VertebratesVertebrates

Hagfish

Lampreys

Sharks

Bonyfish

Landvertebrates

Coelacanth

Man

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Cladogram of vertebrates, stressing early forms from UC Berkeley Museum of Paleontology

Vertebrate charactersVertebrate 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 fromSE China, -530 my

Trends in vertebrate evolutionTrends 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 JawsNo Jaws

• Hagfish* cartilage* partial cranium* slime a defense

mechanism

• Lampreys* cartilage* full cranium* fish parasites &

free living

hagfish tie themselves intoknots to clean themselves

JawsJaws

Carcharodon megalodonMiocene (Cenozoic) shark

recent Swedish shark

• evolved from gill arches

• later bore teeth

• mid Paleozoic (Silurian) origin

Dunkleosteus Devonian(mid Paleozoic) Placoderm

Jaws IIJaws II

Jaws IIIJaws III

• also:* articulated cranium &

spine* appendages (fins) -

some paired

• modern day Cartilaginous Fish* sharks, rays, etc.* no swim bladder –

must swim to “levitate” Manta Ray

1 m

BoneBone• Bony fish = ray-finned

fish* also bony scales

* most numerous & diverse vertebrate

* lungfish have “lungs”• gut pockets

• modified circulation

LegsLegs• 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 IILegs II

• more on Amphibians* land life advantages

• more oxygen

• prey – arthropods & plants

• fewer (no?) predators

* sound / sight / balance improvements (terrestrial sensors)

• ears and eyes

* first amphibians: Devonian (mid Paleozoic)

Northwest Tailed Frog

Shelled eggsShelled eggs

• Reptiles* amniote eggs with:

• extra-embryonic membranes

• shells for protection

* dry scaly skin

* internal fertilization

* adult care for young

* kidneys conserve water

Reptiles IIReptiles 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

BirdsBirds• 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 IIBirds II• Evolved from

theropod dinosaurs, mid Mesozoic

Archaeopteryx lithographica 150 my

Birds IIIBirds III

Sinosauropteryx prima 125 my

Caudipteryx zoui 125 my

Mammals IMammals 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 IIMammals II• Three major lines

* monotremes – egg layers* marsupials – pouched* eutherian – placental

Spiny echidna, egg-layer

Marsupial “mouse” Blue whale, largest mammal

Mammals IIIAMammals 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”

Mammals IIIBMammals IIIB

• Compare with ST Fig 26.2

Early Triassic Late Triassic

Early Cretaceous Late Cretaceous

*

Mammals IIICMammals IIIC

Modern day mammalian distribution

Mammals IV - PrimatesMammals IV - Primates• 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

Galago

Human evolutionHuman 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 timelineHuman evolution timeline

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