Biology multiple choice.

Which element provides strength to the exoskeleton of clams and oysters

After fertilization, which type of cellular division is responsible for the growth and development of a complex, multicellular organism?

Why is the theory of evolution important? it disproves all other theories about how life began. it provides a topic for debate. it is a unifying concept in biology. it explains how life began. i know for sure, it is not "it is a unifying concept in biology."