the free PDF resource
advertisement
Nitrogen cycle questions Look at a copy of the nitrogen cycle and answer the questions below. 1) Decide whether each statement is true or false. Put a tick in the correct box. Statement a Animals and plants get the nitrogen they need directly from nitrogen gas in the air. b There are several types of bacteria involved in the nitrogen cycle. c Plants absorb nitrogen compounds from the soil to provide the nitrogen they need for growth. d Nitrogen-fixing bacteria just live in the soil. e The actions of nitrogen-fixing bacteria and nitrifying bacteria are the only ways to add nitrates to the soil. True False 2) Explain why adding manure to the soil would increase the nitrate content of the soil. ...................................................................................................................................................................................... ...................................................................................................................................................................................... ...................................................................................................................................................................................... ...................................................................................................................................................................................... ...................................................................................................................................................................................... ...................................................................................................................................................................................... 3) Explain why some farmers plant clover every few years in their fields. ...................................................................................................................................................................................... ...................................................................................................................................................................................... ...................................................................................................................................................................................... ...................................................................................................................................................................................... ...................................................................................................................................................................................... ...................................................................................................................................................................................... © www.teachitscience.co.uk 2012 19847 Page 1 of 4 Nitrogen cycle questions 4) Describe how animals get the nitrogen they need to make proteins for growth. ...................................................................................................................................................................................... ...................................................................................................................................................................................... ...................................................................................................................................................................................... ...................................................................................................................................................................................... ...................................................................................................................................................................................... 5) Complete the table. Name of bacteria decomposer bacteria Location Function in the soil feed on dead organisms and waste and turn it into urea and proteins nitrogen fixing bacteria fix nitrogen gas into nitrates. in the soil fix nitrogen gas into nitrates convert ammonia into nitrates denitrifying bacteria other soil bacteria in the soil 6) Evaluate the statement ‘the amounts of plant nutrients in the soil are controlled by bacteria’. ...................................................................................................................................................................................... ...................................................................................................................................................................................... ...................................................................................................................................................................................... ...................................................................................................................................................................................... ...................................................................................................................................................................................... ...................................................................................................................................................................................... ...................................................................................................................................................................................... © www.teachitscience.co.uk 2012 19847 Page 2 of 4 Nitrogen cycle questions Teaching notes and answers These questions were designed to be used with the resource ‘Nitrogen cycle jigsaw’. However, they could be used with other diagrams of the nitrogen cycle. The following are the expected answers: 1) False, true, true, false, false. Statement True False a Animals and plants get the nitrogen they need directly from nitrogen gas in the air. b There are several types of bacteria involved in the nitrogen cycle. c Plants absorb nitrogen compounds from the soil to provide the nitrogen they need for growth. d Nitrogen-fixing bacteria just live in the soil. e The actions of nitrogen-fixing bacteria and nitrifying bacteria are the only ways to add nitrates to the soil. 2) Decomposers break down manure to produce nitrogen compounds, e.g. proteins and urea. Soil bacteria then convert these compounds to ammonia. Nitrifying bacteria in the soil convert ammonia to nitrates. 3) Clover root nodules contain nitrogen fixing bacteria. These bacteria fix nitrogen gas from the air into nitrogen compounds. This can improve the nutrient content of the soil and therefore improve plant growth. 4) Nitrates in the soil are absorbed by plants which are then eaten by animals. © www.teachitscience.co.uk 2012 19847 Page 3 of 4 Nitrogen cycle questions 5) Name of bacteria Location in the soil Function feed on dead organisms and waste and turn it into urea and proteins a decomposer bacteria b nitrogen fixing bacteria in root nodules fix nitrogen gas into nitrates c nitrogen-fixing bacteria in the soil fix nitrogen gas into nitrates d nitrifying bacteria in the soil convert ammonia into nitrates in the soil convert nitrates into nitrogen gas in the soil convert proteins and urea into ammonia denitrifying bacteria e f other soil bacteria 6) Expected answers: example of ‘nitrates’ as a plant nutrient reference to the nitrogen cycle examples of bacteria that do have a role in controlling the amounts of plant nutrients in the soil an explanation of what these types of bacteria do a description that shows understanding that there are bacteria (denitrifying) that reduce nitrates in the soil, whereas there are bacteria that increase nitrates in the soil (e.g. nitrogen-fixing) the conclusion that bacteria are extremely important an understanding that bacteria are not the only part of the nitrogen cycle that controls the amounts of plant nutrients – this is also affected by other factors (e.g. lightning). © www.teachitscience.co.uk 2012 19847 Page 4 of 4
