BIOE 20C Lecture Notes - Lecture 9: Extinction Event, Eukaryote, Multicellular Organism
12 Sep 2016
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Lecture 9 10/27/2015 7:52:00 PM
Evolutionary History of Life on Earth
• Where did we come from?
• Where are we going to?
Origin of Life on Earth
• A simple 5 step program guaranteed to provide you with the
fundamental components necessary to promote an environment
suitable for evolution
Step 1: Formation of Primordial Soup
• Environment that produced the first molecules that are necessary to
produce larger molecules for life
• 3 theories
o Reducing Atmosphere
o Extraterrestrial
o Deep Sea Vent
Reducing Atmosphere
• Miller—1953
• Atmosphere of early earth
o Low O2 (doesn't show up for many thousands of years)
o Rich H2, NH3, CH4, H2O vapor, and energy
o Formed simple organic molecules that accumulated in world’s
growing oceans
• Miller Experiment
o Hypothesis: organic chemical compounds can be generated
under conditions similar to those that existed on primitive
Earth
Extraterrestrial
• Organic compounds delivered via asteroids /meteorites
• Ex. traces of amino acids found in meteors found in Antarctica
Deep Sea Vent
• Organic compounds formed at hydrothermal vents rich in H2S, NH3
find more resources at oneclass.com
find more resources at oneclass.com
• Hypothesizes that formation of compounds occurred deep in the
bottom of the ocean
Step 2: Formation of Organic Polymers
• Clay surfaces may have served as templates against which the first
RNA or amino acid polymers were formed
o Clay would have acted like enzymes
Step 3: Formation of Protobionts
• Protobionts
o have a definitive boundary
o Contain polymers inside
▪ Polymers undergo reactions
o Enzymatic action (“metabolism”)
o Replication ability
• Initially thought to be coacervates
o Solid droplet of protein and carbohydrates with a skin of
water
• Microspheres
o Hollow sphere of protein filled with water
• Most likely possibility=liposomes
o Sphere of phospholipids filled with water
Step 4: Chemical Selection
• New protobionts with enhanced enzymatic or replicating abilities
favored
• RNA may have initially had both information storage and catalytic
role
Step 5: RNA World to DNA World
• Allowed separation of information/catalytic functions
• Originally RNA did both
• DNA—more stable
• Protein—better catalyst
• Starting point for evolution to occur
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Origin of life on earth: a simple 5 step program guaranteed to provide you with the fundamental components necessary to promote an environment suitable for evolution. Step 1: formation of primordial soup: environment that produced the first molecules that are necessary to produce larger molecules for life, 3 theories, reducing atmosphere, extraterrestrial, deep sea vent. Extraterrestrial: organic compounds delivered via asteroids /meteorites, ex. traces of amino acids found in meteors found in antarctica. Deep sea vent: organic compounds formed at hydrothermal vents rich in h2s, nh3, hypothesizes that formation of compounds occurred deep in the bottom of the ocean. Step 2: formation of organic polymers: clay surfaces may have served as templates against which the first. Rna or amino acid polymers were formed: clay would have acted like enzymes. Step 4: chemical selection: new protobionts with enhanced enzymatic or replicating abilities favored, rna may have initially had both information storage and catalytic role.
