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49 Cards in this Set

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chemistry to biology
1. organic soup of amino acids
2. short strands of RNA
3. spontaneous membranes --> "pre-cells"
4. pre-cell --> true living organisms
5. natural selection
chemistry to biology step details
1. organic soup of amino acids
has to be initial step, however amino acids formed
perhaps in special locations, not ubiquitous initially
chemistry to biology step details
2. short strands of rna
required help to initially assemble: clay or other minerals
RNA molecules might catalyze their own replication
initial simulation in the laboratory support this idea
chemistry to biology step details
3. spontaneous membranes --> "pre-cells"
protect chemicals and allow faster reactions
chemistry to biology step details
4. pre-cell --> true living organisms
heredity-machinery was simple
slow evolution through natural selection
chemistry to biology step details
5. natural selection
speeds up with increasing complexity of heredity-machinery
rapid increase in diversity likely due to introduction of DNA
timeline
ss/earth formed
4.55 billion yrs ago
moon formed
4.4 bya
end of hadeon eon
4.0 bya
first isotopic evidence for life
3.85 bya
earliest microfossils
3.5 bya
beginning of proterozoic eon (rising oxygen levels)
3.5 bya
first eukarya fossils
2.1 bya
cambrian explosion
550 million
dinosaurs
200 myr
kt event
65 mill
modern humans
100,000
chemistry to biology step details
2. short strands of rna
required help to initially assemble: clay or other minerals
RNA molecules might catalyze their own replication
initial simulation in the laboratory support this idea
chemistry to biology step details
3. spontaneous membranes --> "pre-cells"
protect chemicals and allow faster reactions
chemistry to biology step details
4. pre-cell --> true living organisms
heredity-machinery was simple
slow evolution through natural selection
chemistry to biology step details
5. natural selection
speeds up with increasing complexity of heredity-machinery
rapid increase in diversity likely due to introduction of DNA
timeline
ss/earth formed
4.55 billion yrs ago
moon formed
4.4 bya
end of hadeon eon
4.0 bya
first isotopic evidence for life
3.85 bya
earliest microfossils
3.5 bya
beginning of proterozoic eon (rising oxygen levels)
3.5 bya
first eukarya fossils
2.1 bya
cambrian explosion
550 million
dinosaurs
200 myr
kt event
65 mill
modern humans
100,000
cambrian explosion 4 factors
sudden rise in oxygen
significant increase in genetic complexity
climate: emerging from snowball earth episodes
no efficient predators
photometry
measure total amount of light from an object
spectroscopy
use a spectrograph to separate the light into its different wavelengths
timing
measure how the amount of light changes with time
imaging
filters are placed in front of a camera to allow only certain colors to be imaged
single color images are superimposed to form true color images
spectroscopy can provide information on
temperature
rotation rate
if atmosphere is present: atmospheric density, temperature, motions
chemical composition
nonvisible light
• Most light is invisible to the human eye.
• Special detectors/receivers can record such light.
• Digital images are reconstructed using false-color coding so that we can see this light.
seeing through the atmosphere
• Earth’s atmosphere causes problems for astronomers on the ground.
• Bad weather makes it impossible to observe the night sky.
• Air turbulence in the atmosphere distorts light.
o That is why the stars appear to twinkle
o Angular resolution is degraded.
• Man-made light is reflected by the atmosphere, thus making the night sky brighter.
o This is called light pollution
atmospheric absorption of light
• Earth’s atmosphere absorbs most types of light.
o Good thing it does, or we would be dead
• Only visible, radio and certain IR and UV light make it through to the ground
4 pieces of evidence presented by scientists that ALH84001 preserves signs of past life on Mars
o Carbonates: precipitated from thicker, warmer, atmosphere?
o Magnetite grains: similar in shape to bacterial magnetite?
o Complex organic molecules: PAHs
o Segmented, “bacterial” (?) morphologies
IO
• Most volcanically active place in whole SS
• Io dramatically shows the power of tidal heating
o Mostly rock now, no water (no life either…)
• For other moons, heating is more mild and may liquefy water ice
angular resolution formula
1.22(wavelength/diameter of telescope)
key roles of water in creation of life
1. provides more contact so organisms can react with each other
2. transportation: brings chemicals in and out of cells
3. participant in important reactions like ATP and photosynthesis
Titan: Cassini View
• Complex organics confirmed
• Radar and infrared imaging reveal complex surface geology, including streaks (from wind? Liquid? Ice?)
• Complex, dendritic patterns carved by liquid methane and shaped by topography. Some of the patterns imply rainfall; others could be liquid methane liberated from (?)
habitable zone
o The region in which temperatures would in principle allow for liquid water to exist on surface if a planet of the right type were located there.
inner boundary
• Inner boundary: distance where a planet will avoid a runaway greenhouse effect
o Somewhere between Earth and Venus
o Optimistic model: .84 AU would produce runaway greenhouse
o Pessimistic model: .95 AU- moist greenhouse
outer boundary
• Outer boundary: distance where even a strong greenhouse would not be warm enough to keep water as a liquid
o Optimistic model: thick atmosphere at 1.7 au (mars 1.52 au) would produce enough greenhouse effect
o Pessimistic model, 1.4 A/u: middle atmosphere too cold → CO2 snow ahhh changing slides!