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Evolution
The Origins of Life I. Cellular Life
Review-Questions About Our
Origins
How did the universe form?
 How did our galaxy form?
 How did the sun and Earth form?
 How/where did life start?
 How did all the life forms on Earth
develop?
 Where do humans come from?

Review-What evidence is there for
evolution?
Fossils
 Geologic
 Age of the Earth
 Anatomy and Physiology
 Molecular (DNA, “primordial soup”)

Review-What is evolution?

A changes in a species over time

process of biological change by which
descendents come to differ from their
ancestors.
What explanations are there for
how life started on Earth?
Christianity-God
 Buddhism-no creator, world constantly
recreates itself
 Islam-Allah
 Native Americans-mother, mother animals
 Aztec-gods-5 births of suns
 Bantu-Bumba vomitted up “life” and
Planets

Review-How was the Earth
formed?



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
Our solar system (Sun and planets) formed from
a rotating disk of gas and dust about 4.6 billion
years ago.
4-3.8 bya Earth cooled down and the impacts
happened less
Solar radiation and lightning produced energy
for reactions on Earth
Water vapor condensed and rain formed large
bodies of water
Presence of water allowed inorganic compounds
to form organic molecules
Origins of Life
Organic molecule hypotheses-(Miller-Urey
and Meteorite Hypothesis)
 Early cell structures-(Iron-sulfide, lipid
membrane)
 RNA-early genetic material

Organic Molecule Hypotheses

Miller-Urey Experiment-Passed an
electrical current through mixture of gases
and created amino acids and nucleotides
Meteorite Hypothesis-Meteorite that
landed in Australia had 90 different amino
acids, possible that aa were brought to
Earth on meteorites
 Question: What do amino acids make?

Early Cell Structures Hypotheses

Iron-sulfide bubbles hypothesis-4 b.y.a,
hot iron sulfide chimneys concentrated
basic organic molecules in small space
Lipid membrane hypothesis-lipid
molecules can form spheres around
organic molecules
 Question: What do lipids make up?

RNA as Early Genetic Material

RNA can chop and copy itself w/out
enzymes

Short chains of RNA can form from
inorganic molecules
Summary-Molecular Origins of Life
Molecules create the structures for life.
 Organisms are made of molecules.
 Under the right conditions, nonliving
molecules such as gases, lipids, amino
acids, and nucleic acids can naturally form
the structures of life.

Summary Questions

What some of the different beliefs that
various religions have on how life started
on Earth?

In your own words explain one of the
biological hypotheses on how life started
on Earth.