Decay and the Carbon Cycle

Question 1

Describe the carbon cycle

Answer 1

1. CO2 is removed from the atmosphere by green plants and algae during photosynthesis. The carbon is used to make the carbohydrates, fats and proteins that make up the bodies of the plants and algae
2. when the plants and algae respire, some carbon is returned to the atmosphere as CO2
3. when the plants and algae are eaten by animals, come carbon becomes part of the fats and proteins in their bodies. carbon then moves through the food chain
4. when the animals respire, some carbon is returned to the atmosphere as CO2
5. when plants, algae and animals die, other animals (called detritus feeders) and microorganisms feed on their remains. when these organisms respire, CO2 is returned to the atmosphere
6. animals also produce waste that is broken down by detritus feeders and microorganism
7. the combustion of wood and fossil fuels, also releases CO2 back into the air
8. so the carbon is constantly being cycled - from the air, through food chains - and eventually back out into the air again

Question 2

How are materials returned to the environment?

Answer 2

• as waste products

- or when the organisms die and decay

Question 3

What does decay do for plants?

Answer 3

• it puts elements back into the soil for plants to grow

Question 4

Why do materials decay?

Answer 4

• they are broken down (digested) by microorganisms

- this happens faster in warm, moist, aerobic conditions as microorganisms are more active

Question 5

What are living things made from?

Answer 5

• materials they take from the world around them
• e.g. plants turn elements like carbon, oxygen, hydrogen and nitrogen from the soil and the air into the complex compounds that make up living organisms. these get passed up the food chain

Question 6

What is a stable community?

Answer 6

• the materials that are taken out of the soil and used by the plants etc are balanced by those that are put back in
• there is a constant cycle happening