At a deep sea whale fall, the Atlantic hagfish, the crustaceans, and the sand make up which of the following?

I would say part of an ecosystem and community.

Explanation:

An ecosystem is a biological community of interacting organisms and their physical environment .In the bottom of the sea,there are already many animals living here and when the whale fall appears at the bottom of the ocean it becomes apart of the ecosystem as it provides them with food.

This is because when a whale dies, its body often falls to the seafloor. The whale's body then becomes food and shelter for organisms in the deep sea. This is called a whale fall. A deep-sea whale  fall might support 200 different species for as long as 10 years! Larger species, such as Atlantic hagfish, are the first to arrive to feed  on the whale flesh. Later, smaller species of snails and crustaceans come to eat the remaining flesh. Worms burrow into the sand beneath  the whale body, and bacteria feed on the whale bones.

segmentation=endoskeleton=backbone=coelom=tissues

the correct answer is:

a population changes in response to a change in the environment.