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(No Transcript)
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Darwinian Evolution
The material we will cover in Biology 114 is very
much different from that covered in Biology 113,
particularly in terms of the perspective and
approach of those who engage in these difference
aspects of biology. It is almost as though
biology consists of two very different sciences,
a reductionist science that seeks to emulate
chemistry or physics (113), and a much more
philosophical science that is interested as much
in the subtleties of history as it is in rigors
of the more exact physical sciences (114). This
is not to say that we will not be learning real
science in Biology 114, but instead that the
general approach of learning that we will employ
in Biology 114 will be somewhat different from
that of Biology 113. In Biology 113, basically,
you sought to understand how a cell works. Here
we will deal with such squishy topics as why it
is the cells that we observe exist at all. Keep
an open mind and study hard. By the end of this
term you will have gained an appreciation of the
most important concept in Biology Darwinian
evolution.
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Darwinian Evolution
"The process of evolution can be summarized in
three sentences Genes mutate. Individuals are
selected. Populations evolve."
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Charles Darwin
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Major Goals of this Chapter

• Get a Feeling for what it means for two organisms
  to be Evolutionarily Related
• Get a feeling for what is meant by Selection
  (a.k.a., Natural Selection) and by Darwinian
  Evolution
• Get a feeling for how we infer that organisms are
  evolutionarily related

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1st Major Goal of Chapter 22

• Get a Feeling for what it means for two organisms
  to be Evolutionarily Related
• Hint It means that the two organisms are related
  by Blood!
• Individuals from different Species are just very
  distantly related Cousins! (All of Diversity of
  Life)
• Just as You and I are, only even more distantly
  related

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Cousins
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A Cladogram A Graphed Phylogeny
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Relatedness ofAll Cellular Organisms
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Relatedness of All Eukaryotes
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Relatedness of All Plants
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Relatedness of All Fungi
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Relatedness of All Animals
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2nd Major Goal of Chapter

• Get a feeling for what is meant by Selection
  (a.k.a., Natural Selection) and Darwinian
  Evolution
• History of Evolutionary Thinking
• Malthus Logic
• Mayrs Logical Summary of Darwinian Evolution and
  Natural Selection
• Natural Selection and Adaptation
• Artificial Selection
• Observation of Selection (in particularly, as a
  consequence of Man the Modifier of Environments)

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History of Evolutionary Thinking
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History of Evolutionary Thinking

• Aristotle, 384-322 B.C.E., Scala Naturae (biology)

• Aristotle, 384-322 B.C.E., Scala Naturae
  (biology)
• Natural Theology (understanding nature for the
  sake of understanding the glory of creators
  universe)
• Carolus Linnaeus, 1707-1778, Taxonomy (organizing
  organisms by phenotypic similarity) (biology)
• Georges Cuvier, 1769-1832, Catastrophism (e.g.,
  Noahs flood) (geology)
• James Hutton, 1729-1797, Gradualism (geology)
• Charles Lyell, 1797-1875, Uniformitarianism (same
  processes today as yesterday) (geology)
• Jean Baptiste Lamarck, 1744-1829, Adaptation
  (environment ? phenotypic change) (biology)
• Thomas Malthus, 1766-1834, Limits on Population
  Growth (biology economics)
• Charles Darwin, 1809-1882, Natural Selection
  (environment ? genotypic change) (biology)
• Alfred Russel Wallace, 1823-1913, Ditto

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Hutton vs. Lyell
Gradualism
Uniformitariansim
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Malthus Logic
Limits Imposed by Environments
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Ernst Mayrs Summation

• Observation 1 ? Populations tend to have high
  reproductive potentials.
• Observation 2 ? Populations tend to be stable in
  size.
• Observation 3 ? Environments tend to possess
  limited resources.
• Inference 1 ? There exists a struggle for
  existence.
• Observation 4 ? There exists phenotypic variation
  within populations.
• Observation 5 ? Some phenotypic variation is
  heritable.
• Inference 2 ? Within populations there is
  differential reproductive success that is
  influenced by phenotypic differences between
  individuals.
• Inference 3 ? Differential reproductive success
  leads to a decline in frequency of genotypes that
  underlie phenotypes that are less fit to the
  environment and a corresponding increase in
  frequency of genotypes that underlie phenotypes
  that are more fit to the environment Darwinian
  Evolution.

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Ernst Mayrs Summation

• Populations tend to have high reproductive
  potentials (?).
• Populations tend to be stable in size (?).
• Environments tend to possess limited resources
  (?).
• Therefore there exists a struggle for existence.

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Ernst Mayrs Summation

• There exists phenotypic variation within
  populations.
• Some phenotypic variation is heritable.
• Within populations there is differential
  reproductive success.
• That differential reproductive success is
  influenced by phenotypic differences between
  individuals.

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Ernst Mayrs Summation

• Differential reproductive success leads to a
  decline in frequency of genotypes that underlie
  phenotypes that are less fit to the environment.
• Differential reproductive success also results in
  a corresponding increase in frequency of
  genotypes that underlie phenotypes that are more
  fit to the environment.
• This idea that differential reproductive success
  modifies genotypic frequencies in a manner that
  in principle may be predicted given knowledge of
  circumstances is know as Darwinian Evolution.
• More specifically, it is known as Natural
  Selection.

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(No Transcript)
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Major Goals of this Chapter

• Get a Feeling for what it means for two organisms
  to be Evolutionarily Related
• Get a feeling for what is meant by Selection
  (a.k.a., Natural Selection) and Darwinian
  Evolution
• Get a feeling for how we infer that organisms are
  evolutionarily related
• By the way, expect a Chapter 23 reading quiz on
  Wednesday! ?

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Ernst Mayrs Summation

• Observation 1 ? Populations tend to have high
  reproductive potentials.
• Observation 2 ? Populations tend to be stable in
  size.
• Observation 3 ? Environments tend to possess
  limited resources.
• Inference 1 ? There exists a struggle for
  existence.
• Observation 4 ? There exists phenotypic variation
  within populations.
• Observation 5 ? Some phenotypic variation is
  heritable.
• Inference 2 ? Within populations there is
  differential reproductive success that is
  influenced by phenotypic differences between
  individuals.
• Inference 3 ? Differential reproductive success
  leads to a decline in frequency of genotypes that
  underlie phenotypes that are less fit to the
  environment and a corresponding increase in
  frequency of genotypes that underlie phenotypes
  that are more fit to the environment Darwinian
  Evolution.

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An Alternative Perspective

• DNA (or RNA for some viruses) relatively stable
  information storage molecule ?
• Mutations changes in nucleotide sequence (new
  alleles) ?
• Change in Genotype (particularly if germ-line
  mutation) ?
• Can result in heritable changes in Phenotype
  (environment can also modify phenotype) giving
  rise to ?
• Variation among individuals making up populations
  (multiple alelles polymorphism variation not
  necessarily adaptive) ?
• Variation comes under the influence of the
  evolutionary forces of drift, selection, or
  migration ?
• Changes in Allele Frequencies ( evolution
  chapter 23) ?
• Changes in allele frequencies combined with
  reproductive isolation can result in Speciation
  (new species see chapter 24 macroevolution) ?
• Species either give rise to new species or are
  evolutionary dead ends (covered in chapter 25) ?
• In either case, all species eventually go extinct

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An Alternative Perspective
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Summation of Darwinism

• From p. 435 of your text (6th edition)
• Natural selection is differential success in
  reproduction
• (unequal ability of individuals to survive
  and reproduce)
• note that the emaphisis on reproduction,
  not survival
• Natural selection occurs through an interaction
  between the environment and the variability
  inherent among individual organisms making up a
  population.
• The product of natural selection is the
  adaptation of populations of organisms to their
  environment

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Intra-Specific Variation (evolutionary potential)
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Natural Selection Adaptation

• Cumulative Adaptation is an important consequence
  specifically of Natural Selection
• Adaptations essentially are better fits between
  phenotypes and environments
• Natural Selection serves to edit less-adaptive
  variation out of populations
• Fitness is defined in terms of reproductive
  success
• Variation that contributes to greater
  reproductive success, in the face of Natural
  Selection, tends to be retained within
  populations
• Note that I qualify the link between Adaptation
  Selection with the term Cumulative because it
  is mutation that gives rise to new alleles, not
  selection
• Natural Selection, in particular, serves to
  increase the likelihood that adaptive mutations
  may be found in the same individuals

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Natural Selection Adaptation
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Artificial Selection Cruciforms
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Artificial Selection Various Animals
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Man Modifier of Environments
Can you see the moths?
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Man Modifier of Environments
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Man Modifier of Environments
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Evolution of Antiobiotic Resistance
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Evolution in Action

• Antibiotic resistance in bacteria
• Antiviral resistance in viruses (including, of
  course, HIV)
• Insecticide resistance in insects (above)
• Industrial Melanism (also above)
• Evolution of resistance to toxins and heavy
  metals (a consequence of toxic-waste dumping)
• Sickle cell anemia (and over dominance)
• Predator selection on guppies (earlier sexual
  development)
• Evolution of sex ratios (towards 11 male to
  female)
• Progression of cancer (and cancer resistance to
  chemotherapeutics)
• Evolution of pathogen virulence
• Etc.

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Important Caveats

• From p. 437 of your text (6th edition)
• Natural selection occurs through interactions
  between individual organisms and their
  environment, but individuals do not evolve.
• Evolution can be measured only as changes in
  relative proportions of heritable variations in a
  population over a succession of generations.
• Natural selection can amplify or diminish only
  heritable variations.
• We must distinguish between adaptations an
  organism acquires by its own actions and
  inherited adaptations that evolve in a population
  over many generations as a result of natural
  selection.

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Important Caveats
It must also be emphasized that the specifics of
natural selection are situational environmental
factors vary from place to place and from time to
time. An adaptation in one situation may be
useless or even detrimental in different
circumstances. p. 437
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3nd Major Goal of Chapter

• Get a feeling for how we infer that organisms are
  evolutionarily related.
• Answer 1 we can infer evolutionary distance via
  phenotypic similarity (but not always easily)
• Answer 2 we can infer evolutionary distance via
  genotypic similarity (easier but not always
  unambiguous)
• Answer 3 From the immense body of evidence
  available it is difficult, by Occams Razor, to
  conclude that organisms are not evolutionarily
  related

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Occams Razor (through the ages)
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Evolution of Artifacts
Isnt it Obvious that these cars are
Related? Isnt Relationship the Simplest
Explanation for Similarity? In biology,
information is carried by genes so relationship
is by decent.
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Homologies

• Homologies are Similarities between organisms
• that are present due to Common Descent,
• which means they (the organisms) share ancestry
• evolutionary relatedness

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Homologies
Homologies tend to predict additional
Homologies ? e.g., if an animal has feathers it
probably also has wings
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Homologies
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Homologies
Note not just similar looking but similar
embryonic origins.
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Homologies
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Modern Criteria for Homology

• Positional Homology Two structures are
  homologous if they have the same arrangements of
  similar parts
• Developmental Homology Two structures are
  homologous if they develop in the same way
• Genetic Homology Two structures are homologous
  if their development is controlled by the same or
  similar genes
• Phylogenic Homology Two structures are
  homologous if they appear to be inherited from a
  common ancestor
• From http//faculty.uca.edu/benw/biol4402/lectu
  re5/sld007.htm
• Also amino acid or nucleotide homologies

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Molecular Homologies
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Skull Homologies
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Human-Bonobo Homologies
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Vestigial Structures
Keep in mind that Vestigeal Structures are
Homologies
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Developmental Error
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Comparative Embryology
Keep in mind that Embryological Similarites are
Homologies
Could you assemble a phylogeny based on this
figure?
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Analogies
Analogies do not tend to predict Homologies,
e.g., if an animal has wings it does not
necessarily also have feathers (analogies,
however, can predict related structural
similarities, e.g., wings flying lightweight
bodies)
Keep in mind that Analogies are NOT Homologies
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Convergent Evolution
Analogies are products of Convergent Evolution
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Complications
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Biogeography

• Organisms, basically, are limited in their
  ability to disperse
• As a consequence, evolutionary lineages are more
  likely to evolve locally (or regionally) rather
  than globally
• If you were inferring the relatedness of three
  species, two of which were found in the same
  region, the third on a different continent, you
  would predict a closer relatedness of the first
  two
• Homologies often correlate with geography (e.g.,
  old-world vs. new-world monkeys)

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The Fossil Record
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Link to Next Presentation
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Acknowledgements
http//207.233.
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Charles Darwin
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Relatedness ofAll Cellular Organisms
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Relatedness of All Animals
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Relatedness of All Chordates
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Relatedness of All Vertebrates
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Relatedness of All Amniotes
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Relatedness of All Mammals
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Relatedness of All Hominids