The shark is a fish while the dolphin is a mammal these are twp completely different types of animals but they have similar characterisics due to their similar these animals may have evolved their similarities by

 The Correct Answer Is (Convergent evolution )

Explanation:

When the organisms in the course of evolution, evolve to develop traits that are similar to each other even though they are not closely related to each other then such type of evolution is known as convergent evolution.

Since both shark and dolphin are not closely related to each other but their characteristics have developed similarly because they have occupied similar habitats their evolution is convergent in nature.

not sure if this is what you'r looking for eubacteria and archaebacteria

geologic time scale (for gradpoint) =)