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