Nothing in biology makes sense

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• Nothing in biology makes sense
• except in the light of evolution.
• Theodosius Dobzhansky (1973)
• Amer. Biol. Teacher 35125-129

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• Evolution change over time in the
  charac-teristics of a population of organisms
• Gene Pool all the genes represented in a
  particular population in each generation
• Evolution change over time in the gene
  frequencies of a populations gene pool

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• Genotype all the genes in an individual that
  determine its characteristics
• Phenotype the actual characteristics (anatomy,
  physiology, behavior) that are seen in an
  individual due to the expression of their genotype

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GodAngelsKings/QueensArchbishopsDukes/Duchesse
sBishopsMarquises/MarchionessesEarls/Countesses
Viscounts/ViscountessesBarons/BaronessesAbbots/
DeaconsKnights/Local OfficialsLadies-in-Waiting
Priests/MonksSquiresPagesMessengersMerchants/S
hopkeepersTradesmenYeomen FarmersSoldiers/Town
WatchHousehold ServantsTennant
FarmersShephards/HerdersBeggarsActorsThieves/P
iratesGypsiesAnimalsBirdsWormsPlantsRocks
The Great Chain of Being
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Sir Isaac Newton (1642-1727)
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• Science does not and cannot produce absolute and
  unquestionable truth. Scientific understanding is
  limited to the best fit to the data under current
  instrumental and philosophical limits of
  thinking. A scientific theory is merely a way of
  organizing tested and retested ideas to describe
  the behavior of natural phenomena. Huffman,
  Eugene Register Guardian, 12/16/07

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• But scientific theories are not hunches or gut
  feelings, which is the context in which the
  nonscientist uses the word theory. Scientists
  place a much higher standard on this word. To
  them, a theory is a powerful statement about the
  workings of nature, a strong explanation that
  ties together many reproducible facts from many
  different sources into an overall, unifying
  concept. Huffman, Eugene Register Guardian,
  12/16/07

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• A scientific theory is always open to
  falsification, if new evidence is presented.
  Theories should change as new discoveries are
  made, which is exactly the progress toward better
  understanding that science seeks. But to say
  "scientific theory" is not to imply "scientific
  uncertainty," a clever term employed by religious
  and political operatives to cast doubt in the
  public mind when a scientific theory challenges a
  traditional manner of thinking. Huffman, Eugene
  Register Guardian, 12/16/07

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• Creationist model
• Species created as independent entities by God
• Species do not change over time (immutable
  Gods creation is perfect)
• Creation is a recent event (e.g., 4004 BC)
• Evolution model
• Life arose from common ancestors
• Change is normal all species are derived from
  common ancestor by modification through time
• Life is immensely old evolution has worked over
  long periods of time

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• Relatedness
• - homology similarity of form due to
  relatedness

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Homology of embryonic structure gill slits
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Cytochrome c homologies

• Humans to chimps no difference
• Humans to primates 1-5 difference
• Among all mammals 5-10 difference
• Among all vertebrates 20 difference
• Among multicellular phyla 40 difference

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• Vestigial structures functionless homologs that
  are functional in other species
• - human appendix
• -eyes of cave fish
• - whale pelvis
• Embryonic vestiges
• - bird fingers
• - gill slits
• Molecular/genetic vestiges
• - pseudogenes

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• Mating female soapberry bug probing for seeds in
  the inflated fruit of native balloon vine in the
  subtropcial Florida Keys

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Georges Cuvier (1769-1832) - father of
Comparative Anatomy established reality of
fossils and extinction
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Archaeopteryx fossil
Reconstruction of Archaeopteryx
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Glossopteris fossil tropical plant found in
rocks of the Antarctic
Fossil seashells that Darwin found at 12,000 in
the Andes
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Charles Lyell (1797-1875) father of modern
geology popularized Uniformitarianism
James Hutton (1726-1797) Theory of
Uniformitarianism
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Marie Curie (1867-1934) isolated radioactive
elements
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a, An unnamed cylindrical prokaryotic filament,
from the  770-Myr Skillogalee Dolomite of South
Australia. b, Gunflintia grandis, a cellular
oscillatoriacean trichome, from the  2.1-Byr
Gunflint Formation of Ontario, Canada. c, d,
Unnamed highly carbonized filamentous prokaryotes
from  3.375-Byr Kromberg Formation of South
Africa. ei, Cellular microbial filaments from
the 3.465-Byr Apex chert of northwestern Western
Australia.
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• A naturalist, reflecting on the mutual
  affinities of organic beings, on their
  embryological relations, their geographical
  distribution, geological succession, and other
  such facts, might come to the conclusion that
  each species had not been independently created,
  but had descended from other species.
  Nevertheless, such a conclusion, even if well
  founded, would be unsatisfactory, until it could
  be shown how the innumerable species inhabiting
  this world have been modified Darwin, 1859.
  The Origin of Species.

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Jean-Baptiste Lamarck (1744-1829)
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Lamarcks mechanism of evolution via the
Inheritance of Acquired Characteristics

• Two principles
• - Use and disuse causes features to be emphasized
  or de-emphasized
• - The changes due to use or disuse are heritable
  and can be passed on to future generations

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Protogiraffes fed on low brush. Those on the
plains had to feed higher in the trees
By stretching their necks to reach the leaves on
the trees, some individuals acquired somewhat
longer necks
The longer neck, acquired by stretching (use) is
heritable and is passed on to the next generation
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Natural selection is based on 4 assumptions

• Individuals within a species are variable for all
  of their traits
• 2) These variations (at least some) can be
  passed on to their offspring (heritable)
• 3) In each generation, more offspring are
  produced than can survive (high reproductive
  potential in all living things)
• 4) survival and reproduction of individuals are
  not random with respect to these variations
  individuals with variations that best suit them
  to the environment will survive longer and
  reproduce more than others

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How Natural Selection works (and doesnt work)

• selection acts on individuals, but its
  evolutionary effects occur only at the population
  level.
• In order for any changes in characters to be
  evolutionary significant, they must be heritable.
• NS cannot produce changes in a population that
  will benefit it in the future.

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• 4. NS only works to alter characteristics that
  are present in the population, i.e., NS does not
  originate variation variation is a pre-existing
  condition.

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• How do necks get longer than the longest necks
  found in the original population?
• Mutation can increase the range of variation
• Potential vs. realized gene expression

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• How do we get new features that werent
• present in the original population?
• Pre-adaptation Features that evolved for one
  purpose
• are co-opted to be used for another,
• e.g., lungs, Pandas thumb

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How Natural Selection works (and doesnt work)

• 5) NS does not produce perfection.

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Viceroy
Monarch
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Constraints on perfection a) genetic/embryonic
constraints b) historical constraints 6)
Randomness sources of variation are random
(e.g., mutation), but selection is not
random. 7) NS is not progressive
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• Problem for Darwin how is variation generated
  and maintained?
• - wouldnt selection constantly tend to decrease
  variation in a population?
• blending inheritance offspring are literal
  blends of both parents. If a long-necked giraffe
  mates with a shorter-necked giraffe, they produce
  a medium-necked offspring. Over time all
  giraffes should blend to some common mean.
• The result of both of these is monomorphy

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Solution to Darwins problem

• Mendel showed that inheritance is particulate
  individual
• elements (genes) that are responsible for
  inheritance do
• not literally blend. They keep their identity
  from
• generation to generation.

Cross 2 brown mice Bb x Bb
B
b
B
b
(1 black mouse, 2 brown mice and 1 white mouse)