Medians and Centroid Dance Recall that a median of a triangle is a segment that connects any vertex to the midpoint of the side opposite that verte
it has 3 medians.

What subject are you on

It explains why rocks appear in layers

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.