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Unformatted text preview: Lecture 25 (18 February 2011) 2 Major lineages of metazoans This phylogeny is in line with results from recent genomic studies, e.g.: Philippe, H. et al. 2009. Phylogenomics revives traditional views on deep animal relationships. Current Biology 19 :706712. doi:10.1016/j.cub.2009.02.052 The older edition of the textbook ( Life, 8 th edition ) presents a different phylogeny in which sponges are paraphyletic this has implications for inferring the ancestral features of metazoans. Organization of animal body plans Animal symmetry : arrangement of body parts Radial symmetry (multiple imaginary planes that divide the animal into equal halves) Bilateral symmetry (single plane divides animal into left and right mirror-image halves) Cephalization and segmentation Developmental patterns Zygote blastula gastrula Cleavage (e.g., radial or spiral) formation of blastula . Gastrulation : in-pocketing of blastula to form gastrula formation of cell layers...
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