The Nitrogen and Carbon Cycles - OCR B4/B6

Description of the cycles for all of part B4 and the additional information needed on the nitrogen cycle for B6

HideShow resource information
  • Created by: NoirRose
  • Created on: 10-06-12 11:44
Preview of The Nitrogen and Carbon Cycles - OCR B4/B6

First 470 words of the document:

The Nitrogen Cycle ­ B4/B6
The atmosphere contains 78% nitrogen and is very unreactive. Nitrogen is needed for
making proteins for growth, so living organisms have to get it somehow plants get their
nitrogen from the soil, so nitrogen in the air has to be turned into nitrates before plants
can use it. Nitrogen compounds are then passed along food chains and webs as animals
eat plants (and each other). Decomposers (bacteria and fungi in the soil) break down
proteins in rotting plants and animals, and urea in animal waste, into ammonia. This
returns the nitrogen compounds to the soil so the nitrogen in the organisms is recycled
Nitrogen fixation is the process of turning N2 from the air into nitrogen compounds in the
soil which plants can use. There are two main ways that this happens: lightning there's
so much energy in a bolt of lightning that it is enough to make nitrogen react with the air
to give nitrates, Nitrogen fixing bacteria in roots and soil. There are four different types of
bacteria involved in the nitrogen cycle:
Decomposers decompose proteins and urea and turn them into ammonia
Nitrifying bacteria turn ammonia into nitrates (in decaying matter)
Nitrogen fixing bacteria turn the atmospheric nitrogen into nitrogen compounds
Denitrifying bacteria turn nitrates into N2 gas (this has no benefit to living organisms)
Some nitrogenfixing bacteria lives in the soil. Others live in nodules on the roots of
legume plants such as peas and beans. This is why legume plants are so good at putting
nitrogen back into the soil. The plants have a mutualistic relationship with the bacteria
the bacteria get food (sugars) from the plant, and the plants get nitrogen compounds the
bacteria then to make into proteins. So the relationship benefits the both of them.
There are certain names for the bacteria that you have to know for B6 these are:
Nitrifying Bacteria:
NitrogenFixing Bacteria:
The Carbon Cycle B4
Carbon dioxide removed from atmosphere by green plants which is turned into
carbohydrates, fats, and proteins. Some Carbon Dioxide is returned to atmosphere when
green plants respire. Some carbon becomes part of the compounds in animals when
plants are eaten. (Carbon moved through food chain). Some Carbon Dioxide is returned
to atmosphere when animals respire. Plants + animals die, detritus feeders
(microorganisms) feed on their remains, when they respire Carbon Dioxide is returned to
atmosphere. Animals produce waste which is then broken down by ditritus feeders and
microorganisms. Carbon is constantly being recycled from air, through food chains and
eventually the air again.


No comments have yet been made

Similar Biology resources:

See all Biology resources »See all resources »