Major Objectives

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Major Objectives
1. Understand the historical context for
evolutionary theory, including Darwin's field
research that helped frame his view of life 2.
Define Darwinism and Darwin's main ideas from the
Origin of Species 3. Discuss examples of natural
selection and other evidence for evolution
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"Nothing in biology makes sense except in the
light of evolution." Theodosius Dobzhansky
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What is Evolution??
Change in gene frequency in a population over time
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Evolution was resisted by Western culture
-Greek philosophers Aristole (scala
naturae) -Natural theology (1700's)
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Ladder of Life
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Lamarkian Evolution
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Figure 22.3 Formation of sedimentary rock and
deposition of fossils from different time periods
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Figure 22.2 Fossils of trilobites, animals that
lived in the seas hundreds of millions of years
ago
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Figure 22.4 Strata of sedimentary rock at the
Grand Canyon
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Galapagos Island Finches Beaks Differed
According to Food Supply
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Darwin's Intellectual Revolution
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Millions of DNA Switches That Power Human
Genome's Operating System Are Discovered ScienceDa
ily (Sep. 5, 2012)  The locations of millions of
DNA 'switches' that dictate how, when, and where
in the body different genes turn on and off have
been identified by a research team led by the
University of Washington in Seattle. Genes make
up only 2 percent of the human genome and were
easy to spot, but the on/off switches controlling
those genes were encrypted within the remaining
98 percent of the genome.
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In the mid-1990s, researchers were surprised to
discover that fruit flies, mice, and humans who
were born missing eye structures had defects in
the same gene. This gene, called Pax6 (or eyeless
in flies), is required for normal eye development
in all animals with bilateral symmetry. Even in
eyes that look very different, Pax6 functions in
much the same way. When placed in a fly, the
mouse Pax6 gene activates all the genes necessary
to form a normal, functional fly eye (not a mouse
eye).
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What the Encode project tells us about the human
genome and 'junk 
ENCODE, the Encyclopedia of DNA Elements, is the
most ambitious human genetics project to date. It
takes the 3 billion letters described by the
Human Genome Project in 2000, and tries to
explain them. 
http//www.youtube.com/watch?vY3V2thsJ1Wc
http//www.youtube.com/watch?vUBQ5a7mCpMs
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Darwinism has a dual meaning
-Evolution as the explanation for life's unity
and diversity (descent with modification)
-Natural selection as the cause of adaptive
evolution
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Figure 22.7 Descent with modification
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Darwin's main ideas from "The Origin of Species"
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Artificial Selection-selecting desired traits
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1. Natural selection is differential success in
reproduction Idea of overreproduction influenced
by Thomas Malthus (1798)
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1. Differential success in reproduction
Not All Organisms Get To Mate Why is this
important?
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2. Natural selection occurs through an
interaction between the environment and the
variability inherent among the individual
organisms making up a population
Why is this important?
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3. The product of natural selection is the
adaptation of populations of organisms to their
environment
How does this result in population change?
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How does natural selection work?
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Peppered Moths Real Natural Selection Example

• Original population white in color, blended into
  lichens on trees
• During industrial revolution, lichens died
  trees covered in soot
• Lighter moths had higher predation rates, darker
  moths had high survival rates
• Over time, population became dominated by dark
  moths

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Darwins Theory of Natural Selection
Favorable traits that are heritable become more
common in successive generations of a population,
and unfavorable traits that are heritable become
less common
If phenotypes have a genetic basis, phenotypes
will increase or decrease in frequency Results in
change in gene frequency over time
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Darwins Theory Lacked Satisfactory Theory of
Heredity

• Modern Synthesis (1920-1940)
• Unification of Mendels theory of heredity and
  Darwinian evolution

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Evidence for Evolution
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Evidence for Evolution
Fossil Record
Natural selection
Homologous structures
Molecular Biology-DNA
Islands
Vestigial Organs
Convergent Evolution
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Same skeletal elements, different functions
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500 endemic species
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Vestigial Organs
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Convergent Evolution- The independent development
of similarity between species as a result of
their having similar ecological roles and
selection pressures
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Major Objectives
1. Do populations or organisms evolve? 2. What
are the major differences between microevolution
and macroevolution? 3. What are the four main
factors that can alter genetic diversity? 4.
Identify the three main modes of natural
selection. 5. Describe the four main reasons why
natural selection cannot produce perfection.
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Populations Evolve, Natural Selection Occurs at
the Level of Organisms
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Types of Evolution
Microevolution-A change in the gene pool of a
population from generation to generation
Macroevolution-Evolutionary change on a grand
scale, encompassing the origin of new taxonomic
groups, evolutionary trends, adaptive radiation,
and mass extinction
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Four Main Factors That Can Alter Genetic
Diversity 1) Genetic Drift
A change in a populations genetic diversity due
to chance
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Why are small populations so vulnerable to
extinction?
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Extinction Vortex
Disturbance lowers population size Reduced
Genetic Variability Reduced ability to survive
environmental stochasticity
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Founder Effectexample for higher risk of breast
or ovarian cancer in women
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Four Main Factors That Can Alter Genetic
Diversity 1) Genetic Drift 2) Natural Selection
Differential success in reproduction
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Four Main Factors That Can Alter Genetic
Diversity 1) Genetic Drift 2) Natural
Selection 3) Gene Flow
Genetic exchange due to the migration of fertile
individuals between populations
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Four Main Factors That Can Alter Genetic
Diversity 1) Genetic Drift 2) Natural
Selection 3) Gene Flow 4) Mutation
An accidental change in an organism's DNA
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Natural Selection Common MisconceptionsNot
Goal-Oriented or Progressive

• Change follows environmental conditions

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"Survival of the Fittest"
-Misleading phrase Does NOT mean
competitiveness contest between individuals
-Darwinian Fitness the contribution an
individual makes to the gene pool of the next
generation relative to the contributions of other
individuals
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Natural Selection Common MisconceptionsIs
Specific to Environmental Conditions

• Specific phenotype is only adaptive in a specific
  environment

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Natural selection does not produce perfection
1) Evolution is limited by historical constraints
2) Adaptations are often compromises
3) Not all evolution is adaptive
4) Selection can only edit existing variations
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All phenotypic variation is NOT heritable
Phenotypes are the result of 1) inherited
genotype 2) environmental influences
Reaction Norms pattern of phenotypic expression
of a single genotype across a range of
environments
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Si el Norte Fuera el Sur A case of squirrel
monkey identities
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http//www.youtube.com/watch?vvI7FYM9_EQE
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Your Assignment Working in your assigned group,
use the information from the case study to
develop a model of evolutionary divergence
between these two populations. You may include as
many details as you like in your story or
scenario, but you must follow some
guidelines 1. Your model should account for at
least some of the data supplied in the case
study.  2. Your scenario must incorporate the
three assigned concepts from the "Concept List"
assigned to your group. For each concept you must
demonstrate its relevance to your story.  3.
Keep in mind that in an evolutionary story you
will describe events in your monkey population(s)
that may have occurred over very long time
periods. Current evidence indicates the ancestors
of S. oerstedii arrived in Central America from
South America some 500,000 years ago, so you
could describe plausible geological or climatic
events during that time which are relevant to
your scenario. In addition, remember the
historical range of S. oerstedii was relatively
continuous along the Pacific Coast of Costa Rica
and western Panama until only 20 years ago. In
other words, S. oerstedii was only very recently
confined to the small populations of Manuel
Antonio and Corcovado.  4. Your group should
submit one written summary of the scenario you
come up with to explain this speciation event.
Rather than writing the story in paragraph
form, please use an outline format. 5. Be
prepared to present a brief summary of your model
to the rest of the class! 
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Four Main Modes of Genetic Selection 1)
Directional Selection 2) Diversifying/Disruptive
Selection 3) Stabilizing Selection 4) Sexual
Selection
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Directional Selection
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Diversifying Selection
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Stabilizing Selection
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Sexual Selection
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Three Main Types of Speciation
1) Allopatric Speciation 2) Sympatric
Speciation 3) Parapatric Speciation
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Elevational parapatry in the I. floralis group
(left/top) and the nepos group I. orpheus
(right/bottom).
Hall J P Proc. R. Soc. B 20052722457-2466
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Major Objectives
1. Define the biological species concept and its
limitations 2. Understand prezygotic and
postzygotic barriers that isolate gene pools of
biological species.
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Biological Species Concept
A species is a population or group of
populations whose members have the potential to
interbreed with each other in nature to produce
viable, fertile offspring.
Lynx rufus
Lynx canadensis
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What about limitations?
Difficult to test reproductive isolation of
morphologically similar fossils
Difficult to test reproductive isolation of
morphologically living species
Doesn't address species that reproduce
asexually (e.g., bacteria)
Doesn't address hybrids (e.g., plants, zoo
animals)
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