BIOL10005 Chapter Notes - Chapter 1-5: Flatworm, Antheridium, Mitosis
26 Oct 2017
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Kingdom anamalia: poriferans: sponges are sessile, aquatic filter-feeders, and are mostly marine. They have layers of cells containing different specialised cells; however, sponges are not considered to be composed of different tissues: cniderians: include jellyfish (pictured), anemones and corals. Their body walls have two cell layers called ectoderm and endoderm, and a middle gelatinous layer called mesoglea. They possess a digestive system with a mouth but no anus, they have a net-like nervous system, and they possess unique organelles called nematocysts in cells called cnidocytes. These cells are present on slender outgrowths called tentacles. When triggered, nematocysts penetrate prey and release toxins to immobilise them: platyhelminthes: (flatworms) are said to be acoelomate (unlike the other protostome phyla) because their middle tissue layer (derived from mesoderm) does not contain a coelom (body cavity). They contain both free-living (like the turbellarian pictured) and parasitic forms, including important human and animal parasites: tapeworms, liver flukes and blood flukes: annelids: are segmented worms.
