BIOL 150 Lecture Notes - Lecture 1: Central Nervous System, Symmetry In Biology, Protostome
Document Summary
1. 4 million named species - includes 1. 2 million arthropods, 1 million insects 350,000 are beetles. Nerves and muscles (except for sponges) (enabled rapid response to external stimuli) There are: 30-35 phyla (depending on who you talk to) All of which seem to have emerged in the cambrian 650-540 mya and none since. Animals at the phylum level have shared traits based on body plan stemming from a common ancestry. Animals are monophyletic (have a single common ancestor) Sponge has no true tissue only specialized cells- basal at the base of the tree sessile. Flatworms and above: organ and organ systems: radial vs bilateral symmetry: Hypothesis: origin of central nervous system (cns) is linked to evolution/origin of bilateral symmetry. Along with cephalization, this enabled more efficient hunting and capturing prey. Bilateral symmetry: origin of coelom a tube within a tube with: development of a fluid-filled cavity between the gut and the outer body wall.
