Basic Animal Evolution

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Basic Animal Evolution

• JP Slovak

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Introduction

• Characteristics of animals
• Multicellular
• Heterotrophic
• Lack cell walls
• Cells are held together by proteins
• Tight junctions
• Desmosomes
• Gap junctions
• Excitable tissue
• Most reproduce sexually
• Blastula
• gastrulation

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Animal Phylogeny and Diversity

• Monophyletic
• Goes back 700 mya
• 1. First key branch was between
  eumetazoan(tissues) and parazoan(no tissues)
• 2. Eumetazoans branch into radiata and bilateria
• Symmetry
• Cephalization in bilateria
• All bilateria have 3 germ layers

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Animal Phylogeny and Diversity

• 3. Evolution of body cavities
• Acoelomates
• Psuedocoelomates
• Coelomates
• 4. Coelomates branch into protostomes and
  deuterostomes
• Differ in
• Cleavage
• Coelom formation
• Fate of blastopore

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Origins of animal diversity

• 35 phyla
• Cambrian explosion
• Lasted approximately 20 my
• Started about 550 mya