EEB267H1 Lecture Notes - Lecture 3: Autapomorphy, Cyclostomata, Cloaca
12 Jan 2017
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Document Summary
Many novel traits, not just vertebral elements) originated in the vertebrate ancestor. Latest hypothesis: ancestor of the vertebrata possessed rudimentary vertebral elements along the dorsal and ventral surfaces of the notochord: based on fossils, histology of extant embryos and gene expression patterns. Myxiniforms (hagfish), petromyzontiformes (lamprey) sister groups. Autapomorphy: molecular characteristics and small morphology, different immune system: lymphocytes have unique antigen receptor genes. About 79 extant species in marine (4 awaiting description); lives in temperate shallow to deep waters (from 15-5000m) Poorly developed (secondarily simplified) eyes: lost the ability to make structure, but have the genetic machinery, have a pair of eyes, lost the lens instead there is a layer of skin. Well-developed chemical (smell/taste) and touch senses: one nostril water enters into olfactory organs, water pumped out through gills. Predators, opportunistic scavengers: have the ability to absorb amino acids from the decaying animal directly across their skin/gills autapomorphy.
