We respire constantly and release carbon dioxide back into the environment. Nitrogen is needed in our bodies to make proteins. When we break down proteins we remove them from our bodies as urea. All organisms have a similar process for the removal of protein products - this is because they are toxic to the body. We cannot obtain nitrogen easily.
Plants are our sole source of nitrogen and they obtain it from the soil as nitrates.
These soil nitrates are absorbed through the roots. Follow the Nitrogen Cycle to see how the products of decay are converted by different bacteria into the useable, soluble nitrates which plants can absorb. Question 1 Question 2 Question 3 Match up the process with the correct description. Question 4 Drag the and drop the boxes to complete the recycling of carbon cycle. This question is for candidates at Higher Level.