Trophic Levels (DP IB Biology)
Revision Note
Trophic Levels
Trophic levels are the position of an organism in a food chain, and indicate how many organisms energy has passed through
Trophic levels can be represented by numbers, beginning with producers at the first trophic level, and progressing to consumers at the second and third trophic levels, etc.
Trophic levels table
Trophic level | Name of trophic level | Description of trophic level |
---|---|---|
1 | Producers | Organisms that produce their own carbon compounds using, e.g. light energy |
2 | Primary consumers | Herbivores that feed on plant tissue |
3 | Secondary consumers | Carnivores that are predators of primary consumers |
4 | Tertiary consumers | Carnivores that are predators of secondary consumers |
5 | Quaternary consumers | Carnivores that are predators of tertiary consumers |
Energy from sunlight enters the food chain at the first trophic level
Producers convert light energy into chemical energy
This occurs during photosynthesis
This chemical energy is then transferred to primary consumers as they consume producers
The chemical energy is then transferred from one consumer to the next as each organism is ingested by organisms higher up the food chain
Primary consumers transfer energy to secondary consumers
Secondary consumers transfer energy to tertiary consumers
Tertiary consumers transfer energy to quaternary consumers
Apex predators are at the very top of the food chain; these top predators have no predators that prey on them
The chemical energy stored within apex predators can be passed on to decomposers when apex predators die and are decomposed
Trophic levels are the levels at which organisms feed in a food chain, and indicate the number of organisms through which energy has been transferred
Trophic levels can also be identified within food webs, which give a clearer representation of the complex feeding relationships present in an ecosystem
Note that some organisms have a varied diet, meaning that a species may be present at more than one trophic level in an ecosystem
Species may be at different trophic levels in different food chains within a food web, e.g. in the food web below:
Sparrowhawks are at the third, fourth and fifth trophic levels in the food chains:
Grass → mouse → sparrowhawk
Tree → butterfly → robin → sparrowhawk
Tree → aphid → beetle → robin → sparrowhawk
Robins are at the third and fourth trophic levels in the food chains:
Tree → caterpillar → robin → sparowhawk
Tree → aphid → beetle → robin → sparrowhawk
Food webs also contain trophic levels. Note that it is possible for an organism to be at different trophic levels in different food chains within a food web.
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