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gcse science B4 - H

specific for ocr gateway additonal science B.

QuestionAnswer
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
 

 



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