Natural Selection

Darwin began to theorize that these species shared a common ancestor and through a process called natural selection adapted to the environment they were in.

A common ancestor of the finches and tortoises must have been trapped on the Islands when sea levels rose and then adapted to the environment they were in.

These adaptations made them different, even though they all came from a common ancestor.

This adaptation Darwin called natural selection.

Let's use the finches as an example. A species of blue finch that eats fruit inhabits a jungle. There's lots of food and the blue helps it find mates. The jungle is huge, it can easily escape predators.

But then the sea rises, and the jungle becomes a bunch of islands. Some birds are stuck on big islands, some on small islands. On some islands there's lots of food, on some there is little food. On some there's lots of fruit, others nuts, on the next insects.

Darwin put all his findings into a book entitled "On the Origin of Species".

It caused waves in the scientific world and still remains one of the most important scientific books ever published.

It also shook peoples understanding of how the world was made and where we came from.

Darwin argued that all species were descended from a common ancestor, and, over time, thanks to changes in the environment, they had adapted and evolved to become the species they are today.