Phylum Platyhelmenthes - A. Phylum Platyhelmenthes With...

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A. Phylum Platyhelmenthes With bilateral symmetry comes development of cephalic region Acoelomate Triploblastic One opening to body cavity –pharynx Tripartite gut 3 channels No circulatory system Simple diffusion for gas exchange and distribution of nutrients Slightly centralized nervous system o Two ventral nerve cells joined at ghanglia Have true muscles Ex: planaria Bilateral symmetry Sac-like gut Mesodermal layer gives rise to muscles Common name: “flatworms” o Flat for diffusion of gases, distribution of food resources, and escaping predators Keeping ionic balance: o Protonephridia “flame cells” Have bundle of cilia, draws water in Several connected by excretory channels, occasional excretory pore where it is excreted Not very selective Reproduction:
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o Simultaneous hermaphrodites Male and female reproductive organs Internal fertilization, then releases eggs into the outside world Unusual capacity for regeneration
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Phylum Platyhelmenthes - A. Phylum Platyhelmenthes With...

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