• Invertebrates evolved several important traits before vertebrates even appeared.
  • These traits are now found in just about all animals.
  • The first animal trait to evolve was multicellularity.
  • Multiple cells could do different jobs and evolve special adaptations.
  • Evolution of tissues was the first step in the evolution of organs and organ systems.
  • Cephalization is the concentration of nerve tissue at one end of the body, forming a head region.
  • This is highly adaptive and allows central control of the entire organism.
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