This is due to the fact that plants have the ability to use atmospheric carbon-di-oxide and convert it into organic compounds with the help of a process called "photosynthesis". Now, these organic forms of carbon i.e. sugars are stored by plants that are then consumed by animals. As animals die, their bodies are decomposed by the scavengers, and the organic carbon returns to the environment in inorganic form. Inorganic carbonates cannot be used by plants and thus can't be processed. Decomposers cannot feed on the combined form of CO₂ present in the atmosphere

This is because in space there are no gases to trap heat or to maintain a particular temperature by stopping the harmful radiations of the sun. So if no atmosphere would have been there on earth, the region, where sunlight was going to fall, would have been heated to more than 100 degrees Celsius while the region away from the sun would have cooled down to -90 degrees Celsius.

This is because humus is nothing but the topmost fertile layer. This layer is fertile because it has all the nutrients required for the growth of plants, also microorganisms are also present in this layer because it is airier as compared to the soil layers below. Since it is the fertile layer, plants are also found in it and the dead decay of plants is received by the top layer only leading to the formation of more humus.

The earth’s natural resources are water, soil, minerals, fuels, plants, and animals.

Answer:–

Oil, coal, natural gas, metals, stone and sand are natural resources. Other natural resources are air, sunlight, soil and water. Animals, birds, fish and plants are natural resources as well. Natural resources are used to make food, fuel and raw materials for the production of goods.

Since we know the soil is formed by a process called "weathering of rocks", I.e. breakdown of rocks occurs and the soil is formed. So the minerals present in the rocks would also be present in the soil formed from it. While other factors like bacteria, plants, and bacteria help in soil formation by helping in breaking down the rocks.

Total earth surface underwater is around 75% which includes all our water bodies I.e oceans, rivers, ponds, lakes, etc. Out of this 75%, 95% of the earth's total water is present in oceans and only 1% is potable water/freshwater.

Option : (c) 71%

The replenishment of forest is necessary because of the following reasons. 

1. It is used to conserve soil. 

2. It provides shelter to wild animals. 

3. It reduces atmospheric pollution. 

4. It controls flood and increases frequency of rainfall. 

1. India has total geographical area of 828 million sq. km. (3280 lakh hectares). The land use data is available for about 93% of the total area. It shows that 151 million hectares (47%) is net sown area. Thus India has a very high percentage (47%) of total area under cultivation. No other big country has such a large area under cultivation.
2. Another satisfying feature is that only 8% of land is fallow which is not cultivated so as to restore the fertility of the land. It is notable that fallow land has risen to 8% from earlier figure of 5%. It reflects that care for land resources has become essential.
3. The area under pastures is also small (4%).
4. The area under cultivable waste is 5%. This wasteland can be brought under cultivation to increase productivity.
5. The forest cover is low, only 22%. It is desirable to have about one third of the total land area under forests to maintain a healthy environment.

1. Motivate the people to conserve water.

2. I will educate the people to avoid wastage of water whenever possible. 

3. Construction of recharge pits in the house, school and in the open areas to increase the underground water level. 

4. Planting trees wherever possible in the village particularly in the vacant lands. 

5. Educate the farmers about the micro irrigation system like drip irrigation, sprin¬klers, etc. 

6. Encourage the farmers to form groups to share available water among themselves. 

7. Construction of percolation tanks in the low lying areas of the village.

Measures to be taken to conserve oil are: 

1. Walk, ride a bike, carpool and use public transportation whenever possible. 

2. Prefer public transport system like bus or train instead of travelling in personal vehicles. 

3. Choose materials other than plastic which uses crude oil for household items. 

4. Use cloth or paper bags instead of plastic bags when shopping. 

5. Use organic fertilizers for agriculture and gardening because fossil fuels are used in making chemical fertilizers. 

6. Produce renewable biofuels to power cars and trucks. 

7. Vehicle owners should keep their vehicles serviced i.e., correct amount of air in fires, oil change, spark plug/fuel injector checks, often-at least quarterly. 

8. Drive in the correct gear. Incorrect gear shifting can lead to as much as 20% increase in fuel consumption. 

9. Consider a hybrid vehicle or an electric vehicle.

If we do not conserve oil, we never get oil after 46-47 years. So all the industries that depend on the oil for energy will break down. Facilities linked with oil will be hampered. So the future generations will suffer.

Forests are important because, 

1. They are rich habitat for plants and animals.

2. They serve as a lung for the world. 

3. They purify air, decrease carbon dioxide, global warming and green house effect. 

4. Thus provide various valuable things such as wood, medicines etc. 

5. They are providing raw materials for several industries. 

6. They maintain ecological balance in nature. 

7. They preserve the soil fertility. 

8. They cause rains.

The gardener removes all the species of plants that grow in the lawn from time to time. Farmer does the same thing on his farm. But the variation is all the plants are removed from lawn just for pleasant look whereas farmer remove only weed plants that compete with the crop plants for space, nutrients, water and sunlight. This is to increase the productivity of crop plants.

(1) The birds are flying in the sky.

(2) The cow is grazing in the pasture (field).

(3) The trees are seen along the river bank.

(4) The river flows from the mountains towards the plains.

(5) The aeroplane is in the sky above the clouds.

(6) Fishes are seen swimming in the river water.

(7) Sail boat is floating on the water.

We use coal, mineral oil and natural gas as fuels.

Correct answer is (d) Coal

Carbon dioxide and Carbon monoxide.

All the above mentioned cycle can be grouped or explained as energy cycle on this earth. In fact sun is the main source of energy for every activity on earth. This energy facilitates the everlasting cycle of all resources in the biosphere. This system ensures that whatever we take from earth and its atmosphere we return it in some way or other. A living organism is made of Carbon, Oxygen, Nitrogen and other elements. All living organisms need regular dose of these elements to continue life. During lifetime all these things are returned to the atmosphere in some way. For example we return oxygen in the form of carbon dioxide and return water in the form of sweat or urine. 

Ultimately when a living being dies, then the body gets decomposed by decomposers, like bacteria. These decompose the body into basic elements out of which it was originally made. That is how the everlasting cycle of life goes on.

RAIN 

• Rain is formed by evaporation and condensation of water through water cycle in which distribution of water takes place. Rain is very important because it carries out all the agriculture processes in the plants. 

• So we should conserve rain by contracting dams, pools etc.

The following steps may help in conservation and reclamation of degraded land:

1. Afforestation and control on overgrazing.
2. Plantation of land reclamation of plants.
3. Regulated use of chemical pesticides and fertilisers.
4. Proper discharge of sewage industrial effluents.
5. Maintain proper mining processes and technique.

Oxygen from the atmosphere is used up in three processes, namely combustion, respiration and in the formation of oxides of nitrogen. Oxygen is returned to the atmosphere in only one major process that is photosynthesis.

Acid Rain 

• When fossil fuels are burnt, gases like sulphur dioxide and nitrogen dioxide (NO₂) are released.

• These gases are dissolving in water form nitric acid and sulphuric acid. 

Nitric acid and Sulphuric acid are present in acid rain.

Water Pollution 

When water becomes unfit for drinking and other uses, then water is said to be polluted. 

Causes of Water Pollution 

• Dumping of wastes from the industries into water bodies.

• Washing of clothes near water bodies. 

• Spraying chemical in water field. 

• Dumping household wastes into the water bodies.

Green House Effect 

• Carbon dioxide keeps the earth warm much like glass which keeps the green house warm. 

• Increase in carbon dioxide (CO₂) : 

(i) intensifies green house effect. 

(ii) leads to global warming. 

(iii) increase in average temperature of earth. 

(iv) may lead to melting of polar caps.  

(v) sub-merging number of coastal cities.

Some gases prevent the escape of heat from the earth. An increase in the percentage of such gases in the atmosphere would cause the average temperatures to increase worldwide and this is called the green house effect. CO₂ is one of the green house gases. An increase in the CO₂ content in the atmosphere would cause more heat to be retained by the atmosphere and lead to global warming.

The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms. This transformation can be carried out through both biological and physical processes. Important processes in the nitrogen cycle include fixation, ammonification, nitrification, and denitrification. Nitrogen makes up 78 percent of the earth’s atmosphere. The percentage of nitrogen in the atmosphere is maintained by nitrogen cycle.

Plants and animals cannot utilize atmospheric nitrogen readily. It has to be fixed by some organisms called as nitrogen fixers. Nitrogen-fixing bacteria like Rhizobium live in symbiotic association in the root nodules of certain leguminous plants. These bacteria convert atmospheric nitrogen into ammonia, which is utilized readily by plants. Nitrogen-fixing bacteria along with free living bacteria in the soil achieve 90 percent of nitrogen fixation. During lightening, the high temperatures and pressures created in the air convert nitrogen into oxides of nitrogen. These oxides dissolve in water to give nitric and nitrous acids and fall on land along with rain. Plants convert these nitrates and nitrites into amino acids. Ammonification is the process by which soil bacteria decompose dead organic matter and release ammonia into the soil. Nitrification is the process by which ammonia is converted into nitrites and nitrates. Denitrification is the process by which nitrates are converted into atmospheric nitrogen.

Carbon occurs in the elemental form as diamonds and graphite. The carbon cycle starts in plants. Plants use carbon dioxide in the atmosphere to synthesize glucose in the presence of sunlight by the process of photosynthesis. Living things break these glucose molecules to produce energy and release carbon dioxide through respiration. Burning of fuels for various needs like heating, cooking, transportation and industrial processes adds carbon dioxide to the atmosphere.

The wind we feel is nothing but the flowing air due to a very simple but important phenomenon called “convection currents”. When the air above the land gets heated during the daytime it becomes light in weight and starts moving up and an area of low pressure is created. 

We know that air moves from an area of high pressure to an area of low pressure, so the air from over the sea which is at high pressure moves towards the land, while at night the opposite occurs. 

So, during day air flows from "sea to land" while at night air flows from "land to sea".

The Carbon Cycle starts in plants as : 

Step I. Plants use CO₂ in the atmosphere, convert it into glucose in the presence of sunlight by the process of photosynthesis. Plants and animals break these carbohydrates for energy and release CO2 through respiration. 

Step II. When the plants and animals die, fungi and bacteria decompose the dead remains. This releases the carbon in the remains as carbon dioxide. 

Step III. Some of the dead plants and animals which get buried under the earth under certain temperature and pressure get transformed into fossil fuels like coal and petroleum. 

On burning these fuels, CO₂ is released into the atmosphere.

Carbon dioxide and water vapour are the two forms of oxygen found in the atmosphere.

The physical and human factors control the utilization of land. These include :

1. relief of features,
2. climatic conditions,
3. soils,
4. density of population,
5. technical level of the people,
6. land tenure,
7. duration of the occupation of the area etc.

Yes, I support this statement for the following reasons. 

1. Natural resources are our natural wealth which is very essential for our well-being and economic growth. 

2. The growth and development of any nation depend on its natural resources and their proper utilisation. 

3. We are enjoying the fruits of these resources which is provided by our nation to us. 

4. In return, it is our responsibility to safeguard our nation’s wealth. 

5. For this it is very essential to utilise these natural resources in such a way that they will remain in our nation and available for the future generations. 

6. If we don’t utilize them in proper way there will be crisis for these resources and we have to depend on other nations for it.

7. Such a situation will damage our economy and life standard, for which we are the responsible persons. 

8. So, proper utilisation of natural resources is surely the way to show gratitude to our nation.

All organisms require water for their survival. All cellular processes take place in a water medium. All the reactions that take place within our body and within the cells occur between substances that are dissolved in water. Substances are also transported from one part of the body to the other in a dissolved form. In this way water is essential to us.

True 

Greenhouse gases are those which have the ability to trap heat, carbon dioxide has the ability to trap heat and that is why is kept in the category of greenhouse gases.

The air we inhale or live in contains 21% oxygen. If this percentage is increased it could lead to the formation of oxygen free radicals which are a highly reactive form of oxygen. Inside a living system, these free radicals can lead to membrane disintegration, protein breakdown, the slower exchange rate of gases, chest pain, and many more lethal issues. In bacteria nitrogen fixation occurs anaerobically and elemental oxygen can be poisonous for them.

Firstly, nitrogen is required by plants for their growth and preparation of food and we derive products from them, so it becomes important for us. Another factor is, most of our metabolic and biological compounds like DNA, RNA, and proteins contain nitrogen hence, it becomes an essential part of our life. Also, some vitamins, alkaloids, and urea contain nitrogen.

All cellular processes take place in a water medium. All the reactions that take place in a water medium. All the reactions that take place within our body and within the cells occur between substances that are dissolved in water.

Substances are also transported from one part of the body to the other in a dissolved form. Hence organisms need to maintain the level of water within their bodies in order to stay alive. Hence organisms need water.

The whole process in which water evaporates and falls on the land as rain and later flows back into the sea via rivers is known as the water cycle. Water is capable of dissolving a large number of substances. As water flows through or over rocks containing soluble minerals some of them get dissolved in the water. Thus rivers carry many nutrients from the land to the sea, and these are used by the marine organisms.

Since ground water resources are getting depleted at a fast pace we have to construct percolation tanks to collect run off water. Water shed management projects should be adopted to renew the ground water levels.

Any biogeochemical cycle has certain basic components, like producers, decomposers, etc. 

Producers are required because they convert simple forms of molecules to complex forms while decomposers decompose these complex molecules into simpler ones again. In nature, molecules exist in a simpler form and the complex form is unstable. Hence for this process, decomposers play an important part in every biogeochemical cycle.

The cycling of chemicals between the biological and the geological world is called biogeochemical cycle.

(A) 2.5 – 2.75%

B) percolates down

The addition of substances that adversely affect soil fertility is called soil pollution. Use of fertilizers killed lot of useful microorganisms and reduced soil fertility. Deforestation has lead to erosion of topmost fertile layer of the soil. Overgrazing by animals also led to the soil erosion. 

Fine particles of soil are also carried away by wind and water.

People in China and Mexico reuse much of their waste paper, including writing paper, wrapping paper and card board.

The reason for depletion of water are : 

1. Increase in population. 

2. Pollution and Destruction of forests. 

3. Improper use of water.

(B) Recycling

Answer is (B) IUCN