1) Explain resources on the earth
Ans: The natural resources of the earth are air, water, soil, minerals and living organisms. The outer crust of the earth is the lithosphere. The water on the earth is the hydrosphere. The layer of the air around the earth is the atmosphere. Living organisms are found where the atmosphere, hydrosphere and lithosphere interact and is the biosphere.
2. write a note on Air (Atmosphere)
Ans: Air is a mixture of gases like nitrogen, oxygen, carbon dioxide, water vapour and other gases.
Ø During respiration living organisms use oxygen to break down glucose and get energy for their activities. This results in the release of carbon dioxide. Burning of fuels also use oxygen and release carbon dioxide.
Ø During photosynthesis green plants convert carbon dioxide into glucose in the presence of sunlight. This results in the release of oxygen.
Ø These processes help to maintain the oxygen – carbon dioxide balance in nature.
3. Explain the role of atmosphere in climate control
Ø The atmosphere covers the earth like a blanket. Air is a bad conductor of heat. It prevents sudden increase in temperature during the day and also slows down the escape of heat during the night. So the atmosphere keeps the average temperature of the earth fairly steady during the day and throughout the year.
4. Write a note on the movement of air (Winds)
Ø When air gets heated, it rises up and produces low pressure and cool air moves in to take its place. The movement of air causes winds.
Ø During the day the land gets heated faster than the sea. So the hot air above the land rises up and cool air from the sea moves towards the land. During the night sea cools down slowly than the land. So the hot air above the sea rises up and cool air from the land moves towards the sea.
5. How does Rain occur?
Ø When water bodies are heated during the day, a large amount of water evaporates and rises up. Some water vapour also get into the atmosphere due to biological activities like transpiration. As the water vapour rises, it cools and condenses to form tiny droplets of water. This appears as clouds. When the tiny droplets of water join together to form bigger drops of water, they fall down as rain, snow or hail.
6. write a note on Water : A wonder liquid :-
Ø A very large area of the earth’s surface is covered with water. Water is also found inside the earth, in the atmosphere as water vapour. The water in seas and oceans is saline. Fresh water is found in rivers, lakes, ponds and as ice and snow at the poles and mountains in cold regions.
Ø Water is needed by living organisms because all life processes and cellular activities need water. So all organisms need water to survive.
Ø The amount of water and other factors like temperature and nature of soil decides the diversity of species and the number of individuals of each species in an area.
7. how does Water pollution get polluted?
Ø The increase in the content of harmful substances in water is called water pollution.
Ø Water pollution is caused by addition of harmful substances like fertilisers and pesticides from farms, sewage from towns, cities and factories, harmful chemicals from factories, disease causing microorganisms, changes in the amount of oxygen dissolved in water or changes in the temperature of water.
8. How is soil formed?
Ø Soil is formed by the breaking down of rocks on the surface of the earth by physical, chemical and biological processess.
Ø The sun heats the rocks during the day and the rocks expand and at night the rocks cool and contracts. This causes the rocks to crack and break into smaller pieces.
Ø Water enters the cracks in the rocks and when water freezes, it expands and causes the cracks in the rocks to widen and break into smaller pieces. The flowing water carries the rock pieces. These pieces rub against each other and become smaller and smaller particles.
Ø Strong winds also breaks rocks into smaller particles and carries it from one place to the other.
Ø The roots of large trees grow into the cracks in rocks and breaks it into smaller pieces. Lichens which grow on rocks produce some substance which cause the rock surface to powder and become soil.
9. Explain composition of soil :-
Ø Soil is a mixture of rock particles, decayed organisms called humus, living organisms, minerals, air and water. The amount of minerals, humus, air and water are the factors which decides the biodiversity in that area.
10. How does Soil get polluted ?
Ø The addition of harmful substances which affects the fertility of the soil and kills the diversity of organisms living in it is called soil pollution.
Ø Soil pollution is caused by the excessive use of fertilisers and pesticides. It kills the organisms like earthworms and bacteria which makes the soil rich in humus. The removal of useful components and addition of other harmful substances reduces the fertility of soil and causes soil pollution.
11. Explain Soil erosion and its prevention?
Ø The carrying away of soil from one place to the other by flowing water and wind is called soil pollution. Large scale deforestation also causes soil erosion.
Ø Soil erosion can reduced or prevented by vegetative cover on the ground, afforestation, construction of bunds, terraces, dams etc.
12. What is Biogeochemical cycles and name different biogeochemical cycles
Ø Biogeochemical cycles are the transfer of matter and energy between the biotic and abiotic components of the biosphere.
The common biogeochemical cycles are :-
i) Water cycle,
ii) Nitrogen cycle,
iii) Carbon cycle
iv) Oxygen cycle.
13. Write a note on Water cycle
Ø When water bodies are heated during the day, a large amount of water evaporates and rises up. Some water vapour also get into the atmosphere due to biological activities like transpiration and respiration. As the water vapour rises, it cools and condenses to form tiny droplets of water. This appears as clouds. When the tiny droplets of water join together to form bigger drops of water, they fall down as rain, snow or hail. Some of this water enters the ground and forms ground water. When water flows from the land to the seas it carries many nutrients and minerals which are used by marine organisms.
Draw cycle from text book
14. Explain about Nitrogen cycle
Ø The nitrogen in the atmosphere is fixed into nitrogen compounds in the soil by nitrogen fixing bacteria in the root nodules of leguminous plants and also during lightning. These nitrogen compounds are taken by plants and used to make proteins. When animals eat plants they also get proteins. When plants and animals die, bacteria convert the proteins into nitrogen compounds like nitrites and nitrates. Other bacteria convert these nitrogen compounds back into nitrogen in the atmosphere.
Ø Nitrogen is an essential component of biological molecules like proteins, nucleic acids and some vitamins.
Draw cycle from text book
15. Explain Carbon cycle
Ø Carbon in the form of carbon dioxide is used by plants to prepare glucose by the process of photosynthesis. The glucose is used to provide energy and to convert into other organic compounds When animals eat plants it enters the body of animals. During respiration energy and carbon dioxide are produced. The carbon dioxide goes back into the atmosphere. Another process which adds carbon dioxide back into the atmosphere is the combustion of fuels like coal and petroleum. The organic compound in plants and animals are also converted into carbonates, limestone, coal, petroleum, exoskeletons (shells) of some animals.
Ø Carbon is an essential component of biological molecules like carbohydrates, fats, proteins, vitamins, nucleic acids etc.
draw cycle from text book
16. Explain Oxygen cycle
Oxygen in the atmosphere is used for respiration, combustion and formation of oxide of elements. Oxygen is sent back into the atmosphere during photosynthesis.
Oxygen is an essential component of biological molecules like carbohydrates, fats, and proteins.
Draw cycle from text book
17. Explain the greenhouse effect
Ø Gases like carbon dioxide, methane, chlorofluro carbon(CFCs) traps the heat radiated by the earth and prevents the escape of heat from the earth. The increase in the presence of these gases in the atmosphere causes increase in the temperature of the atmosphere. This is called the greenhouse effect.
Ø Greenhouse effect can cause melting of polar ice, increase in sea levels, flooding of coastal areas and submerging of islands.
18. Explain Ozone layer
Ø Ozone molecule contains three atoms of oxygen (O3). It is present in the upper layers of the atmosphere. It is poisonous gas. It protects the earth from the harmful ultra-violet radiations from the sun which is harmful for living organisms.
Ø The ozone layer is being damaged by carbon compounds like chloro fluoro carbons (CFCs). To prevent the damage to the ozone layer, the use of (CFCs) is being reduced.
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