Flatworm Essay

There are numerous differences between flatworms, roundworms, and segmented worms, both externally and internally. Flatworms is part of the phylum named Platyhelminthes, that is part of kingdom Animalia. They are usually soft and flat, and they also have internal organ systems and tissues. Flatworms are the simplest organisms that have three embryonic germ layers, are bilaterally symmetrical, and have the feature of cephalization. Cephalization is the concentration of sensory organs and some other organs at the anterior end of the body, or the front end. This forms a head and a brain both during evolution and in the course of a developing embryo. Flatworms have a digestive cavity with just one opening, which is its mouth. Very close to the mouth is muscular tube that is called a pharynx that pumps into the digestive cavity. Free-living flatworms have several ganglia, which are just …show more content…
Many roundworm species are free-living. They have a body cavity that is between the endoderm and mesoderm tissues. The endoderm germ layer is like an internal layer and the mesoderm germ layer is like a middle layer. The body cavity is known as a pseudocoelom, due to it only being relatively lined with the mesoderm tissue. Roundworms have a digestive tract that consists of two openings, which are a mouth and an anus. Roundworms need to depend on diffusion, or the natural spreading of particles from a high to a low concentration, for their circulation, excretion, and respiration, as they also have no circulatory system like the flatworms. In roundworms, the fluid and muscles that are contained in the pseudocoelom operate as a hydrostatic skeleton, or an exoskeleton that maintains its form due to the pressure of fluid inside the skeleton. Roundworms have two nerve cords that transmit impulses in the roundworm. Also, they are able to reproduce sexually by internal