Not what you think???

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Darwin and Evolution

• Not what you think???

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What is Evolution?
CHANGE OVER TIME And by time, we mean 100s of
years
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Darwin said

• DESCENT WITH MODIFICATION

• MODIFICATION IS DRIVEN BY
• NATURAL SELECTION

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Before Darwin 1831

• Plato
• Aristotle
• Linnaeus 1707-78
• Leclerc 1708-88
• (aka Count Buffon)
• Erasmus Darwin 1731-1802
• (grandpa)
• Cuvier
• Lamark 1744-1849

• Variations are imperfections
• scala naturae-scale of nature based on complexity
• Classification of organisms, supported Aristotle
• Descent with modification, suggested
  mechanism-migration, isolation
• Physician and naturalist, common descent
• Comparative Anatomy, fossils, classification,
  Catastrophism
• Evolution, diversity, adaptation, Acquired
  Characteristics

FIXITYPERFECTIONCREATION
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DARWINOH THE ROCKS, FOSSILS AND BIODIVERSITY HE
DID SEE

• GEOLOGY FOSSILS
• Hutton and Lyell
• Principles of Geology
• Earth experienced slow but continuous cycles of
  erosion and uplift
• Creates sedimentary rocks with fossils
• Uniformiatarianism
• EARTHS CHANGES ARE SLOW
• EARTH MUST BE VERY OLD

• BIOGEOGRAPHY
• DARWIN FOUND
• Ocean shells inland
• Fossils of extinct organisms
• Saw relationships between organisms on different
  continents
• Adaptations fit the environment
• Similar environments created similar organisms
• Similar species replaced each other

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DARWIN REASONED

• Similar species could be modified based on the
  environment
• Ancestral tortoise?
• Ancestral finch?
• ADAPTATION TO ENVIRONMENT ACCOUNTS FOR
  BIODIVERSITY
• One species can give rise to many species, each
  adapted differently

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Darwin NATURAL SELECTION CAUSES EVOLUTION

• Preconditions
• Members of a population are different
  (at the genetic level)
• Variation was essential to NS process
• Variations are random (mutations)
• Variation that make adaptation possible are
  passed on
• Variation arises out of mutation and sexual
  reproduction

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More preconditions

• 2. Organisms struggle to exist
• Not enough food to go around (Malthus)
• Reproductive potential leads to
  overpopulation-exponential
• Each generation has same reproductive potential
• Do resources increase exponentially, too?
• ONLY CERTAIN MEMBERS WILL SURVIVE TO REPRODUCE

• 3. Organisms differ in fitness-reproductive
  success
• Most fit gets the resources
• Convert these resources to viable offspring
• Fitness varies for different poulations
• Environment
• Adaptations
• For example Camouflage

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Consequences

• Adaptation
• More and more, the genes that allow individuals
  to survive show up within the population
• Moths
• Finches
• Guppies

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WHAT WE KNOW TODAYTHAT DARWIN DIDNT

• FOSSILS
• From simple to complex
• Transition fossils
• Archaeopteryx-reptile or bird?
• Eustheopteron-amphibian or fish?
• Seymournia-reptile or amphibian?
• Therapsids-mammal or reptile?
• Tell a storywhich came first?
• Superposition
• Fish then reptiles then birds then mammals

• Evolution of the Horse

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WHAT WE KNOW TODAYTHAT DARWIN DIDNT

• Biogeography
• Evolution is influenced by the mix of plants and
  animals on a continent
• Why masupials in Australia? COMPETITION
• No rabbits in SA?
• Evolved somewhere else and had no way to get
  there
• RELATED FORMS EVOLVE IN ONE LOCATION, THEN
  DIVERSIFY AS THEY SPREAD OUT

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WHAT WE KNOW TODAYTHAT DARWIN DIDNT

• Anatomy
• If it looks like a duck, sounds like a duck, acts
  like a duck, then
• Homologous
• Analogous
• Vestigial

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WHAT WE KNOW TODAYTHAT DARWIN DIDNT

• Biochemistry
• DNA, RNA and Protein
• More similar, more closely related
• Common ancestors

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Breaking Down NS---To The Genes

• Remember
• adaptations are controlled by genes
• different adaptations come about through random
  mutations
• mutations can make an organism more or less fit
• SO BY LOOKING AT GENES WE CAN DETERMINE WHEN
  EVOLUTION HAS OCCURRED

• Population Genetics
• Studying genes within a population
• Populations are where evolution occurs
• All of the genes in a population are called the
  GENE POOL
• Dominant, recessive, incompletely dominant or
  codominant

Hardy-Weinberg Equillibrium. No change in gene
frequencies no EVOLUTION
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Changing the gene pool EVOLUTION

• MICROEVOLUTION-a couple of generations
• Genetic mutations-where it all starts
• GENES CHANGE
• PHENOTYPES CHANGE
• DIVERSIFIES THE GENE POOL
• No mutationsgene pool stays the sameNO
  EVOLUTION
• http//www.phschool.com/science/biology_place/labb
  ench/lab8/mutation.html

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Changing the gene pool EVOLUTIONMICROEVOLUTION-
a couple of generations

• Gene flow-2 populations become one, increases
  genes in pool but decreases numbers of species

RESULTS Within a populationIt can introduce
or reintroduce genes to a population, increasing
the genetic variation of that population. Across
populationsBy moving genes around, it can make
distant populations genetically similar to one
another, hence reducing the chance of speciation.
The less gene flow between two populations, the
more likely that two populations will evolve into
two species.
http//evolution.berkeley.edu/evosite/evo101/image
s/geneflow_beetles.gif
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Changing the gene pool EVOLUTIONMICROEVOLUTION-a
couple of generations

• Nonrandom mating-one genotype/phenotype becomes
  prevalent, less diversity in the pool
• BUT EVOLVED TO FIT ENVIRONMENT (SWALLOWS)

RESULTS Within a populationIncreases numbers
of homozygous genotypes Across
populationsDifferent populations in different
areas will experience different selection
criteria. So biogeography plays a role here in
that different traits will become dominant in
different areas depending on what makes that
population better able to survive. (finches,
turtles)
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Changing the gene pool EVOLUTIONMICROEVOLUTION-a
couple of generations

• Genetic drift-loss of genes due to chance, big
  effect on small populations, bottleneck, founder

RESULTS Within a populationChanges gene
frequency at random. The lucky survive to pass on
their genes. Decreases diversity within the
pool. Across populationsDoes not produce
adaptations.
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MICROEVOLUTION-a couple of generations

• Natural selection
• Results in adaptation to biotic and abiotic
  factors
• Abiotic
• Weather
• Temp
• precip
• Biotic
• Competition for resources
• Predators
• Parasites

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Types of Selection
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Speciation

• Isolating Mechanisms
• Prezygotic
• Habitat
• Temporal
• Mechanical
• Gamete isolation
• Postzygotic
• Zygote mortality
• Hybrid sterility
• F2 fitness

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Modes of speciation

• Allopatric
• Geographic barrier
• Different fathers, one great granddaddy
• Adaptive radiation

• Sympatric
• No geographic barrier
• Same father

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Evolution

• Convergent

• Divergent