Wich lists the correct sequence of events for evolution to occur through isolation?

What function does the limb sever in each animal? how are the limb bones of the four animals similar? based on these similarities what can be inferred about the evolution of the four animals.

Several billion years ago which gas was the least prevailant in the atmosphere

Which statement describes compounds a. compounds are made of one type of atom. b. compounds cannot be represented by models. c. compounds are represented by chemical formulas. d. compounds cannot be broken down into simpler forms.