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Animal Evolution: Introduction & Diversity

Explore the unique characteristics, phylogeny, and diversity of animals, from parazoans to coelomates. Understand key concepts like gastrulation, body symmetry, and coelom formation. Learn about the evolution of animal forms and their relationships in the tree of life.

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Animal Evolution: Introduction & Diversity

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  1. Lecture #14 Date ______ • Chapter 32 ~ 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’; sea anemones) & Ctenophora (comb jellies)~ radial body symmetry; all other animals~ bilateral body symmetry (also: cephalization)

  4. Hydra The mouth and the anus consist of the same opening.

  5. Jellyfish Cnidaria – true tissues with radial symmetry

  6. Sea Anenome w/ clown fish The sea anenome and clown fish share a symbiotic relationship: commensalism

  7. 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 layers • 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

  8. Flatworm Triploblastic with no body cavity - acoelomate

  9. 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

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