Nematodes
Nematodes also known as roundworms are one of the most diverse animal phyla with over 28,000 described species, scientists believe that there are many more species of nematodes, but many of them look very similar and hard to differentiate. Nematodes have successfully adapted to every ecosystem on earth, they have been found in water, soil, the highest mountains, hot springs, and polar regions. Most nematodes have separate male and female individuals and reproduction is usually sexually, nematodes however do represent a wide variety of modes of reproduction. Some nematodes are hermaphroditic, while some exhibit androdioecy, which is when there is one male population and one hermaphroditic population.