Why cant food chain be indefinitely long​

Because:

Explanation:

Some energy is lost gradually in several ways at each trophic level:

Energy is lost through respiration, generating heat at each trophic level.

Energy is lost through waste (waste through excretion, feces, leftovers, etc. or energy lost through shedding of leaves in plants, shedding, molting of animals, ..) at each trophic level.

The higher the food chain (or trophic level), the less energy accumulates and to a certain extent there is no longer enough to maintain a link (of a trophic level). When a link (actually a species or group of card fish of a species) has too few individuals (smaller than the minimum size of the population) will not exist.

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