Nematoda
The Nematoda Phylum is a very interesting Phylum. Just for roundworms alone there are over 15,000 species that we know of. Some species of roundworms lay 200,000 eggs just in one day. Just imagine over thousands of years how fast they can populate. It is one of the most diverse species on earth. They can live in almost every single environment on earth and survive.
Nematoda don't really have a set skeletal structure like most other organisms do. Nematoda also known as Roundworm are pretty much like there names, Long round worms. They have small round like bodies and can either be at a parasitic level or can grow up to a foot or two in length.