Phylum Platyhelminthes
Platyhelminthes are one of the simplest animals that are both bilaterally symmetrical and triploblastic. Being triploblastic means they are composed of three fundamental cell layers. Often referred to as flatworms, these animals have no body cavity except for a gut, and they also don't have a anus. Since they have only a gut, this causes them to be flat and their gut is highly branches so it will be able to distribute food throughout the entire body. Since they are flat they must breath through diffusion. Flatworms are divided into three main groups; Flukes, planarians, and tapeworms. Flukes are all types of parasites. Tapeworms are all intestinal parasites in other vertebrates. Planarians are the most free living type of Platyhelminthes. They can be found in oceans, freshwater, and very few are parasitic. |