When a grasshopper eats grass, only some of
the energy from the grass is stored in the grasshopper's body. How does
the grasshopper use the rest of the energy?

Answer

the rest of the energy is used to help it jump

Explanation:

The rest of the energy from grasshopper will be transferred to the next trophic level in the food chain with in the ecosystem.

Explanation:

All the organisms with in an ecosystem are part of some food chain. Hence when ever an organism feed upon some other organism/plant to get energy , retains some part of it and  transfers the rest of energy to the next trophic level.

Usually in a food  chain, all organisms retain 10% of the energy they get from the preceding trophic level and transfers 90% of the energy to the next trophic level.

Thus, whichever organism feed on grasshopper or depend for food on grasshopper in some or the other way will get the rest of the energy.

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the question isn't complete here so i can't right an answer '_'