BIOL 117 Lecture Notes - Lecture 23: Germ Layer, Choanoflagellate, Multicellular Organism
28 Apr 2016
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Document Summary
The early evolution of animals consisted of a gradual change in (evolution of) mechanisms for extracting energy from other organisms, which became increasingly sophisticated as other organisms evolved defenses from becoming prey. What follows are a few notes about some of the key characteristics of animals and some of the traits used to define the major groupings within the kingdom. Additionally, there is a brief overview of the diversity of the animal kingdom and some of the key innovations for the phyla within this kingdom. The vast majority of animals show locomotion, at least in their larval stages (in chordates, only the adult sea squirts are attached to their substrate): no alternation of generations between multicellular haploid and diploid life history stages. In animals that are attached to a substrate, many have dimorphism (two body forms) in their life history stages, with attached non-reproducing and unattached, gamete-generating life forms (fig.
