66 CBSE ClassIX Biology NaturalResources RN

7/21/2019 66 CBSE ClassIX Biology NaturalResources RN

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BIOLOGY NATURAL RESOURCES

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1. All life-forms on Earth require the Suns energy as well as the resources on Earth such as land, waterand air to survive.

2. Life is possible only in the biosphere, where the atmosphere, lithosphere and hydrosphere interact.

3. Biosphere comprises both biotic and abiotic factors, which interact with each other and maintain abalance.

4. Life on Earth is responsible for the present atmosphere on Earth, consisting of gases such as nitrogenoxygen, carbon dioxide and water vapour.

5. The atmosphere plays a significant role in climate control. It prevents undue fluctuations intemperature during the 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 Earths surface, air expands and rises over

the hotter regions and condenses and sinks over the cooler regions.ii. During the day, the air above the land gets heated faster than the air above the water, whereas

during the night, the air above the land cools faster than the air above the water.iii. This results in formation of regions of low and high pressure.iv. Air moves from a high-pressure region to a 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 rainformation.

8. The steps of rain formation are as follows: Suns heatEvaporation of water from water bodiesRising of hot air carrying water vapourExpansion and subsequent cooling of air Condensation of

water vapour as droplets on condensation nucleiIncrease in size of water dropletsFormation ofrain

9. The wind patterns in a particular region direct the rainfall patterns of that region.

10. Burning of fossil fuels releases harmful oxides of sulphur and nitrogen which give rise to acid rain.

11. Increased suspended particles in the atmosphere released because of burning fossil fuels causereduced visibility, smog (in cold weather) and health hazards.

12. Water exists in solid, liquid and gaseous forms. It occurs in atmosphere, on the surface of land and

underground.

13. Water is important to living organisms because

I. All cellular processes require an aqueous medium.II. Dissolved substances are needed for body reactions and for transportation

14. Osmoregulation is carried out by all organisms to sustain life.

15. There is a direct relationship between availability of water and species richness as well as the numberof members of each species present in a given region.


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16. Water pollution is caused by the addition of the following to water bodies:i. Fertilisers and pesticidesii. Sewageiii. Waste from factoriesiv. Hot water from factoriesv. Cold water from dams

17. Both addition of undesirable substances and removal of desirable substances from water bodiesconstitute water pollution.

18. Reducing the dissolved oxygen and nutrients from water bodies is harmful for aquatic organisms.

19. Aquatic organisms survive best in their optimum temperatures; hence, significant sudden changes inwater temperatures can disrupt their life processes and breeding activities.

20. Weathering of rocks due to physical, chemical and biological processes finally produces the fineparticles of soil over long periods of time.

21. Continuous, uneven expansion and contraction of different parts of the rocks during the day and nightleads to crack formation, followed by breakdown of large rock pieces into smaller ones.

22. Freezing of water in cracks of rocks causes widening of the cracks.

23. Continuous friction between various rock pieces carried by flowing water also results in soil formation.

24. Strong wind is another factor resulting in soil formation.

25. Soil formation is also carried out by living organisms. Materials released by lichens growing on therock surface powder down the surface forming soil. Further breakdown of rocks is caused by thegrowth of other small plants in such soil as well as the entry of tree roots into the cracks of rocks.

26. Soil is a mixture of rock particles, humus and microscopic organisms.

27. Humus aerates the soil and keeps it porous.

28. The nutrient and humus content of the topsoil influences the biodiversity of a region.

29. An important cause of soil pollution is the recent agricultural methods which destroy the soil structureby killing nutrient-recycling soil microorganisms and earthworms.

30. Trees and other plants prevent soil erosion and help in deep percolation of water. Hence,

deforestation greatly accelerates soil erosion.

31. The cyclic transformation of chemicals through interacting biological, geological and chemicalprocesses that causes transfer of energy and matter among the various components of the biosphereleading to a balance among them is called a biogeochemical cycle.

32. Biogeochemical cycles make possible the transfer of energy and matter among the variouscomponents of the biosphere, leading to a balance among them.


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33. The water cycle is the process in which water evaporates and falls on the land as rain and later flowsback into the sea via rivers.

34. In addition to evaporation of water from water bodies, water is added to the atmosphere through

transpiration and respiration carried out by living organisms.

35. Condensation of atmospheric water leads to rain and snow.

36. Underground water comes to the surface through springs, wells and tube wells.

37. Flowing water transports nutrients from one place to another and eventually to the sea.

38. Nitrogen is a vital element found in all living organisms.

39. Most life forms cannot use atmospheric oxygen directly, except a few nitrogen-fixing bacteria foundmainly in root nodules of leguminous plants.

40. Combination of lightning and rain also creates usable forms of nitrogen.

41. Plants utilise nitrates and nitrites to produce proteins, nucleic acids and vitamins, which are thenpassed on to consumers.

42. Certain soil bacteria convert nitrogen compounds of dead organisms to nitrites and nitrates.


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43. Denitrification, carried out by certain bacteria, releases nitrogen back to the atmosphere.

44. Carbon occurs in elemental form as well as in organic and inorganic compounds. The basic structureof all life molecules such as carbohydrates, proteins, fats, nucleic acids and vitamins is composed ofcarbon.

45. Carbon dioxide is used by green plants during photosynthesis as well as by marine animals duringshell formation.

46. Photosynthesis converts carbon dioxide to glucose, which is converted back to carbon dioxide throughrespiration.

47. Combustion of fuels also releases carbon dioxide to the atmosphere.


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48. Carbon dioxide is an important greenhouse gas that prevents the escape of heat from Earth andcauses global warming.

49. Oxygen exists on Earth in elemental form as well as in combined form.

50. The vital life molecules of proteins, lipids, carbohydrates and nucleic acids are composed of oxygen.

51. The process of respiration, combustion and formation of nitrogen oxides utilises atmospheric oxygen.

52. Photosynthesis returns oxygen back to the atmosphere.

53. Ozone is present in the upper atmospheric strata and contains three atoms of oxygen.

54. The ozone layer absorbs the Suns harmful ultraviolet radiations, thus preventing them from reachingthe Earths surface and damaging life.

55. Chlorofluorocarbons (CFCs) and other man-made compounds react with ozone molecules and causedepletion of the ozone layer.

56. The greenhouse effect is the process in which greenhouse gases, such as carbon dioxide, causethermal radiation emitted from the Earth's surface to be reflected back down, thereby causing anincrease in worldwide average temperature.

57. Global warming is an increase in the average temperature of the earth's atmosphere, brought about bythe enhanced greenhouse effect.

66 CBSE ClassIX Biology NaturalResources RN

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