BIOL 1002 Chapter : Chapter 23 Notes
Document Summary
Chapter 23: animal diversity i, invertebrates: key features of animals, animals possess all of the following characteristics. Are able to respond rapidly to external stimuli. They obtain energy by consuming other organisms. They are motile at some point in the life cycle. Most reproduce sexually: animal evolution, most animal phyla that currently populate earth were present by the. Cambrian period (544 million years ago: the scarcity of pre-cambrian fossils led systematists to search for clues about the evolutionary history of animals by examining features of: Dna sequences: certain features represent evolutionary milestones. Protostome and deuterostome development: these features mark major branching points on the animal evolutionary tree. Individual cells may be specialized, but they act independently. Sponges and other phyla arose from an ancient common ancestor without tissues. Endoderm (inner layer, lines most hollow organs: tend to be either sessile (fixed to one spot) or medusa (free floating, drift around on currents) [ex jellyfish]