• 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

Origin of the Solar System

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

Ancient Earth

Organic Molecules

Hypothesis: Energy from lightning created organic materials from inorganic ingredientsExperimental Set-Up:

Ammonia, H2O vapor, Methane, CO gases addedElectricity added (simulate lightning)Result: Amino Acids & later nucleotides were created

1. Miller - Urey Experiment

2. Meteorite Hypothesis

Murchison Meteorite

• 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??????

Early Cell Formation

• 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.

EARLY GENETIC MATERIAL

– 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.

Eukaryotic Cell Formation

• Evolution of sexual reproduction led to increased diversity/variation.

• Sexual reproduction may have led to multicellular life.

Multicellular Life & Biodiversity

ReviewThese 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?