The chemical energy of these plants all started with what energy source?

Sun(solar energy)

Explanation:

The sun is the ultimate source of energy in our solar system.

The chemical energy in plants all started out with solar energy from the sun.

During the process of photosynthesis;

Photosynthetic reaction simply converts solar energy from the sun into chemical energy.

Almost all animals obtain their own energy needs from the plants converting the chemical energy into other forms of energy.

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