Principles of Evolution

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Principles of Evolution
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1.  Indicate how each term below relates to
evolution.

• a)  population -  a group of individuals living
  in the same geographical area and sharing a
  common gene pool.
• Population of wild turkeys in Illinois vs
  population of wild turkeys in Missouri
• Different populations but same species
  interbreed.

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1. Terms cont

•  b)  gene pool  -all genetic information carried
  by the members of a population.
• c)  mutationheritable change in DNA. Can be
  changes of a single nucleotide base or changes in
  chromosome number.

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2.   Describe differences in mutations that are
good, neutral or harmful.

• Good rabbit has mutation for running faster,
  escapes predators better
• Neutral manx cats have bobbed tail never
  helps or harms animal six toed cat
• Harmful enzyme altered in humans that controls
  mucus production. Causes Cystic fibrosis.

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3.  Describe different ways mutations occur.

• Gene mutations provide new alleles, making these
  mutations the ultimate source of variation.
• A gene mutation is an alteration in the DNA
  nucleotide sequence, producing an alternate
  sequence, termed an allele.

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3. Mutations, cont

• Mutations occur at random or increasing can be
  due to environmental chemicals.
• Ex. Thaliamide, 2 headed animals, 5 legged frogs

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3. Mutations, cont
Miscoding, example inversion

• Some chromosomal mutations are changes in the
  number of chromosomes inherited, ex. Downs
  syndrome.
• others are alterations in arrangement of alleles
  on chromosomes due to miscoding.

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4.  What is a polygenic trait? 

• Occurs when a trait is controlled by several gene
  pairs
• usually results in continuous variation.
• Ex. Skin color, height

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5.  What is the Hardy Weinberg law? 

• This law states an equilibrium of allele
  frequencies in a gene pool remains in effect in
  each succeeding generation of a sexually
  reproducing population if five conditions are
  met.

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5. HW law b) What are the conditions necessary
for populations to stay in an equilibrium
(evolutionary change).

• No mutation no allelic changes occur.
• No gene flow migration of alleles into or out of
  the population does not occur.
• Random mating individuals pair by chance and not
  according to their genotypes or phenotypes.
• No genetic drift the population is large so
  changes in allele frequencies due to chance are
  insignificant.
• No selection no selective force favors one
  genotype over another.

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6.   What is the difference between random and
assortative mating?  Which leads to more
evolutionary changes?

• Random mating involves individuals pairing by
  chance, not according to their genotypes or
  phenotypes.
• Nonrandom mating involves individuals inbreeding
  and assortative mating

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7.   What is a genetic bottleneck?  Describe the
problem with Cheetahs.

• Bottleneck Drastic short-term reductions of
  population size result in survivors representing
  only a small portion of the original gene pool.
  Inbred.
• Causes natural disasters, disease, or predators
• Cheetahs, 10,000 years ago, now all nearly
  identical

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8.   Describe each of the following types of
selection and give an example?                    

• Stablizing selection -  Natural selection that
  tends to favor genotypic combinations that
  produce an intermediate phenotype selection
  against the extremes in variation.

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  Types of selection cont

• directional selection Natural selection favors
  extremes of the phenotypic range.
• Larger individuals favored (or smaller)
• Rapaports rule larger sizes in northern
  latitudes
• Ex. Bear family

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Types of selection cont

• disruptive selection - favors individuals at both
  extremes of a phenotypic range.

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9.  What are reproductive isolating mechanisms? 
Give an example.

• Biological or behavioral characteristics that
  reduce or prevent interbreeding with other
  populations.
• essential for development of a new species.
• Hybrids sterile mules

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10.  Why is evolution such a controversial
theory?  What do you think about it?

• For or against?
• Which evidence do you believe why?

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References

• http//www.estrellamountain.edu/faculty/farabee/bi
  obk/BioBookEVOLII.html