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Origin of Life
Origin of Universe
Origin of Elements
Origin of Sun & Solar System
Origin of Living Systems
Evolution of Living Systems
Arguments for Origin
• Divine
• Extraterrestrial
• Chemical evolution
In the beginning…a big bang
• About 15 billion years ago
• Evidence
– Hubble Expansion
– Big Bang Nucleosynthesis
– Microwave background radiation
Big bang – Hubble Expansion
• Galaxies appear to be moving away from our galaxy
• Initially observed by Edward Hubble in 1927
• Galaxies have a red shift in light produced by the Doppler
effect similar to sound (also used in radar)
• The movement of galaxies away from us corresponds to an
equation called "Hubble's Law"
• The time elements in Hubble's Law permit the estimation
of the age of the universe – about 13 billion years (+ or – a
few billion)
Big Bang - Nucleosynthesis
• Occurred during seconds 100 to 300 following big bang
temperature cools allowing hydrogen to form
• Result of temperature of universe dropping below that
required for nuclear fusion (4 H to He) forms Helium
• Produced a large amount of Helium which is very stable
and cannot be converted easily into heavier elements
• Amount of background Helium measured in universe is
consistent with Big Bang Nucleosynthesis
Big Bang – Background Radiation
• If big bang then there should exist remanentt heat
• The cosmic microwave background was predicted in 1948
• 1964-65Arno Penzias and Robert Woodrow Wilson
measured the temperature to be approximately 2.725 K
which translates to specific background radiation in the
microwave range.
• This radiation as a signature of the big bang.
• Penzias and Wilson received the 1978 Nobel Prize in
Physics for their discovery.
• Existence of this radiation inconsistent with steady state
model that Einstein and others favored.
Origin of Elements
• Hydrogen fuses to form helium
– Hydrogen & Helium most abundant
– Sun’s energy drives life processes
• Stars become red giants as hydrogen runs
low (about 10 billion years)
• Helium fuses into other elements
• Star goes nova (blows up)
• Heavier elements released into space
Sun and Planets
• Sun formed about 5 billion years ago
– Gravitational attraction of gases
– Gravitational field becomes great enough to
initiate fusion reactions
• Accretion forms inner planets & moons
from dust and debris of supernova
• Process occurs quickly-earth & moon about
same age
Early Earth
• Earth 4.6 billion years old (U238 dating)
– Moon rocks & meteorites
• Early Atmosphere mostly non-oxidizing
– Nitrogen
– Carbon dioxide
– Water (as water vapor)
• Lesser amounts
– CO, H2, NH3, H2S and CH4
Venus, Earth & Mars Comparison
Venus
Earth
Mars
Pressure
CO2 (>98%)
N2 (1%)
Ar (1%)
O2 (0%)
91 atm
CO2 (0.03%)
N2 (79%)
Ar (1%)
O2 (20%)
1 atm
CO2 (96%)
N2 (2.5%)
Ar (1.5%)
O2 (2.5%)
0.006 atm
Temperature
740 K*
290 K **
240 K ***
Gravity
8.87 m/s2
9.87 m/s2
3.72 m/s2
Atmosphere
*870º F
**70º F
*** -30º F
Characteristics of Life
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Composed of Cells
Reproduce in kind
Metabolism / Energy Transformations
Respond to stimuli
Abiogenesis
• The process of life from the inanimate
• Formation of organic monomers from
inorganic molecules
• Formation of organic polymers from
organic monomers
• Evolution of membranes
• Evolution of DNA based reproduction
Chemical Evolution
• Requires a non-oxidizing atmosphere
– No oxygen initially
• Requires a source of energy
– Lightening, UV light, Volcanoes & Meteorites
• Requires hydrogen, nitrogen, carbon,
oxygen
– Components of organic and biological
compounds
– water, ammonia, carbon dioxide/methane
• Requires time
Chemical Reactions &
Chemical Reactions
• Need to speed up chemical processes
• Reactions are sped up by
•Increasing concentrations of reactants
•Temperature
•Common phases
• Solvent effects
• Catalyst
Molecular Clues to Origins
• The following suggest common origin:
– Organisms use molecules based mostly on hydrogen,
nitrogen and carbon present on early earth
– Only L-amino acids found in proteins
– DNA & RNA are universal in all organisms
– ATP is energy intermediate in all organisms
– All organisms initiate carbohydrate metabolism with
similar steps
– Genetic code is universal
– All cells bound by a plasma membrane composed of a
lipid bylayer
Organic Monomers
• Oparin & Haldane
suggest organic
molecules could form
from precursors
(1930)
• Miller & Urey test
using an apparatus
which simulates early
earth (~1950)
Stanley Miller
Organic Polymers
• Major Groups - Nucleic acid, proteins,
lipids, polysaccharides - have been formed
synthetically
• Information vs. Structural vs. Catalytic
• Protenoids will form spontaneously on clay
• D & L amino acids can be selected on
calcite - a common crystalline mineral
• RNA - has all three capabilities
RNA “Life”
• Ribose, a component of RNA will form
spontaneously from formaldehyde and HCN
• Some RNA’s have been found to have
catalytic activity - ribozymes
• RNA has structural capability in ribosomes
• RNA’s have an information carrying
capacity in viruses & RNA’s have been
induced to take on new traits
RNA Life
• Book segment by B. Alberts
http://www.ncbi.nlm.nih.gov/books/NBK26
876/
• http://exploringorigins.org/timeline.html
• https://www.princeton.edu/~achaney/tmve/
wiki100k/docs/RNA_world_hypothesis.htm
l
DNA Life
• Separation of functional roles of molecules
related to constant input of energy
• Separation of information carrying capacity
from other roles of molecules in cells
• RNA to DNA
• RNA to Protein - catalytic capacity
• Protein & polysacharides take on structural
roles in cells
Membranes
• Why cells?
– Inside vs. outside
– Concentration effect on reactions
• Indications of process
– Microspheres - hydrocarbons in water form
microsperes which can contain other molecules
– Liposomes - artificial lipid bilayers very similar
to cell membranes but smaller - used for drug
transport
Prokaryotic Cells
• Appear about 3.5 billion years ago
• Photosynthesis in blue-green algae begins to
modify atmosphere
• Oxygen in atmosphere begins to modify
types of organisms
Stromatolites
Eukaryotic Cells
• Begin to appear in fossil record about 2.5
billion years ago
• Considerable internal structure relative to
prokaryotic cells
• Precursors to multicellular organisms
Fossil Record
• Dating
– Stratographic analysis
– Radiometric dating
• Geologic Time
– Precambrian - 4.6 to 0.57 billion years ago
• Fossils all unicellular
– Caambrian – 0.57 billion years ago to present
• Multicellular organisms
• Extinction Level Events
Evidence for Evolution
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Physical methods – radiometric dating
Fossil record
Anatomical comparisons
DNA sequence analysis
Laboratory experiments showing selection