Where every food chain starts: producers make their own food by photosynthesis. So they always form the first trophic level of a food chain.
The points to remember
- Producers make their own food by photosynthesis.
- They are mostly plants, algae and photosynthetic bacteria.
- They form the first trophic level of every food chain.
- Every other organism in the chain gets its energy from them, directly or through other organisms.
Remember it as: Producers produce: they make the food everyone else eats.
Plants
- On land.
- Grass, trees, crops such as wheat.
Algae
- Mostly in water.
- Seaweeds and phytoplankton.
Photosynthetic bacteria
- Single cells, in water and soil.
- For example cyanobacteria.
Real example: the tiny phytoplankton of the oceans carry out about half of all the photosynthesis on Earth, so they are the producers for almost every ocean food chain.
Photosynthesis in one line: How photosynthesis works is taught in 2.2.4. Here you only need: producers use it to make their own food.
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To find an organism's trophic level, start at the producer and count along the arrows. Each step is one level up.
Counting the levels
- Count from the producer: the producer is level 1.
- Level 2 = primary consumer (a herbivore, it eats the producer).
- Level 3 = secondary consumer; level 4 = tertiary consumer.
- Level 5 = quaternary consumer, often the top carnivore.
- Give the name and the number: 'tertiary consumer, fourth trophic level'.
Remember it as: Producer 1, herbivore 2, then count the arrows.
Real example: in the Southern Ocean, krill are primary consumers at the second trophic level, and leopard seals are tertiary consumers at the fourth.
Words that do not score on their own: 'Top predator', 'top consumer', 'tertiary' or 'third' alone may not get the mark. Write the full name and the number, for example 'tertiary consumer, fourth trophic level'. Only your first answer is marked.
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How this comes up: Paper 2, Section A, or a Paper 1 resource: a food chain or web. State the trophic level of one organism [1].
Figure 1 shows a simplified food chain in the North Sea.
State the trophic level of the Atlantic puffin.
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