Atoms get recycled. Energy doesn't.
- The idea
- Predict
- See it
- Why
- Check
The idea
“Decomposers recycle everything, so energy goes back to plants like nutrients do.”
Decomposers really do return nutrients to plants, so it seems a dead body's energy should come back too. Only the atoms do.
The short version
The mistake: Decomposers recycle everything, so energy goes back to plants like nutrients do.
What's actually true: Matter cycles through an ecosystem. Energy flows through once and leaves as heat, so new energy must keep coming in.
- Atoms aren't used up. Carbon and nitrogen pass from producers to consumers to decomposers and back. That's matter cycling.
- Plants store light energy in sugar. Every organism's cellular respiration releases it, and it ends up as heat.
- No organism can turn heat back into sugar, so energy can't cycle. An ecosystem needs a steady energy input, usually sunlight.
On the exam: Atoms go around. Energy goes through once and leaves as heat.