All of the following (corals, jellyfish, and sea anemones) have only one opening into their digestive system, except roundworms, which have more than one.
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Answer:
quaternary consumers
Explanation:
they occupy the top position in a pyramid because nothing preys upon them in return. also a prey of one species could be another predator of species!
Deoxygenated blood could get to body cells which would be useless since oxygen is needed for functioning