31 - endoderm Gastrulation: forms these three layers and...

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Are all animals descended from a common ancestor? Probably all except sponges. All animals share these derived traits: Similar small subunit rRNA Similar Hox genes Special cell-cell junctions (gap/tight junctions) Collagen and other common extracellular matrix molecules What is an animal? Multicellular heterotroph with internal digestion and specialized cells Usually has circulatory system- blood steam Diploblastic - 2 distinct cell layers for things with radial symmetry we categorize animals by: number of layers in the embryo, number or types of cavities-if any, whether mouth or anus forms first, if there is a functional brain, the type of body symmetry. Diploblasty : outside ectoderm (usually develops into skin and related organs), jelly cavity, inside endoderm (usually develops into digestive system) Triploblasty : outside ectoderm , mesoderm (usually develops into various internal organs), inside
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Unformatted text preview: endoderm Gastrulation: forms these three layers and the blastopore Humans are triploblastic organisms. If the anus forms first, this is a deutorostome; if the mouth forms first this is a protostome. Anterior is front, posterior is back, dorsal is top, ventral is down ACOELOMATE: No enclosed body cavity PSEUDOCOELOMATE: Cavity lined with mesoderm, NO mesoderm surrounding internal organs COELOMATE: Cavity lined with mesoderm, Mesoderm also surrounds internal organs Ctenopheres: comb jellies complete gut, radial symmetry, ctenes for movement, tentacles to trap food Cnidarians: 2 cell layers, radial symmetry, blind gut, cnidocyte cells capture larger prey Contain Nematocysts: very potent weapons. Anthozoans: Sea anemones, Coral- lack medula stage Hydrozoans: Man-of-war, dominated by polyp stage, Scyphozoans: Jellyfish, dominated by medulla stage...
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This note was uploaded on 04/24/2008 for the course BIOLOGY 020.152 taught by Professor Pearlman during the Spring '08 term at Johns Hopkins.

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