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 ComparisonVenus Earth Mars

Atmosphere CO2 (>98%)

N2 (1%)

Ar (1%)

O2 (0%)

CO2 (0.03%)

N2 (79%)

Ar (1%)

O2 (20%)

CO2 (96%)

N2 (2.5%)

Ar (1.5%)

O2 (2.5%)

Pressure 91 atm 1 atm 0.006 atm

Temperature 740 K* 290 K ** 240 K ***

Gravity 8.87 m/s2 9.87 m/s2 3.72 m/s2

*870º F **70º F *** -30º F

Characteristics of Life

• 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/NBK26876/

• http://exploringorigins.org/timeline.html

• https://www.princeton.edu/~achaney/tmve/wiki100k/docs/RNA_world_hypothesis.html

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

• Physical methods – radiometric dating

• Fossil record

• Anatomical comparisons

• DNA sequence analysis

• Laboratory experiments showing selection