AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
Further trophic levels are numbered subsequently according to how far the…
Full specification wording
Trophic levels: Further trophic levels are numbered subsequently according to how far the organism is along the food chain.
Once level 1 is fixed as the producer, every later feeding step is numbered by adding one.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 3 of 9
- 3 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Once level 1 is fixed as the producer, every later feeding step is numbered by adding one. An organism that eats the producer is at level 2, an organism that eats that consumer is at level 3, and an organism that eats the level 3 consumer is at level 4. The number therefore measures how many feeding steps separate the organism from the producer, not how large or fierce it is. In the chain algae to water flea to small fish to heron, the algae are level 1, the water flea level 2, the small fish level 3 and the heron level 4. An omnivore may occupy more than one level in different chains, depending on what it eats.
What earns the marks
- Each successive feeding step along a food chain increases the trophic level number by one.
- The trophic level number shows how far the organism is from the producer in terms of feeding steps.
- Level 2 organisms feed on producers, level 3 organisms feed on level 2 organisms, and level 4 organisms feed on level 3 organisms.
- The same species can occupy different trophic levels in different food chains if its diet differs.
- Trophic level number is determined by diet and position in the chain, not by body size, abundance or habitat.
Common mistakes and how to put them right
Numbering organisms by size, with the largest predator always called level 4.
Put it right by numbering according to feeding steps from the producer.
Skipping a number when an organism eats more than one type of food.
Put it right by assigning the level that matches its position in the particular chain being described.
Assuming a named species always has one fixed trophic level.
Put it right by checking what it eats in the food chain shown.
Exam tips
- Count the arrows from the producer to the organism; each arrow represents one feeding step and one increase in level number.
- Write the level number next to each organism before answering a question about differences or energy transfer.
- If a species appears in two chains with different diets, state the level separately for each chain.
Try the lesson
The start of the Trophic levels: Further trophic levels are numbered subsequently according to how far the organism is along the food chain. lesson, made from checked teaching notes for this specification point.
Have a go first
In a food chain, a snail eats a cabbage leaf. The cabbage is at trophic level 1. Which trophic level is the snail at?
Listen
Once level 1 is fixed as the producer, every later feeding step is numbered by adding one. An organism that eats the producer is at level 2, an organism that eats that consumer is at level 3, and an organism that eats the level 3 consumer is at level 4. The number therefore measures how many feeding steps separate the organism from the producer, not how large or fierce it is.
See it
Put it in order
Put these steps in the order they happen.
- 1. Small fish — level 3
- 2. Heron — level 4
- 3. Water flea — level 2
- 4. Algae — level 1
Key words
Say what each word means before you turn the card.
Trophic levels
Try answering aloud or in your head before turning the card.
Sequential numbering of feeding positions
Try answering aloud or in your head before turning the card.
Diet-dependent classification of consumers
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See every definition
- Trophic levels
- Feeding positions along a food chain that are numbered subsequently according to how far the organism is along the food chain.
- Sequential numbering of feeding positions
- Once level 1 is fixed as the producer, every later feeding step is numbered by adding one.
- Diet-dependent classification of consumers
- The same species can occupy different trophic levels in different food chains if its diet differs.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
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