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Question 1.
Why is the atmosphere essential for life ? (CCE 2012)
Answer:
Question 2.
Why is water essential for life ?
Answer:
Organisms need water due to following reasons :
Question 3.
How are living organisms dependent on soil ? Are organisms that live in water totally independent of soil as a resource ? ‘
Answer:
All terrestrial organisms depend upon plants for their food and its contained energy. Plants are dependent on soil for anchorage, absorption of water and nutrients. Without them plants cannot manufacture food. So, all living terrestrial organisms depend upon soil.
Aquatic organisms are apparently not connected with soil. However, aquatic autotrophs require inorganic nutrients for manufacture of food. Nutrients reach water bodies only when rain water passes over and inside the soil. Therefore, aquatic organisms are not totally independent of soil as a resource.
Question 4.
You have seen weather reports on television and in newspapers. How do you think we are able to predict the weather ?
Answer:
Weather reports depict areas of low and high pressure, prevailing direction of wind, dryness or wetness of air masses, clouds and their progress, presence and progress of any cyclone, etc. Predictions are then made whether a particular area will or will not receive rain, have calm weather or high speed wind and dust storm.
Question 5.
We know that many human activities lead to increasing levels of pollution of air, water bodies and soil. Do you think that isolating these activities to specific and limited areas would help in reducing pollution ?
Answer:
Restricting pollution related activities to specific and limited areas will not reduce pollution in those areas. The same may rather increase. There are two benefits of such a practice
Question 6.
Write a note on how forests influence the quality of our air, soil and water resources. (CCE 2012)
Answer:
Air Resources:
Soil Resources: Roots of the forest plants hold the soil firmly. Forest cover protects the soil from direct pounding by rain drops. Forest soil is also sufficiently porous to reduce run off and increase infiltration of rain water. All the three factors prevent soil erosion.
Water Resources:
Question 1.
How is our atmosphere different from the atmosphere of Venus and Mars ?
Answer:
Atmosphere over Earth | Atmosphere over Venus and Mars | ||
1. | Nitrogen and Oxygen. | It contains nitrogen and oxygen. | The two are absent |
2. | Carbon Dioxide. | Carbon dioxide content is little (0-03%). | Carbon dioxide is the major component of atmosphere forming 95-97%. |
3. | Water Vapours. | The atmosphere contains water vapours which form a component of water cycle. | The atmosphere does not contain water vapours. Living beings, being absent, have no role in |
4. | living Beings. | Composition of atmosphere is maintained by living beings. | determining composition of atmosphere. |
Question 2.
How does atmosphere act as a blanket ?
Answer:
Atmosphere or air is a bad conductor of heat. It, therefore, functions as a blanket.
Question 3.
What causes winds ?
Answer:
Winds are basically caused by heating of air in certain parts. The hot air rises upwards. This creates an area of low pressure. Cooler air from adjacent higher pressure areas passes into this area. This creates wind. The factors which control movement of winds in different directions in different parts of the earth are
Question 4.
How are clouds formed ? (CCE 2011)
Answer:
Clouds are wet air masses that float in the direction of prevailing wind. They develop when water vapours are formed in large number. There is evaporation from the surface of water bodies and wet areas due to their heating during the daytime. Plants also give out water vapours in transpiration while animals do so in exhaled air and perspiration. Air also heats up during daytime. The hot air along with water vapour rises up. At a height, air expands and becomes cool. Cooling causes the water vapours to condense. Suspended particles of dust and other materials function as nuclei around which water vapours condense. When a large wet air mass collects, cloud is formed.
Question 5.
Answer:
List any three human activities that you think would lead to air pollution.
Question 6.
Why do organisms need water ? (CCE 2011)
Answer:
Organisms need water due to following reasons :
Question 7.
What is the major source of fresh water in the city/town/village where you live ?
Answer:
Ground water which is pumped out by tube wells (In some it is local reservoir, canal or river.
Question 8.
Do you know of any activity which may be polluting this water source ?
Answer:
Dumping of industrial wastes from where pollutants seep into soil to reach ground water (sewage and industrial effluents in case of canal or river water).
Question 9.
How is soil formed ? What is the function of humps in soil ? (CCE 2011, 2012)
Answer:
Soil is formed through two processes of weathering and humification.
Weathering
It is pulverisation of rocks or breaking of rocks into fine particles. There are three types of weathering — physical (atmospheric changes and mechanical forces), chemical and biological. Sun, water, wind and living organisms perform them.
Humification
Partially decomposed organic matter or humus mixes with weathered rock particles to form soil. Humus helps in formation of soil crumbs which are essential for maintaining proper hydration and aeration of soil.
Question 10.
What are the methods of preventing or reducing soil erosion ?
Answer:
Soil Erosion: It is removal of top soil by agency of wind or water. Wind and water are also the agencies which cause weathering of rocks and carrying the fine particles to other places for the formation of soil. Removal of top soil by water or wind leaves the underneath subsoil and rocky base exposed. Very little plant growth occurs there.
Factors Promoting Soil Erosion
Question 11.
What are two different states in which water is found during the water cycle ?
Answer:
Liquid and vapour, occasionally solid (snow) as well.
Question 12.
Name two biologically important compounds that contain both oxygen and nitrogen. . (CCE 2014)
Answer:
Proteins and nucleic acids.
Question 13.
List any three human activities which would lead to an increase in the carbon dioxide content of air.
Answer:
Question 14.
What is green house effect ? (CCE 2011, 2012, 2013)
Answer:
Green house effect is keeping an area warm by allowing the solar radiations to pass in but preventing long waves to escape due to presence of radiatively active gases and glass panes.
Question 15.
What are the two forms of oxygen found in the atmosphere ? (CCE 2011, 2014)
Answer: