evolution

• What was Charles Darwin's book

  On the Origin of Species by Means of Natural Selection
• Process by which new species evolve is called Natural Selection
• Genetic variation


  how are changes in species produced over time
• • Changes can be produced by a combination of random genetic mutation and selection of particular traits that increase the organisms chances of survival and breeding in a particular environment
• Asexual vs. sexuall

  • random genetic mutations generate variety in all organisms but more so in organisms that usually reproduce asexually
  • sexual reproduction provides genetic variety in all organisms in every generation - made from meiosis
• Determining relatedness

  • a goal of taxonomy s to determine the evolutionary history of groups of organisms
• Four methods to determine relatedness

  • Evidence from anatomy
  • Evidence from development
  • Evidence from biochemistry
  • Evidence from DNA
• Evidence from anatomy

  • Organisms with similar structures may have acquired these traits from a common ancestor - shows that organisms may be more similar than they appear
• Homologous features

  • structures that share a common origin but may serve different functions in modern species
  • EX: flippers and hands
  • Same origin, different now
• Analogous features

  • structures similar in function but not in origin or anatomical structure
  • EX. wings in birds vs. bees
  • Same now, different origin
• Vestigial features

  • Rudimentary and non-functioning structures that are homologous to fully functioning structures in closely related species
  • EX. appendix
  • No function anymore
• Evidence from development

  • when an organism's appearance doesn't suggest much about its relatedness to other organisms, comparisons of early stages of embryonic development can reveal relationships among species that are not obvious from comparisons of adult organisms alone
• Evidence from biochemistry

  • studying what molecules are found in an organism can indicate similarity in genetic makeup of these organisms
• Evidence from DNA

  • we use mitochondrial DNA
  • easier and maternal
  • can be a precise method for determining the closeness of relationships among different organisms
• Microevolution

  • evolution at the species level
• Speciation

  • macroevolution
  • formation of entirely new species
• species

  • members of a population that have the ability to breed with each other under natural conditions
  • we can differentiate species solely on physical or morphological differences but sometimes behavior or biological methods are needed
• Reproductive isolating mechanisms

  • prezygotic --> prevent fertilisation
  • postzygotic --> isolation AFTER zygote is formed
• prezygotic isolation mechanisms

  • ecological isolation - occupy different habitats
  • temporal isolation - different plants bloom at different times of day
  • behavioral isolation - wrong signals, won't attract a mate
  • mechanical isolation - parts won't fit
  • gametic isolation - ex. biological markers, releasing gametes into water
• postzygotic isolation mechanisms

  • some reproduction between species produces hybrids which are often sterile
  • zygotic mortality - the zygote dies
  • hybrid inviability - it doesn't live long
  • hybrid infertility - ex. mule
• modes of speciation

  • within isolated gene pools any mutations and subsequent selection processes that occur in one population can no longer be shared with others
  • most commonly result from geographical isolation
  • Allopatric
  • Sympatric
• Allopatric speciation

  • evolution of populations into separate species as a result of GEOGRAPHICAL isolation
• Sympatric speciation

  • evolution of populations within the same geographical area into separate species
• Pathways of evolution

  • divergent evolution
  • convergent evolution
  • adaptive radiation
  • coevolution
• Divergent evolution

  • 2 or more species evolve increasingly different traits, resulting from different selection pressures or genetic drift
• Convergent evolution

  • 2 or more species become increasingly similar in phenotype in response to similar selection pressures
• Adaptive radiation

  • divergent evolution occurring so fast that one species gives rise to 3 or more species
• coevolution

  • when 2 species are totally dependant on each other for survival
  • common among flowering plants and the insects that pollinate them
• Fossils

  • preserved remains of an organism or its activity (bones only)
  • rare are impressions of burrows, footprints, and chemical remains
  • even more rare are whole bodies
  • fossilization is extremely rare
  • microfossils are most abundant
• Evolution

  • change in the genetic makeup of a population over time
  • change is directed by natural selection
  • occurs when natural selection causes changes in the relative frequencies in the gene pool
• Patterns of selection

  • mutations provide a continuous supply of new genetic variation
  • natural selection leads to a variety of outcomes
• Types of selection

  1. Stabilizing selection
  2. Directional selection
  3. Disruptive selection
  4. Sexual selection
  5. Cumulative selection
• Stabilizing selection

  • most common and misunderstood
  • nature selecting the same characteristics because the environment hasn't changed
  • most common phenotypes are most favoured by the environment
  • Eliminates extreme variations of a particular trait
• Stabilizing selection

  
• directional selection

  
• Distruptive selection

  
• directional selection

  • environment favours individuals with an extreme variation of a trait
  • Can result in observable changes
• Disruptive selection

  • favours individuals with variations at opposite extremes over individuals with intermediate variations
• sexual selection

  • favors the selection of any trait that influences the mating success of the individual
  • not environmental or else both sexes would have the trait
  • can result in detrimental traits
  • ex. becomes more obvious to predators
• Cumulative selection

  • evolving piece by piece over millions of generations