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17 - BIO LECTURE NOTES Key Concepts o Animals are...

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BIO LECTURE NOTES (2/18/09) Key Concepts: o Animals are particularly species-rich and morphologically diverse lineage of multicelluar organisms o Major groups of animals are recognized by their basic body plan, which differs in the number of tissues observed in embryos, symmetry, the presence or absence of a body cavity, and the way in which early events in embryonic development proceed o Recent phylogenetic analyses of animals have shown that there were three fundamental splits as animals diversified, resulting in two protostome groups ( Lophotrochozoa and Ecdysozoa ) and the deuterstomes o Within major groups of animals, evolutionary diversification was based on innovative ways of feeding and moving. Most animals ... intro o Animals are a monophyletic group that can be recognized by three traits: (1) They are multicellular (2) They are heterotrophs -- they ingest their food (3) They move under their own power at some point in their life cycle o Over 1.2 million animal species have been described and named to date, and biologists predict that tens of millions more have yet to be discovered Characteristics of Animals o In addition to multicellularity, eating and moving, several other traits are shared by animals (1) Animal cells have no cell walls but do have an extensive extracellular matrix (2) Animals are the only lineage wit muscle and nerve tissue (3) No animals undergo alternation of generations (4) Adults of most species are diploid; only gametes are haploids o Beyond these characteristics, animals are incredibly diverse, particularly in morphology o About 34 major animal phyla are recognized The Evolution of Tissues o All animals have tissues -- tightly integrated structural and functional units of cells o All animals have epithelium, a layer of tightly joined cells that covers the boy surface o Diploblasts are animals whose embryos have two types of tissues or germ layers: the ectoderm (outer skin) and endoderm (inside skin) o Triploblasts
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