carbon cycle

Question 1

describe how carbon is cycled in the environment

Answer 1

1. Carbon enters the atmosphere as carbon dioxide from respiration and combustion.
2. Carbon dioxide is absorbed by producers to make carbohydrates in photosynthesis.
3. Animals feed on the plant passing the carbon compounds along the food chain. Most of the carbon they consume is exhaled as carbon dioxide formed during respiration. The animals and plants eventually die.
4. The dead organisms are eaten by decomposers and the carbon in their bodies is returned to the atmosphere as carbon dioxide. In some conditions decomposition is blocked. The plant and animal material may then be available as fossil fuel in the future for combustion.

Question 2

describe how nitrogen is cycled in the environment

Answer 2

1. Nitrogen gas is converted to nitrate compounds by nitrogen-fixing bacteria in soil or root nodules. Lightning also converts nitrogen gas to nitrate compounds. The Haber process converts nitrogen gas into ammonia used in fertilizers. Ammonia is converted to nitrates by nitrifying bacteria in the soil.
2. Plants absorb nitrates from the soil and use these to build up proteins. The plant may be eaten by an animal, and its biomass used to produce animal protein.
3. Urea and egested material is broken down by decomposers. This results in nitrogen being returned to the soil as ammonia.
4. Decomposers also break down the bodies of dead organisms resulting in nitrogen being returned to the soil as ammonia.