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First exams 2025

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Trophic Levels (HL IB Biology)

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Naomi H

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Naomi H

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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

Food chain showing trophic levels

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

woodland food webFood 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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Naomi H

Author: Naomi H

Expertise: Biology

Naomi graduated from the University of Oxford with a degree in Biological Sciences. She has 8 years of classroom experience teaching Key Stage 3 up to A-Level biology, and is currently a tutor and A-Level examiner. Naomi especially enjoys creating resources that enable students to build a solid understanding of subject content, while also connecting their knowledge with biology’s exciting, real-world applications.