what is the distinctive feature of a predator-prey relationship?

Answer 1

It is a sinusoidal relationship. As the prey population decreases from overfeeding by predators, the predator population begins to decrease because there is not enough to eat. As the predator population decreases, the prey population begins to increase because there are fewer enemies. The cycle goes on and on.

Answer 2

A distinctive feature of this relationship could be the "arms race". The pray evolves behaviors, armor, and other defenses that reduce their vulnerability to predators. In return the predators seek new ways of becoming better at catching their evolving pray.

Predator-prey relationships lead to evolution.