Students need to understand the key role that microorganisms play in the recycling of chemical elements within ecosystems. This encompasses the role of decomposers, such as saprobionts, and the roles of Nitrosomonas, Nitrobacter, Azotobacter and Rhizobiaa in the recycling of nitrogen. Students will need to describe the processes of saprobiotic nutrition, ammonification, nitrification, nitrogen fixation and denitrification.
Linked to the nitrogen cycle students should be aware of the impact that the use of natural and artificial fertilisers can have. These are routinely used to replace the nitrates and phosphates lost by harvesting plants and removing livestock. There are environmental issues arising from the use of these fertilisers including leaching and eutrophication.
The importance of the carbon cycle should also be covered in this topic, with students being aware of factors that can affect the carbon cycle.
Some specifications also require students to demonstrate understanding of the recycling of other nutrients such as phosphorus.
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