B2c - recycling

Question 1

Explain why recycling of nutrients takes longer in waterlogged or acidic soils than it does in well drained neutral soils(2)

Answer 1

inwaterloggedsoils there is a lackofoxygenfor the microbes to respire

inacidicsoils the pHtoolowformicrobes

Question 2

Describe the carbon cycle(6)

Answer 2

1. plants removing carbon dioxide from the air by photosynthesis, which is builtintosugarsusedtobuildmolecules(cellulose,fatsprotein)togrow
2. feeding passes carbon compounds along a food chain or web
3. carbon dioxide is released back into the air through:
   - plants/animalsreleasecarbon dioxideintoairasa product of respiration
   - combustionoffossilfuelsforenergyreleasesthestoredcarbonas carbon dioxide
   - soil bacteria and fungi, acting as decomposers, releasing carbon dioxide into the air through respiration

Question 3

Explain how carbon is recycled in nature(4)

Answer 3

1. marine organisms making shells made of carbonates
2. when they die their shells sink to the bottom of the ocean and gets compressed to form limestone
3. carbon returning to the air as carbon dioxide during volcanic eruption or weathering
4. oceans absorbs carbon dioxide, acting as carbon sinks.

Question 4

Describe the nitrogen cycle(6)

Answer 4

1. nitrates in the soil absorbed by plant, used to build compounds such as proteins in plant
2. nitrogen ­containing compounds pass through food chains to animals through feeding
3. nitrogen compounds(e.g. protein and urea) in dead plants and animals broken down by decomposers into ammonia and return to the soil
4. nitrifying bacteria in soil convert ammonia to nitrates
5. the fixing of nitrogen gas by nitrogen-fixing bacteria living in root nodules or in the soil, or by the action of lightning into nitrates/ammonia

denitrifying bacteria in soil convert nitrates to nitrogen gas, releasing it into air

Question 5

Describe ways that nitrogen gas is fixed(3)

Answer 5

lightning releases enough energy to cause nitrogen in air to react w/ oxygen to form nitrates, which dissolve in rainwater and wash into soil

nitrogen ­fixing bacteria living in root nodules of plants or in soil combine nitrogen in air with oxygen to make nitrates

Haber process used to make ammonia industrially