Natural Selection and other mechanisms of evolution

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Natural Selection and other mechanisms of
evolution

• Presented by Autumn Konz and Benedict Christen

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DARWINS CONCEPT OF EVOLUTION

• All species are capable of producing offspring
  faster than the food supply increases.
• All living things show variation individuals of
  a species are likely to vary.
• Because there are more individuals than can
  possibly survive, there is a struggle for
  existence and those with favorable variation in
  characteristics that are necessary for survival
  will possess an advantage over others that dont
  have those characteristics.
• Those individuals with an advantage will do
  better and leave more offspring so their
  favorable traits should become more frequent.
• Over time, these successful variations produce
  differences that result in significant change in
  species (and new species).
• This is natural selection.

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Natural selection

• differential net reproductive success
• WHY IS THIS?
• Some genetic variations within a population will
  influence reproductive success. Therefore
  individuals with those variations contribute more
  offspring to succeeding generations.

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Factors that produce and redistribute variation

• Mutation-Changes that occur at multiple levels in
  the DNA , base substitutions, reordering of
  bases, rearrangements within chromosomes, entire
  chromosomes added or deleted.
• Recombination-The process by which progeny derive
  a combination of genes different from that of
  either parent. In eukaryotes, this is
  supplemented by crossing over.
• Dispersal (one-time?) and migration (seasonal)
  movement of organisms from one local to another
  (Founder effect)
• Genetic drift-the random change in gene
  frequencies in populations.

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OTHER MECHANISMS OF EVOLUTION

• Sexual selection Really a subset of natural
  selection - evolution based on the selective
  advantage of traits that improve reproductive
  success, even if otherwise deleterious.
• Polyploidy- (Usually combined with hybridization)
  the instant formation of new polyploid often
  hybrid species
• Kin Selection/ group selection -evolution of
  traits (often behavioral) that increase numbers
  of its genes an individual contributes to the
  next generation by way of the individuals
  contribution to the reproductive success of its
  relatives.

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OTHER IMPORTANT CONCEPTS IN EVOLUTION

• Gene Flow- ( immigration and emigration) maintain
  integrity of species (biological species concept)
• Pleiotropy When a single gene has more than one
  phenotypic manifestation (i.e. sickle cell
  trait).
• Heterochrony Changes in timing of gene
  activation in an organism's developmental
  timetable
• Anagenesis vs. cladogensis (vertical evolution
  vs. speciation)
• Speciation (allopatric vs. sympatric)
• Phyletic gradualism vs. punctuated equilibrium