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Lecture #15 Date ______

s Chapter 34 ~VertebrateEvolution and Diversity

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Chordatess Notochord: longitudinal, flexible rod

located between the digestive and thenerve cord

s Dorsal, hollow nerve cord; eventually

develops into the brain and spinal cords Pharyngeal slits; become modified for

gas exchange, jaw support, and/or hearing

s Muscular, postanal tail

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Invertebrate chordatess

Both suspension feeders..s Subphy: Urochordata (tunicates; sea squirt); mostly sessile & marines Subphy: Cephalochordata (lancelets); marine, sand dwellerss Importance: vertebrates closest relatives; in the fossil record, appear 50 million

years before first vertebrates

Paedogenesis: precocious development of sexual maturity in a larva (link withvertebrates?)

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Subphylum: Vertebratas Retain chordate characteristics with

specializations.s Neural crest: group of embryonic cells

near dorsal margins of closing neural tubes Pronounced cephalization: concentration

of sensory and neural equipment in thehead

s Cranium and vertebral columns Closed circulatory system with a ventral

chambered heart

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Vertebrate diversitys Phy: Chordatas Subphy: Vertebratas Superclass: Agnatha~

jawless vertebrates(hagfish, lampreys)

s Superclass: Gnathostomata~ jawed vertebrates with 2 setsof paired appendages; includingtetrapods (4-footed) andamniotes (shelled egg)

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Superclass Agnathas Jawless vertebratess Most primitive, living

vertebratess Ostracoderms (extinct);

lamprey and hagfish (extant)s Lack paired appendages;

cartilaginous skeleton;notochord throughout life;rasping mouth

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Superclass Gnathostomata, Is Placoderms (extinct): first with hinged jaws and paired appendagess Class: Chondrichthyes~ Sharks, skates, rayss Cartilaginous fishes; well developed jaws and paired fins; continual water flow over

gills (gas exchange); lateral line system (water pressure changes)s Life cycles:s Oviparous - eggs hatch outside mothers bodys Ovoviviparous - retain fertilized eggs; nourished by egg yolk; young born lives Viviparous - young develop within uterus; nourished by placenta

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Superclass Gnathostomata, IIs Class: Osteichthyess

Ossified (bony) endoskeleton; scales operculum(gill covering); swimbladder (buoyancy)s Most numerous vertebrates Ray-fined (fins supported by long, flexible rays): bass, trout, perch,

tuna, herrings Lobe-finned (fins supported by body skeleton extensions): coelocanths Lungfishes (gills and lungs): Australian lungfish (aestivation)

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Superclass Gnathostomata, IIIs Class: Amphibias 1st tetrapods on lands Frogs, toads, salamanders, caecilianss Metamorphosis; lack shelled egg;

moist skin for gas exchange

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Superclass Gnathostomata, IVs Class: Reptilias

Lizards, snakes, turtles, and crocodilianss Amniote (shelled) egg with extraembryonic membranes (gas exchange,waste storage, nutrient transfer); absence of feathers, hair, and mammaryglands; ectothermic; scales with protein keratin (waterproof); lungs;ectothermic (dinosaurs endothermic?)

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Superclass Gnathostomata, Vs Class: Avess Birdss Flight adaptations: wings

(honeycombed bone); feathers(keratin); toothless; one ovary

s Evolved from reptiles (amniote eggand leg scales); endothermic (4-chambered heart)

s Archaeopteryx (stemmed from anancestor that gave rise to birds)

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Superclass Gnathostomata, VIs Class: Mammalias Mammary glands; hair (keratin);

endothermic; 4-chambered heart;large brains; teeth differentiation

s Evolved from reptilian stock beforebirds

s Monotremes (egg-laying): platypus;echidna

s Marsupials (pouch): opossums,kangaroos, koalas

s Eutherian (placenta): all other mammals

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Order: Primates (evolution)s

Characteristics: hands & feet for grasping;large brains, short jaws, flat face; parentalcare and complex social behaviors

s Suborder: Prosimii lemurs, tarsierss Suborder: Anthropoidea monkeys, apes,

humans (opposable thumb)s 45-50 million years agos Paleoanthropology: study of human originss Hominoid: great apes & humanss

Hominid (narrower classification): australopithecines (all extinct) genus Homo (only 1 exant,sapiens )

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Human evolutions Misconceptions:s 1- Chimp ancestor (2 divergent branches)s 2- Step-wise series (coexistence of human species)s 3- Trait unison vs. mosaic evolution (bipedalism, upright,

enlarged brain)

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The first humanss Ape-human split (5-7 mya)s Australopithecus; Lucy (4.0 mya)s Homo habilis; Handy Man (2.5 mya)s Homo erectus; first to migrate (1.8 mya)s

Neanderthals (200,000 ya)s Homo sapiens (1.0 mya?)s Multiregional model

(parallel evolution)s Out of Africa

(replacement evolution)