Evolution and Natural Selection

  1. What is Dalton's Theory of Evolution?
    The unequal ability of individuals to survive and reproduce leads to gradual change in a population, with favourable characteristics accumulating over generations.
  2. What are antibiotics?
    Chemicals produced by micro-organisms (fungi, bacteria) that kill or inhibit the growth of other micro-organisms.
  3. What are the three general modes of selection?
    They are:

    • Stabilizing selection
    • Directional selection
    • Disruptive selection
  4. Image Upload 1
    Directional, disruptive or stabilizing selection?
    Disruptive selection
  5. Image Upload 2

    Directional, disruptive or stabilizing selection
    Directional selection
  6. Image Upload 3
    Directional, disruptive or stabilizing selection?
    Stabilizing selection
  7. What is stabilizing selection?
    It is where the extremes of the phenotype are selected against. It leads to a reduction in variation as more individuals conform to the mean. It favours intermediate phenotypic classes and causes a decrease in the frequency of the alleles representing the extremes
  8. Where does stabilizing selection usually occur?
    In an unchanging environment
  9. What is directional selection?
    It is where a selection pressure acts on species/population numbers. The phenotype best adapted to the new condition increase in number and the least well adapted die.
  10. When does directional selection usually occur?
    It occurs when there is a change in the environment
  11. What is disruptive selection?
    It is where selection pressures favour extremes of the phenotype.
  12. When does disruptive selection usually occur?
    It is very rare but can occur when a variety of selection pressures operate within one environment
  13. What is polymorphism?
    The form of selection that promotes the coexistence of more than one phenotype. It plays an important role in speciation.
  14. What is gene flow?
    it is the movement of alleles from one population to another or the interchange of alleles within and between species. It only occurs as long as members of the population are able to interbreed and is considered to be the same gene pool with free gene flow between organisms.
  15. What is a species according to the biological species concept?
    A group of individuals that actually or potentially interbreed in nature but not with other species. A species can be considered the biggest gene pool possible under natural conditions.
  16. What are the limitations of the biological species concept?
    It cannot account for asexually reproducing organisms

    It cannot clearly define species when barriers to reproduction are incomplete (eg. formation of hybrids)
Card Set
Evolution and Natural Selection
Evolution and Natural Selection