Nitrogen cycling Summary
Nitrogen is an important element for plants.
Bacteria play important roles in the cycling of Nitrogen.
1. Plants need the element Nitrogen to synthesise _________ ________ and build
these into _________.
2. Plants CANNOT use the nitrogen gas from the ____________
3. Atmospheric nitrogen is converted into a form plant can use (_________ and
________ ) in the process of ___________ __________ by ______________
bacteria. Nitrogen may also be fixed from the atmosphere by ____________.
4. Leguminous plants e.g. _______ and ________ have nitrogen fixing bacteria in
their ________ _________. These bacteria fix atmospheric nitrogen into
__________ which they can use. (farmers sometimes grow leguminous plants in a
field to replace lost nitrogen)
5. Additional sources of nitrogen containing compounds are dead plants and animals,
and animal waste. Saprobiotic bacteria and fungi feed on waste and dead organisms
by releasing ________ which result in extra-________ -___________.
6. The amino acids released, and the urea in waste is converted into __________ by
___________ bacteria.
7. A different kind of bacteria convert ammonia into ________ and then
__________ in a process called ____________. These bacteria are called
__________________.
8. The Nitrates can be taken up by plant roots via the process of ________
________ which requires energy from __________. A good oxygen supply in the
soil is therefore needed. Plants can’t take up nitrates easily in soil which is
waterlogged.
9. When soil is waterlogged, ___________ bacteria utilise the oxygen within
________ for respiration and convert the nitrates into nitrogen ____.
10. The nitrogen containing compounds in plants (amino acids, proteins, nucleic acids) are
passed onto consumers via _________.
11. The animals convert excess amino acids into ammonia which is excreted in _____