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The Origin and Early Evolution of Life
The Origin and Early Evolution of Life
Biology 1010Biology 1010
The Big BangThe Big Bang
12-15 billion years ago all matter was
compressed into a space the size of our sun
Sudden instantaneous distribution of matter and energy throughout the known universe
12-15 billion years ago all matter was
compressed into a space the size of our sun
Sudden instantaneous distribution of matter and energy throughout the known universe
Archaean Eon and Earlier Archaean Eon and Earlier
4,600 mya: Origin of Earth
4,600 - 3,800 mya (about 800 million years)
Formation of Earth’s crust, atmosphere
Chemical and molecular evolution
First cells (anaerobic bacteria)
4,600 mya: Origin of Earth
4,600 - 3,800 mya (about 800 million years)
Formation of Earth’s crust, atmosphere
Chemical and molecular evolution
First cells (anaerobic bacteria)
Earth FormsEarth Forms
About 4.6 and 4.5 billion years ago Minerals and ice orbiting the sun started
clumping together Heavy metals moved to Earth’s interior,
lighter ones floated to surface Produced outer crust and inner mantle
About 4.6 and 4.5 billion years ago Minerals and ice orbiting the sun started
clumping together Heavy metals moved to Earth’s interior,
lighter ones floated to surface Produced outer crust and inner mantle
First AtmosphereFirst Atmosphere
Hydrogen gas
Nitrogen
Carbon monoxide
Carbon dioxide
No gaseous oxygen
Hydrogen gas
Nitrogen
Carbon monoxide
Carbon dioxide
No gaseous oxygen
Earth Is “Just Right” for LifeEarth Is “Just Right” for Life
Smaller in diameter, gravity would not be great enough to hold onto atmosphere
Closer to sun, water would have evaporated
Farther from sun, water would have been locked up as ice
Smaller in diameter, gravity would not be great enough to hold onto atmosphere
Closer to sun, water would have evaporated
Farther from sun, water would have been locked up as ice
Stanley Miller’s ExperimentStanley Miller’s Experiment
Mixed methane, hydrogen, ammonia, and water
Simulated lightning Amino acids and
other small molecules formed
Mixed methane, hydrogen, ammonia, and water
Simulated lightning Amino acids and
other small molecules formed
to vacuum pump
CH4
NH3
H2OH2
gases
electrodes
spark discharge
water out
condenser
water in
water droplets
water containingorganic compounds
liquid water in trapboiling water
Animation
How Did Cells Originate?How Did Cells Originate?
In the first 600 million years or so of Earth history, enzymes, ATP, and other crucial organic compounds probably assembled spontaneously
In the first 600 million years or so of Earth history, enzymes, ATP, and other crucial organic compounds probably assembled spontaneously
Possible SequencePossible Sequencemembrane-bound proto-cells living cells
self-replicating system enclosed in aselectively permeable, protective lipid sphere
DNA RNAenzymes andother proteins
formation ofprotein-RNA systems,
evolution of DNA
formation oflipid spheres
spontaneous formation of lipids,carbohydrates, amino acids, proteins,nucleotides under abiotic conditions
RNA WorldRNA World
DNA is genetic material now
DNA-to-RNA-to-protein system is
complicated
RNA may have been first genetic material
RNA can assemble spontaneously
How switch from RNA to DNA might
have occurred is not known
DNA is genetic material now
DNA-to-RNA-to-protein system is
complicated
RNA may have been first genetic material
RNA can assemble spontaneously
How switch from RNA to DNA might
have occurred is not known
The First CellsThe First Cells
Originated in Archaean Eon
Were prokaryotic heterotrophs
Secured energy through anaerobic pathways
No oxygen present
Relied on glycolysis and fermentation
Originated in Archaean Eon
Were prokaryotic heterotrophs
Secured energy through anaerobic pathways
No oxygen present
Relied on glycolysis and fermentation
Proterozoic EonProterozoic Eon
Origin of photosynthetic eubacteria
Oxygen accumulates in atmosphere
Origin of aerobic respiration
Origin of photosynthetic eubacteria
Oxygen accumulates in atmosphere
Origin of aerobic respiration
Advantages of OrganellesAdvantages of Organelles
Nuclear envelope may have helped to protect genes from competition with foreign DNA
ER channels may have similarly protected vital proteins
Nuclear envelope may have helped to protect genes from competition with foreign DNA
ER channels may have similarly protected vital proteins
Possible Origin of ERPossible Origin of ERDNA
infolding of plasma membrane
Theory of EndosymbiosisTheory of Endosymbiosis
Lynn Margulis
Mitochondria and chloroplasts are the descendents of free-living prokaryotic organisms
Prokaryotes were engulfed by early eukaryotes and became permanent internal symbionts
http://www.sumanasinc.com/webcontent/anisamples/nonmajorsbiology/organelles.html
Lynn Margulis
Mitochondria and chloroplasts are the descendents of free-living prokaryotic organisms
Prokaryotes were engulfed by early eukaryotes and became permanent internal symbionts
http://www.sumanasinc.com/webcontent/anisamples/nonmajorsbiology/organelles.html
Evolutionary TreeEvolutionary Treehydrogen-rich anaerobic atmosphere atmospheric oxygen, 10%
archaean lineage
ancestors ofeukaryotes
endomembrane system and nucleus
origin ofprokaryotes
cyclic pathwayof photosynthesis
noncyclic pathwayof photosynthesis
aerobic respiration
3.8 billion years ago
3.2 billion years ago
2.5 billion years ago
Evolutionary TreeEvolutionary Tree