Introduction to Evolution

  1. Biological evolution

    1. Change in allele frequencies within a population across
      generations.

    2. Change in allele or genotype frequencies within a population over time.

    3. Does not occur within individuals, communities, ecosystems, biomes, etc

  2. 5 forces of evolutionary change

    1. selection

      1. natural and sexual

    2. mutation

    3. random genetic drift

    4. migration

    5. non-random (assortative) mating

  3. Selection

    1. changes in allele frequency due to different survival or reproduction caused by

      1. abiotic environment: temperature, drought, flood

      2. biotic environment: food availability, competition within own species or other species, predation

      3. members of your own species

        1. males competing for access to mates

        2. females being choosy about who they will mate with

  4. Mutation

    1. random changes in the nitrogenous base sequence of DNA

    2. can occur anywhere in the genome, if it occurs in a part of the genome that is functional the mutation can have varied effects

  5. Random genetic drift

    1. random changes in allele frequency due to random occurrence of death

    2. more pronounced in small populations

    3. special case is population bottlenecks where a population experiences a dramatic reduction in size

  6. Migration

    1. founder effect: when a small group migrates and establishes a new population with the same genetic diversity of the original population

  7. Non-random (assortative) mating

    1. individuals mate with individuals with the same genotype or phenotype

    2. individuals mate with individuals with different genotype or phenotype

    3. tend to alter genotype frequency but does not necessarily alter the allele frequency

  8. Discovery of the theory evolution via natural selection

    1. contributors: Charles Darwin and Alfred Russel Wallace in the 1800s

    2. state of evolutionary though in the 1800s:

      1. earth is young

      2. earth is now as it was when created (stasis)

      3. species are unchanged

    3. Jean-Baptistse Lamark’s theory of evolution was that acquired variation is passed on to descendants

    4. Thomas Robert Malthus laid out that populations grow exponentially

    5. William Paley supported the idea that creation was designed by a divine creator

    6. both Darwin and Wallace noted similarities and differences between species on continents and neighboring islands

    7. Darwin introduced idea of species descending from a common ancestor in tortoises in the Galapagos Island

    8. Wallace published ideas of species being geographically isolated by rivers specifically Amazonian monkeys

  9. 4 predictions for evolution via natural selection

    1. more offspring are produced that can survive

      1. leads to the struggle for existence

      2. population growth

    2. Interindividual phenotypic variation exists

      1. differences in observable traits between individuals in the same species

      2. central dogma

    3. Interindividual phenotypic variation is heritable

      1. genetic basis for these variations

      2. genetics

    4. Interindividual phenotypic variation results in interindividual variation in either reproductive success or survivals

      1. selection part of the idea

      2. genetics, selection, ecology, diversity

  10. How do we know evolution has occurred

    1. fossil records show different stages of evolutionary development within lineages

    2. homology shows structures that have the same evolutionary origin

    3. molecular evidence shows signs of cumulative change at the nucleotide level that indicates a shared evolutionary relationship