Describe the carbon cycle and add a note on the impact of human activities on the carbon cycle. - Biology

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Answer in Brief

Describe the carbon cycle and add a note on the impact of human activities on the carbon cycle.

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Solution

i. Reservoir of carbon:

  1. All life forms on earth are carbon-based because carbon is the main component of all the organic compounds of protoplasm. It constitutes 49% of the dry weight of organisms.
  2. 71% of carbon is found dissolved in oceans. The oceanic reservoir regulates the amount of carbon dioxide in the atmosphere.
  3. Carbon present in the rock and fossil fuels like oil, coal, and natural gas has been away from the rest of the carbon cycle for a long time. These long-term storage places are known as the sink.
  4. The element carbon is a part of seawater, the atmosphere, rocks such as limestone and coal, soils, as well as all living things.

ii. Cyclic pathway of carbon:

  1. Carbon as CO2 moves from the atmosphere to plants during the process of photosynthesis to produce food.
  2. Carbon moves from plants to animals, through food chains.
  3. At the time of exhalation, the CO2 gas is released into the atmosphere. Thus, carbon moves from living things to the atmosphere.
  4. Decomposers also contribute substantially to CO2 in the atmosphere, by their processing of waste materials and dead organic matter of land and oceans.
  5. When fossil fuels burn to power factories, power plants, motor vehicles, most of the carbon quickly enters the atmosphere as carbon dioxide gas.
  6. Most of the remainder is dissolved in seawater and deposited as calcium or magnesium carbonate compounds that make up shells of marine animals.
  7. The additional sources for releasing CO2 in the atmosphere are the burning of wood, forest fire and combustion of organic matter, fossil fuel, and volcanic activity.
  8. The ocean absorbs some carbon in the form of CO2 from the atmosphere. This carbon gets dissolved in the ocean water. Some amount of the carbon which is fixed is lost to sediments and removed from circulation.

iii. The impact of human activities on the carbon cycle

  1. The carbon cycle is significantly influenced by human activities.
  2. Rapid deforestation and the massive burning of fossil fuels for energy and transport have significantly increased the rate of release of carbon dioxide into the atmosphere.

Carbon cycle

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Chapter 14: Ecosystems and Energy Flow - Exercises [Page 320]

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Balbharati Biology 12th Standard HSC for Maharashtra State Board
Chapter 14 Ecosystems and Energy Flow
Exercises | Q 4.5 | Page 320

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