Darwin

• Charles Darwin

  Background

  • 1809-1882
  • on board the beagle (ship) from 1831-1836
  • on the boat he was known as the naturalist on the boat
  • in charge of collecting and recording samples (recording diversity)
  • made observations about geology + fossils
  • on the beagle he read books of those before him (like lyll, lamarck)
• Charles Darwin

  Background cont. - after voyage

  • well-known naturalist
  • he published books about his trips
  • obtained evidence for evolution AND developed important mechanism of biology
  • this is the * theory of natural selection*
• Charles Darwin

  Background

  • in 1858, he recieves manuscript from alfred russell wallace
  • ARW was a naturalist with the same theory of natural selection
  • Darwin + Wallace became BFFS, both present their findings to Linnaen society (scientific organization) (1858)
• After presentation

  • Darwin later publishes "On the Origin of Species by Natural Selection" in 1859
  • GAME CHANGER
• NS is the mechanism for evolution

  • Two major observations Darwin made:
  • 1st = VARIATION (world is full of variation)
  • every individual has a unique combo of traits
  • This variation causes every ind. to differ in their survival + reproduction
  • 2nd = OVERPRODUCTION
  • each spp has the capacity to produce more offspring than the env can support
• Two major inferences Darwin made:

  • Differential reproductive success (some reproduce alot, alittle etc.)
  • ind. with most favorable combo of characteristics is the most likely to do : survive and by extension reproduce
  • best adapted individual for an env produces most offspring
  • 2nd inference: unequal ability to survive + reproduce
  • accumulation of favorable traits in populations over generations
  • because of these 2 inferences, only those with most favorable traits reproduce, thus solving overproduction problem and explains variation.
• Natural Selection + Overproduction

  • Darwin based this idea off of Thomas Malthus work
  • studied human population growth + food population growth
  • proposed that human pop growth increases geometrically (1-2-4-8-16)
  • proposed food pop growth increases arithimetically (1-2-3-4-5)
  • based off this idea, natural resources are limited (think overproduction)
  • competition for these limited resources
• NS + Overproduction

  • Darwin believed more ind are in environment than can be supported
  • env cannot support every single person
  • not all individuals will survive and reproduce**
  • other limits (predation, diseases, abiotic factors like a storm)
  • STRUGGLE IS REAL
  • individuals have the capacity to reproduce but they won't because natural resources are limited, theres competition, might die, not everyone will survive + reproduce)
• Natural Selection

  • mechanism for evolution
  • better adapted individuals are more likely to survive and reproduce "survival of the fittest"
  • fitness is not about being strongest, it is the ability to have offspring
  • individual who reproduces the most is the fittest
  • As a result of better adaptations, pops change over time which is evolution (evolution occurs in pops)
  • freq of favorable traits will increase
  • freq of less favorable traits decrease
  • over long time (usually not in one gen), organisms become better adapted to their env