4c + d - Human Impacts/Cycles Flashcards
What are the two ways nitrogen can be taken out of the air and converted?
- nitrogen fixing bacteria
- lightning
Where is nitrogen fixing bacteria found?
In soil and in the root nodules of plants
How does a lightning convert nitrogen gas?
Splits the bond between the two atoms and turns them into nitrous oxide that dissolve in rainwater
Why do plants absorb the nitrates
To make proteins
How does the nitrogen go back into the soil?
As ammonium compounds in animal faeces
What does nitrifying bacteria do?
Converts the ammonium compounds to nitrites then to nitrates
What does denitrifying bacteria do?
Takes the nitrates out the soil and converts them back into nitrogen gas
Where is denitrifying bacteria found?
Poorly aerated soil
How can famers reduce unhelpful bacteria
Ploughing and turning over soil
Name 3 sources of water pollution?
- toxic chemicals
- untreated sewage
- fertilisers
What’s the conditions for decomposition?
Warmth, moisture and air
What are detritus feeders’ role?
To start the decay process
What is eutrophication?
Water pollution caused by sewage or fertiliser
What is the effect of fertilisers in water?
- causes increased plant growth (algal bloom)
- which blocks sunlight so plants die
- bacteria eats the dead plants using up o2
What is the effect of sewage in water?
provides food for bacteria which use up o2 therefore fish die
What pollutes the air?
Sulphur dioxide and nitrogen oxides
How can acid rain effect plants?
damages leaves, buds, flowers and roots of trees
How can acid rain effect fish?
- Makes rivers too acidic
- causes leaching of toxic minerals eg aluminium
What’s leaching?
The washing of chemicals into the soil or water by rain.
What is a greenhouse gas?
A gas that absorbs infrared radiation from the sun
What are the most important greenhouse gases?
Water vapour Carbon dioxide Methane Nitrous oxides CFCs
How is carbon dioxide produced?
Combustion of fossil fuels
How is methane produced?
- by cattle
- fermentation in rice fields
- decomposition of waste In landfill sites
What is the greenhouse effect?
- sun emits rays to the earth
- some heat bounces back to space
- some heat is absorbed by green house gases
- which is within earths atmosphere
