Just like Platyhelminthes, the Nematoda phylum includes worms. They are called the Roundworms. These types of worms are more round in shape as they present a more cylindrical or slender shape. Similar to the platys, the roundworms come in free-living species and parasitic species that can live in marine waters, fresh waters, terrestrial and in a host. The separation of the mouth and anus, just like in flatworms creates a more steady and smooth function in digestive organ systems. The body plan of nematoda members is almost identical to those of Platyhelminthes. They have bilateral symmetry and have three germ layers as they are triploblastic. Differences arise when we shift our attention to the coelom however. Roundworms have a pseudocoelmate which is Latin for false coelom, although the body cavity shows scientist that maybe a coelom is starting to show, its really just a trick question. In order to reproduce its offspring to the next generation, roundworms reproduce mostly sexually as some species are hermaphroditic and can use internal fertilization. Whereas others will mate with a separate sex and once again use internal fertilization. Diffusion plays a dominant role in both phylum's as they depend on it for circulation and respiration as neither are advanced enough to supply specialized organs and systems in play for self-circulation or respiration. Once food has been hunted and ingested it will enter through the mouth and be eliminated through the anus. In between these two processes a long digestive tube has been created for the development of the digestive tract. Free-living roundworms tend to eat small animals depending on where they live. Soil-dwelling and aquatic forms will eat algae fungi or pieces of decaying matter just like those of flatworms. But in order to have a smooth and developed digestive system, an excretion system must also be developed. This area of the body proves to bring up many differences between flatworms and roundworms. In flatworms, a primitive kidney was created. This body function was known as the flame cells which removed metabolic waste from the worms body. In roundworms, diffusion pushes wastes out of cells and it activates the anus to get rid of solid wastes. The nervous system on the other hand has a simple brain with a nerve cord on the ventral and dorsal side of the body. Just like flatworms, roundworms contain ganglia that run from the head through the length of the body. These nerves transmit and give off signals controlling movement.
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