life on earth through time
DESCRIPTION
Life on earth through time. Let’s start at the beginning. How did the solar system (and earth) form from a rotating cloud of dust, particles and gases?. 4.6 By. Half-a-billion years later. Lava plains and moon craters date back to ~3.9 By How did the moon form?. Life, maybe. - PowerPoint PPT PresentationTRANSCRIPT
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Life on earth through time
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Let’s start at the beginning...
• How did the solar system (and earth) form from a rotating cloud of dust, particles and gases?
4.6 By
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Half-a-billion years later...• Lava plains and
moon craters date back to ~3.9 By
• How did the moon form?
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Life, maybe• Marine sediment by
3.8 By; evidence for liquid water on earth
• Oldest fossil in 3.5 By old rocks in Western Australia
• Debate continues… is this really evidence for life at 3.5 By?
3500 Ma
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Cyanobacteria
• Suggested to be an early form of cyanobacteria
• Stromatolites- layers formed by webs of filimentous cyanobacteria
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Prokaryotes to Eukaryotes
• About a billion years of evolution gave us membrane-bound organelles
• Endosymbiotic theory
2100 Ma
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O2 rich atmosphere• Photoautotrophs:
– 6 CO2 + 6 H2O-> C6H12O6 +6 O2
• Oxygenated atmosphere by 1.8 Ba• Aerobic organisms- use O2 to
covert food to energy is favorable relative to fermentation
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Complex multi-cellular life• See a surge in
diversity of multi-cellular life ~600 My…
• Improvement in fossil record
• First chordates
600 Ma
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Phanerozoic
• Apparent life
• Rich fossil record starts in middle age of the earth
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Early fish
• Appear in upper Cambrian (550 Ma)• Jawless, cartilagenous and eventually the
bony fishes• Importance of the bony lineage
440 Ma
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Land plants• A progression from
marine algae to freshwater algae to green algae
• Vascular land plants- have the ability to transport water and nutrients within plant
430 Ma
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Trees• What are the
benefits of a woody trunk?
• With plants and trees well established, what is next?
370 Ma
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Amphibians• Land dwellers• Return to water to lay eggs and for larvae to mature• Adaptations: 3-chambered heart, limbs and girdle
bones, sturdy but flexible spinal column, ear structure
360 Ma
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Insects• First insects were
wingless• Wings appear in
late Carboniferous• Extensive
radiation before the Permian
300 Ma
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Reptiles• Reproduce
without returning to water– Enclosed eggs– Pass through
larval stage– Born in essentially
adult form
290 Ma
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Dinosaurs• Dinosaurs: started off small with
light build (225 Ma)• Large carnivores Jurassic and
Cretaceous• Were they cold or warm-blooded?
– Vascular development of bones– Relation to birds
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210 Ma
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Early Mammals
• Tiny shrew-like creatures• Reliable temperature control• Co-existing with Dinosaurs through
Mesozoic
210 Ma
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Birds• Poor fossil record• Archaeopteryx: the
perfect evolutionary link between theropods and modern birds– Feathers on a reptile– Jaw bone with teeth– Wings retained claws
150 Ma
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IMPACT!
65 Ma
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K-T boundary• Bolide ~10 km in diameter crashed
into Earth sending up dust, ejecta into the atmosphere
• Cloud blocked sunlight and led to the demise of plants, base of food chain
• Marine and terrestrial animals perished
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Whales• From land to sea• Descendents of
carnivorous land mammals, the earliest of whom could walk and swim
• With increasing size, lost limbs
• Adapted feeding strategy
50 Ma
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Primates• Grasping, mobile
hand• Overlapping field
of vision• By 34 Ma-
anthropoids (apes, monkeys, humans)
34 Ma
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Genus Homo• 2.4 Ma: Homo
habilis• 1.8 Ma: Homo
erectus• Increased cranial
capacity; sloped forehead, jutting jaw, robust teeth
2.4 Ma
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Homo sapiens neaderthalensis• Heavy brow ridges,
chinless jaws, large brain cavity, short limbs, bulky torso
• Hunted, used fire for warmth, light, cooking, constructed shelters from the skins
• 34,000 yrs-replaced by Homo sapiens sapiens
320 ky
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K-T boundary
Permo-Triassic boundary
Mass Extinctions
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“Mother of all extinctions”• Late Permian: 90% of all marine species
lost or reduced; tropical marine invertebrates hardest hit
• On land, spore bearing ferns gave way to conifers, ginkoes and gymnosperms
• Amphibians, reptiles lost• Causes: Configuration of the continents,
loss of epeiric seas, ice on poles, volcanic activity
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• Late Ordivician (440 My) and late Devonian ME’s triggered by global cooling with the growth of the ice caps- due to compressed biomes, lowered sea level
• Impacted: marine invertebrates• Late Devonian: again cooling- reefs
communities hit hardest
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The influence of tectonics on climate
• Position of continents dictates:– Ocean circulation and heat transport– Sea level (freeboard)- Pangaea– Ability to form ice caps
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Example: Miocene grasslands and horse evolution
• Closure of Tethys (~35 Ma) with collision of Africa and Eurasia
• Cooling & drying with loss of forests, expansion of grasses
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Horse adaptations• Horses in Eocene (50
Ma): small, 4 toed, fed on shrubs and foliage
• Grasses expanded• Horses in Miocene
– Higher crowned teeth– Fewer toes– Bigger, stronger, faster
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Organisms effect on the environment?
• Examples: – Photosynthesis– Spread of land plants– Nutrient cycling
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The marine N cycle• Nitrogen is an essential nutrient the limiting nutrient• When there is more available
nitrogen in a useful form, primary productivity is higher, CO2 removed from atmosphere
“The biological pump”
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Sedimentary 15N• Use stable
isotopes of N to identify relative inputs/outputs in ocean in past
• Sediment and microfossil samples
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Peru-Chile Margin
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Goals• Changes in productivity through
time• Variability in denitrification (the
removal of nitrate) in the Eastern Tropical North Pacific
• Understanding the role of the N-cycle in glacial-interglacial CO2 cycles