If the grass contains 100,000 kcal of energy, how much energy will a fox obtain from eating a bird?

1,000 kcal

Explanation:

As a general rule, every trophic level only gains 10% of the energy from the trophic level.

So, the grass has 100,000 kcal of energy.  Assuming the bird eats grass, it only gets 10,000 kcal of energy.  Assuming the fox eats the bird, it only gains 1,000 kcal of energy.

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