Bullies: you know what they're like - always trying to push you around, and always bigger than you. You can try and ignore them, but they never seem to go away. Some of the smaller animals swimming and crawling in the ancient seas had a worse problem. One false move and they could end up as the bullies' breakfast.
One way to avoid hungry predators like this was to escape to somewhere they couldn't follow. And this is just what some animals did nearly 500 million years ago, by taking their first steps on land. From the time when life first evolved animals had lived in the sea. But then some arthropods (those animals with lots of armoured legs and crunchy outer shells) were able to
spend more time out of water. So they could more readily escape from the large animals that were forever trying to eat them.
Was this article helpful?