Vertebrates

Which of these is most closely related to you?

Which of these is most closely related to you?

Echinoderms and Chordates are the only two phyla of deuterostomes.

Vertebrates

Chordata fish, amphibians, reptiles, birds, mammals

Deuterostome coelomates

Notochord serves as axis of body

Dorsal, hollow nerve cord

Tails. Human coccyx is vestigial tail.

Birds & mammals = homeotherms (constant body temperature)

All others are poikilotherms (cold-blooded) though some reptiles are endothermic.

Mammalsclass

Nurse their young with milk

Have hair or fur made of keratin

Homeotherms

• Placental = develops in womb

• Marsupial = born early, develops in pouch

• Monotreme = egg-laying (duck-billed platypus and spiny anteater).

Primatesorder

Hands with opposable thumbs

Claws have become nails

Eyes are in front and close together for binocular vision

Nurture their young for a long time.

Chordate Characteristics

•A flexible rod between the nerve cord and the digestive tube•All chordates have this as embryos•Most develop later into complex, jointed skeleton.

NotochordChordate Characteristics

•Develops from a plate of ectoderm that rolls into a tube•Unique to chordates. (Other phyla have solid, ventral nerve cords)•Develops into central nervous system, spinal cord, and brain.

Dorsal, hollow nerve cordChordate Characteristics

•Just posterior to the mouth•Used for suspension feeding and gas exchange (gills)•In land animals, they develop into parts of the ear.

Pharyngeal slits or cleftsChordate Characteristics

•Lost during embryonic development in many species•Provides propulsion for many aquatic species.

Muscular, post-anal tailChordate Characteristics

Classes of Chordates

TunicatesClasses of Chordates

TunicatesClasses of Chordates

TunicatesClasses of Chordates

TunicatesClasses of Chordates

LanceletsClasses of Chordates

LanceletsClasses of Chordates

HagfishClasses of Chordates

•Craniate (has brain and skull)•No jaws•No vertebrae

HagfishClasses of Chordates

HagfishClasses of Chordates

HagfishClasses of Chordates

LampreyClasses of Chordates

•Vertebrate (has backbone)•Still no jaws

LampreyClasses of Chordates

LampreyClasses of Chordates

LampreyClasses of Chordates

Sharks and RaysClasses of Chordates

•Gnathostomes (“jaw-mouths”)•Bones have some mineralization but are still mostly cartilage•Acute senses (lateral line, nostrils, black-and-white vision)•Oviparous, ovoviviparous, or viviparous.

Sharks and RaysClasses of Chordates

Sharks and RaysClasses of Chordates

Sharks and RaysClasses of Chordates

Ray-Finned FishesClasses of Chordates

Lobe-Finned Fishes

Classes of Chordates

Lungfishes

Classes of Chordates

Tetrapods

Classes of Tetrapods

Amphibians

Urodela (“tailed ones”)Salamanders

Anura (“tailless ones”)Frogs and toads

Apoda (“legless ones”)Caecilians

Classes of Tetrapods

Amphibians

Adaptations:•Camouflage•Poison •Metamorphosis / paedomorphosis•Complex social behavior•Eggs lack shells, dehydrate quickly•Gas exchange through moist skin

Amniotes

Amniotes

•Amniotic egg may be laid on land.

•Contains extra-embryonic membrane

•May be calcified (birds) or leathery (reptiles) or may implant in the uterus (mammals)

Phylogeny of Amniotes

Ancestral amniote

Synapsidia

Diapsidia

Anapsidia

Phylogeny of AmniotesMammals

Turtles

Lizards & Snakes

Crocodiles

Dinosaurs

Birds

Ancestral amniote

Synapsidia

Diapsidia

Anapsidia

Phylogeny of AmniotesMammals

Turtles

Lizards & Snakes

Crocodiles

Dinosaurs

Birds

Ancestral amniote

Synapsidia

Diapsidia

Anapsidia

Reptiles

Adaptations:•Keratinized skin•Lungs•Leathery shells on eggs•Ectotherms.

Birds began as feathered reptiles

Adaptations:•Feathers•Honeycombed bones•Missing some organs•Gizzard instead of teeth•Endothermic•Four-chambered heart•Good vision•Relatively large brains.

Mammals diversified in the wake of the Cretaceous extinctions

Adaptations:•Mammary glands•Hair•Four-chambered heart•Endothermic•Placenta / live birth•Large brains•Differentiated teeth.

Primatesand Human Evolution

Adaptations:•Brain size•Jaw shape•Bipedal posture•Size difference between sexes•Long-term pair bonding•Long-term infant dependency.

Multiregional Hypothesis

African European Asian Austalasian

Homo erectusIn Africa

interbreeding

1-2 million years ago

Replacement Hypothesis

African European Asian Austalasian

Homo erectusIn Africa

100,000 years ago

1-2 million years ago