1
Q
How is carbon recycled in the sea?
A
- millions of marine organisms make shells made of carbonates
- when they die the shells fall to the ocean floor and eventually form limestone rocks
- the carbon in the rocks return to the atmosphere as CO2 during volcanic eruptions or when the rocks are weathered down
- oceans also absorb large amounts of CO2, acting as huge stores of carbon called ‘carbon sinks’
2
Q
Why is decomposition slower in waterlogged and acidic soils?
A
- because bacteria and fungi that decompose organic material usually need oxygen to respire and produce energy
- waterlogged soil doesn’t have much oxygen, so the decomposers have less energy and work more slowly
- also extreme pH slow down the reproduction of decomposers, or kills them outright
3
Q
What takes carbon out of the atmosphere?
A
-photosynthesis, plants are then eaten
4
Q
What puts carbon into the atmosphere?
A
- decay into fossil fuels, combustion
- released in decay
- plant respiration
- animal respiration
5
Q
How does nitrogen fixation work?
A
- it is turning nitrogen gas from the air into nitrogen compounds in the soil which plants can use. Two ways this happens:
- lightning:enough energy is in a bolt of lightning to make nitrogen gas react with oxygen in the air to give nitrates
- nitrogen-fixing bacteria in roots and soil. Some live in soil, other in nodules on the roots of legume plants, therefore legumes are good at putting nitrogen back into the soil
6
Q
What takes nitrogen away from the atmosphere?
A
- nitrogen fixing bacteria in the roots, plants eaten, decomposition, ammonia, nitrifying bacteria
- nitrogen fixing bacteria in the soil
- lightning
7
Q
What puts nitrogen into the atmosphere?
A
-denitrifying bacteria
8
Q
What bacteria are involved in the nitrogen cycle?
A
- decomposers: decompose proteins and urea and turn them into ammonia
- nitrifying bacteria: turn ammonia in decaying matter into nitrates
- nitrogen fixing bacteria: turn atmospheric N2 into nitrogen compounds plants can use
- denitrifying bacteria: turn nitrates back to N2 gas (this is of no benefit to living organisms)
9
Q
What mutualistic relationship is in the nitrogen cycle?
A
-bacteria get sugar from the legumes and the legumes get nitrogen compounds from the bacteria to make proteins
