Bio - Chapter 32: An Introduction to Animal Diversity-1.3...

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Unformatted text preview: Chapter 32: An Introduction to Animal Diversity-1.3 million species identified (millions more though)-animal life began in Precambrian seas-evolution of multicellular forms-early animals lived in water, not land I. Animals are multicellular,heterotropic eukaryotes with tissues that develop from embryonic layer. i. Nutritional Mode-hetertrophs (ingest food)-animals cannot construct all of their own organic molecules and so, in most cases, they ingest them-use enzymes to digest their food only after they’ve ingested it ii. Cell Structure and Specialization A. Animal cells lack cell walls-collagen (or other extracellular proteins) holds multicellular bodies-intercellular junctions: tight junctions, desmosomes, gap junctions B. Unique Tissues-nervous tissue-muscle tissue for movement iii. Reproduction and Development i. Most reproduce sexually w/ diploid stage dominating life cycle-zygote undergoes cleavage(mitosis) -> forms blastula- gastulation – embryo folds forming pouch characteristic of gastrula; gives rise to 3 germ layers (endoderm, mesoderm, ectoderm)- cleavage->morala (solid ball of cells)->blastula(hollow ball)->gastrula ii. Hox genes – controls development; turns on proteins (regulates expression of other genes) *instructions for the developing embryo* II. The history of animals span more than a billion years- monophyletic – lineage can be traced back to a common ancestor-mos tlikely colonial flagellated protist-cells evolved to hollow spheres; then cells in sphere became specialized. i. Neoproterozoic Era (1 billion – 542 million years ago)-oldest fossils = 575 million years old = Ediacaran fauna-time of rising level of diversity ii. Paleozoic Era (542-251 Million Years Ago)-diversification accelerated dramatically = “Cambrian explosion”-predator prey relationship developed, more oxygen available-vertebrates went from water to land 360 million years ago. iii.Mesozoic Era (251-65.5 Million Years Ago)-animal phyla spread to new ecological niches-flight equipment-first mammals iv.Canozoic Era (65.5 million years ago to present)-insects and flowering plants have dramatic diversification-mass extinction of both terrestrial and marine animals (i.e. large non-flying dinosaurs)-global climate gradually cooled III. Animals can be characterized by “body plans”-categorize by morphology and development-same level of complexity = grade-“body plan” = grade’s functional whole i. Symmetry A. Asymmetric – lacking B. Symmetric:-radial – equal all sides; arranged around major axis-bilateral – two sided symmetry...
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This note was uploaded on 03/31/2008 for the course BIO 119 taught by Professor O'donnellandspear during the Fall '07 term at SUNY Geneseo.

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Bio - Chapter 32: An Introduction to Animal Diversity-1.3...

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