B2e

Question 1

How is carbon recycled in the sea?

Answer 1

• 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’

Question 2

Why is decomposition slower in waterlogged and acidic soils?

Answer 2

• 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

Question 3

What takes carbon out of the atmosphere?

Answer 3

-photosynthesis, plants are then eaten

Question 4

What puts carbon into the atmosphere?

Answer 4

• decay into fossil fuels, combustion
• released in decay
• plant respiration
• animal respiration

Question 5

How does nitrogen fixation work?

Answer 5

• 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

Question 6

What takes nitrogen away from the atmosphere?

Answer 6

• nitrogen fixing bacteria in the roots, plants eaten, decomposition, ammonia, nitrifying bacteria
• nitrogen fixing bacteria in the soil
• lightning

Question 7

What puts nitrogen into the atmosphere?

Answer 7

-denitrifying bacteria

Question 8

What bacteria are involved in the nitrogen cycle?

Answer 8

• 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)

Question 9

What mutualistic relationship is in the nitrogen cycle?

Answer 9

-bacteria get sugar from the legumes and the legumes get nitrogen compounds from the bacteria to make proteins