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Introduction to Animal Evolution

Introduction to Animal Evolution. Def : an•i•mal (n). Unique characteristics: Heterotrophic eukaryotes; ingestion Lack cell walls; collagen Nervous & muscular tissue Sexual; diploid; cleavage; blastula; gastrulation; larvae; metamorphosis Regulatory genes: Hox genes.

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Introduction to Animal Evolution

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  1. Introduction to Animal Evolution

  2. Def: an•i•mal (n) • Unique characteristics: • Heterotrophic eukaryotes; ingestion • Lack cell walls; collagen • Nervous & muscular tissue • Sexual; diploid; cleavage; blastula; gastrulation; larvae; metamorphosis • Regulatory genes: Hox genes

  3. Animal phylogeny & diversity, I • Monophyletic; colonial flagellated protist ancestor 1- Parazoa-Eumetazoa dichotomy: • sponges (Parazoa)~ no true tissues; • all other animals (Eumetazoa)~ true tissues 2- Radiata-Bilateria dichotomy: Cnidaria (hydra; ‘jellyfish’; anemones) ~ radial body symmetry; all other animals ~ bilateral body symmetry (allows cephalization)

  4. Animal phylogeny & diversity, II • 3- Gastrulation: germ layer development; ectoderm (outer), mesoderm (middle), endoderm (inner); radiata are diploblastic-2 layers; no mesoderm; bilateria are triploblastic-all 3 layer • 4- Acoelomate, Pseudocoelomate, and Coelomate Grades: triploblastic animals~ solid body, no body cavity called acoelomates (Platyhelminthes-flatworms); body cavity, but not lined with mesoderm called pseudocoelomates (Rotifers); true coelom (body cavity) lined with mesoderm called coelomate

  5. Side view of blastula and developing layers. Blue = ectoderm, Red = endoderm, White = mesoderm

  6. Animal phylogeny & diversity, III • 5- Protostome-Deuterostome dichotomy among coelomates: protostomes (mollusks, annelids, arthropods); deuterostomes (echinoderms, chordates) • a) cleavage: protostomes~ spiral and determinate; deuterotomes~ radial and indeterminate • b) coelom formation: protostomes~ schizocoelous; deuterostomes~ enterocoelous • c) blastopore fate: protostomes~ mouth from blastopore; deuterostomes~ anus from blastopore

  7. Acoelomate- no cavity • Pseudocoelom-cavitity between endoderm and mesoderm • Coelomate- cavity located within the mesoderm.

  8. Coelomate development

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