LIFESCI 1 Lecture Notes - Lecture 8: Metabolic Waste, Cambrian Explosion, Oviparity
Document Summary
Phylogeny of major animal phyla: ctenophores are not bilaterally symmetrical. All chordates have the following synapomorphies at some developmental stage. Opening into the throat called pharyngeal slits. Small, mobile suspension feeders in the ocean. Dorsal hollow nerve cord runs parallel to a notochord. Jaws and gill arches have similar bony or cartilaginous morphology. Muscles that move both structures have the same embryonic origin. Both structures derived from neural crest cells. Gene expression patterns similar in both structures. Both groups have brains protected by a cranium, but lack jaws. Hagfish lack a vertebral column (thought to be lost since common ancestor) Lampreys have cartilage along the dorsal hollow nerve cord. Class chondrichthyes (cartilaginous fishes as sharks, skates, rays, chimaeras) Cartilaginous endoskeleton, harder than muscle but softer than bone. Mostly marine, but some species of freshwater rays. Embryos develop inside the female and are attached to the mother by a placenta. Embryos develop in an egg case external to the mother.
