Overview of Lecture: Animal Diversity - Vertebrates Read Text ch 34, A survey of human evolution. Bullet Points: • chordate clades and shared derived characters • notochord, dorsal hollow nerve cord, pharyngeal slits, post-anal tail • segmentation, shingles • Urochordates: sea squirts • Cephalochordates: amphioxus • Hagfish • Vertebrates Gnathostomes Chondrichthyes Osteichthyes Tetrapods Amniotes ‘ Reptiles' & Birds MammalsSonic Hedgehog expression in the Notocord and Neural Tube floorplate. - Lance Davidson In most adult chordates the notochord disappears … {remnants become spongy discs between vertebrae} In some non-vertebrate chordates and fishes the notochord persists as a flexible rod that prevents collapse of the body during swimming. 2nd 1st The notochord appears early in embryogeny and plays an important role in organizing the embryonic development of nearby structures. Human neural fold closes at 22 days2nd 1st{+4. Muscular postanal tail } 2nd 1st Human Fetus at 40 days (in humans) Jaw bones of fish evolved & develop from anterior arches Ear bones of mammals evolved from posterior jaw bonesNearly all are sessile as adults but they have free-swimming larvae. The larva swims until it attaches by its head to a surface and undergoes metamorphosis, during which {it becomes sedentary &} most of its chordate characteristics disappear.Adult post-dispersal movements might have selected for retention of ‘svelte’ juvenile morphology What is wrong w/ this song? (aside from the obvious!)Single-loop circulation - OK for low metab. rate ectotherms Fishes & vert. descendants cannot synthesize ‘essential’ aromatic Amino Acids (ch 41)The Shark Research Institute (SRI) is engaged in a worldwide study to locate, tag and document the behavior of whale sharks, Rhincodon typus, the largest fish in the sea.4modern “Reptiles” are paraphyletic phylogeny of turtles is still unresolved There is an incredibly rich and diverse array of fossil reptilesAncestors of the fearsome T rex were clothed in delicate feathers, a fossil discovered in China suggests. … Xu X., et al. Nature, 431. 680 - 684 (2004). Almost every part of a bird’s anatomy is modified to enhance flight. The bones are honeycombed – strong but light. The skeleton of a frigate bird has a wingspan of more than 2 m but weighs only about 113 g (4 oz) {≈ a Quarterpounder!}http://evolution.berkeley.edu/evosite/lines/IIIBgeography.shtml Warren et al. 2008 Nature 453, 175-183.Genome analysis of the platypus reveals unique signatures of evolution Warren et al. 2008 Nature 453, 175-183. ... exhibits a fascinating combination of reptilian and mammalian characters. Human breasts are more than mammary glands. They have been shaped by sexual selection – (possibly as a signal of youth &
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