Trophic levels — AQA GCSE Biology
Test yourself on Trophic levels with AQA GCSE practice questions.
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Trophic levels explained
Trophic levels are numbered so that feeding positions can be compared across different food chains.
Read the full explanation
Numbering always begins at level 1, which contains plants and algae. These organisms are producers: they absorb light energy and use photosynthesis to make glucose, converting carbon dioxide and water into organic compounds. Because they generate the organic matter that other organisms eat, they occupy the first step of every food chain and receive no energy from other organisms. A consumer that eats a plant or alga is at level 2, and each further feeding step increases the number by one. Using numbers makes it possible to compare a grassland chain such as grass to rabbit to fox with an aquatic chain such as algae to water flea to fish.
Your focus
- Assign level 1 correctly to plants and algae in any given food chain.
- Explain why numbering begins with producers rather than consumers.
- Use trophic level numbers to compare feeding positions across different ecosystems.
Trophic levels exam tips
Marking Points
- Trophic levels are numbered in sequence, and the numbering always starts at level 1.
- Level 1 is occupied by plants and algae, which are producers.
- Producers make their own food by photosynthesis, using light energy, carbon dioxide and water.
- Because producers do not consume other organisms, they form the base of the food chain and supply energy to all higher levels.
- Numbering allows feeding positions in different food chains to be compared directly, for example grass at level 1 in a field and algae at level 1 in a pond.
Examiner Tips
- 💡When labelling a food chain, write the level number beneath each organism and check that the first organism is a plant or alga.
- 💡Use the phrase starting at level 1 with plants and algae when explaining the numbering convention.
- 💡If a question gives an unfamiliar producer such as phytoplankton, still assign it level 1 because it photosynthesises.
Common Mistakes
- Starting the numbering at level 0 or at the first consumer; correct this by stating that level 1 is always the producer, such as a plant or alga.
- Assuming only land plants can be level 1; correct this by including algae and other photosynthetic organisms such as phytoplankton.
- Describing producers as organisms that eat dead material; correct this by stating that producers synthesise their own food by photosynthesis.