Evolution - Exam Study

• Speciation


  The formation of a new species (macro evolution)
• Species


  Members of a population that have the ability to breed with each other under natural conditions, producing offspring that can reproduce
• Prezygotic isolating mechanisms


  • Ecological: occupy different habitats
  • Temporal: breed at different times
  • Behavioural: give wrong mating signals
  • Mechanical: parts wont fit
  • Gametic: gametes won't join
• Postzygotic isolating mechanisms


  • Zygotic mortality: zygote dies
  • Hybrid invariability: it doesn't live long
  • Hybrid infertility: it is infertile
• Modes of speciation


  • Allopatric Speciation: speciation as a result of geographical isolation
  • Sympatric Speciation: evolution of populations within the same geographical area into separate species
• Most common mode of speciation is from geographical isolation
• Darwin's theory of evolution by natural selection explains how species change over time through the accumulation of small genetic changes (mutations) and selective pressures from environmental factors.
• Divergent Ecolution: 2+ species evolve increasingly different traits
• Convergent ecolution: 2 or more species bome increasingly similar in phenotype in response to selection pressures
• Adaptive Radiation: divergent evolution occuring so fast that 1 species gives rise to 3+ species
• Coevolution: 2 species that are totally dependant on each other for survival, and therefore evolve together
• homologous features: same origin, different functions now
• analogous features: similar in funciton but not in origin
• vestigial features: non-functioning structures homologous to functioning structures in related species.
• Darwin's postulates


  • Many more are born in each generation than will survive and reproduce
  • There is variation among individuals
  • Individuals with certain characteristics have a better chance of surviving and reproducing than individuals with other characteristics
  • At least some characteristics resulting in differential reproduction are inheritable
  • Enormous spans of time were available for slow change
• Darwin sailed on the HMS Beagle along the South American coast


  1831
• Darwin's role


  Captain's mate, became the naturalist
• Darwin published 'On the Origin of Species by Means of Natural Selection'
• Lamarck


  Organisms respond to felt needs
• Characteristics acquired by an individual during its lifetime


  Are transmitted to their offspring
• Characteristics of each generation


  Would be by all that happened to the members of the preceding generation