BIS 2C Lecture Notes - Lecture 26: Chemical Warfare, Hexactinellid, Endoderm
6 Mar 2018
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Diplontic life cycle (gametes produced by meiosis) Choanoflagellates: small group of aquatic protists, unicellular or colonial, collar cell: ovoid in shape, with a collar of microvilli (tentacles) surrounding the flagellum, movement of flagellum function to provide , locomotion, feeding (bacteria trapped on collar) Evidence that choanoflagellates are a sister group of metazoa: collar cells: similar cells (choanocytes) are present in sponges, have homologues of metazoan cell signaling and adhesion genes not found in other eukaryotes, supported by dna sequence data. Characteristic features of metazoa: multicellular organisms, cell specialization, complex systems of communication and nutrient exchange. Interdependency: heterotrophs, require organic compounds as food, food ingested, usually followed by extracellular digestion in a gut. In bilaterally symmetrical animals: distinct anterior and posterior ends, cephalization: differentiation of anterior end into a head, with concentration of sensory organs, segmentation: serial repetition of body parts in well-defined segments.
