What do homologous and vestigial structures suggest about the process of evolutionary change?

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.

Describe how a non-resistant staphylococcus aureus bacterium can produce a bacterium that is resistant to methicillin

Which could be a pathway of food through an ecosystem