Question

Explain the carbon cycle with the help of a simplified model.

Explain the simplified model of carbon cycle in nature.

G~ve schematic representation of carbon cycle.

Answer 1

Carbon cycle in nature:

(i) The main source of carbon in this Universe is CO2 which is dissolved in water and present in air (0.03–0.04%).

(ii) Plants take up carbon dioxide from the atmosphere and form organic compounds during photosynthesis. These organic compounds are transferred to animals as food.

(iii) The carbon dioxide returns to the atmosphere during respiration, decay and
combustion of plants and animals.

(iv) The organic compounds of plants and animals are buried in the deep soil where they are acted upon by decomposers to change them to petroleum, coal, oil and carbonate rocks. These substances on their combustion release carbon dioxide in the atmosphere.

(v) Some carbon dioxide is found in the dissolved state in water. This gets converted to calcium carbonate in limestone. The weathering and combustion of carbonate-containing rocks or treatment of their minerals give CO2.

(vi) The hot springs and volcanic eruptions also give out CO2 in the atmosphere.

Answer 2

Key process involved in carbon cycle is photosynthesis and respiration.

1. In photosynthesis, carbon-dioxide and water produce carbohydrate and oxygen while respiration oxidizes food to give carbon-dioxide and water.

2. In oceans, carbon-dioxide dissolves readily in water. In rock it gets stored as calcium carbonate.

3. Carbon can either be liberated to atmosphere through respiration or can be passed to animal when being eaten or remain in plant even after death.

4. After death of plant or animal, decomposition takes place and carbon dioxide gets released into the atmosphere. They can also be buried inside the earth and converted to coal or natural gas. Natural gas and coal are fuels and on combustion they release carbon dioxide back into the atmosphere.

5. Excess of carbon-dioxide can cause global warming.