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gcse science B4 - H
specific for ocr gateway additonal science B.
| Question | Answer |
|---|---|
| what is carbon dioxide? | a compound containing carbon |
| how is carbon dioxide taken out of the atmosphere? | by plants for photosynthesis. carbon is then passed along the food chain when animals feed |
| how is carbon dioxide put back into the atmosphere? | -plants and animals which respire -fungi and bacteria which respire when they decompose -burning fossil fuels such as coal and oil -erupting volcanoes and forest fires |
| how is carbon recycled at sea? | -shells of marine organisms (e.g. molluscs) contain carbonates. -when they die, their shells turn into sedimentary rock called limestone -limestone is attacked by acid rain, giving off carbon dioxide |
| how much nitrogen is in the atmosphere? | 78% |
| why do plants and animals need nitrogen? | to make proteins for growth |
| why can't plants and animals use nitrogen directly? | its inert - unreactive |
| how does nitrogen get into plants? | in the form of nitrates |
| how do decomposers contribute to the nitrogen cycle? | they break down proteins in dead bodies and urea into ammonia |
| how do nitrifying bacteria contribute to the nitrogen cycle? | they convert ammonia into nitrates |
| how do nitrogen-fixing bacteria contribute to the nitrogen cycle? | they 'fix' nitrogen by converting it into ammonia or nitrates and then into amino acids to form proteins |
| how does lightning contribute to the nitrogen cycle? | fixes nitrogen by combining nitrogen and oxygen to form oxides. the oxides dissolve in rain and form nitrates in the soil |
| how do denitrifying bacteria contribute to the nitrogen cycle? | convert nitrates back into nitrogen gas |
Created by:
jirwin