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Evolution Unit
Chapters 10 and 11
1
History of
Evolutionary
Thought
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2
Evolutionary Timeline
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3
Early Ideas On Earth’s
Organisms

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Linnaeus – 1st to
group similar
organisms and
assign them Latin
names
Two word name
(Genus species)
Known as Binomial
nomenclature
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4
:
Contributor’s to Darwin’s
thinking included:
 Leclerc de Buffon – proposed that
species shared ancestors instead of
arising separately
 Erasmus Darwin – organisms could
evolve from a common ancestor
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5
:
Contributor’s to Darwin’s
thinking included:
 Cuvier – Catastrophism
– Stated that species disappear due to a
catastrophic event of the earth’s crust
(volcano, earthquake…)
 Hutton – Gradualism
– Changes on Earth formed as product of slow but
continuous and cumulative processes
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6
Contributor’s to Darwin’s
thinking included:

Charles Lyell –Uniformitarianism
– Geologic processes that shape the Earth
are uniform through time

Alfred Wallace
– organisms evolved from common
ancestors
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7
Lamarck’s Theory of
Evolution
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Was first scientist to
recognize that organisms have
changed over time
Stated that changes are
adaptations to environment
acquired in an organism’s
lifetime
Said acquired changes were
passed to offspring
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8
Lamarck’s Theory of
Evolution

Law of Use and Disuse
– Organisms Could Change
The Size Or Shape Of
Organs By Using Them
Or Not Using Them
– If a body part were
used, it got stronger
– If body part NOT used,
it deteriorated
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9
Lamarck’s Theory of
Evolution
 Inheritance
of Acquired
Characteristics
– idea that an organism can pass on
characteristics that it acquired during
its lifetime to its offspring
– Over Time This Led To New Species
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10
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11
Lamarck’s Mistakes


Lamarck’s theories were INCORRECT!
Lamarck Did NOT Know how traits
were inherited (Traits are passed
through genes)
– Genes Are NOT Changed By
Activities In Life
– Change Occurs Through Mutations
Before An Organism Is Born
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12
Charles Darwin the
Naturalist
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13
Voyage of the Beagle
Charles Darwin

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Joined Crew of HMS Beagle,
1831
Naturalist
5 Year Voyage around world
Become known as the
“Father of Evolution”
Astounded By Variety of
Life
Wrote “The Origin of
Species”
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14
Darwin’s Voyage of Discovery
A reconstruction of the HMS Beagle sailing off Patagonia.
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15
Darwin Left England in 1831
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Darwin returned
5 years later in 1836
16
HMS Beagle’s Voyage
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17
The Galapagos Islands

Small Group of Islands West of
South America
 Very
Different Climates
 Animals On Islands Unique
»Tortoises
»Iguanas
»Finches
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18
The Galapagos Islands

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Volcanic islands off
the coast of South
America
Island species
varied from
mainland species &
from island-toisland species
Each island had long
or short neck
tortoises
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19
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20
The Galapagos Islands
Finches on the islands resembled a
mainland finch
 More types of finches appeared on
the islands where the available food
was different (seeds, nuts, berries,
insects…)
 Finches had different types of
beaks adapted to their type of
food gathering

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21
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22
Darwin’s Observations
& Conclusions
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23
Voyage of the Beagle
– During His Travels, Darwin
Made Numerous Observations
And Collected Evidence That
Led Him To Propose A
Revolutionary Hypothesis
About The Way Life Changes
Over Time
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24
Darwin’s Observations

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Patterns of
Diversity were
shown
Unique Adaptations
in organisms
Species Not Evenly
Distributed
» Australia,
Kangaroos, but
No Rabbits
» S. America,
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Llamas
25
Definition
• Evolution is
the gradual
change in a
population of
organisms
over time
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26
Darwin’s Observations
Left unchecked, the
number of organisms of
each species will increase
exponentially, generation
to generation
 In nature, populations tend
to remain stable in size
 Environmental resources
are limited.

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27
Darwin’s Conclusion
• Production of more
individuals than can be
supported by the
environment leads to a
struggle for existence
among individuals
• Only a fraction of
offspring survive each
generation
• Survival of the Fittest
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28
Darwin’s Observations
• Individuals of a
population vary
extensively in their
characteristics with
no two individuals
being exactly alike.
• Much of this
variation between
individuals is
inheritable.
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29
Darwin’s Conclusion
 Individuals who inherit characteristics most
fit for their environment are likely to
reproduce more offspring than less fit
individuals.
 The unequal ability of individuals to survive
and reproduce leads to a gradual change in a
population, with favorable characteristics
accumulating over generations.
This is called Natural Selection
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30
Darwin’s Theory of
Evolution
Organisms Change Over Time
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31
Natural Selection

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Driving force for
evolution
During the struggle for
resources, the strongest
survive & reproduce
Idea that at least some
of the differences
between individuals,
which impact their
survival and fertility, are
inheritable
Therefore, natural
selection acts upon
mutations.
.
32
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Origin of Species
Darwin Presents His Case
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33
Publication of “On The Origin
of Species”
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Upon His Return To England, Darwin
Developed His Observations Into
The Theory of Evolution
But He Did Not Publish For 25
Years –
Why?
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34
Publication of “The Origin of
Species”
Darwin Knew That His Theory
Would Be Extremely Controversial
And Would Be Attacked
 His Theory Challenged Established
Religious & Scientific Beliefs

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35
Publication of “On The Origin
of Species”

He Refused To Publish Until
He Received An Essay From
Alfred Wallace
– Fellow Naturalist
– Independently Developed
The Same Theory
– After 25 Years, Someone
Else Had Come To The
Same Conclusions From
Their Observations Of
Nature
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36
Wallace’s Contribution
• Alfred Wallace:
• Independently came to
same Conclusion as
Darwin that species
changed over time
because of their
struggle for existence
• When Darwin read
Wallace’s essay, he knew
he had to publish his
findings
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37
Natural Variation and
Artificial Selection
Abandoned The Idea That Species
Were Perfect & Unchanging
 Observed Significant Variation in
All Species Observed
 Observed Farmers Use Variation To
Improve Crops & Livestock
– Called Selective Breeding

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38
Natural Variation and
Artificial Selection
 Natural
Variation
– Differences Among Individuals Of
A Species
 Artificial
Selection
– Selective Breeding To Enhance
Desired Traits Among Stock or
Crops
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39
Natural Variation and
Artificial Selection
Key Concept:
In Artificial Selection, Nature
Provided The Variation Among
Different Organisms, And
Humans Selected Those
Variations That They Found
Useful
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40
Evolution by Natural
Selection Concepts
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41
Four Main Principles of
Natural Selection
Genetic Variation
 Overpopulation
 Adaptation
 Descent with Modification
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Genetic Variation

Genetic Variation
– Variations come from mutations and
gene shuffling that result from sexual
reproduction.
– In genetics terms, evolution is any
change in allele frequency in a
population.
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Overpopulation
 Overproduction:
Organisms
reproduce more than its environment
can handle.
– Overproduction leads to competition
– Competition: the struggle for existence
» Organisms compete for food, living
space, and reproduction.
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Adaptation
Adaptation
– Inherited Characteristic That
Increases an Organisms Chance for
Survival
 Examples of Adaptations

– Mimicry: one species mimics (imitates) the
color, pattern, or behavior of another in
order to gain protection
– Camouflage: a species’ ability to conceal
itself from its predators by blending into45its
environment.
Mimicry
Which is the poisonous snake??
• Another example of
mimicry involves the
monarch butterfly,
which is toxic and very
nasty when eaten. Its
bright orange coloration
is a warning to birds to
leave it alone. The
non-toxic viceroy
butterfly has developed
colors and wing
patterns that are very
similar to those of the
monarch and so most
birds won’t take a
chance by taste-testing
it!
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Camouflage
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Descent with Modification
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Darwin proposed that
organisms descended
from common
ancestors
Idea that organisms
change with time,
diverging from a
common form
Caused evolution of
new species with
better adaptations
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Survival of the Fittest

Fitness
– Ability of an Individual To Survive
& Reproduce
– Fitness is central to the process of
evolution
 Individuals
With Low Fitness
– Either Die or Produce Few Offspring
Survival of the Fittest
AKA Natural Selection
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Survival of the Fittest
Key Concept
Over Time, Natural Selection
Results In Changes In The
Inherited Characteristics Of
A Population. These Changes
Increase A Species Fitness In
Its Environment
50
Theory of Evolution
Today
Supporting Evidence
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51
Evidence of Evolution


Darwin Argued That Living Things
Have Been Evolving On Earth For
Millions of Years. Evidence For
This Process Could Be Found In:
– The Fossil Record
– The Geographical Distribution of
Living Species
– Anatomical Structures of Living
Organisms
– Similarities In Early Development
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52
Fossil Record
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Fossils In Different Layers of Sedimentary
Rock showed evidence of gradual change over
time
Fossil: preserved remains of ancient
organisms
Fossil Record: provides evidence about the
history of life on Earth
– Most fossils form in sedimentary rock
______________________

Fossils that are found in a lower layer are
older than fossils that are found in a higher
strata
Fossils

Radioactive (Radiometric) dating
– Technique used to calculate age of fossils based
on the amount of remaining radioactive isotopes
it contains
» Age of fossil is based on half-lives

Half life: length of time required for half
of the radioactive atoms in a sample to
decay
Half-life Practice Problems

What percentage of a radioactive element
will be left after:
– a. 1 half-life b. 2 half-lives c. 3 half-lives

If a rock sample originally contained 12 g
of Uranium-235, how much will be left
after:
– a. 1 half-life b. 2 half-lives c. 3 half-lives

Gold-198 has a half-life of 2.7 days. How
much of a 96 g sample of gold-198 will be
left after 8.1 days?
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Comparative Anatomy
Homologous
Structures: Same
structure with a
different function
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57
Comparative Anatomy

Analogous Structures: Different
structures that have the same
function
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58
Comparative Anatomy

Vestigial Organs: Remnants of structures
that were functional in ancestral species
– Organs or structures that have lost their
function in the organism and have become
reduced in size
– Modern animals may have structures that
serve little or no function
» Example: Appendix In Man
Eyes on a cave fish (blind)
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Comparative Embryology

Comparative embryology: comparing the
formation and development of embryos
– Embryo – early stages of vertebrate
development

Early stages of development in many
vertebrates are very similar
– Same development order
– Similar tissues and organ structure such as
gills and a tail
– Similar features in young embryos suggest
evolution from a distant common ancestor
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A
B
C
D
E
F
G
H
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Biochemistry
All living things are biochemically
similar.
 Similarities in amino acid sequences can
determine relatedness.

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Geographic Distribution of
Living Species

Biogeography:
– Different Animals On
Different Continents
But Similar
Adaptations To
Shared Environments
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63
3 Ways Natural Selection
Affects Phenotype Distribution
1.
Directional Selection
2.
Stabilizing Selection
3.
Disruptive Selection
Directional Selection

Individuals at one end of a distribution curve
have a higher fitness than individuals in the
middle or at the other end
– In diagram, birds w/ big beaks have higher
fitness
Key
Directional
Directional Selection
Directional
Selection
Selection
Food becomes scarce.
Food becomes scarce.
Low mortality,
Low
mortality,
high
fitness
high fitness
High mortality,
High
mortality,
low
fitness
low fitness
Stabilizing Selection

Individuals near the
center of the curve
have higher fitness
than individuals at
either end
– In this diagram,
birds w/ median
birth weight have
higher fitness than
heavy or light
weight birds
Stabilizing Selection
Stabilizing
Selection
KeyStabilizing Selection
Key
Low mortality,
Low
mortality,
high
fitness
high fitness
High mortality,
High
mortality,
low
fitness
low fitness
Birth Weight
Birth Weight
Selection
Selection
against
both
against
both
extremes keep
extremes
keep
curve
narrow
curve
narrow
and
in same
and
in same
place.
place.
Disruptive Selection
Individuals at the upper and lower ends
of the curve have higher fitness than
individuals near the middle
– In diagram, birds with small and large beak
sizes have higher fitness than birds with a
medium beak size
Disruptive
Selection
Disruptive
Selection
Beak
Beak Size
Size
Population splits
Population
splits
into
two subgroups
into two subgroups
specializing
in
specializing
in
different seeds.
different seeds.
Number of Birds
Low mortality,
high fitness
High mortality,
low fitness
of Birds
Number
in Population
in Population
Key
Key
Number of Birds
Largestand
andsmallest
smallestseeds
seedsbecome
becomemore
morecommon.
common.
Largest
of Birds
Number
in Population
in Population

Beak
Beak Size
Size
Patterns of Evolution

Three patterns of evolution:
– Convergent Evolution
– Divergent Evolution
– Coevolution
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Convergent Evolution

Convergent Evolution
– Evolution toward similar characteristics in
unrelated species
– Analogous structures are examples of convergent
evolution.
Divergent Evolution

Divergent Evolution
– When closely related species evolve in
different directions
– Also called
adaptive
radiation
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Coevolution


Sometimes organisms that are closely
connected to one another by ecological
interactions evolve together.
Example: Flowering plants and
a specific pollinator
Coevolution:
Two species evolve in
response to changes
in each other.
