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Part I. History
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The continuing process of genetic
change in a population of organisms
over long periods of time is called:
EVOLUTION
Over a large number of years,
evolution produces tremendous
diversity in forms of life.
Scientific Theory

A well supported testable explanation of
phenomena that have occurred in the
natural world.
– Evolution
– Theory of Relativity
– Atomic theory
– Quantum theory
Science at work
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Observation: Every swan I've ever seen is white.
Hypothesis: All swans must be white.
Test: A random sampling of swans from each continent where
swans are indigenous produces only white swans.
Publication: "My global research has indicated that swans are
always white, wherever they are observed."
Verification: Every swan any other scientist has ever observed
in any country has always been white.
Theory: All swans are white.
History of Evolution
Original Beliefs
• species could not change
•Geology has not changed
•fixed number of species
•species had a given set of traits that remained with
it forever.
Jean Babptiste de Lamarck, Charles Darwin, Charles
Lyell, Alfred Wallace led the way in the search for
the mechanisms that caused this change.
1. Jean Baptise Lamarck
1809 –proposed a hypothesis
to explain the variation in organisms.
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Acquired Characteristics- traits that
developed during a lifetime could be passes
on to the offspring.
 I.e. giraffes stretched their necks over a
lifetime to reach food. They then passed on
the longer neck trait to their offspring.
Rejecting Lamarck’s Hypothesis
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Large amounts of
data showed that
acquired traits are
not hereditary.
2. Charles Lyell (1797 – 1875)
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Geologist
 Theorized that
geologic features
are constantly
changing.
3.Charles Darwin
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1831 took a voyage on the H.M.S
Beagle to the Galapagos Islands
and collected a lot of data.
 Natural Selection- a mechanism
for change in a population that
occurs when individuals with the
most favorable variations for a
particular environment survive and
pass these traits on to offspring.
Natural Selection
1. Variations exist within populations.
2. Some variations are more advantageous
for survival and reproduction than others.
3. Organisms produce more offspring than
can survive.
4. Over time, offspring of survivors will
make up a larger proportion of the
population.
Peppered Moths
Variation in moths some
black some light colored.
In 1850 most were light.
Industrial revolution
covered trees with smoke
and soot. Now the dark
moths were better suited
for the environment.
4. Alfred Wallace (1823-1913)
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Father of Biogeography
 Studied plants and animals
in Amazon vs. Australia.
 Independently of Darwin
and proposed the same
theory.
Part II. Mechanisms of Evolution
Without environmental pressures genetic
equilibrium is established.
How can the equilibrium be changed?
A. Changes in genetic Equilibrium
1. Mutations are changes in genetic
material of an organism. Provides new
genetic material in a species.
Mutations are random
Changes in genetic equilibrium
2. Genetic Drift – the change in allele
frequencies of a population as a result
of chance processes.
The survival and
reproductions of
organisms is
subject to
unpredictable
accidents
See an example
Changes in genetic equilibrium
continued
3. Gene Flow is the movement of genes
in and out of the gene pool.
Gene flow increases genetic variation within a
population
Patterns of Evolution
Patterns of Evolution
c. Adaptive Radiation – species adapting
to different environments and become
a new species.
Recap
video
Evidence for change
Fossils- provide scientists with strong
records of the earth’s past.
A fossil is the remains of an organism
preserved in the earth’s crust
Where are fossils found?
Found in layers of
sedimentary rocks.
 Organisms were
buried in layers of
mud and or sand.
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4 types of fossils
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Imprint
 Mold
 Cast
 Petrified
Imprint Fossils
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The soft parts of
buried organisms
decay and leave an
imprint in the stone.
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I.e. animal tracks
and plants
Mold fossils
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The hard parts of an
organism decay and
leave indentation in
the rock.
Cast Fossil
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A mold fossil fills
with mineral or rocks
Cast Dinosaur eggs
Petrified Fossils
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Highly porous
materials like bones
or wood can
become petrified if
they are buried
quickly and
thoroughly.
More Petrified Fossils
Relative Dating
Relative dating tells scientists if a rock
layer is "older" or "younger" than
another.
 fossils found in the deepest layer of
rocks in an area would represent the
oldest forms of life in that particular rock
formation.
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Evolution of the horse
Living organisms
resemble most
recent fossils in
the line of descent;
underlying
similarities allow
us to trace a line of
descent over time.
Absolute Dating
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The use of
radioactive isotopes
to date fossils and
rocks.
 A radioactive
isotope is an atom
with an unstable
nucleus and decays
at certain rate.
Half-Lives of Selected
Radioactive Isotopes
Isotope Half-Life
 14-C
5730 y
 24-Na
15.0 h
 32-P
14.3 d
 36-Cl
3.1 x 10+5 y
 40-K
1.28 x 10+9 y
 45-Ca
165 d
 226-Ra
1.62 x 10+3
y
 235-U
7.1 x 10+8 y
 238-U
4.51 x 10+9 y
 239-Pu
2.44 x 10+4
Homologous Structures
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Structures that are similar and are
derived from the same body parts.
Vestigial Structure
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Body parts that are reduced in size and serve no
apparent function.
I.e – Human tail bone – no function
Examples of Vestigial Structures
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Human appendix useless yet in other
mammals, including primates, it is necessary
to aid in digestion of high cellulose diet
Human external ear muscles still present but
useless
Humans have tailbones and some babies
occasionally have tails
Human wisdom teeth vestigial compared to
other primates
Some snakes have skeletal limbs
Cave dwelling crayfish have eyestalks yet no
eyes
Analogous Structures
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Body part that have
similar functions but
originate from
different structures.
Examples of Analogous
structures
structures "fitted" for a particular
purpose tend to be similar, regardless of
origin
 flippers in dolphins, penguins and fish.
 wings have developed independently in
insects, reptiles, birds, and bats
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Embryonic Development
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Gill slits and tail in
human embryo
show similarities of
embryos of
dissimilar
organisms.
Biochemical Analysis or
DNA/RNA Comparisons
•Comparison of nucleic acid sequences shows similarities
between species. The more closely related organisms are,
the more similar is their biochemical makeup
•Cytochrome C, a protein, The more closely related
organisms are, the more similar their amino acids are.
•Humans differ by 1 nucleotide compared to monkeys
•Humans differ by 19 nucleotides compared to turtles