Food chains are short

The idea

Because so little energy passes to each next level, food chains generally have only three or four steps; very little usable energy remains after four trophic levels.

A long chain?

Imagine a food chain with ten steps: grass, then ten kinds of animals, each eating the one before.

Do food chains generally have so many steps?

• No, generally three or four steps
• Yes, ten or more steps
• Yes, they go on until the energy is zero

Pass the energy down

Press Next step. The energy amounts are an example.

Little energy left

At each step only about 10% of the energy passes on, so very little is available for the next level of consumers. The loss of energy at each step is so great that very little usable energy remains after four trophic levels. That is why food chains generally have only three or four steps.

Because so little energy passes to each next level, food chains generally have only three or four steps; very little usable energy remains after four trophic levels.

Notes

So little energy passes on that food chains have three or four steps.

Check yourself

Why do food chains generally have only three or four steps?

The producers hold 20000 J (an example). Using 10% at each step, how much reaches the fourth trophic level, in J?

Answer: 20 J

Level 2 has 2000 J, level 3 has 200 J and level 4 has 20 J.

After how many trophic levels does very little usable energy remain?

If a food chain had one more step beyond the fourth level, about how much of the fourth level's energy would reach it, on average?

• Energy increases at each step, and there is too much of it. Energy diminishes at each step. It does not increase.
• Producers are found at the fourth trophic level. Producers are at the first trophic level.
• So little energy is available for the next level of consumers — correct. Yes!
• Four — correct. Yes!
• One. The first trophic level, the producers, holds the most energy in the chain.
• Two. The second level still gets about a tenth of the energy of the producers, which is more than the very little left after four levels.
• All of it. Much of the energy is lost at each step. On average only 10% passes on.
• About a tenth of it — correct. Yes!
• Ten times as much. Energy diminishes at each level, so the next level cannot get more than the one before.