Food chain and trophic levels

The idea

A food chain is a series of organisms feeding on one another, each step being a trophic level: producers form the first, herbivores (primary consumers) the second, small carnivores the third and larger carnivores the fourth.

Grass to snake

A snake eats a frog. The frog ate an insect. The insect ate grass.

How many steps, or trophic levels, are in this series of feeding?

• Four
• Two
• Six

Build the chain

Press Next step.

Levels in a chain

Each organism in the series is a step, a trophic level. Producers are first. Herbivores, the primary consumers, are second. Small carnivores, the secondary consumers, are third. Larger carnivores, the tertiary consumers, are fourth.

A food chain is a series of organisms feeding on one another, each step being a trophic level: producers form the first, herbivores (primary consumers) the second, small carnivores the third and larger carnivores the fourth.

Notes

A food chain is a series of organisms feeding on one another; each step is a trophic level.

Check yourself

Which organisms are at the first trophic level?

Herbivores are also called what?

At which trophic level are the small carnivores (secondary consumers)?

In the picture, an arrow runs from the insect to the frog. What does it show?

• Herbivores. Herbivores are at the second trophic level.
• Small carnivores. Small carnivores are at the third trophic level.
• Producers — correct. Yes!
• Primary consumers — correct. Yes!
• Secondary consumers. Secondary consumers are the small carnivores.
• Tertiary consumers. Tertiary consumers are the larger carnivores.
• The second. The second trophic level is for the herbivores.
• The third — correct. Yes!
• The fourth. The fourth trophic level is for the larger carnivores.
• The insect eats the frog. The arrow points to the eater. Here it points to the frog, so the frog is the one that eats.
• The insect and the frog are at the same trophic level. The insect is a herbivore at the second level. The frog is a small carnivore at the third level.
• The frog eats the insect — correct. Yes!