Energy in most ecosystems must flow through autotrophs because ______.

Autotrophs, such as plants and algae, capture energy from sunlight and store it as chemical energy in organic molecules. Heterotrophs obtain energy by consuming those molecules or other organisms, so energy in most ecosystems enters the food web through autotrophs. The statement that autotrophs are simpler is not the reason, and heterotrophs do not generally make energy through photosynthesis.

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