Download Trophic Levels and Pyramids

Trophic Levels and Pyramids
The food chain shows the direct transfer of food energy between
the trophic levels (a trophic level is a feeding level in the chain of
energy transfer)
There are 4 trophic levels;
Trophic level 1 = autotrophs (producers capable of producing
solar energy into food energy for their own use and for the
consumption of others)
(The next 3 levels are heterotrophs – consumers which cannot
produce their own food energy but have to feed on other
organisms in order to obtain energy)
Trophic level 2 = herbivores (plant eaters e.g. rabbits)
Trophic level 4 = Carnivores (meat eaters e.g. foxes)
Trophic level 4 = Top carnivores (e.g. birds of prey )
There are also omnivores (eaters of both plants & meat e.g.
humans and detritivores (decomposers e.g. fungi & bacteria)
Only about 1% of the energy from insolation is converted by
photosynthesis in which the green plants convert sunlight, H2O
and CO2 into carbohydrates such as glucose.
This provides energy for the producers that they can use in;
 Growth
 Reproduction
 Movement
 Respiration
- but also food energy that can be used by herbivores.
At each trophic level energy is used by the organisms and so at
each successive level there is less energy available, so the amount
of living organic matter that can be supported is reduced.
This reduction in energy leads to a pyramid structure known as a
trophic pyramid. The width of each stage is considered to be
proportional to the amount of energy stored (the biomass – the
amount of living matter or stored energy in an ecosystem or in a
trophic level)
While the idea of a food chain is simple, in any ecosystem there
are more complex feeding patterns which can be shown by using a
food web.