Biology
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Earth's Early History
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17-2 Earth's Early History
Formation of Earth
Formation of Earth
Hypotheses about Earth’s early history are based on
a relatively small amount of evidence.
Gaps and uncertainties make it likely that scientific
ideas about the origin of life will change.
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17-2 Earth's Early History
 Universe is about 13.9 billion years old.
 Universe is thought to have begun as
an infinitesimally small, infinitely hot,
infinitely dense, something gravitational singularities (they are
thought to exist in the center of black
holes – areas of gravitational pressure
so intense it “squishes finite matter into
infinite density).
 The “singularity was thought to have
“inflated,” expanded, and cooled, going
from very, very hot, to the size and
temperature of our current universe.
 It continues to expand and cool to this
day. (We are inside of this constantly
expanding universe that began as an
“infinitesimal singularity which
“appeared out of nowhere.”)
Big Bang Theory
 “Misconception”:
Not really an “explosion” but
a continual “expansion.”
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Primordial
Soup
Theory
 1924 Alexander Oparin suggested the early
Earth did not have any oxygen but did
contain other gases (carbon dioxide,
methane, ammonia and water).
 Lightning produced a spark of energy that
split the gases and allowed them to
recombine into heavier particles that fell to
the Earth.
 They recombined in the warm waters to
produce a “primordial soup” rich in organic
compounds. (Chemicals formed amino acids
which then formed proteins.)
 It is believed that life arose in this “soup”.
 Early life forms resembled present day
bacteria which then gave rise to primitive
invertebrates, plants, and then animals.
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(Also Known as the
Biochemical Theory of
Evolution
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17-2 Earth's Early History
The First Organic Molecules
The First Organic Molecules
Could organic molecules have evolved under
conditions on early Earth?
In the 1950s, Stanley Miller and Harold Urey tried
to answer that question by simulating conditions on
the early Earth in a laboratory setting.
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17-2 Earth's Early History
The First Organic Molecules
Miller and Urey’s Experiment
Mixture of gases
simulating
atmosphere of
early Earth
Spark simulating
lightning storms
Condensation
chamber
Water
vapor
Cold water cools
chamber, causing
droplets to form.
Liquid containing amino
acids and other organic
compounds
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17-2 Earth's Early History
The First Organic Molecules
Miller and Urey's experiments suggested
how mixtures of the organic compounds
necessary for life could have arisen from
simpler compounds present on a
primitive Earth.
Although their simulations of early Earth
were not accurate, experiments with current
knowledge yielded similar results.
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Abiogenesis
(Spontaneous Generation)
 The process by which a living
organism arises naturally from nonliving matter.
 Ex: Decaying flesh produced flies,
frogs and mice came from mud,
birds came from the trees, and a
dirty shirt (soaked with human
sweat) and a few grains of wheat
would produce mice.
 Francisco Redi proved flies did
not come from decaying flesh.
 Louis Pasteur with his curvedneck flask, disproved the theory
of spontaneous generation.
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Bubble Model Theory
(Lerman’s Bubble Model Theory)
1. Ammonia, methane and other
gases from undersea
volcanoes trapped in
underwater bubbles.
2. Gases were protected in the
bubbles from UV radiation and
chemical reactions occurred
faster than primordial soup
model.
3. Bubbles rose to the surface
releasing simple organic
molecules into air.
4. Exposure to UV radiation and
lightning produced more
reactions.
5. More complex molecules
formed by further reactions
and fell into ocean with rain, Slide
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continuing the cycle.
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Creationism
 Religious belief that God created all things
including the Earth and the Universe.
 The Word of God, the Bible, gives an account of
creation win the book of Genesis.
 Day 1: God separated day into light and darkness
 Day 2: Separation of the sky and oceans.
 Day 3: Separation of the land from oceans,
spreading of plants, grass and trees
 Day 4: Sun, Moon and Stars
 Day 5: Creation of the seawater animals and birds
 Day 6: Creation of land animals and man
 Day 7: God rested.
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Cairns – Smith Theory
(Clay Theory)
 1982, Cairns Smith, a Scottish Chemist proposed that the first organisms were
derived from clay crystals (the self-replication of clay crystals might provide a
simple intermediate step between biologically inert matter and organic life.
 1. Clays can form from dissolved silicates. Preserved crystal shapes with the most
stable growth patterns would dominate resulting in a stable, uniform micro or macro
environment.
 2. Interaction of the specific clay type with organic molecules. The uniform shape of
crystals allows for selection of certain organic molecules and complex molecules
could originate because of catalytic properties of clay.
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 Helps to explain how high concentrations of complex organic molecules for
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origin of life can be achieved.
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Panspermia
 Life orginated from microorganisms that originated from outer space.
 Life “seeds” (extremophiles trapped in debris ejected into space )
came to earth from meteorites.
 Earlier life forms like bacteria are able to live in harsh
environments.
 Some organisms may travel dormant for an extended amount of
time before colliding randomly with other planets.
 If ideal conditions, the organisms become active and process of
evolution begins.
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Endosymbiont Theory



Proposes eukaryotic cells arose from living communities formed by
prokaryotic organisms.
~2 billion years ago prokaryotic cells began evolving internal cells
membranes resulting in the ancestors of all eukaryotic cells.
Chloroplasts and mitochondria are the result of years of evolution initiated
by the endocytosis of bacteria and blue-green algae.
 According to the theory, blue-green algae and bacteria were not
digested and instead became symbiotic and mitochondria and
chloroplasts evolved.
 he endosymiotic theory proposes that eukar
Th theory proposes that eukaryotic cells
arose from living communities formed by
prokaryotic organisms. e theory proposes
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that eukaryotic cells arose from living
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communities formed by prokaryotic
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17-2 Earth's Early History
Aerobic
bacteria
Origin of Eukaryotic Cells
Ancient Prokaryotes
Nuclear
envelope
evolving
Ancient Anaerobic Prokaryote
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17-2 Earth's Early History
Origin of Eukaryotic Cells
Prokaryotes that carried out
photosynthesis evolved into
chloroplasts.
Chloroplast
Photosynthetic
bacteria
Primitive Photosynthetic Eukaryote
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17-2 Earth's Early History
Origin of Eukaryotic Cells
Mitochondrion
Prokaryotes that
use oxygen to
generate energyrich molecules of
ATP evolved into
mitochondria.
Primitive Aerobic Eukaryote
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17-2 Earth's Early History
Origin of Eukaryotic Cells
Endosymbiotic Theory
Ancient Prokaryotes
Chloroplast
Aerobic
bacteria
Nuclear
envelope
evolving
Ancient Anaerobic
Prokaryote
Photosynthetic
bacteria
Plants and
plantlike
protists
Mitochondrion
Primitive Aerobic
Eukaryote
Primitive Photosynthetic
Eukaryote
Animals,
fungi, and
non-plantlike
protists
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Intelligent Design
 Certain biological features
are too complex to be the
result of natural processes,
and therefore these features
are evidence of design.
 States that intelligent causes
are necessary to explain
complex life forms of today.
 It does not say that God
created all things but that an
intellectual being formed the
Earth and the living things
on it.
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Darwin’s Theory of Natural Selection
1.
2.
3.
4.
5.
Overproduction – most organisms produce far
more offspring than are actually needed to
carry on the species.
Struggle for existence – organisms compete for
food and space.
Variation – In any species the characteristics
of the individuals are not exactly alike. Some
variations may not be of importance, while
others may interfere with the organism’s ability
to obtain food or mates.
Survival of the fittest – Only the strong survive;
therefore they will have a greater chance to
survive.
Natural selection – organisms possess traits
that give them an advantage in the
environment. Those with less favorable
variations disappear, while those with favorable
traits are able to grow and reproduce.
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Jean Lamarck’s Theory of Evolution
1. The Theory of Need – An
organism changes because of
an inner need to change.
2. The Theory of Use and Disuse
– Organs and structures that an
organism possesses may soon
disappear if they are not used.
3. The theory that acquired traits
could be passed on to the
offspring. Giraffes with short
necks had to stretch them to
reach the leaves on trees.
Gradually giraffes with long
necks appeared.
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17-2
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17-2
Which of the following gases was probably NOT
present in the early Earth’s atmosphere?
a. hydrogen cyanide
b. oxygen
c. nitrogen
d. carbon monoxide
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17-2
Miller and Urey's experiment was a simulation of
Earth's early
a. volcanic activity.
b. formation.
c. atmosphere.
d. life.
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