[Jaysun]

As for why there are still worms, etc., those critters are specifically adapted for their particular ecological niches. Part of evolution is adaptation to an environment.

That part is stupid on its face. Why aren't worms secluded to the one place that they could survive? And if they could survive anywhere, why evolve? As to the other part, give me a minute.....

[Junior]

Worms aren't everywhere, though they are in a lot of environments. Note that not all worms are identical. There are 5500 species of earthworms in the world alone. There are dozens of other types of worms, with thousands of different species, inhabiting environments ranging from the sea floor to the leaf mould of northern forests. And each of those species is specifically adapted for its environment.