Trophic Levels (Edexcel IGCSE Science (Double Award)): Revision Note

Exam code: 4SD0

Trophic Levels

  • The trophic level is the position of an organism within a particular food chain

  • Within a food web an organism can be in different food chains and have a different trophic level for each

Level

Organisms

Energy transfer

First trophic level

Producers (plants, algae)

Producers convert light energy from the sun into chemical energy stored in glucose during photosynthesis.

Second trophic level

Primary consumers

Eat producers and transfer chemical energy from plant tissues into their own.

Third trophic level

Secondary consumers

Eat primary consumers and gain energy from their tissues.

Fourth trophic level

Tertiary consumers

Eat secondary consumers and gain energy from their tissues.

A food chain starting with grass, then showing a grasshopper, a frog, a snake and an eagle a
  • At any trophic level organisms produce waste, or may die; the energy in waste or dead matter is then transferred to decomposers (bacteria and fungi)

    • Decomposers break down dead organisms and waste, recycling nutrients back into the ecosystem

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