Unit 5: The Evolutionary History of Diversity Extras  Study Guide

Chapter 32 An Introduction to Animal Diversity Review Notes Point
  1. Animals are multicellular, heterotrophic eukaryotes that ingest their food.
     
     
     
     
  2. The ancestor of animals diverged from those of fungi about 1.2 billion-800 million years ago, and may have resembled modern choanoflagellates .
     
     
     
     
  3. The kingdom diversified about 525 million years ago, during the Cambrian explosion, when many animal phyla appeared.
     
     
     
     
  4. Animals can be categorized by how their cells are organized according to a body plan.
     
     
     
     
    • Radial symmetry is like a flower pot, the body radiates from the center.
       
       
       
       
    • Bilateral symmetry has a single plane of symmetry.
       
       
       
       
    • Most animals have tissues that develop from embryonic layers of the gastrula .
       
       
       
       
    • Diploblastic animals such as jellyfish have two germ layers: ectoderm and endoderm .
       
       
       
       
    • Triploblastic animals have three germ layers, including a mesoderm .
       
       
       
       
    • The mesoderm may develop into tissue that line a fluid-filled space called a coelom .
       
       
       
       
      • A pseudocoelom is a body cavity only partially lined by mesoderm tissues.
         
         
         
         
      • Organisms without a body cavity are considered acoelomates .
     
     
     
     
  5. The coelomates show two major modes of development.
     
     
     
     
    • Protostomes develop their mouth from the blastopore of the gastrula.
       
       
       
       
    • Deuterostomes develop their anus from the blastopore.
     
     
     
     
  6. Current phylogeny places Eumetazoa as a clade with true tissues , and divides the Bilateria into three clades: Deuterostomia , Lophotrochozoa, and Ecdysozoa.
     
     
     
     
    Review and exercise: