Roundworm (phylum Nematoda)

Roundworms, or nematodes, are the most abundant group of animals living on Earth today. The combined weight of all nematodes makes up only about 1% of the animal biomass on the planet, but they far surpass any other animal phyla in terms of population number. It is estimated that the average gram of soil contains about one hundred nematodes! They are simplistic animals, a round body with a round gut that runs from front to back, that have successfully adapted to and populated almost every known habitat. They have colonized the deepest trenches, the highest mountains, and everything in between. Their wide distribution and adaptation to very unique habitats also makes them one of the most diverse groups of animals. Some estimates say that there could be over 1 million unique species of nematodes living today. However, determining differences between nematode species is very difficult as a vast majority of them look virtually the same...