture of gases like nitrogen, oxygen, carbon dioxide and water vapour.
8. Carbon dioxide constitutes up to 95-97% of the atmosphere on planets—Venus and Mars.
9. Carbon dioxide is produced by activities like:
- Respiration in eukaryotic cells and prokaryotic cells.
- Combustion (it includes burning of fuels to get energy and forest fires).
10. Carbon dioxide is ‘fixed’ in two ways:
- By green plants during photosynthesis to make glucose.
- Carbonates dissolved in sea water are used by many marine animals to make their shells.
11. Role of atmosphere:
- It keeps the average temperature of the Earth fairly constant.
- It prevents the sudden increase in temperature during the daylight hours.
- It slows down the escape of heat into outer space during night.
12. The temperature ranges from -190°C to 110°C in the moon as it does not have atmosphere.
13. Changes occur in the atmosphere due to:
- Heating of air
- The formation of water vapour.
14. Convection currents are set up in air when the atmosphere gets heated from below by the radiation that is reflected back by the land or water bodies.
15. During the day in the coastal regions, the air above the land gets heated faster and warm air being lighter rises up thereby creating a region of low pressure. The air over the sea then moves towards the area of low pressure. The movement of air from one region to the other creates winds. At night, water cools down slower than the land, so the air above water would be warmer than the air above the land. This causes air over the land to move towards the region of low pressure over water.
16. Two main factors which influence winds:
- the rotation of the Earth
- the presence of mountain ranges in the paths of wind
17. Heating of water bodies and the activities of living organisms result in evaporation of water and formation of water vapour.
18. As the air containing water vapour rises up, it expands and cools to condense in the form of tiny droplets. This condensation of water is facilitated if particles like dust and other suspended particles act as the ‘nucleus’ for these drops to form around. Once the water droplets are formed, they grow bigger by the ‘condensation’ of these water droplets. These drops grow big and heavy and then fall down in the form of rain.
19. If the temperature of air is low, then precipitation may occur in the form of snow, sleet or hail.
20. The prevailing wind patterns in an area decide the rainfall patterns there.
21. The rains in India are mostly brought by the southwest or north-east monsoons.
22. The burning of fossil fuels like coal and petroleum releases:
- Oxides of nitrogen and sulphur which dissolve in rain to give rise to acid rain.
- Suspended particles which are unburnt carbon particles or substances called hydrocarbons. In cold weather conditions, high levels of these pollutants cause visibility to be lowered when water condenses out of air. This phenomenon is known as smog.
23. Most of the water on the Earth’s surface is found in seas and oceans and is saline.
24. Fresh water is found frozen in the ice-caps at the two poles and on snow covered mountains.
25. The underground water and the water in rivers, lakes and ponds is also fresh.
26. Water is essential for the various metabolic and the biochemical processes taking place in a living organism.
27. Water pollution is caused due to:
- Addition of undesirable substances (like pesticides, fertilisers, disease causing organisms)
- removal of desirable substances (like dissolved oxygen)
- Change in temperature of water (e.g., addition of hot water released from industries into rivers or the water released from dams into rivers which would be colder than water on the surface).
28. The outermost layer of our Earth is called the crust and the minerals found in this layer supply a variety of nutrients to life-forms.
29. Soil is a mixture of minerals, organic matter, gases, liquids, and various organisms that together support life on Earth.
30. Soil is formed due to various physical, chemical and biological processes which result in breakdown of rocks into fine particles of soil over millions of years. The formation of soil occurs due to factors and processes like Sun, water, wind, living organisms and lichens.
31. Removal of useful components from the soil and addition of undesirable substances into it which adversely affect the fertility of the soil and kill the diversity of organisms that live in it, is called soil pollution.
32. Constant recycling of nutrients and materials occurs between the biotic and the abiotic components in an ecosystem. The pathway by which a chemical substance moves through biotic and abiotic components of the Earth is called biogeochemical cycle.
33. Nitrogen gas constitutes 78% of our atmosphere and is a part of many molecules like proteins, nucleic acids (DNA and RNA) and some vitamins which are essential for life.
34. Legumes (like pulses) have nitrogen-fixing bacteria in their root nodules which convert the nitrogen molecules into nitrites and nitrates.
35. The high temperatures and pressures created in the air during lightning convert nitrogen into oxides of nitrogen which dissolve in water to give nitric and nitrous acids. They can be utilised by various living organisms when they fall on land along with rain.
36. The phenomenon in which the incoming sunlight is allowed to pass through the atmosphere but heat radiated back from the planet’s surface is trapped by the gases like carbon dioxide, water vapour and methane present in the atmosphere is called as greenhouse effect.
37. Increase in percentage of the gases like carbon dioxide and methane prevents escape of heat from the Earth. Greenhouse effect is responsible for the increase in average temperature worldwide and is causing global wanning.
38. Ozone is a molecule containing three atoms of oxygen with a formula of 03 and contains three atoms of oxygen. It is a poisonous gas but does not harm us as it is present in the upper reaches of the atmosphere. It plays an important role as it absorbs harmful radiations from the Sun which can harm living organisms.
39. Ozone layer is getting depleted due to the use of CFCs. CFCs are carbon compounds having both fluorine and chlorine which are very stable and not degraded by any biological process. These react with the ozone molecules and result in its reduction.
40. An ozone hole caused due to the reduction of ozone molecules has been discovered above the Antarctica.
Class 9 Science Chapter 14 Notes Important Terms
Natural resource: Anything that comes from nature and can be used by humans for various purposes is called a natural resource.
Lithosphere: The outer crust and the upper mantle part of the Earth is called the lithosphere.
Hydrosphere: All the water on, under and above the surface of the earth comprises the hydrosphere.
Atmosphere: The blanket of air that covers the whole of the Earth is called atmosphere.
Biosphere: The region comprising of lithosphere, hydrosphere and the atmosphere which can sustain life or living organisms is called biosphere.
Components of biosphere: The two components of biosphere are biotic (living) component and abiotic (non living) component.
Wind: Moving air is called wind.
Air pollution: The addition of undesirable substances in air which adversely affect its physical, chemical or biological characteristics is called air pollution.
Pollutant: The undesirable substances added to air, water or land which pollutes them is called pollutant.
Biodiversity: The variety of life forms present on Earth constitutes its biodiversity.
Water pollution: The addition of undesirable substances in water which adversely affect its physical, chemical or biological characteristics is called water pollution.
Biogeochemical cycle: The pathway by which a chemical substance moves through biotic and abiotic components of the Earth is called biogeochemical cycle.
Greenhouse effect: The phenomenon in which the incoming sunlight is allowed to pass through the atmosphere but heat radiated back from the planet’s surface is trapped by the gases like carbon dioxide, water vapour and methane present in the atmosphere is called greenhouse effect.
Ozone: The triatomic molecule of oxygen with formula 03 which prevents the harmful UV radiation of the Sun from reaching the earth’s surface.