GCSE Biology Unit 2 - Pyramids of Biomass

Pyramids of number, Pyramids of Biomass, Energy Transfer, Managing Food Production, The Carbon Cycle

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Pyramids of Number

Pyramids of number show how many organisms there are in the food chain for a particular area.

For example; a whole field of grass could feed 15 rabbits, which would feed 1 fox. This would be shown as;

                         _____                            Fox
                 ______________                    Rabbits
__________________________________ Grass

Not all pyramids of number will be pyramid shaped, e.g a single oak tree could feed a hundred caterpillars, which would feed around 10 blue **** which would feed 1 sparrowhawk. This would be shown as;

                           __                      Sparrowhawk
                   ___________              Blue ****
            ___________________      Caterpillar
                          __                       Oak

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Pyramids of Biomass

Pyramids of biomass are always pyramid shaped. They show the transfer of biomass in a food chain. Biomass is how much a group of organisms weigh all together. Each time you go up a step (trophic level) in the food chain, you lose biomass.
For example, the food chain grass --> rabbits --> fox would be shown as;

                           _____                          Fox
                  ______________                   Rabbits
__________________________________ Grass

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Energy Transfer

As biomass decreases, then so does energy. Energy is lost through the food chain because;
- some is used in photosynthesis and respiration
- some is lost in excrement
- some is lost through heat and movement

This loss of energy means that after a few stages there is not enough energy to support another organism. 

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Managing Food Production

Energy and biomass lost in a food chain can be reduced by;

- reducing the number of stages in the food chain
- keeping animals in small and heated conditions, so that less energy is lost as heat and movement

This is good for farmers as their animals will grow faster, and won't need as much food, and so they will make more profit.

However, it is also considered wrong because it's unnatural for the animals, allows diseases to spread easily, and uses up fossil fuels unnecessarily.

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The Carbon Cycle

CO2 in the air is taken out of the atmosphere by photosynthesis.

The carbon in plants is removed in respiration, or passed on to animals when they are eaten.

The carbon in animals is removed in respiration, or in decay by micro-organisms.

Micro-orgnanisms also respire, and release CO2 back into the atmosphere.

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