Transcript Quantum Well Electron Gain Structures and Infrared

Development of Life
(continued)
Stephen Eikenberry
28 January 2013
AST 2037
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Evolutionary Timeline
• 530 MYa – first
footprint fossil found on
land
• 505 Mya – first true fish
in the sea
• 475 MYa – first land
plant fossils
• 360 MYa -- Beginning
of the Carboniferous
Age (lots of land plants
and trees!)
• 360 MYa – First
amphibians, followed
quickly by first reptiles;
insects on land/air;
sharks in the ocean
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Permian Era
• 285 MYa to about 250 MYa
• Earth would now have been “recognizable” (if somewhat
weird!)
• Land has immense forests of trees and other plants (but no
flowers!)
• Ocean has lots of fish (including sharks), marine mammals,
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still trilobites too
Permian Era
• Land has insects, amphibians, reptiles
• Reptiles could reach sizes of 10-20 feet (!)
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Permian Era: Pangaea
• One of several supercontinents formed over the history of
Earth
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End-Permian
• By the late Permian, things seem to be going very well!
• Tremendous diversity of life:
• Plants and animals
• Sea and Land
• Then … it all stopped (!)
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Permian Extinction
• AKA “The Great Dying”
• 96% of all marine species extinct
• 70% of land vertebrates extinct
• Note – not individual critters, but entire species!
• Overall mortality of living creatures even for “survivor”
species might have been >95-99% (!)
• “Fungal spike”:
• Large jump in fungal fossils after this
• Why? lots of dead plant/animal matter!
• What caused it ???
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Mesozoic Era
• Defined to begin postPermian Extinction
• Includes Triassic, Jurassic,
Cretaceous
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Mesozoic Era
• Big “bounce” in the development of life after the Permian
Extinction
• Big developments:
• Dinosaurs (which come to dominate)
• Flowering plants (angiosperms)
• Marine reptiles
• Flying reptiles
• First Mammals
• Etc.
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Mesozoic Dinosaurs
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Mesozoic Angiosperms
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Mesozoic Mammals
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Mesozoic Reptiles
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Late Cretaceous
• Again, unprecedented diversity of life on land and sea
• Then (again!) it all ends!
• The Cretaceous-Tertiary (K-T) extinction
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K-T Boundary
• Clear geologic signature
“break” found worldwide
• Thin, whitish line in the
rock
• Interestingly, lots of
dinosaurs BELOW the line;
none ABOVE the line (!!)
• Many other species also
disappear then
(pteranodons; many marine
reptiles)
• About 65 Mya …
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K-T Extinction
• Species extincted included:
• Almost ALL large vertebrates on land (dinosaurs, etc.)
• Most species of plankton and reef-dwelling animals
• Tropical marine invertebrates
• Many land plant species
• Again … these are entire species lost! Death toll for
individual living beings >90% in many cases
• The greatest loss of species in the last 100 million years on
Earth
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K-T: What caused it?
• Iridium:
• Rarely found on Earth’s surface
• Large concentrations in the K-T
Boundary worldwide
• Found in similar concentration
ins METEORS
• Alvarez & Alvarez developed the
KT Impact Theory based on this
• Initially, many people skeptical
• But … shocked quartz also found
worldwide in K-T Boundary
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K-T: How did that kill everything?
• Energetics:
• A meteor about 30 meters across has the energy of a large
hydrogen fusion weapon
• A small asteroid a few miles across would hit with more
energy than 1,000 times the world’s entire nuclear arsenal
(going off at one time in one place!)
• But … even that wouldn’t kill critters worldwide, would it?
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K-T: Impact Climate Change
• That large of an impact
would have sent literally
tons of dust into the
atmosphere
• We used to worry about
“nuclear winter” – this
would be MUCH larger,
colder, longer
• Subsequent freezing of food
sources and death of many
photosynthetic organisms
would kill/starve higher
animals as well
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K-T Impact: Chicxulub!
• Site just north of Yucatan
peninsula in Mexico
• Evidence of large impact
crater
• Crater age matches K-T
• Crater size matches K-T
energetics
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Mass Extinctions
• We have seen the K-T and Permian extinctions
• Evidence for several others
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Impacts: How often?
• Depends on the size:
• 1-ton bomb – EVERYDAY! (Why don’t we notice it?)
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Impacts: Tunguska
• Atomic bomb size – every
100-200 years
(TUNGUSKA)
• Shattered windows in
Moscow (2000 miles
away)
• Heard on the streets of
London (3000 miles
away)
• Flattened a forest of trees
• No crater; center trees
still standing; suggests
“airburst” (possibly
comet?)
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Impacts: Future?
• Atomic bomb size – every 100-200 years (TUNGUSKA)
• Extinction-level hit – every ~100-200 MY
• Aren’t we about due??
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Later evolution
• Tertiary – age of mammals
• Human evolution timeline
• Note: agriculture and human settlements about 13,000 years
ago
• Writing, etc. about 5,000 years ago or so
• Pyramids and Ziggurats
• Transport via boats, etc.
• Telecommunication
• Space travel
• Most signs of “intelligence” limited to the past 50-100 years
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