13.3 Nutrient cycles Flashcards
What is a natural ecosystem?
One that hasn’t been changed by human activity
What are saprobionts
A type of decomposer, that feed on the remains of animals and plants as well as their waste. Allow chemical elements to be returned to the cycle.
How do saprobionts digest food?
externally by secreting enzymes and breaking organic molecules into inorganic ions
What fungi have symbiotic relationships with plants?
Mycorrhizae
How do mycorrhizae help plants?
They increase the surface surface area of the roots helping the plant absorb ions and water which can be scarce.
What are the steps of the nitrogen cycle?
1) Nitrogen fixation
2) Ammonification
3) Nitrification
4) Denitrification
What is Nitrogen fixation?
Nitrogen gas in the atmosphere is turned into nitrogen containing compounds.
What is Ammonification?
Nitrogen compounds from dead organisms are turned into ammonia by saprobionts - which then forms ammonium ions.
What is nitrification?
Nitrification is when ammonium ions in the soil are changed into nitrogen compounds that can be used by plants.
What is Denitrification?
Nitrates the soil are converted into nitrogen gas by denitrifying bacteria
Name a bacteria nitrogen fixation is carried out by
Rhizobium
Where can rhizobium be found?
root nodules of leguminous plants
What changes ammonium ions to nitrites and then into nitrates, in nitrification?
nitrifying bacteria
What do denitrifying bacteria do?
Convert nitrates to nitrogen gas in anaerobic conditions - puts nitrogen back into the atmosphere
Give an example of an environment with anaerobic conditions
Waterlogged soils
