Transcript The Origin of Life

Primordial Earth
Theories on the Origin of Life
Early Earth and Evolution
A THEORY of the origins of the universe
Big Bang
When?
-Approx. 13.5 Billion years ago
expansion from singularity
-MASSIVE AMOUNTS OF ENERGY!
-Energy eventually converted to
fundamental building blocks of matter.
Evidence?
-Expanding universe
-Background radiation
-Abundance of Hydrogen
After Big Bang…….
• Stars!
– Need hydrogen gas fusion
– Form heavier elements
– Really big stars go out with a bang 
supernova!
• Planets!
– Leftover “mess” from supernova start to
accrete into larger objects. (NEWTONS LAW!)
– Typically these objects will orbit around a star
• SOLAR SYSTEMS!
LIFE!!!!
• Spontaneous Generation.
– Theory (hypothesis actually) that life can
randomly emerge from non-living thing
• Biogenesis
– Theory that life only comes from pre-existing
life.
• Common Ancestor
– Theory that every living organism on the
planet is a descendent of an original cell
• Question : Where did first life come
from???
Oparin-Haldane Hypothesis
• All the elements were already
present on Earth.
• Early atmosphere contained mostly
ammonia NH3, hydrogen gas H2,
water H2O, and methane CH4.
• High temperatures might cause
gases to form simple organic
compounds.
“Prebiotic Soup”
• As Earth cooled simple organic
compounds collected in the
lakes and seas.
• Energy from lightning and UV
radiation caused chemical
reactions to build
macromolecules.
Key Experiments
• Francisco Redi’s Flies –
– Where do maggots come from
– Bottom Line: no spontaneous generation
Key Experiments
• Spallanzani –
– Bacteria in broth come from air? Or other
microbes?
– Bottom Line: no spontaneous generation
Key Experiments
• Louis Pasteur –
– Bacteria in broth come from air? Or other
microbes?
– Key difference from spallanzani?
– Bottom Line: no spontaneous generation
1953: Miller- Urey
• Stanley Miller and Harold Urey
set up an apparatus to
simulate the proposed
primordial Earth conditions.
1953: Miller- Urey
• Stanley Miller and Harold Urey
set up an apparatus to
simulate the proposed
primordial Earth conditions.
• Found organic compounds.
Debatable points:
• Atmosphere probably contained
CO, CO2, and N2
• Presence of O2, and CO2 interfere
with production of organic
compounds.
–Organic compounds produced
in undersea volcanoes.
• Organic compounds came from
outer space.
Pre-Cell Structures
• Organic molecules aggregate
spontaneously.
• Microsphere: Protein
membrane structure
• Coacervates: Droplets of lipids
amino acids, and sugars.
Microspheres
Coacervates
First Cells: Prokaryotic
• Environment: Little or no oxygen
 Cells were anaerobic.
• Environment: Organic food
molecules
 Cells were heterotrophs.
• Oldest fossils look like
prokaryotes.
 Cells were prokaryotes.
Archaea
• Present day cells, thought to
be similar to earliest cells.
• Unicellular organisms that
thrive in harsh environmental
conditions.
–Anaerobic metabolism.
–Inorganic energy sources.
Endosymbiotic Theory
Creating the first eukaryotes:
• Large prokaryotes engulfed
smaller prokaryotes.
• Mutually beneficial relationship:
small cells are protected and
large cell gets energy.
• Small aerobic cells evolved into
mitochondria
• Small photosynthetic cells
evolve into chloroplast.
• Mitochondria and chloroplast
have their own DNA.
• DNA is circular, like
prokaryotes.
• Replicate independently of cell.
•
http://www.youtube.com/watch?v=dSjg_uYS_QY&feature=related
Summary
1. Small organic molecules were
synthesized.
2. Small organic molecules
(monomers) joined to form polymers,
like protein and nucleic acids.
3. Molecules could self-replicate.
4. Molecules were packaged into
membrane structures- resembling
the first prokaryotic cell.