Insects are the most species-rich type of animal life on Earth. We already know a million of their species, but there might be even ten times as many, and they probably comprise about 90% of animal species. Why is that?
They were the first to colonize land about 480 million years ago. This gave them a head start before larger creatures made this move as well. Furthermore, they were also the first to evolve powered flight. This made it easy for them to spread even to habitats difficult to reach, like islands where other animals couldn’t walk.
They are so small that sometimes it’s enough that the wind accidentally carries them to remote islands and places, and they can quickly colonize them. Many species multiply fast. Since they are so tiny, there can be many species occupying larger landmasses. Their populations can even fragment and evolve new species.
They have a segmented body, and evolution via natural selection made it easy to develop new uses for these segments, especially since they have short lives and each generation is shorter than that of larger animals. Natural selection can act on them faster to develop new traits if the environment changes or if they reach a new habitat, making it easy to colonize it.
Many species are very hardy. Only one extinction event of multicellular life dented their diversity. It was the Great Dying 252 million years ago. During the extinction of non-avian dinosaurs 66 million years ago, their diversity didn’t drop when so many other creatures ceased to exist. They are great survivors of natural disasters, and some can even withstand radiation. Incredible creatures!
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