ORIGINS Planet earth – 4. 6 bya The first life forms – 3 ORIGINS Planet earth – 4.6 bya The first life forms – 3.5 bya The first eukaryotes – 3.0bya The origin of an oxygen-rich atmosphere – 2.1bya

“The Mother of all questions” 1. Not observable 2 “The Mother of all questions” 1. Not observable 2. Even simple life very complex

Life…Boiled Down Self-replicating molecule with a boundary around it that creates internal vs. external environment

4 Problems / Questions 1. How did organic molecules arise from non-organic materials? 2. How were organic monomers assembled into complex polymers? 3. How did the self-replicating molecules needed for inheritance arise? 4. How were the organic molecules packaged into membranes with an internal chemistry different from their surroundings?  

1. How did organic molecules arise from non-organic materials? Miller & Urey (1950) Attempted to recreate the conditions of primitive earth; believed that earth’s early atmosphere was made up of methane, water vapor, ammonia, and hydrogen gas, so these were the components included in the experiments. Has been repeated many times and yielded similar results. “primordial soup model” ; methane, ammonia, hydrogen, steam  what can out in “soup” at the end was all 20 amino acids commonly found in organisms, along with nucleic acids, several sugars, lipids, adenine, and even ATP (if phosphate was added to the flask)

1. How did organic molecules arise from non-organic materials? From space? Panspermia hypothesis

2. How were organic monomers assembled into complex polymers?

2. How were organic monomers assembled into complex polymers? Transition metals can lend and take away electrons from molecules A combination of transition metal elements (copper, nickel) and ligands (small organic molecules) could have catalyzed monomers in hydrothermal ocean vents

2. How were organic monomers assembled into complex polymers? Transition metals can lend and take away electrons from molecules A combination of transition metal elements (copper, nickel) and ligands (small organic molecules) could have catalyzed monomers in hydrothermal ocean vents

3. How did self-replicating molecules needed for inheritance arise? Reactive surfaces model

RNA World = Variation for Free! DNA VS. RNA 1/1x106 errors

4. First membranes? “All spontaneous processes proceed in the direction that increases entropy of the universe” (entropy = a measure of the disorder in a system)”

4. First membranes? ORDER FOR FREE! Lipids in water… Bilayers form spontaneously! Why?

The First Membranes… Order For Free! Lipids in water… Initial State Final State Lipids Free molecules (High S) Fluid membrane (Intermediate S) Water Ice-like shells (Low S) Free molecules (High S) Spontaneous biological order at the expense of universal disorder!

Other examples of entropy-driven order – “self-assembly” Self-folding of small polypeptides

TED Talks – Lee Cronin “Making Matter Come Alive” How does he propose to define life?

TED Talks – Lee Cronin “Making Matter Come Alive” How is Lee Cronin’s lab attempting to “make matter come alive?” What are some of the implications of his research? How does he propose to define life?

The Earliest Life was Prokaryotic…How Did Eukaryotes Evolve?

The Origin of the Mitochondria and Chloroplasts: Early 1900s – Konstantin Merezhkovsky “Chlorophyll bodies…behave like independent organisms… They are symbionts, not organs”

The Origin of the Mitochondria and Chloroplasts: Early 1960s – Lynn Margulis The Origin of Mitosing Eukaryotic Cells Convincingly developed the view that chloroplasts and mitochondria have prokaryotic origins National Medal of Science, 1999

Theory of Endosymbiosis Ancestral anaerobic eukaryote engulfed another formerly free-living organism; became so tightly ingrained with one another  no longer free-living  gave rise to today’s aerobic and photosynthetic eukaryotic cells

Margulis’ Data Size Ribosomes Membrane DNA Characteristic Eukaryote Prokaryote Mitochondria Chloroplast Size Ribosomes Membrane DNA Characteristic Eukaryote Prokaryote Mitochondria Chloroplast Size 100 m 1m Ribosomes 80S 70S Membrane Single membrane Single membrane Double membrane DNA Joined with proteins in chromosomes Naked, circular

Quick Side-Note Another example of non-mendelian genetics! No!

Mitochondria and Chloroplasts reproduce by binary fission! Margulis’ Data Both prokaryotes and mitochondria and chloroplasts reproduce by binary fission!; Mitochondria and Chloroplasts reproduce by binary fission!

Total Independence? Mitochondrial Genome No! Mitochondria has lost important genes! Cannot be cultured independently! Where did these genes go They’ve been transferred to the nuclear genome! Mitochondrial Genome

Is the loss of genes unusual? NO! Ants and Mealybugs Moranella bacteria inside a Tremblaya bacterium inside a Mealybug!

Is the loss of genes unusual? NO!

Other Endosymbionts? Cilia and Flagella were once spirochete bacteria? Viral origin of the nucleus? No!