Question

What evolutionary milestone involving animals occurred during the Devonian Period?

Answer 1

Walking on land.

Explanation:

The Devonian period (420 million years ago to 360ish million years ago) is also sometimes called the "Age of Fishes". Life was evolving a lot in the oceans and in freshwater, but the land was plants, algae and some arthropods. During the Devonian period we see fish adapting to live on land which would eventually evolve into the first amphibians. During this period it is likely that insects evolved, as the oldest known insect fossil is from this period.