Step-by-step explanation:
In the given sentences:
"The poisonous plantlike anemone lives in a coral reef. When a small fish ventures near THIS CREATURE, IT is stung and eaten."
In this sentence, "THIS CREATURE" is referring to "the poisonous plantlike anemone." "IT" is referring to "the small fish."
"For some reason, the anemone makes an exception of the clown fish. When the clown fish is endangered by another fish, IT hides among the anemone’s tentacles. IT even builds its nest where the anemone can protect IT."
In this sentence, "IT" is referring to "the clown fish."