Natural resources
13) Biogeochemical cycles make possible the transfer of energy and matter amid the various components of the biosphere, leading to a balance between them.
14) In addition to evaporation of water from water bodies, water is also added to atmosphere through transpiration and respiration carried out by living organisms.
15) Condensation of atmospheric water leads to rain and snow.
16) Underground water comes to surface through springs, wells and tube wells.
17) Flowing water transport nutrients from one place to another and eventually to the sea.
18) Nitrogen is a vital element found in all living organisms.
19) Most life forms cannot use atmospheric oxygen directly, except a few nitrogen fixing bacteria found mainly in root nodules of leguminous plants.
20) Combination of lightning and rain also creates usable forms of nitrogen.
21) Plants utilise nitrates and nitrites to produce proteins, nucleic acids and vitamins, which are then passed on to the consumers.
22) Certain soil bacteria convert the nitrogen compounds of dead organisms into nitrites and nitrates.
23) Denitrification, carried out by certain bacteria, releases nitrogen back to atmosphere.
24) Carbon occurs in elemental form as well as in organic and inorganic compounds. The basic structure of all life molecules like carbohydrates, proteins, fats, nucleic acids and vitamins is composed of carbon.
25) Carbon dioxide is fixed by green plants during photosynthesis as well as by marine animals during shell formation.
26) Photosynthesis converts carbon dioxide to glucose, which is converted back to carbon dioxide through respiration.
27) Combustion of fuels also releases carbon dioxide to atmosphere.
28) Carbon dioxide is an important green house gas that prevents the escape of heat from Earth and causes global warming.
29) Oxygen exists on Earth in elemental form as well as in combined form.
30) Vital life molecules like proteins, lipids, carbohydrates and nucleic acids are also composed of oxygen.
31) The process of respiration, combustion and formation of nitrogen oxides utilizes atmospheric oxygen.
32) Photosynthesis returns oxygen back to atmosphere.
33) Ozone is present in the upper atmospheric strata and contains 3 atoms of oxygen.
34) The ozone layer absorbs the Sun’s harmful ultraviolet radiations, thus preventing them from reaching the Earth’s surface and damaging life.
35) CFCs and other man-made compounds react with the ozone molecules and causes ozone layer depletion.
36) We should work towards preventing ozone layer depletion.
37) Our natural resources should be used in a sustainable manner so as to prevent their depletion and pollution.
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NCERT 9 Science