01:119:115 Lecture Notes - Lecture 6: Gastrointestinal Tract, Sequential Hermaphroditism, Symmetry In Biology
8 Jul 2015
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Basal animals at root of phylogenetic tree. Lack true tissues but have cell types: epidermal cells, pore cells, mesohyl (middle matter, most distinctive type of cells are choanocytes (figure 33. 4) Choanocytes are flagellated cells that create current of h2o through pore cells into spongocoel and out osculum. As the water comes in the phagocytize food gets trapped on collar of finger-like projections: amoebocytes are another type of cell that moves food around body and help digestion. Amoebocytes can also become other cell types; also known as being totipotent. Sponges reproduce sexually; most are hermaphrodites: each individual acts as male and female, sequential hermaphroditism. Sponge will be a male and then after reproducing switch to a female and so on. Eumetazoans is clade of true animals (have true tissues) All animals except sponges are eumetazoans: phylum cnidaria (hydras, jellies, sea anemones, corals) Can be sessile and motile; one of oldest eumetazoans.
