In the early 1900s, a scientist named Alfred Wegener noticed how the continents seem to fit together and developed the theory of continental drift. Continental drift is the theory that continents can drift apart from one other and have done so in the past. Wegner's theory also explained why fossils of the same plant and animal species are found on both sides of the Atlantic Ocean. In addition, similar types of rock and evidence of the same ancient climatic conditions are found on several continents.

Wegner hypothesized that all the separate continents of today were once joined in a single landmass that he called Pangaea.

See if you can trace how Earth's continents have shifted over time. Below are a series of 5 images showing the positions of Earth's continents during 4 different geologic time periods. Drag the images to the correct location on the timeline.

See if you can trace how Earth's continents have shifted over time. Below are a series of five images showing the positions of Earth's continents during four different geologic time periods. Drag the images to the correct location on the timeline.

As continents shift, separate, or move together, varied species are either isolated in a particular place, or they are able to move from one location to another. As they move, these species either adapt to new conditions or they perish. As time passes, species evolve and become more suited to their environment.