how do protists help other animals?

Answer 1

Unicellular aquatic Protista (plankton) form a very important component of the food chain. The photosynthetic ones are called phytoplankton and the heterotrophic ones are called zooplankton (which also includes many animal larvae or tiny crustaceans)

Phytoplankton (from Greek phyton, or plant), autotrophic pro- or eukaryotic algae that live near the water surface where there is sufficient light to support photosynthesis. Among the more important groups are the diatoms, cyanobacteria and dinoflagellates.

Zooplankton (from Greek zoon, or animal), small protozoans or metazoans (e.g. crustaceans and other animals) that feed on other plankton. Some of the eggs and larvae of larger animals, such as fish, crustaceans, and annelids, are included here.

Plankton is food for bigger animals.

Answer 2

It's hard to understand your question. Do you mean protests or protection?