Evolution

• Darwin's observations in the Galapagos islands


  • Remarkable population of plants, birds and reptiles that had developed in isolation from the mainland, but often differed on almost identical islands next to one another
• Evolution


  Change in frequency of a trait in a population over time. Evolution creates new phenotypes
• Gene pool


  All of the alleles in a populations
• Causes of changes in the gene pool


  • Mutations
  • Natural selection
  • Genetic drift (Radiation, chemicals, environmental changes)
• Mechanisms of evolution


  • Natural selection
  • Genetic drift
  • Gene flow
  • Non-random mating
  • Mutations
• Natural selection


  Where an organism most first for an environment can survive and reproduce better than other in the population
• Fitness


  The ability to survive and reproduce
• Genetic drift


  The result from a drastic decrease in the population size, leaving only those genes present in the remaining individuals in the gene pool
• Genetic bottleneck


  A change in gene frequency following a dramatic reduction of population size, is a RANDOM EVENT that happens at RANDOM CHANCE
• Founder effect


  Where the new gene pool starts out with different frequencies and grows in size because of individuals carrying alleles that differ from those from the main population
• Gene flow


  The transfer of genetic material from one population to another
• Non-random mating


  A mating system in which at least some individuals are more or less likely to mate with individuals of a particular genotype than with individuals of other genotypes
• Mutation


  A change in the DNA sequence of an organism. Mutations can result from errors in DNA replication during cell division, exposure to mutagens or a viral infection
• Species


  A population or group of populations whose members can interbreed and produce fertile offspring in nature
• Speciation


  The formation of a new species from an existing species
• Speciation


  Two new populations must be formed from one original population, and they must evolve in such a way that it becomes impossible for individuals from the two new populations to interbreed
• Reproductive isolation


  When two populations can no longer interbreed
• Ways a population can reach reproductive isolation


  • Behavioral isolation
  • Geographic isolation
  • Temporal isolation
• Behavioral isolation


  Two populations develop different mating rituals or other behaviors
• Geographic isolation


  Two populations differ by geographic barriers such as rivers, mountains, etc.
• Temporal isolation


  Two or more species reproduce at different times
• Major types of speciation


  • Allopatric speciation
  • Sympatric speciation
• Allopatric speciation


  Occurs when a population becomes separated by a geographic barrier
• Sympatric speciation


  Occurs when a population within a population becomes isolated by a mean other than geographic isolation (Like sexual selection)
• Genetic equilibrium is a condition in which a populations allele frequencies remain the same over time
• Conditions for Hardy-Weinberg equilibrium


  • Extremely large populations
  • No mutations
  • Random mating
  • No gene flow
  • No natural selection
• The 4 pieces of evidence for evolution are...