When they find these similarities, they conclude that these organisms have a common ____________________.

As organisms __________________ over time, changes in their anatomical structures can be seen in the fossil record.

When organisms remain the same for long periods of geological time, they are in __________________, and the fossils remain the same.

If organisms gradually change over long periods of geological time, they represent _____________________________.

If organisms suddenly change, new species often arise due to ___________________________ equilibrium.

As scientists study the fossils of different species, they begin to find _________________ between different types of species.

Evolution can also be seen through biogeography. Biogeography studies two organisms that are _____________________ isolated from each other.

Fossils of bivalves show that areas that are now above sea level were once the bottom of seas. The idea is that the supercontinent Pangea split to form separate ___________________.

Species of animals became separated by water and changed over time to become ___________________________ species.

The new, separate species no longer have the ability to _________________________.

Organisms are the same _______________________ if they have the ability to interbreed.

Sometimes rather than looking at the position of fossils in the fossil ______________________, scientists are working to determine the significance of similarities in the structures of organisms and their functions.

When they study ______________________, they are studying similar anatomical features such as patterns of bone growth. These anatomical homologies are similar structures although they may function differently. Examples include the forelimbs of humans, dogs, birds, and whales.

Some structures are _________________________, which means that their anatomical structures are very different, but have the same function. An example is bird wings and insect wings; they have different structures, but both are used for flying.

Some homologies are on the ______________________ level and can be seen in the similarities of DNA and proteins between species.

Other homologies can be seen only in the embryos; these are _________________________ homologies.