Bio 201 F07 True lect 14 v2 post

Bio 201 F07 True lect 14 v2 post - Exam documented absences...

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Unformatted text preview: Exam documented absences • If you have a documented medical or bereavement absence for the first mid term you MUST present Ellen Lopez the documentation today by 4PM in order to take a make-up exam today • Ancestor of all metazoans • Sponges • Cnidarians and ctenophores – Radial symmetry themes • Complexity – Sponges are the simplest metazoans – Metazoan life (and all life on Earth) had to start out simple, BUT • Is complexity always “progress”? • Can complex life evolve into more simple life? – Why would this happen? themes • “higher” and “lower” organisms – Biased, human-centric view • Every living species on earth represents a lineage that has survived – i.e. EVOLUTIONARY SUCCESS – Very simple and very complex organisms live today Precambrian Porifera Cnidaria Ctenophora Platyhelminthes Rotifera Nemertea Bryozoa Phoronida Brachiopoda Mollusca Annelida Nematoda Arthropoda Echinodermata Chordata Ancestral Colonial choanoflagellate Parazoa Radiata Eumetazoa Bilateria Protostomia Deuterostomia Lophotrochozoa Ecdysozoa Respect other species Putative ancestor of all metazoans • Believed to be like a choanoflagellate • Choanoflagellates – Aquatic protist (single celled, 5-10 microns) – “collar flagellate” • Collar = closely packed collar of microvilli • Collar surrounds single flagellum – Eats bacteria and other small particles • Flagellum draws water carrying food through collar – Some species form colonies – Other species strictly solitary Choanoflagellate colony Why do we think metazoan common ancestor was choanoflagellate-like? • Choanocytes of sponges look like choanoflagellates • Colonialism could be what the first animal cellularity looked like • DNA evidence (phylogenetic tree) • Evidence from their genomes – Have some families of cell signalling and cell adhesion proteins that were previously known only in metazoans http://biodidac.bio.uottawa.ca/thumbnails/images/PROT021B.gif Precambrian Porifera Cnidaria Ctenophora Platyhelminthes Rotifera Nemertea Bryozoa Phoronida Brachiopoda Mollusca...
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This note was uploaded on 04/09/2008 for the course BIOCHEMIST 361 taught by Professor Haltiwanger during the Fall '08 term at SUNY Stony Brook.

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Bio 201 F07 True lect 14 v2 post - Exam documented absences...

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