B2c

Question 1

How is carbon dioxide put back into the atmosphere after being eaten by animals (through plants)

Answer 1

• Plants and animals respiring
• Decomposes (bacteria and fungi) in soil respiring
• Burning of fossil fuels like coal and oil

Question 2

How is carbon recycled in the sea

Answer 2

The shells of marine organisms contain carbonates, or cover themselves in calcium carbonate. When they die, their shells collect on the sea floor and (over millions of years) form limestone (very soft rock). When attacked by acidic rain, the carbon dioxide reacts with the rain to form carbonic acid. The acid rain weathers the rock and carbon dioxide is released; which is absorbed into the ocean to form a carbon sink.

Question 3

How much nitrogen is in the atmosphere and why is it difficult for plants and animals to use

Answer 3

78% of the air is nitrogen, and it is not a reactive gas; doesn’t combine well with other elements, and so animals and plants find it difficult to use

Question 4

Why do plants an animals need nitrogen

Answer 4

To make proteins for growth, and for making enzymes that control the reactions that are necessary for life

Question 5

What is the simple version of the nitrogen cycle

Answer 5

Plants and animals die and decay -> turn into decomposes and release nitrates in the soil -> proteins in the plants are made -> proteins in the animals are made -> plants and animals die and decay

Question 6

What does nitrifying bacteria do

Answer 6

Converts ammonia into nitrates

Question 7

What does nitrogen fixing bacteria do

Answer 7

In the soil or in root nodules, they ‘fix’ nitrogen gas and turn it into ammonia or nitrates, and then into amino acids or proteins

Question 8

What does denitrifying bacteria do

Answer 8

Breaks down nitrates in the soil and converts it back into nitrogen gas

Question 9

How does lightning ‘fix’ nitrogen gas in the atmosphere

Answer 9

The energy from the lightning combines nitrogen and oxygen to form nitrogen oxides. These nitrogen oxides dissolve in the rain, forming nitrates in the soil

Question 10

How much carbon dioxide is in the atmosphere, and is there enough of it

Answer 10

There is 0.04% carbon dioxide in the atmosphere, and it can supply every plant all over the world