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Bio153_lecture11_Intro_anim_sv - Introduction to Animals...

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Origin of Animals recognized by three traits: (1) multicellular (2) heterotrophs (3) movement Introduction to Animals Multicellular Animals • tissue differentiation • division of labor, more complex functions • larger body size Constraints: • surface area - volume ratio • small animals: diffusion • larger animals organ systems Distinguishing Animals (1) have no cell walls (2) the only lineage with muscle and nerve tissue (3) do not undergo alternation of generations (4) adults of most species are diploid; only gametes are haploid Animals: Diverse in Form and Function • sessile, planktonic • motile: crawl, walk, run, swim, burrow, sail, glide, fly… • great anatomical complexity • taxonomy is based on body plan
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Habitats • marine animals must eliminate salts • freshwater animals must eliminate water • terrestrial animals: • lack of buoyancy • water conservation • protection of gametes Analyzing Comparative Morphology • Most morphological diversity in animals is based on differences in mouths and limbs natural selection: Four features define an animal's body plan : (1) number of embryonic tissue layers (2) type of body symmetry and degree of cephalization (3) presence or absence of a fluid-filled body cavity (4) how the earliest events of embryo development proceed Analyzing Comparative Morphology All animals have tissues : tightly integrated structural and functional units of cells epithelium : a layer of tightly joined cells that covers the body surface diploblasts : animals whose embryos have two types of tissues or
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Bio153_lecture11_Intro_anim_sv - Introduction to Animals...

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