How do consumer obtain energy and nutrients

Consumers constitute the upper trophic levels. Unlike producers, they cannot make their own food. To get energy, they eat plants or other animals, while some eat both. ... They eat primary producers—plants or algae—and nothing else.

Explanation:

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the answer is true when observing or determining population size, a direct observation is use, in which each organism is counted in a population or in an area. one benefit of this measure is that you get the exact population count but it will take a long time to  determine  the  size  of a  population.