CP Biology
2015-2016
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UNIT 3A: Origins of Life
How did Life Begin?
 For thousands of years people believed that living
Where did the first life come from? _there are many
theories but nobody knows for sure
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organisms originated from nonliving matter.
1) Abiogenesis or Spontaneous Generation: the idea
that life can arise from nonliving material.
(Ex: haystacks; flies come from rotting meat;
bacteria arise from broth)
 Francisco Redi in the 1600’s and Louis Pasteur in
1862 conducted experiments which disproved the
theory of spontaneous generation.
2) Biogenesis: the idea of life arising from other living
things.
(Ex. Cats make cats; humans make humans, etc.)
Origins of the Earth
Big Bang Theory (1927): idea which explains what
happened at the very beginning of our universe (~13.7 bya)
– began as an infinitely small, hot dense “speck” that
inflated, expanded and cooled to the size and temperature
of our current universe. Earth formed around 4-5-4.6 bya.
Franceso Redi’s Experiment:_Two jars of meat, one jar
covered in cheese cloth and the other left open to the
air. Maggots formed on the meat in the jar left open
and did not form in the covered jar. This disproved the
theory of spontaneous generation.
Louis Pasteur’s Experiment: He had the goose neck
flask of boiled broth that allowed air to enter but not
living organisms (bacteria). As a result the broth
remained clear without any bacteria appearing.
Compounds in the Primitive Atmosphere
Compound
Elements Present
Molecular
Formula
methane
carbon, hydrogen
CH4
ammonia
nitrogen, hydrogen
NH3
hydrogen
hydrogen
H2
water
hydrogen, oxygen
H2O
carbon dioxide
carbon, oxygen
CO2
Your personal notes, summary of the lesson, and/or questions that you may have:
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Formation of the Oceans
Label the following in the diagram below: He, Ni, Cu, Fe, H2
1) Tremendous amounts of hydrogen and oxygen were
trapped below the crust. These elements combined
to form water vapor, which was released to the
atmosphere
atmosphere.
2) The water vapor condensed in the atmosphere and
NH3
rained down to form vast oceans for 40 million yrs. H2
Sequence of Conditions on Primitive Earth:
He
CH4
CaCO3
crust
core
Cl
Fe Cu
Ni
H2
1) Heavy particles such as iron, copper and nickel were
pulled to the center of the earth.
He
2) Lighter particles such as helium and hydrogen
remained at the surface.
3) Radioactive material and great pressure kept the
center of the earth in a molten state.
4) Over a period of years, the outer surface or crust of What major gas, necessary for life, is missing from the atmosphere
the earth formed over the molten center (4 BYA).
of primitive Earth? _oxygen gas (O2)_______
5) As the outside of the earth cooled, hot gases from the
interior escaped to form the primitive atmosphere.
Look at the pictures of Primitive Earth and Modern
Earth to the right 
What are the similarities between Primitive Earth and
Modern Earth? _Oceans were present along with the_____
__sun; Water vapor is present___________________
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What are the differences between Primitive Earth and
Modern Earth? _the gases in the atmosphere are _
_different (P: H2, CH4, NH3 and M: O2, N2, CO2);
ozone layer on modern earth; life on land; P: volatile
(lots of lightning and UV radiation)
Your personal notes, summary of the lesson, and/or questions that you may have:
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Primitive Earth’s Atmosphere
Two major differences between primitive Earth and
modern earth set the stage for the formation of organic
compounds (hydrocarbons) and, eventually, the origin of
living things.
1) Oxygen (O2) – a highly reactive compound. Will
break bonds that form between simple organic
compounds and destroy them. NOT PRESENT!
2) The atmosphere had abundant energy that could be
used to join atoms that form hydrocarbons.
a) Lacking an ozone (O3) layer, the atmosphere
had abundant UV radiation.
b) Lightning in the atmosphere.
c) Heat from volcanoes above and below ocean level
Theory of Chemical Evolution
In 1924, Alexander Oparin and J.B. Haldane developed
a theory for the origin of organic compounds:
Use your own words to describe the conditions of the
early Earth and the early atmosphere.
(This is #1 from the checklist on the USG of what you
should be able to do by the end of this unit)
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Use the word bank to fill in the blanks below:
precursors, inorganic, spontaneously,
oxygen, primitive Earth
Conditions on primitive Earth gave rise to simple
organic compounds, the precursors to life.
1) CO2, H2 and NH3 are types of __inorganic___
molecules found in the atmosphere on __primitive
Earth__________.
1) Inorganic Matter: like CO2 and NH3, (plus organics
like CH4) in the atmosphere combined using the
energy sources listed above.
2) Scientific evidence indicates that organic molecules
and cells may have formed __spontaneously__ on
ancient Earth.
2)
Simple Organic Molecules: like HCN (hydrogen
cyanide) and formaldehyde formed primitive clumps
of organic matter. – not life (living)…may have
eventually led to life!!!
3) The lack of free atmospheric _oxygen______ and the
abundance of energy on early Earth facilitated the
formation of organic compounds from inorganic
_precursors (to life)_____.
Your personal notes, summary of the lesson, and/or questions that you may have:
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