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
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