Chap 21

• 3 conditions of natural selection

  1. Phenotypic variation must exist in the population.
  2. This variation must lead to differences among individuals in lifetime reproductive success.
  3. Phenotypic variation among individuals must be genetically transmissible to the next
• Industrial melanism Phenomenon in which darker individuals come to predominate over lighter ones.
• Today geologists determine the absolute age of rocks using isotopic dating.
• Homologous structures - Different functions, same ancestor structure (human hands, horse hooves)
• Imperfections – some organisms do not appear perfectly adapted
• Vestigial structures have no apparent function, but resemble structures ancestors possessed (appendix)
• Pseudogenes Fossil gene - traces of previously functioning genes
• Biogeography Study is the geographic distribution of species.
• Convergent evolution- Similar forms having evolved in different, isolated areas because of similar selective pressures in similar environments
• Darwin Critics were

  1. Evolution is not solidly demonstrated
  2. There are no fossil intermediates.
  3. The intelligent design argument
  4. Evolution violates the Second Law of Thermodynamics
  5. Proteins are too improbable
  6. Natural selection does not imply evolution
  7. The irreducible complexity argument
• Analogous structures - same function different origin (fins for fish and penguins)
• Domestication Human-imposed selection has produced a variety of cats, dogs, pigeons, and others Some breeds developed for specific purposes (dachshunds for badger pursuit, greyhounds for running ability)
• Fossil Evidence of Evolution

  • Fossils are the preserved remains of once-living organisms Rock fossils are created when three events occur
  • Organism buried in sediment.
  • Calcium in bone or other hard tissue mineralizes.
  • Surrounding sediment hardens to form rock. Process of fossilization is rare event
• Oldest known bird fossil is the Archaeopteryx

  • Clearly intermediate between bird and dinosaur.
  • Possesses some ancestral traits of reptiles and some traits of present day birds
• Tiktaalik: a species that bridged the gap between fish and the first amphibian.
• Convergent evolution - Similar forms having evolved in different, isolated areas because of similar selective pressures in similar environments
• Biogeographical studies Darwin concluded:

  • Many islands have never been connected to the mainland.
  • Species arrive on islands by dispersing across the water. •
  • Dispersal from nearby areas is more likely than distant sources. •
  • Species that can fly, float or swim are more likely to inhabit islands.
  • Colonizers often evolve into many species
• Pseudogenes - Fossil genes; traces of previously functioning genes When a trait disappears, gene does not just vanish from the genome
• Darwin noted on his voyage that z Islands are often missing plants and animals common on continents. • Can live there if introduced. • Species present on islands often diverged from continental relatives. • Occupy niches used by other species on continents. • Island species usually are more closely related to species on nearby continents.
• Darwin noted on his voyage that

  • Islands are often missing plants and animals common on continents.
  • Can live there if introduced.
  • Species present on islands often diverged from continental relatives.
  • Occupy niches used by other species on continents.
  • Island species usually are more closely related to species on nearby continents.