Trophic Levels
Get to grips with Trophic Levels for GCSE Biology with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. A separate (triple) biology topic where producers form trophic level 1 and apex predators sit at the top, while decomposers recycle materials.
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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
Trophic levels describe the position of an organism in a food chain, and they are numbered. This is a Triple-only topic.
Level 1 is the producers — plants and algae that make their own food by photosynthesis. Level 2 is the herbivores, or primary consumers, that eat plants. Level 3 is the carnivores, or secondary consumers, that eat herbivores. Level 4 is the carnivores that eat other carnivores, and apex predators are carnivores with no predators of their own.
Decomposers break down dead plant and animal matter by secreting enzymes into the environment. The digested food is then absorbed into the decomposer's body, which is why decomposition is described as extracellular digestion.
Revision notes
The numbered levels
Level 1: producers — plants and algae making food by photosynthesis.
Level 2: herbivores, or primary consumers. Level 3: carnivores that eat herbivores, or secondary consumers. Level 4: carnivores that eat other carnivores. Apex predators have no predators of their own.
Decomposers
Decomposers break down dead plant and animal matter.
They secrete enzymes into the environment, digesting the material outside their bodies. The soluble products are then absorbed into the decomposer's body — this is extracellular digestion.
Why levels matter
The trophic level determines what an organism eats and what eats it.
Energy and biomass are lost at each transfer between levels, which is why food chains rarely have more than four or five levels.
Key points
- Level 1 is the producers.
- Level 2 is the herbivores or primary consumers.
- Level 3 is the carnivores that eat herbivores.
- Apex predators have no predators of their own.
- Decomposers secrete enzymes into the environment.
- Decomposers absorb the digested products.
Worked examples
Example 1
Name the organisms found at trophic level 1 and explain why they are at this level. [2 marks]
Model answer
Plants and algae (1 mark), because they are producers that make their own food by photosynthesis rather than eating other organisms (1 mark).
Example 2
Describe how decomposers break down dead material. [3 marks]
Model answer
They secrete enzymes into the environment surrounding the dead material (1 mark). The enzymes digest the material outside the decomposer's body (1 mark), and the soluble products are then absorbed into the decomposer (1 mark).
Example 3
Explain what is meant by an apex predator. [1 mark]
Model answer
An apex predator is a carnivore at the top of a food chain with no predators of its own (1 mark).
Common mistakes
Numbering producers as level 0.
Producers are level 1.
Saying decomposers digest food inside their bodies.
They secrete enzymes outside and absorb the products — extracellular digestion.
Confusing primary and secondary consumers.
Primary consumers eat producers; secondary consumers eat primary consumers.
Forgetting this is a Triple-only topic.
It is not required for Combined Science.
Exam tips
- Learn the four numbered levels precisely.
- Describe decomposition as extracellular digestion.
- Define an apex predator as having no predators.
- Remember this is a Triple-only topic.
Key terms
- Trophic level
- The position of an organism in a food chain.
- Producer
- An organism making its own food by photosynthesis.
- Apex predator
- A carnivore with no predators of its own.
- Extracellular digestion
- Digestion outside the body, used by decomposers.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.