An example of natural selection

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An example of natural selection

• The premises
• 1. Phenotypic variation among a surplus of
  individuals.
• 2. Phenotypic variation has a genetic component
• 3. Differential reproductive success
• Survival and reproduction is nonrandom
• 4. Phenotypic variation shifts between
  generations to reflect parental adaptations to
  the environment.

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Medium ground finch Geospiza fortis generation
time 4.5 years life span c. 16 years
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Research of Peter and Rosemary Grant 1973 -
present
120 m N c. 1,200
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1 Is the population phenotypically variable?
Geospiza fortis
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2 Is the variation heritable? (heritability
proportion of phenotypic variation due to genetic
variation c. 65)
Evolution!
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Effect of natural selection
1977 drought 130 to 24 mm precipitation A
natural selector Was there differential
survival?
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The interplay
Number of finches
2.
Seed abundance
1.
Seed characteristics of surviving plants
3.
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Had evolution taken place? Significant difference
in the mean beak depth
Note natural selection is always one
generation behind the expression of
modified phenotypes
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Natural selection cannot anticipate future
needs of a population

• Natural selection is always one generation behind
  exposing a new generation to the environment.
• Parental population environment (natural
  selective agents)
• Part of population selected to reproduce
• Transmission of heritable characteristics to the
  new generation (e.g., bird beak characteristics).
• But the change was based on phenotypic variation
  among their parents.

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Biological diversity created or product of
evolution

• A random survey of 2,000 adults
• 42 believed that biological diversity has not
  increased since the beginning of time.
• Special creation
• 48 believed that biological evolution has taken
  place.
• Descent with modification

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Special creationThe intelligent design argument

• 1. Fixity of species
• 2. Each species was independently created
• No relationships among species
• 3. Biblical evidence origins are recent
• Movement called creation science attempts to
  legitimize special creation.
• Not a science.
• Argument is based on idea of Intelligent Design
  supported by the idea of irreducible complexity.

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Bacterial flagellum irreducible complexity?
E. coli Mobility
Yersinia Type III Export System
30 protein components 20 proteins involved in
assembly
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Ciliary body
Sclera
1 Cornea
Fovea
Pupil
2 Iris
3 Lens
Choroid
4 Retina
Ora serrata
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Darwins 1859 illustration (On the Origin of
Species by Means of Natural Selection)
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Cladistic evolution vs. anagenesis or phyletic
evolution
species originate from common ancestors