How can a change to the population of one species affect an entire ecosystem?

please help!!

When change occurs in the population of one species affect the entire ecosystem. If the population of herbivores goes very high then all the producers i. e. Plants are eaten by the herbivores and no vegetation is available for other animals and they will die because of hunger.

For example, if the population of deer increases in a forest ecosystem, so all plants are eaten by the deer and no plants are available for another herbivores.

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