B3 Life on Earth. Lesson 4: Recycling Nutrients. Objectives. MUST describe the carbon cycle SHOULD describe the nitrogen cycle. Key Words. You need to be able to define the following: Carbon Carbon cycle Carbon dioxide Combustion Respiration Decomposition Nitrogen cycle Nitrates
Lesson 4: Recycling Nutrients
1) a) Through combustion (burning); decomposition and respiration. b) By photosynthesis.
2) Increased combustion of fossil fuels; the reduction of forest cover on Earth.
3) In the form of proteins that plants have made; in food as proteins from other animals (or animal products).
4) By decomposition.
5) Some bacteria and fungi decompose dead matter, releasing nitrates into the soil; denitrifying bacteria turn these nitrates back into nitrogen; nitrogen-fixing bacteria in the roots of beans and peas turn nitrogen gas from the air into nitrates that plants can use to make proteins.
6) Peas and beans contain nitrogen-fixing bacteria in their roots that can ‘fix’ atmospheric nitrogen into nitrates; this means these plants are able to access more nitrates than most other plants; these nitrates are used to make proteins.
Activity 2 (Standard demand)
Activity 3 (High demand)
1) Lightning; nitrogen-fixing bacteria in the roots of beans and peas; nitrogen-fixing bacteria in the soil; decomposition by bacteria and fungi.
2) By the decay of nitrogen-containing plants and animals and their urine and faeces; and by denitrifying bacteria.
3) Fertilisers contain nitrates; plants need nitrates to create proteins, which help them grow; fertilisers are added to help plants grow.