Lecture23_AnimalsI - Are sponges lower animals? Why or why...

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Animals I Where are animals on the tree of life? Animals = a monophyletic group distinguished by 1) multicellularity: 2) directed movement: 3) ingestive feeding: A. Phylogeny of animals B. Morphological diversity in animals Origins Choanoflagellates =
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Sponges = Tissues = groups of cells that are specialized for a particular function Four key characteristics of animals: Elements of the body plan or architecture **A few basic body plans, then diversification based on 1. Embryonic tissues Ectoderm: Mesoderm: Endoderm: 2. Symmetry radial vs. bilateral What kind of symmetry do sponges have? Importance of bilateral symmetry: 3. Presence of a body cavity Coelom = a fluid-filled cavity lined with mesoderm Mesoderm gives rise to: Importance =
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4. Protostome versus deuterostome patterns of development zygote cleavage forms mass of cells cell movements form invagination in ball tissue layers cleavage = series of mitotic divisions without cell growth Questions: What is the adaptive significance of the protostome versus deuterostome patterns of development?
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Unformatted text preview: Are sponges lower animals? Why or why not? Are sponges less fit than chordates because they are less advanced or derived or complex? Are invertebrates monophyletic? If so, what synapomorphy defines them? If not, should the term invertebrate be used? Which phyla are most species-rich? Phylum # species Sponges 9,000 Cnidaria (jellyfish, corals, sea anemones) 9,000 Ctenophora (comb jellies) 100 Platyhelminthes (flatworms) Nematodes (roundworms) 12,000 Annelids (segmented worms) ,. Arthropods Crustaceans (crabs, Daphnia , isopods. Chelicerates (spiders, mites, ticks) Insects (beetles!) Molluscs (clams, snails, squid) . . Echinoderms (sea stars, sea urchins) . 7,000 Chordates ....
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Lecture23_AnimalsI - Are sponges lower animals? Why or why...

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