Nutrient cycles - Finished Flashcards
How does Atmospheric CO2 get into organic compounds in plants?
Through photosynthesis
How does CO2 get into the organic compounds in animals?
THrough the animals feeding on the plants
How does CO2 get into the organic compounds in decomposers such as sacrobionts?
Through the death and decay of plants and animals
How does CO2 become fossil fuels?
Through the fossilisation of animals and plants.
How does CO2 get back into the atmosphere?
Combustion of fossil fuels
Respiration of Decomposers, animals and plants
What is nitrogen fixation?
Atmospheric nitrogen is converted straight into ammonia by nitrogen fixing bacteria.
Azotobactor - Free living bacteria
Rhizobium - Found in the root nodules of legumes - Uses the enzyme nitrogenase. Nitrogenase enzyme is inhibited by Oxygen so heamoglobin in the nodules fixes to the oxygen and facilitates nitrogen fixation
What is putrefaction (ammonification)?
Decomposers and sacrobionts result in the decay of dead plants and animals into ammonium ions
What is nitrification?
The conversion of ammonium ions into nitrites and then nitrates.
Requires aerobic conditions
Ammonia -> Nitrites = Nitrosomonas
Nitrites -> Nitrates = Nitrobacter
What is Denitrification?
Reduction of nitrates and ammonium ions back into atmospheric nitrogen
requires anaerobic conditions
Bacteria called Pseudomonas
Why is it important that ammonia is converted into nitrates?
So that they are in a form which can be absorbed by root hair cells by active transport.
Once taken in by the roots, the plant can then use the nitrogen from the nitrate ions to synthesise amino acids (to make proteins) and nitrogenous bases
Why should farmers plough/drain feilds?
This removes the anaerobic conditions and prevents denitrification (conversion of soil nitrates into atmospheric nitrogen)
Why add manure to the soil?
Contains organic nitrogen compounds which can be broken down by putrefying bacteria into ammonium ions. These can be converted into nitrates which are taken up by plant roots by active transport to encourage crop growth
