• Earth is estimated
to be ~4.6 bill. yr old
– Evidence:
Radiometric dating
of rocks & meteors
• Nebula Hypothesis:
– Nebula: cloud of gas
& dust in space
– Gravity pulled much
material together
(forming the Sun)
– Planets formed from
remaining materials
What was it like?
• Atmosphere contents:
– Ammonia, H2O vapor,
Methane (CH4), CO2
• Climate:
– Extreme heat due to
meteor impacts &
volcanic activity
• Eventually Cooling:
Water vapor
condensed (oceans
formed)
Click on picture to play video clip
1. Miller - Urey Experiment
• Hypothesis: Energy from
lightning created organic
materials from inorganic
ingredients
• Experimental Set-Up:
– Ammonia, H2O vapor,
Methane, CO gases added
– Electricity added (simulate
lightning)
• Result: Amino Acids & later
nucleotides were created
2. Meteorite Hypothesis
• Hypothesis: Amino acids may have arrived on
Earth through meteorite or asteroid impacts.
• Fun Fact! 90 amino acids were found from this meteorite,
only 19 of them can be found on Earth.
• Lipid membrane
hypothesis
– Liposomes
• Spheres of lipids
• Can form around
organic molecules
• Hypothesis: 1st cell
membranes??????
• A hypothesis proposes that RNA was the first
genetic material.
– Ribozymes are RNA
molecules that catalyze their
own replication.
– DNA needs enzymes to
replicate itself.
– Because of this, scientists think that DNA evolved from RNA
• Endosymbiosis is a relationship in which
one organism lives within the body of
another.
• Mitochondria and chloroplasts may have
developed through endosymbiosis.
• Evolution of sexual reproduction led to
increased diversity/variation.
• Sexual reproduction may have led to
multicellular life.
Review
These are questions that I would ask you on the test, so you
should do your best at answering them accurately and completely.
• What is a nebula?
• What does the nebula hypothesis try to explain?
• What materials/ingredients did Miller & Urey use in
their experiment? Why these and not other
ingredients?
• Why was Miller and Urey’s experiment of great
importance?
• How did eukaryotic cells form?
• How would sexual reproduction lead to diversity and
multicellular life?