• 1) The Tree of Life reveals that life has a history: it is a grand vision

• 2) The Tree of Life can be read partly from traits of living organisms:
  
  a) multicellular 'animals' likely arose from colonial protists
  b) early branches yielded cellular, then tissue (diploblastic, radial), then organ-system (triploblastic, bilateral) grades of organization
  c) bilaterians split into two major branches (Protostomia & Deuterostomia) within which coeloms and a complete gut evolved independently

• 3) The Tree of Life can also be read partly from fossils and molecules:
  
  a) A literal reading of the fossil record suggests animal phyla arose in an 'explosion' near the beginning of the Cambrian (approx. 580 MYA)
  b) But recent molecular evidence (Oct. 1996; 8 molecules) suggests protostomes diverged from deuterostomes nearly 1,200 MYA!

• 4) The study of comparative anatomy and development continues to yield essential insights into the evolution of animal form & diversity; much exciting research remains to be done

• 5) Major questions about the Tree of Life remain (e.g., placement of ctenophores, 'pseudocoelomates', lophophorates, origin of chordates)
  
  a) excitement about phylogenetic relations is as high now as it was in the years following the Darwinian revolution
  b) we have lots more to learn about the history of life on this planet

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