Saclike structure that stores materials for use by the cell is called

A vacuole  

Explanation:

A vacuole is a fluid-filled organelle found in all plant cells. It is enclosed by a membrane called the tonoplast and can store materials for use by the cell.

the answer to this question is a

the reason the two sea urchins don't compete with each other for food, resources, etc. is because the urchins have adapted to the environment but they have also adapted to each other. this is most likely because the genes of the sea urchins.