Eohippus
Scientists think the eohippus was the ancestor of the modern horse. The
eohippus was a small animal that had toes instead of hoofs.
Change or die!
Suppose that all the milkweed plants in the world suddenly died. What
would happen to monarch butterfly caterpillars? They eat only milkweed
leaves.
The mother monarch butterflies would have to lay their eggs on another
kind of plant. And the caterpillars would have to learn to eat the
leaves of that plant. Otherwise the caterpillars would die, and soon
there would be no monarch butterflies.
If the monarch butterflies changed, and learned to eat another kind of
plant, we would say they had adapted. And if they didn’t change, and all
died, we would say they were extinct.
Millions of years ago giant reptiles called dinosaurs were everywhere.
Maybe the world got too cold for them. Maybe something happened to their
food. But
whatever happened, the dinosaurs weren’t able to adapt. There are no
dinosaurs alive today. They are all extinct.
Millions of years ago there were tiny horses with toes instead of hoofs.
They lived in forests and ate leaves. Then something happened. Maybe
there wasn’t enough food. Maybe the forests became too dangerous. But
the horses learned to live on the plains and eat grass. They adapted.
The horses of today came from those long-ago horses that adapted. In
fact, every kind of animal in the world today came from animals that
adapted long, long ago.
American Saddle Horse
The American saddle horse is a favorite of people who like to ride
horses. The adult horse is 4.8 to 5.4 feet (1.44 to 1.62 meters) high at
the withers (shoulders).
