P2 4c cycles within the ecosystem

Question 1

how does water enter the atmosphere?

Answer 1

as water vapour by

• energy from the sun heating and evaporating water from oceans, rivers and lakes
• or transpiration from plants releases water

Question 2

how does air rise?

Answer 2

warmer air from the lower atmosphere rises, taking the water with it

Question 3

what happens as air rises?

Answer 3

• moist air cools down as it rises

Question 4

what happens to water as the air rises?

Answer 4

water vapour condense back into liquid water, forming clouds

Question 5

how does water return to earth?

Answer 5

by precipitation

- as water droplets in the cloud get bigger and heavier they begin to fall as rain, snow or sleet

Question 6

why is there a carbon and nitrogen cycle?

Answer 6

there is a finite amount of carbon and nitrogen on the planet so it needs to be recycled to allow new organisms to be made and grow

Question 7

how is carbon taken out of the atmosphere?

Answer 7

in the form of carbon dioxide, by plants used for photosynthesis

Question 8

how is carbon passed on to animals and microorganisms?

Answer 8

by feeding

Question 9

how is carbon returned to the atmosphere?

Answer 9

in the form of carbon dioxide as a result of respiration (from plants and animals)
and in increasing amounts by the combustion of fossil fuels

Question 10

what happens if animals die in conditions where decomposing microorganisms are not present?

Answer 10

the carbon in their bodies can be converted over millions of years and with pressure into fossil fuels

Question 11

where is carbon stored?

Answer 11

in fossil fuels

Question 12

what are the effects of mass deforestation on the carbon cycle?

Answer 12

its reducing the amount of producers

Question 13

what is nitrogen required for?

Answer 13

to make proteins

Question 14

can animals and plants absorb nitrogen from the air?

Answer 14

no because the the gas is very stable, so big amounts of energy would be needed to break them.

Question 15

how is nitrogen taken out of the air?

Answer 15

• nitrogen fixing bacteria
• lightning can ‘fix’ N2 gas

they both convert it to be easier to absorb

Question 16

how does nitrogen fixing bacteria convert N2 into something easier to absorb

Answer 16

• found in free living soil and also root nodules of peas beans and clover
• they take the gas and change it into nitrates in the soil

Question 17

how does lightning convert N2 into something easier to absorb

Answer 17

• splitting the bond between the two atoms and turning them into nitrous oxide
• like N2O and NO2
• they dissolve in rainwater and leach into the soil

Question 18

what do plants do with nitrates?

Answer 18

absorb the nitrates they find in the soil and use the nitrogen to make proteins

Question 19

how do animals get nitrates?

Answer 19

animals eat plants or other animals and get the nitrogen they need from the proteins

Question 20

how does nitrogen end up back in the soil?

Answer 20

by waste (urine and faeces) 
- send back to the soil as ammonium compounds (urea contains nitrogen)

Question 21

what is another way nitrogen can end up back in the soil?

Answer 21

animals and plants die, they then decay and all the proteins inside them are broken down into ammonium compounds and put back into the soil be decomposers

Question 22

how do plants absorb the ammonium compounds?

Answer 22

they can’t so a second type of soil bacteria, nitrifying bacteria convert the ammonium compounds to nitrites then to nitrates

Question 23

what bacteria is found in poorly aerated soil?

Answer 23

denitrifying bacteria

Question 24

what does denitrifying bacteria do?

Answer 24

the anaerobic bacteria take the nitrates out of the soil and convert them back into gas

Question 25

how can denitrifying bacteria be stopped?

Answer 25

ploughing and turning over the soil