Nutrient cycles Flashcards
Name 4 substances that animal cells require a source of nitrogen to make.
DNA and RNA
Amino acids and Proteins
NAD and NADH
ATP
What is nitrogen fixation?
Nitrogen gas is converted into ammonia/nitrate
Name the bacteria that carry out nitrogen fixation
Nitrogen fixing bacteria
Where are nitrogen fixing bacteria found?
Free in the soil
In root nodules of legumes
What does the term symbiotic relationship mean?
Two organisms of different species interact
What does the term mutualistic relationship mean?
Two organisms of different species interact.
Both organisms benefit from the relationship
Give the main benefit
Nitrogen fixing bacteria - gain protection in the nodule and a source of organic substances from the plant
Plant gains a source of ammonium/nitrate ions
What is ammonification?
Formation of ammonium ions from organic material (eg urea, faeces, dead organisms)
Name the organisms that cause ammonification
Saprobiontic bacteria
What is nitrification?
Conversion of ammonium ions into nitrites and then nitrates
Name the organisms that cause nitrification
Nitrifying bacteria
What is denitrification?
Conversion of nitrates in the soil into nitrogen gas
Why does dentification take place in waterlogged soils
Denitrifying bacteria require anaerobic conditions.
No air pockets in the soil when saturated with water
Name 4 biological molecules that contain phosphate
Phospholipids
DNA
RNA
ATP
How do phosphates get into the soil
Weathering of rocks containing phosphate minerals
Describe how phosphates or nitrates can get into water bodies
Dissolve in rain water
Leached/run off into the water body
Name the process that causes the death of fish in water containing lots of phosphates and nitrates
Eutrophication
Describe how the presence of nitrates/phosphates cause the death of fish
Leached into water body
Causes increased growth of algae (algal bloom)
As lack of nitrates and phosphate was a factor limiting their growth
Blocks light so less photosynthesis of plants which causes death of plants
Increase in number of decomposers/bacteria
Increased respiration by bacteria
Reduces oxygen content of water
Anaerobic bacteria increase, releasing toxin into water
Fish die
Outline the role of mycorrhizae
Mutualistic relationship between plants and fungus
Increases the surface area for absorption of minerals and water by roots.
Give 3 benefits of planting a different crop in the same field each year
Nitrogen fixing crops increase soil nitrate content
Different crops have different pathogen
Different crops removed different proportions of ions
Why do farmers add fertiliser to their fields?
Increase primary productivity
More minerals for plant growth
What is an organic fertiliser?
Derived from living organisms
eg manure, slurry
What is an inorganic fertiliser?
Manufactured fertiliser
g ammonium nitrate
Why are organic fertiliser better than inorganic fertilisers?
Minerals released at a slower rate
Minerals available for longer
Less likely to be leached from the soil
Improves soil structure
Why are inorganic fertilisers better than organic fertilisers?
Control proportion of nitrates, phosphates and potassium added to the soil
