Vertebrates

Sharks Lampreys Bony fish Coelacanth Hagfish Cladogram of vertebrates, stressing early forms from UC Berkeley Museum of Paleontology Land vertebrates

Vertebrate characters

• • • • Cranium – brain case Vertebrae (spinal protection of cartilage or bone) – almost all * agility * speed No larval stages Evolved during Cambrian (early Paleozoic)

Myllokunmingia

fossil from SE China, -530 my

• • • • • •

Trends in vertebrate evolution

improvements in vertebral column – cartilage, bone gill slit supports – jaws, other head bones appendages – fins, legs, wings respiration – gills & lungs circulation – heart reproduction – eggs, shells, “live” young • existing (& some extinct) classes trace some of the most important advances along the vertebrate evolutionary path – next slides follow these

No Jaws

• • Hagfish * cartilage * partial cranium * slime a defense mechanism Lampreys * cartilage * full cranium * fish parasites & free living hagfish tie themselves into knots to clean themselves

Jaws

• • • evolved from gill arches later bore teeth mid Paleozoic (Silurian) origin

Dunkleosteus

Devonian (mid Paleozoic) Placoderm recent Swedish shark

Carcharodon megalodon

Miocene (Cenozoic) shark

Jaws II

Jaws III

• also: * articulated cranium & spine * appendages (fins) some paired • modern day Cartilaginous Fish * sharks, rays, etc.

* no swim bladder – must swim to “levitate”

1 m

Manta Ray

Bone

• Bony fish = ray-finned fish * also bony scales * most numerous & diverse vertebrate * lungfish have “lungs” • gut pockets • modified circulation

Legs

• Amphibians * the mosses of the animal world * limbs supported by bones • support • movement * articulated to “girdles” • connections to spines • hips and shoulder * but amphibians tied to water: • at least eggs (shell-less) • & larval stages young Rough-skinned Newt

Legs II

• more on Amphibians * land life advantages • more oxygen • prey – arthropods & plants • fewer (no?) predators Northwest Tailed Frog * sound / sight / balance improvements (terrestrial sensors) • ears and eyes * first amphibians: Devonian (mid Paleozoic)

Shelled eggs

• Reptiles * amniote eggs with: • extra-embryonic membranes • shells for protection * dry scaly skin * internal fertilization * adult care for young * kidneys conserve water

Reptiles II

• • Evolved in late Paleozoic (Carboniferous) Huge diversity – polyphyletic with many long-lived lines from the end of the Paleozoic • Two early lines * Sauropsids – most of the diverse lines * Synapsids – ultimately gave rise to mammals

• • • • • • •

Birds

Just another reptilian group?

Feathers – insulating, flight (modified scales) Bones hollow Beaks Thermoregulation – high metabolism rates All adaptations for flight Patterns of behavior * Elaborate mating behavior * Maternal/paternal care * Migration

Birds II

• Evolved from theropod dinosaurs, mid Mesozoic

Archaeopteryx lithographica

150 my

Birds III

Sinosauropteryx prima

125 my

Caudipteryx zoui

125 my

Mammals I

• • • • • Hair (modified scales) Milk fed to young Live young (except for 3 that lay eggs) Precise teeth that fit together 3 middle ear bones (derived from jaw bones)

Mammals II

• Three major lines * monotremes – egg layers * marsupials – pouched * eutherian – placental Spiny echidna, egg-layer Marsupial “mouse” Blue whale, largest mammal

Mammals IIIA

• • Evolved in early Paleozoic 200 mya Adaptive radiation during mesozoic & cenozoic tied to continental drift – see ST Fig 26.2

* End of mesozoic opened habitats * Mammals much more efficient terrestrial forms • Drifting continents isolated mammalian groups on “rafts”

Early Triassic

Mammals IIIB

Late Triassic Early Cretaceous * Late Cretaceous • Compare with ST Fig 26.2

Mammals IIIC

Modern day mammalian distribution

Mammals IV - Primates

• • •

Galago

3 present groups * prosimians – lemurs, galagos * tarsiers * monkeys, apes, humans Early primates evolved in early Cenozoic from rodent ancestors 5 features preadapted early primates to modify later in the line toward humans * enhanced vision * upright walking * modifications in hand bones & muscles * generalized teeth * social behavior (& increases in brain capacity and complexity) Barbary Macaque Tarsier

Human evolution

• • • • • • • Humans evolved in Africa Earliest huminoids – mid Cenozoic (25 mya) * cooler climate led to challenges * later radiation of “southern apes” (

Australopithecus

) 4-3 mya * first appearance of

Homo

~ 2.5 mya

Homo erectus

leaves Africa ~2 mya

Homo sapiens

evolved 150,000 ya

Homo neanderthalensis

evolved 250,000 ya; extinct 35,000 Recent studies show no DNA mixing or carryover of H. n. DNA in modern human lines Most evidence supports Out of Africa theory rather than multiregionalism • Best site for current status of human evolution facts: http://www.talkorigins.org/faqs/homs/

Human evolution timeline

Chart from: http://www.talkorigins.org/faqs/homs/species.html

Interactive Human Evolution