Describe how converting adp to atp is a key reaction in organisms

The conversion of adenosine diphosphate (ADP) to adenosine triphosphate (ATP) is a key reaction in organisms because it allows for later use of ATP as a source of energy.

Grape jelly so a y did you ask this question

Although i don't know what is the simulated system, starfish are predators that eat mostly  microalgae,  snails, sponges, bivalves, mussels and other small marine animals. removing starfish from any system would definitely increase this animals that they prey.