Nutrient cycling
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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Decomposition
This resource is one of the many in-depth topic booklets available in the Institute of Biology series. Chapters included in this booklet are:
- Biochemistry of decomposition
- The role of the microorganisms
- The role of detritivores
- Decomposition and the functioning of ecosystem
The whole booklet would make useful reading for teachers who need to refresh their knowledge on this particular topic before delivering it to students.
There are also sections of the booklet which could be used with students to develop subject knowledge and scientific reading skills. The first couple of pages would make for good pre-topic reading and chapter four could be used in its entirety or split into sections.
Measuring Carbon Cycling
This article from the Catalyst magazine focuses on how parts of carbon cycling, as it happens in forests, can be measured. Two of the processes used in this measure, flux towers and soil chambers, are described in the article.
Although measurement of the carbon cycle may not be identified within A level specifications, this article does provide useful background/around the subject reading at a suitable level.
The article itself is quite short, with one of the two pages devoted to photographs of the equipment used.
It would be possible to use this article as stimulus for a discussion on the limitations of either of these approaches or for devising equipment for specific purposes in biological measurement (what other examples can they name?) or the use of data loggers.
The other Catalyst article on carbon cycling in this list and this article would work well together. You could ask students to read, review and summarise each for homework/independent study.
Plants and Nitrogen
This resource is one of the many in-depth topic booklets available in the Institute of Biology series. This booklet focuses on the processing of nitrogen in the biosphere by following the steps of the nitrogen cycle. This highlights not only the biochemical and physiological subtleties of the processes involved but also their ecological and agricultural significance.
The book is both comprehensive and detailed in its coverage of this topic and does include a level of detail that is above the requirement for A level. It would however make for useful reading for teachers who need to refresh their understanding of this particular topic before delivering it to students.
There are also sections of the booklet which could be used with students to develop subject knowledge and scientific reading skills. Chapter two for example, pages three through to 29, are detailed, but students could be asked to read these over a number of homework/directed study periods.
Throughout the booklet there are useful tables of data, images and illustrations that could be used by teachers.
Role of Bacteria in Nitrogen Cycle
In this investigation, students culture a free-living nitrogen-fixing bacterium (Azotobacter) from the soil. The protocol for this investigation is quite simple, but the understanding of why there is/isn't bacterial growth can be extended to ensure that it is suitable for A level students.