A River, Not a Loop

You'll learnthat energy flows one way and leaves as heat, while matter cycles.

Follow the energy through a grassland — sun to grass to grasshopper to sparrow to hawk — and it is tempting to picture a loop, energy going round and round. It is a river: energy enters once, flows one way up the levels, and leaves as heat at every step, about 90% of it gone each time. Twelve short steps; press Next for each one.

12 STEPS · 6 QUICK CHECKS · ENERGY IS ONE-WAY · ~10% UP, ~90% AS HEAT · MATTER CYCLES, ENERGY DOES NOT · v6

energy · one way up the chain · out as heat · never back

Before you start

What you're looking at

A grassland food chain — sun to grass to grasshopper to sparrow to hawk — with heat leaving at every step.

The question

Does energy cycle around the ecosystem like a loop, or flow one way and leave?

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