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
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• 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
Cyanobacteria
• Suggested to be an early form of cyanobacteria
• Stromatolites- layers formed by webs of filimentous cyanobacteria
Prokaryotes to Eukaryotes
• About a billion years of evolution gave us membrane-bound organelles
• Endosymbiotic theory
2100 Ma
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
Complex multi-cellular life• See a surge in
diversity of multi-cellular life ~600 My…
• Improvement in fossil record
• First chordates
600 Ma
Phanerozoic
• Apparent life
• Rich fossil record starts in middle age of the earth
Early fish
• Appear in upper Cambrian (550 Ma)• Jawless, cartilagenous and eventually the
bony fishes• Importance of the bony lineage
440 Ma
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
Trees• What are the
benefits of a woody trunk?
• With plants and trees well established, what is next?
370 Ma
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
Insects• First insects were
wingless• Wings appear in
late Carboniferous• Extensive
radiation before the Permian
300 Ma
Reptiles• Reproduce
without returning to water– Enclosed eggs– Pass through
larval stage– Born in essentially
adult form
290 Ma
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
210 Ma
Early Mammals
• Tiny shrew-like creatures• Reliable temperature control• Co-existing with Dinosaurs through
Mesozoic
210 Ma
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
IMPACT!
65 Ma
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
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
Primates• Grasping, mobile
hand• Overlapping field
of vision• By 34 Ma-
anthropoids (apes, monkeys, humans)
34 Ma
Genus Homo• 2.4 Ma: Homo
habilis• 1.8 Ma: Homo
erectus• Increased cranial
capacity; sloped forehead, jutting jaw, robust teeth
2.4 Ma
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
K-T boundary
Permo-Triassic boundary
Mass Extinctions
“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
• 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
The influence of tectonics on climate
• Position of continents dictates:– Ocean circulation and heat transport– Sea level (freeboard)- Pangaea– Ability to form ice caps
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
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
Organisms effect on the environment?
• Examples: – Photosynthesis– Spread of land plants– Nutrient cycling
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”
Sedimentary 15N• Use stable
isotopes of N to identify relative inputs/outputs in ocean in past
• Sediment and microfossil samples
Peru-Chile Margin
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