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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