Natural resources
1) All life-forms on Earth require Sun’s energy as well as the resources on Earth like land, water and air to survive.
2) Life is possible only in the biosphere, where the atmosphere, lithosphere and hydrosphere interact.
3) Biosphere comprises of biotic and abiotic factors, which interact with each other and maintains a balance.
4) Life on Earth is responsible for the present atmosphere of Earth, consisting of gases like nitrogen, oxygen, carbon dioxide and water vapour.
5) Atmosphere plays a significant role in climate control. It prevents undue fluctuations in temperature during day and night as well as throughout the year.
6) Formation of winds occurs as follows:
i) As the Sun unevenly heats the various regions on the Earth’s surface, air expands and rises over the hotter regions; and condenses and sinks over the cooler regions.
ii) During daytime, air above land gets heated faster than air above water; whereas during night, air above land cools faster than air above water.
iii) This results in formation of regions of low and high pressure.
iv) Air moves from the high pressure region to the low pressure region to balance the differences in pressure, thereby resulting in wind formation.
7) Evaporation of water from water bodies followed by condensation of the vapours results in rain formation, the steps of which are as follows: Sun’s heat → Evaporation of water from water bodies → Rising of hot air carrying water vapour → Expansion and subsequent cooling of air →
Condensation of water vapour as droplets on condensation nuclei → Increase in size of water droplets → Formation of rain
8) The wind patterns in a particular region direct the rainfall patterns of that region.
9) Burning of fossil fuels releases harmful oxides of sulphur and nitrogen, which gives rise to acid rain.
10) Increased suspended particles in atmosphere released due to fossil fuel burning causes reduced visibility, smog (in cold weather) and health hazards.
11) Water exists in solid, liquid and gaseous forms. It occurs in atmosphere, on land surface as well as underground.
12) Water is important to living organisms because:
i) All cellular processes require an aqueous medium.
ii) Dissolved substances are needed for body reactions as well as for transportation.
13) Osmoregulation is carried out by all organisms to sustain life.
14) There is direct relationship between availability of water and the species richness as well as number of members of each species present in a given region.
15) Water pollution is caused by addition of following to water bodies:
i) Fertilizers and pesticides
ii) Sewage
iii) Waste from factories
iv) Heated water from factories
v) Cold water from dams
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NCERT 9 Science