Download LECTURE 2: Precambrian Era: Origin of Life

Krakowski 1
Lane Tech College Prep High School
LECTURE 2: PreCambrian: Origin of Life
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ORIGIN OF EARTH REVIEW:
1. Universe is 13.7 Billion Years Old
2. Solar System formed 4.6 BYA
 Most likely Scenerio for formation:
 Most matter in universe is light elements (Hydrogen)
 Heavy Elements (Carbon, Nitrogen, Oxygen) are formed only in core of dying stars
 Nearby Star Exploded
 Shockwave through Gas/Dust Cloud caused lumps to form
 Lumps Gravitationally move matter to themselves and cloud collapsed upon itself
 99.9% of matter formed into the sun, the rest formed bodies such as planets, comets, etc.
o The early Earth was a very different place:
 atmosphere :mostly carbon dioxide, nitrogen, and water vapor
 Earth was bombarded with asteroids and meteors
 Volcanic Eruptions formed first continents 4.1 BYA
 Oceans formed when Earth cooled 4.1 BYA
 Late Bombardment till about 3.9 BYA
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What is the Oldest Fossil of Life on Earth?
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How did the First Life Form Come to Exist?
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Spontaneous generation theory accepted until 1862
________________________ (“life creation”) was a mystery…
What is Spontaneous Generation?
o
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First Life Fossils: __________________________ ~3.5 BYA
 Filamentous Strings of up to 40 cells
Prokaryotes:
 _____________________________ organisms
 These prokaryotes began to __________________________
 Produced oxygen
Living things could arise from ____________________________things
 Examples:
 Francesco Redi’s Experiment  fly maggots life arises from life NOT air
 Lazzaro Spallanzani’s experiment  microorganisms arise from others not AIR
 Louis Pasteur’s experiment  microorganisms arise from others not AIR
How did First Life Form?
o
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Conditions on early Earth made the Origin of Life Possible
In a sequence of stages about 3.8 BYA:
 1. Abiotic synthesis of small organic molecules (inorganic  _______________)
 2. Joining of these small molecules into polymers (monomers ______________)
 3. Packaging of molecules into “protobionts” (“precells/protocells”)
 4. Origin of self-replicating molecules
Lane Tech College Prep High School
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How did Step 1 Abiotic Synthesis occur?
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Hypothesis 1:
 1920’s Oparin and Haldane (primordial soup)
 atmosphere = HIGH energy levels contributed to SPONTANEOUS chemical evolution
 Suggested early atmosphere= NH3, H2, CH3, some H20
 Energy was supplied by _________________________________________
 1st organic (“life”) compounds may have been synthesized near submerged volcanoes and deep-sea
vents
o
Hypothesis 2:
 Some organic compounds may have come from ____________________________
 Carbon compounds have been found in some ___________________________ that landed on Earth90 Amino Acids have been found in meteors
How did Step 2: Polymer Formation occur?
Stanley Miller: Graduate student at UIC working with Harold Urey
Build Apparatus to Test __________________________________Synthesis
Simulated Early conditions on Earth
Electrical Energy provided by spark discharge
They found Amino Acids, Nucleic Acids, Fatty Acids, and other Organic Molecules!
Repeated many times under many conditions (___________________- simulating the sun)
Demonstrated that Oparin/Haldane Hypothesis _______________________________
 Nobel Prize for Miller and Urey
Did Extra-Terrestrial Sources Bring Complex Organic Molecules to Earth?
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Small organic (carbon) molecules polymerize when they are concentrated on hot sand, clay, or rock
These molecule form polymers (_______________) of huge life molecules (biomolecules)
Miller-Urey Experiment
What was the Miller-Urey Experiment?
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2 Hypothesis:
 1. Oparin/Haldane Hypothesis
 ___________________________- Soup
 2. _____________________________ Source of Complex Organic Molecules
STEP 1: CHEMICAL EVOLUTION
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Krakowski 2
Miller/Urey Experiment will ___________________________if Oxygen is present
______________________________ probably were an important second source of organic compounds
Comets and Meteorites are rich in organic compounds formed abiotically in deep space (water, ammonia, 74
amino acids)
Recent experiments show that these molecules would survive impact!
Step 3: Packaging of molecules into “(“precells/protocells”)
How did this Occur?
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1. Organic Molecules Accumulate
2. Polypeptides Form
3. Some assemblages were capable of carrying out primitive living reactions
4. Conversion of pre-cellular assemblages into organized cells enclosed by outer boundary membranes
Lane Tech College Prep High School
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What are the Hypothesis for Protocell Formation?
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Prokaryotic ______________________!!!!! use chemicals to make their OWN food/energy
Cyanobacteria (Prokaryotic __________________________) evolve  pump O2 in air (around 3.5 bya)
Oxygen (O2) in atmosphere results in EARLY mass extinctions b/c it KILLS most life
Prokaryotic __________________________________ (“O2 loving”) survive
Cellular Respiration evolves
Single Celled Eukaryotic organisms (around 2.1 BYA)
 Made by Endosymbiosis
7. Multicellular eukaroytic organisms
Photosynthesis and the Oxygen Revolution
o
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RNA! Trapped inside a “protocell” by chance about 4.0 BYA
 RNA came 1st b/c has the following properties:
 _____________________________!!! Less complex/less stable than DNA
 RNA into protein more direct than DNA into Protein
 Has 3 different phenotypes (characteristics), can fold into diverse shapes
 RIBOZYMES: ________________________ that can carry out reactions
 RNA can self assemble from individual nucleotides (polymerize easy into 1 strand)
 SHORT STRANDS OF RNA CAN REPLICATE
Which Came First Autotrophs or Heterotrophs?
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Protocells – _______________________molecules surrounded by membrane - like structures
 Some properties associated with life
 Simple reproduction and metabolism
 Maintenance of internal environment
 Has membrane
All were spontaneously FORMED by chance!
Step 4: Which Came First RNA or DNA?
o
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2 Hypothesis
 Lipid Membrane Hypothesis
 ___________________________- lipids(fatty acids) that form vesicles
o Coacervates- combo’s of proteins, lipid membranes and carbs
 Iron-Sulfide Chimney Hypothesis
 When hot iron sulfide in deep ocean vents, meets the cooler ocean, some of the mineral
forms into chimneys
 These chimneys acted as ________________________________________
What were the First Cells?
o
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Oxygenic photosynthesis probably evolved about 3.5 BYA in _______________________
 A.k.a- Blue/green algae in oceans
 They made _____________________________________(fossils)
What were the Effects of O2 accumulation in atmosphere about 2.7 billion years ago?
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Formed _________________________________ (reduced UV, warmed Earth) ~2.5 bya
_________________________________ by UV radiation = ozone
 Protected from _________________________rays and provides _______________
 Provided opportunity to gain energy from light
 Allowed organisms to exploit new ecosystems
Lane Tech College Prep High School
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What were the First Eukaryotes?
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Single cell  Multicellular eukaryotes appeared ~1.5 bya
Oldest known fossils of eukaryotes  relatively small algae (~1.2 bya)
What were the Earliest Multicellular Eukaryotic Animals (METAZOA)?
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______________________________in inner membrane structures and functions
 Both have their own circular ___________________________
 Both have their own ___________________________
What were the First Multicellular Organisms?
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The oldest fossils of eukaryotic cells date back 2.1 billion years
___________________________________ eukaryotics
The theory of endosymbiosis proposes that _____________________________________ and
CHLOROPLASTS were formerly small, free-living prokaryotes that were ________________________ by
larger host cells
Oldest known fossils of eukaryotes  relatively small algae (~1.2 BYA)
What Evidence Supports Endosymbiosis?
o
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600 MYA
 _______________ then ___________________________ then _______________________
 Marine and ________________________________________
What was the Ancestor of Metazoa?
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Choanoflagellates
 based on _____________________________ and ______________________________________
 Protists that form spherical colonies