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Introduction to Animal Diversity Chapter 32 What is an animal? Eukaryote? Multicellular? Large and furry? Cambrian explosion 542-251 MYA Few phyla before About ½ of all extant (existing) phyla developed in this time period Why? Animals • Multicellular – No cell wall – Cells held together by structural proteins (eg. collagen) Cells of plants and fungi have rigid cell walls (cellulose or chitin) Animals • Multicellular – No cell wall – Cells held together by structural proteins (eg. collagen) • Heterotrophic • Have unique tissues – Muscle – Nervous Reproduction and Development • Most animals reproduce sexually – Small sperm fertilizes a large egg – Forms a zygote • Zygote undergoes mitotic cell divisions (cleavage) • Forms hollow blastula • Folds to form a gastrula – Folds form tissues Embryonic tissue – embryonic stem cells – pluripotent stem cells Reproduction and Development • Maturation processes – Embryo → Adult – Embryo → Larva → Adult – Larvae undergo metamorphosis to mature to adult Homeotic (Hox) genes • Hox genes regulate the expression of other genes during development • Therefore Hox genes regulate body patterning in animals • Many Hox genes contain homeoboxes – 180 bp DNA sequence common to almost all animals as well as plants and prokaryotes Animal Body Plans • Symmetry – Radial, with a central axis – Bilateral, left/right symmetry • Often with “cephalization” Dorsal side Posterior Anterior Ventral side Animal Body Plans • Symmetry • Tissue Types – – – – Form from germ layers Ectoderm forms outer layers (skin) Endoderm - inner layers (gut) Mesoderm – middle layers (muscle) • Body cavity – Called the coelom – Animals can be acoelamate, pseudocoelomate, or coelomate Protostomes vs Deuterostomes • Cleavage • Coelom formation • Blastopore Cell retains flexible potential, one may grow into intact embryo Human cloning report sparks calls for ban Lawmakers, church leaders aghast over 'unethical science' The Associated Press Updated: 9:33 p.m. ET Feb. 12, 2004 SEATTLE - In a clash of politics and science, the first successful cloning of a human embryo — and the extraction of stem cells from it — has ignited new calls for a ban on all forms of human cloning in the United States. Coelom Formation Fate of Blastopore • Protostome = first mouth (blastopore forms mouth) –Mollusca, Annelida, Arthropoda • Deuterostome = second mouth (mouth forms from an opening other than blastopore); anus forms from or near blastopore –Echinodermata and Chordata Animal Diversity • Definition of an animal – Multicellular – Heterotrophic – Having unique tissues (nervous, muscle) – Reproduction – Development Animal Diversity • • • • • What are major groupings of animals? How are they related to each other? What features do they share (similarity)? What features differ (dissimilarity)? What are major themes of variation?