Lecture 3 - Deep Time and Biogeography

the fossil record, dating, plate tectonics, inferring transitions

every evolutionary transition in vertebrate happened

at a specific place and time

geologic time hierarchy

eon → era → period → epoch

eon

full earth history

• 4.6 billion years to present

era

Phanerozoic eon

• 541 million years ago to present

period

Cenozoic era

• 66 million years ago to present

epoch

neogene and quaternary period

• 23 million years ago to present

relative dating (stratigraphy)

in an undisturbed sequence, older layers lie beneath younger ones

• index fossils and cross-cutting relationships refine ordering

absolute dating (radiometric)

radioactive isotopes decay at known, constant rates, giving numerical ages for datable minerals in or near a fossil-bearing layer

what fossilizes

hard parts (bone, teeth, shell) in settings with rapid burial and low oxygen

fossil underrepresention

soft tissue, small/fragile organisms, and non-dispositional environments

absence of evidence is not

evidence of absence

a lineage’s first known fossil is

a minimum age for its origin, not a claim about when that lineage evolved

Paleozoic

cambrian → ordovician → silurian → devonian → carboniferous → permian

• 541 Ma - 252 Ma

Paleozoic - Cambrian

• continental masses of the late Proterozoic broke into smaller blocks of land covered by shallow seas

• atmospheric O2 approached current levels

• representation of most major animal phyla and first vertebrates appeared in the fossil record (in middle)

Paleozoic - Ordovician

• 458 Ma

• widespread shallow seas covered continental shelves

• global climates with equable until end of the period, drop in sea level

• terrestrial plants appeared

• echinoderms and other marine invertebrates radiates

• evidence of jawless fishes with bony skeletons

conodont -

first vertebrates with mineralized skeletal elements in their mouth and pharynx

Paleozoic - Silurian

• 444 Ma

• sea levels rose and large land masses emerged

• climates were equable following the Ordovician glaciations

• vascular plants and arthropods colonized land

• osteognathostomes radiated

  • gnathostomes appeared

Paleozoic - Devonian

• 419 Ma

• extensive terrestrial forests formed

• terrestrial arthropods diversified

• fresh water basin formed

• jawless + jawed fish diversified, but major extinction at the end

• disappearance of all jawless osteognathostomes

• sarcoterygian fishes gave Rish to tetrapods at end

Paleozoic - carboniferous

• 356 Ma

• cooled climate

• land mass in southern and slight norther hemisphere

• low CO2 and high O2

• insects with flying forms

• non-amniote tetrapods in terrestrial and aquatic habitats

• first aminionates at the end

Paleozoic - permian

• 255 Ma

• greatest glaciation then retreated

• ancestor and mammals and reptiles

• non-mammalian synapsids become dominant large terrestrial tetrapods

• O2 levels dropped and Pangaea formed

• largest mass extinction event

Mesozoic - triassic

• 237 Ma

• hot, humid climate, arid, no glaciation

• Pangaea began to break up

• conifers are primary land negation

• extant sharks, coelacanths, lungfishes

• mass extinction affect on sea

• sauropods are most abundant tatrapods

• vertebrates groups present at end of period

Mesozoic - Jurassic

• 195 Ma

• Pangaea splits into Gondwana and Laurasia

• evolutionary arms race between vertebrates and shelled invertebrate pray

• insects and non-avid dinosaurs on top

• first birds, lizards, and salamanders

Mesozoic - Cretaceous

• 94 Ma

• angiosperms (flowering plants) appeared

• marine reptiles flourished

• terrestrial revoltion

• first snakes appeared

• dinosaurs on top

• asteroid mass extinction

marginocephalia

fringed dinosaurs

• found only in western North America, Asia, and Europe

  • cretaceous age strata

Cenozoic parts

paleogene → neogene → quaternary

paleogene parts

paleocene → eocene → oligocene

neogene parts

miocene → pliocene

quaternary parts

pleistocene → holocene

Cenozoic - palogene

• anoretic caps forms

• angiosperm and pollinators dominate

• marsupials arrive on Australian continent

Cenozoic - neogene

• continents approach modern look

• grasslands make first appearance

• hominin lineage arises

Cenozoic - quaternary

• glacations in north hemisphere

• deserts and tropical grasslands appear for first time

• modern genera and species appear

• humans start to appear

• modern world look of continents

evidence for plate tectonics

1. continental fit

2. matching stratigraphy and fossils

3. sea-floor spreading

4. paleomagnetism

evidence for plate tectonics - continental fit

south amreicand Africa fit together like a puzzle, highlighting matching coastlines

evidence for plate tectonics - matching rocks and fossils

continuous, identical rock layers and fossil remains are found on separated continents

evidence for plate tectonics - sea-floor spreading

upwelling at mid-ocean ridges creates new oceanic crust, pushing tectonic plates apart

evidence for plate tectonics - paleomagnetism

symmetrical, alternating bands of normal revered polarity record the Earth;s magnetic history on the seafloor

dispersal is a

lineage led process

• organism actively or passively cross a pre-existing barrier to establish new populations

vicariance is a

earth system process

• post-existing barrier arises within a continuous range, splitting the ancestral population

barrier timing - dispersal

pre-existing

barrier timing - vicariance

post-existing

process nature - dispersal

active/passive migration

process nature - vicariance

passive earth-driven split

speciation mode - dispersal

peripatetic

• founder effect

speciation mode - vicariance

allopatric

• symmetrical

macro ecology focuses on

large-scale spatial patterns and the responses of biodiversity to broad earth systems interactions

macroevolution deals primarily with

temporal pattern such as the timing of clade diversification

the nomothetic shift

dinosaurs shifting from purely descriptive phase to nomothetic, where general evoltionary and ecological principles are quantitively tested against the fossil record

idiographic

purely descriptive