Precambrian Eukaryotes

Acritarchs

Ediacaran

Vendian

AcritarchsCysts of unicellular eukaroytes, perhaps algae or egg cases of

multicellular orgs. 1800 my through Devonian

Ediacaran

• 600 my-545 my• Soft-bodied• Many organisms of

uncertain affinity

Possible annelids, cnidarians (coral

relatives)

Possible mollusc?

Probable cnidarian

Total mysteries

Vendian

• “little shellies”• Right at Cambrian

boundary

Phanerozoic Life, Part I.

1. Cambrian, Paleozoic and Modern Faunas slides

2. Phanerozoic Aquarium project: with your partners, go through your Aquarium pages. Identify each organism using your handouts: Invertebrates, Fish, Tetrapods

3. Time Travel Submarine

Trilobites:Extinct arthropods(like lobsters or shrimp but withcalcite skeleton)

Cambrian

Lingulate brachiopods

Strange echinoderms

Sponge reef

Burgess Shale

• Middle Cambrian• Excellent preservation of soft-bodied orgs.• 5 kinds of arthropods (only 3 kinds today)• First vertebrate• Mysterious critters

Cambrian• Smallish• Skeletons (if any) of phosphate or thin CaCO3• Live on or near ocean floor• Sponges, trilobites, early molluscs, echinoderms, lingulate

brachiopods

Why the Cambrian explosion in diversity?

• Proterozoic glaciation

• Atmospheric oxygen

• Proterozoic rifting

• Changes in ocean nutrients

• Extinction of cyanobacteria

• Evolution of predators

Ordovician

Brachiopods(articulate)

Bryozoans

Crinoids (echinoderms)

Cephalopods

Corals

Graptolites

Ordovician invertebrates

• More robust skeletons

• Calcite skeletons

• Taller, deeper (take up more ecological space)

• The Paleozoic fauna appears: rhynchenelliform brachiopods, bryozoans, crinoids/blastoids, primitive cephalopods, graptolites, rugose/tabulate corals

Middle-Late Paleozoic

Middle-Late Paleozoic

• Increasing height, increasing depth

• Increasing diversity

• New organisms– Eurypterids (giant sea scorpions)

• Fish/amphibians

Eurypterid

Fish

Jawless (bony plates on outside)Ostracoderms

Armored:Acanthodians & Placoderms

Chondrichthyes:

Osteichthyes:

Lobe-finned fish

Forerunners of quadrapeds

Mesozoic Life

• Oceans - a whole new crew

• The Modern Fauna– Mollusks– Crustaceans– Echinoids– Fish

Molluscs

Bivalves

Gastropods

Crustaceans

Echinoids

Mesozoic Life

• Oceans - a whole new crew

• The Modern Fauna– Mollusks– Crustaceans– Echinoids– Fish

• Plus marine reptiles and ammonites

Marine reptiles

Ammonites

Cenozoic Oceans

• Like Mesozoic: Modern Fauna• Minus marine reptiles and ammonites• Plus whales and marine mammals

Phanerozoic Life, Pt. II

1. Find your Phanerozoic Terrarium pages.

2. As we go through the Powerpoint slides, find organisms in the appropriate time period.

3. Safari Through Time

4. Extinction

Evolution of Tetrapods

• Arise from sarcopterygians (lobe-finned fish)• Amphibianish creatures• Reptiles (to birds)• Mammals

Tiktaalik - recent transitional find

Amphibians

Adaptations for life on land

• Breathe!• Locomotion• Avoid dessication• Reproduction - amniotic egg allows longer

development (no swimming larvae)– Leathery covering or eggshell– Larger size of egg– Larger yolk

Adaptations for life on land: plants

• Avoid dessication – thicker outsides

• Reproduction – – Fancy fertilization methods, seeds– Marine plants release gametes into water

• More complicated dispersal mechanisms for young

Reptiles• Anapsids: turtles and their ancestors

• Synapsids: pre-mammals & mammals

Synapsids

Therapsids: immediate

forerunners of mammals

Reptiles• Anapsids: turtles and their ancestors

• Synapsids: pre-mammals & mammals

• Diapsids: Rest of reptiles– Marine reptiles– Snakes, lizards– Pterosaurs – Crocodilians– Dinosaurs and birds

DiapsidsPterosaurs

Marine reptilesCrocodiles

Marine reptiles

Diapsids

Dinosaurs

Birds

What were dinosaurs like?

• At your table, address one of these questions:– How did dinosaurs stand? Were they capable

of fast movement?– Were dinosaurs social animals?– Were dinos warm-blooded?

• How do you know?

Brontosaurus, 1953

Apatosaurus, 2007

Bone strength of ceratopsians could sustain a 35mph gallop

T. rex had weak leg bones, delicate skull:Probably walking, not running Maybe scavenger?

Maiasaurs built nests in a large nesting colony, each a mom’s length apart.Nests have no broken egg shells in them, so mom cleaned them out.Babies may have been incapable of walking, like baby birds, so required care

Maternal care

Bone beds may represent mass mortality of a herd -for example, trying to ford a river in flood, just likecaribou and wildebeest disasters of recent years.

Herding

Trackways

Some trackways have little footprints on the inside, suggesting a herd structure like elephants, where the babies are protected by the adults on the outside

Pack Hunting

Popular idea, not much evidence:•One specimen of multiple raptors with prey•Large optic lobes, used in reptiles for higher brain functions

Warm-bloodedness

• Predator-prey ratios

• Thermal inertia

• Haversian canals

• O-18 isotopic ratio

Dino bone

Tortoise bone

O-18 to O-16 ratio varies with:•Season•Internal temperature

Cold blooded animals have growth rings and large O-18 variability.

Warm-blooded animals have no growth rings, uniform O-18 levels

Mammal evolution

• Permian: Dimetrodon-like synapsids

• Triassic: modern mammals appear

• Oligocene: giant mammals

• Pleistocene: megafauna

Mass Extinction Causes

• Coincidence: lots of organisms happened to die at the same time. Can be ruled out statistically.

Mass Extinction Causes

• Coincidence

• Physical causes: changes in climate, salinity, living space, etc.

Mass Extinction Causes

• Coincidence

• Physical causes

• Biological causes: competition, predation

Mass Extinction Causes

• Coincidence

• Physical causes

• Biological causes

• Catastrophe: impact, volcanoes

Permo-Triassic extinction

• Over 90% of life dies, so definitely real

Permo-Triassic extinction

• Over 90% of life dies, so definitely real

• Continental configuration and regression– Reduced continental shelf space– Glaciation– Severe climate

Permo-Triassic extinction

• Over 90% of life dies, so definitely real

• Continental configuration and regression

• Appearance of biological “bulldozers”: – Shallow burrowers– Earlier life was immobile bottom dwellers

(brachiopods, bryozoans, crinoids, etc.)

Permo-Triassic extinction

• Over 90% of life dies, so definitely real

• Continental configuration and regression

• Appearance of biological “bulldozers”

• Catastrophe:– Impact? Probably not

Permo-Triassic extinction

• Over 90% of life dies, so definitely real

• Continental configuration and regression

• Appearance of biological “bulldozers”

• Catastrophe:– Impact? Probably not– Volcanoes

Cretaceous-Tertiary Extinction

• 85% species extinction, so it’s real• No big physical changes - many small

continents with lots of shelf space, mild climate

• No big biological changes preceding the extinction, no big change in ecological structure of the oceans after the extinction

K/T Catastrophe

• Impact hypothesis

• Volcanic hypothesis

Impact hypothesis

• Asteroid about 10 km (6 mi.) struck, probably in Yucatan at Chicxulub

Impact hypothesis

• Asteroid about 10 km (6 mi.) struck, probably in Yucatan at Chicxulub

• Immediate heat shock and wildfires near impact site

Impact hypothesis

• Asteroid about 10 km (6 mi.) struck, probably in Yucatan at Chicxulub

• Immediate heat shock and wildfires near impact site

• Particulates of gypsum (Ca2SO4) cause acid rain, killing plankton

Impact hypothesis

• Asteroid about 10 km (6 mi.) struck, probably in Yucatan at Chicxulub

• Immediate heat shock and wildfires near impact site

• Particulates of gypsum (Ca2SO4) cause acid rain, killing plankton

• Particulates create clouds, block sun, killing plants

Impact hypothesis

• Asteroid about 10 km (6 mi.) struck, probably in Yucatan at Chicxulub

• Immediate heat shock and wildfires near impact site

• Particulates of gypsum (Ca2SO4) cause acid rain, killing plankton

• Particulates create clouds, block sun, killing plants • Temperature drops, killing organisms with no

tolerance for cold

Evidence

• Crater at Chicxulub

Evidence

• Crater at Chicxulub• Iridium spike

Asteroids have higher iridium abundance than Earth’s crust. Iridium of Earth is mostly in the mantle and core.

Evidence

• Crater at Chicxulub• Iridium spike• Shocked quartz

Two directions of lamellae typical of

impacts

Evidence

• Crater at Chicxulub• Iridium spike• Shocked quartz• Tektites

Glass globules from melting of surface and

striking object

Evidence

• Crater at Chicxulub• Iridium spike• Shocked quartz• Tektites• Soot

Carbon in boundary clay from wildfires

Biological effects

• Who dies?– Planktonic orgs.

– Ocean surface ecosystem

– Orgs. with poor thermoregulation

• Who lives?

Biological effects

• Who dies?– Planktonic orgs.

– Ocean surface ecosystem

– Orgs. with poor thermoregulation

• Who lives?– Bottom dwellers who

eat dead things

– Orgs. with dormancy capability

Biological effects

• Who dies?– Planktonic forams– Marine reptiles– Ammonites– Dinosaurs– Birds– Non-flowering

plants– Marsupials

Biological effects

• Who lives?– Bottom communities:

clams, snails, crustaceans, etc.

– Placental mammals

– Angiosperms

– Amphibians

– Turtles

– Insects

Volcanic hypothesis

• Huge volcanic eruption produces climatic change, acid rain

• Volcanoes bring up iridium• BUT:

– Problems demonstrating that the eruption is the right age

– Basaltic eruptions produce little ash, so little climate change