Nutrient Cycles Flashcards
describe the nitrogen cycle
- nitrogen fixed into ammonium compounds by nitrogen fixing bacteria
- ammonium compounds converted to nitrites then nitrates via nitrifying bacteria
- nitrates then used to synthesise proteins and organic compounds in the plant
- organisms eat the plants, make proteins, die
- saprobionts decompose proteins to produce ammonium compounds to the soil
- denitrifying bacteria convert nitrates in the soil to nitrogen in the air in anaerobic conditions
what are saprobionts
- bacteria that decompose proteins to produce ammonium compounds to the soil
how do farmers increase nitrate levels
- ploughing/drainage of soil to decrease denitrification
- add fertilisers to increase nitrates
- plough legumes into fields to increase nitrate levels
how do legumes increase soil fertility
- they form associations with nitrogen fixing bacteria
- their roots have swellings called nodules containing colonies of nitrogen fixing bacteria
what type of relationship is formed between legumes and nitrogen fixing bacteria
- symbiotic/mutualistic
what does each party gain from the mutualistic relationship between bacteria and legumes
- nitrogen fixing bacteria obtain carbohydrates and vitamins produced by plant during photosynthesis
- plant gains fixed nitrogen in the form of ammonia which can be used to form amino acids/proteins
what is the relationship between fungi and plant roots called
- mycorrhizae
how does the fungi benefit the plants in a mycorrhizae
- fungi consists of long thin strands called hyphae which connect with plant roots and increase surface area for absorption of water and inorganic ions such as phosphate
what do the fungi receive in a mycorrhizae
- organic compounds such as glucose from photosynthesis of the plant
how are phosphate released from their compounds in faeces, urine, remains etc
- by saprobionts during decomposition
what is the difference between natural and artificial fertilisers
- natural fertilisers - includes dead and decaying remains of organisms, manure and bone meal which decay and release mineral ions
- artificial fertilisers - contain a mixture of inorganic compounds of nitrogen, phosphorous and potassium (NPK)
how are nitrogen and potassium absorbed by plants
- via active transport
what is leaching
- when fertilisers are washed away into rivers and lakes
what type of fertiliser is more susceptible to leaching and why
- artificial fertilisers as they tend to contain soluble nitrates and phosphates which are leached more readily
what can leaching lead to
- eutrophication - a large increase in nutrients in an aquatic ecosystem
what are the dangers of eutrophication
- it can reduce the presence of aquatic aerobic species
describe how leaching and eutrophication can lead to a decrease in aquatic aerobic species
- leaching of fertilisers causes the nitrogen and phosphorous concentration in the water to increase
- algal bloom on the surface of the water which blocks light reaching the sub-aquatic plants
- this causes the plants to die as they can no longer photosynthesise increasing the decomposition by saprobionts
- the saprobionts use oxygen as they decompose causing a decrease in oxygen in the water causing the aquatic organisms (e.g. fish) to die
