The Origin and Early Evolution of Life Lecture 19

The Big Bang  (13.8) billion years ago all matter was compressed into a space the size of?  Our Galaxy  Our Solar System  Our Plant  Our Atom  Sudden instantaneous distribution of matter and energy throughout the known universe  (13.8) billion years ago all matter was compressed into a space the size of?  Our Galaxy  Our Solar System  Our Plant  Our Atom  Sudden instantaneous distribution of matter and energy throughout the known universe

Timeline  4.6 to 3.8 billion years ago - Leads to solid crust  3.8 Water forms  2.8 to Life starts as prokaryotic cells  1.5 Eukaryotic cells develop  545 Cambrian explosion  500 Fish  350 Amphibians  300 Reptiles  1.6 humans  4.6 to 3.8 billion years ago - Leads to solid crust  3.8 Water forms  2.8 to Life starts as prokaryotic cells  1.5 Eukaryotic cells develop  545 Cambrian explosion  500 Fish  350 Amphibians  300 Reptiles  1.6 humans

Timeline: Archaean Eon and Earlier  4,600 mya: Origin of Earth  4, ,800 mya (about 800 million years)  Formation of Earth’s crust, atmosphere…  Formation of the Moon  Chemical and molecular evolution only  Then came the First cells (anaerobic bacteria)  4,600 mya: Origin of Earth  4, ,800 mya (about 800 million years)  Formation of Earth’s crust, atmosphere…  Formation of the Moon  Chemical and molecular evolution only  Then came the First cells (anaerobic bacteria)

Earth Forms  About 4.6 billion years ago  Gas, Minerals and ice orbiting the sun started clumping together  Heavy metals moved to Earth’s interior, lighter ones floated to surface  Iron core  Produced outer crust and inner mantle  About 4.6 billion years ago  Gas, Minerals and ice orbiting the sun started clumping together  Heavy metals moved to Earth’s interior, lighter ones floated to surface  Iron core  Produced outer crust and inner mantle

First 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 Life  IF…Earth was;  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  IF…Earth was;  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 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 Animation

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 - nothing came of it!  Then, by a still disputed mechanism, the concoction came together randomly to make some primitive organic molecule…  In the first 600 million years or so of Earth history, enzymes, ATP, and other crucial organic compounds probably assembled spontaneously - nothing came of it!  Then, by a still disputed mechanism, the concoction came together randomly to make some primitive organic molecule…

Possible Sequence

RNA World  DNA is genetic material now  DNA-to-RNA-to-protein system is complex!  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 complex!  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 Cells  Originated in Archaean Eon  There were prokaryotic cells  These were heterotrophs  Secured energy through anaerobic pathways  No oxygen present, therefore they must have  Relied on glycolysis and fermentation only!  Originated in Archaean Eon  There were prokaryotic cells  These were heterotrophs  Secured energy through anaerobic pathways  No oxygen present, therefore they must have  Relied on glycolysis and fermentation only!

Proterozoic Eon  FIRST  Origin of photosynthetic eubacteria, as a result…  SECOND  Then, Oxygen accumulates in atmosphere, and  THIRD  Origin of aerobic respiration  FIRST  Origin of photosynthetic eubacteria, as a result…  SECOND  Then, Oxygen accumulates in atmosphere, and  THIRD  Origin of aerobic respiration

Advantages 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 ER

Theory 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  amples/nonmajorsbiology/organelles.html amples/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  amples/nonmajorsbiology/organelles.html amples/nonmajorsbiology/organelles.html

Evolutionary Tree