Natural Resources

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A constant interaction between the biotic and abiotic components of the biosphere makes it a dynamic, but stable system. These interactions consist of a transfer of matter and energy between the different components of the biosphere.

0.03-0.04% carbon is present in the atmosphere in the form of CO₂.

1. Carbon cycle maintains the balance of the element carbon in the atmosphere. Carbon is found in various forms on the earth.
2. Carbon is present in the atmosphere as carbon dioxide.
3. Carbon can also occur as carbonates and bicarbonate salts in minerals.
4. Carbon is the essential part of nutrients like carbohydrates, fats, proteins, nucleic acids and vitamins.
5. Carbon cycle keeps the level of a CO₂ constant in the atmosphere.

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.

1. The nitrogen cycle is the biogeochemical cycle that describes the transformations of nitrogen and nitrogen-containing compounds in nature. It is a cycle which includes gaseous components.
2. Nitrogen gas makes up 78% of our atmosphere and nitrogen is also a part of many molecules essential to life like proteins, nucleic acids (DNA and RNA) and some vitamins.
3. Plants and animals cannot utilize atmospheric nitrogen readily.
4. It has to be fixed by some organisms called nitrogen fixers.
5. Nitrogen-fixing bacteria like Rhizobium live in symbiotic association in the root nodules of certain leguminous plants.
6. These bacteria convert atmospheric nitrogen into ammonia which is utilized readily by plants.
7. Nitrogen-fixing bacteria along with free-living bacteria in the soil achieve 90% of nitrogen fixation.
8. Lightning plays an important role in nitrogen fixation. When lightning occurs, the high temperature and pressure convert nitrogen and water into nitrates and nitrites.
9. Nitrates and nitrites dissolve in water and are readily used by aquatic plants and animals.

Ammonification: It is the process by which soil bacteria decompose dead organic matter and release ammonia into the soil.

Nitrification: It is the process by which ammonia is converted into nitrites and nitrates.

Denitrification: It is the process by which nitrates are converted into atmospheric nitrogen.

The % of oxygen in the air is 21%.

1. The cyclic process by which oxygen element is circulated continuously through the living and non-living components of the biosphere constitutes oxygen cycle.
2. Human beings and animals take oxygen from the atmosphere during the process of respiration.

The decomposition of dead organisms also takes in oxygen from the atmosphere. Respiration and decay of dead organisms release CO₂ and water.

1. The carbon dioxide and water are used by the green plants during the process of photosynthesis.
2. They give out oxygen during this process. This oxygen is again used by human beings and animals.

Thus, the oxygen cycle keeps repeating in nature.

The water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the surface of the earth.

Water evaporates from the water bodies and subsequent condensation of this water vapour leads to rain.

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.