Apod of dolphins hunting and feeding on a school of fish is an example of

a community interaction.
an ecosystem interaction.
a biome interaction.
a population interaction.

A community interaction would be correct!
A community is when multiple populations interact with each other, in this case the dolphins and fish.

This type of galaxy is an approximately ellipsoidal shape and a smooth, nearly featureless image. they are the largest single star systems, in the universe and are built by the collisions of many smaller galaxies.