December1 - Biology 442 Developmental Biology Lecture 11...

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Biology 442 Developmental Biology Lecture 11 Developmental Evolution
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Lecture outline I. Metazoan phylogeny and characteristics of main phyla II. The evolution of morphological diversity - The Urbilaterian ancestor - Darwin’s theory of Natural Selection - Evidence supporting evolution: paleontology, comparative anatomy and molecular biology III. The genetic toolkit - Evolution of the toolkit - Example: evolution of the Hox complex IV. Human evolution - Hominoid evolutionary tree - Features of hominid evolution: bipedelism, increased brain size
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Learning objectives for this class Describe the general organization of the metazoan phylogenetic tree and the characteristics of the main phyla. Explain the theory of Natural Selection. Explain how duplication and divergence fueled the evolution of the genetic toolkit. Describe the general organization of the hominoid evolutionary tree and the characteristics of our hominid ancestors.
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I. Metazoan phylogeny Sponges Jellyfish and comb jellies Bodies covered by exoskeleton Soft tissue exposed to the environment-use of cilia Bony endoskeleton Metazoans: multicellular organisms in the animal kingdom
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Porifera (sponges): - No coherent epithelium or symmetry - Bodies consist of jelly-like mesophyl sandwiched between two thin layers of cells - No nervous, digestive or circulatory systems - Bodies are adapted to maximize the efficiency of the water flow Porifera, Cnideria and Ctenophora web2/jellyfish.jpg Cnidaria and Ctenophora: - Dipoblastic (2 embryonic layers, no mesoderm) - Radial symmetry - Cnideria (Jelly fish): Cnidocytes (stinging cells) Decentralized nerve net and simple receptors - Cnetophora (Comb jellies): No Cnidocytes tolweb.org/ tree?group= Ctenophora&contgroup=An... Cnidaria Cnetophora
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Protostomes Form their mouth from the blastopore opening 3 germ layers Bilateral symmetry Protostomes Ecdysozoa: body covered by exoskeleton (Nematoda, Arthropoda) Lophotrochozoa: soft tissue in contact w/ environment (Mollusca) nematode.jpg motm/ spider/page7.html hutchinson/ m0008425.html Nematoda - Worm-like animals Arthropoda - Insects, arachnids, crustaceans - Segmented body - Jointed appendages Mollusca - Gastropods: snails, slugs Cephalopods: squid, octopus - Have a mantle used for breathing and excretion
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Deuterosteromes Form their mouth secondarily - blastopore becomes the anus Bilateral symmetry (some exceptions such as starfish are radial) Chordata, Hemichordata, Echinodermata Hemichordata IST192/v3052010/ Hemichordata (acorn worms): - Dorsal nerve cord resembles the nerve cord of chordates. - Pharynx below the collar has gill slits. - Larva of hemichordates resembles the larva of echinoderms.
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