This type of fossil is tree sap hardened and replaced by minerals.

The fossil record shows life has evolved from -------------- to more -----------------.

The ancestors of whales had back legs. Small leg bones still protrude from the skeletons of whales today, although modern whales no longer use legs. These leftover structures are

When organisms develop variations that make them better suited to their environment, these variations are called

What is the study of the earliest development of an organism, before it’s born, called?

Butterflies and birds use their wings to fly, but the structure of their wings is different because the wings did not evolve from a common ancestor. These are an example of __________ structures.

As shown in the picture, dolphin flippers, bat wings, human arms, and frog legs all have similar structures since these animals all shared a common ancestor.  Scientists call these structures ___________________________.

Using DNA to determine which organisms are related to others is called:

If modern organisms have a lot of homologous structures, what inference could be made about those organisms?