3.5.4: Nutrient cycles Flashcards
What are the 5 key processes of the nitrogen cycle?
1) saprobiotic nutrition
2) ammonification
3) Nitrification
4) Nitrogen fixation
5) Denitrification
What is nitrogen fixing?
When nitrogen gas is converted into other N compounds by nitrogen fixing bacteria and in the root nodules of some leguminous plants. N2 gas is reduced to ammonium ions
What is ammonification?
Saprobiotic bacteria react with N containing polymers to release ammonia in the soil. First proteins are broken down into amino acids. then broken down further to remove the amino groups
What is nitrification?
Ammonia is oxidised into NO2- then NO3- by nitrifying bacteria
What is denitrification?
Where nitrate ions are converted into nitrogen gas by nit drying bacteria. Happens in waterlogged and anaerobic conditions
What are mycorrhizae?
associations between specific type of fungi and root systems of plants
Why is mycorrhizae beneficial for plants? (3)
1) increase total surface area of the plants roots
2) Increase absorption of water
3) Increase absorption of mineral ions e.g. phosphates and nitrates
Describe the phosphorus cycle? (7)
1) Phospholipids, RNA and DNA from dead organisms into phosphate ions
2) Decomposed by saprobionts
3) Phosphate ions also found in waste and remains e.g. guano, bones and shells
4) Phosphate ions transported by streams, rivers, lakes and oceans
5) Form sedimentary rocks
6) Weathering and erosion of rocks help phosphate ions dissolve in oceans, lakes and soil
7) Phosphates available for absorption by active transport in plants to incorporate into biomass
What are the two types of fertilisers?
- Natural
- Artifical
Why are fertilisers used?
To replace the nitrates and phosphate ions lost when plants are harvested and removed from nutrient cycles as crops
Natural fertiliser:
Advantage (1)
Disadvantage (1)
- Cheaper, free if farmer owns animals
- Exact minerals and proportions can’t be controlled
What are artificial fertilisers?
Manufactured, man made powders produced in factories
How do fertilisers reduce species diversity?
Plants which are adapted to soils with high nitrate concentration outcompete other species
How do fertilisers cause environmental issues?
crops are removed so less decomposition so less nitrates returned to the soil
How do fertilisers cause leaching?
more ions applied to soil than taken up by plants. causes leaching and ions dissolve in soil water and washed from soil into streams, rivers and lakes.
