02/06/06

From Biol301

Notes from 02/06/06

The 4 Tenets of Darwinian Theory

1. More offspring bore than can survive on resources
2. Individual offspring vary every which way
3. Variation is heritable
4. Because of the first, there is competition and only the fittest survive

• Mayfly example
  • Those who minimize drag get killed less and live longer to produce more
  • This is called directional selection

Other stuff

• Evolution is not about the development of an organism
  • It is not aobut a higher or lower organism ( this is Aristotle, Linnaeus, and Lamarck)
  • Darwin does not assert the idea that we came from apes
  • Darwin says there is no necessry increase in complexity
    • example: cavefish & moles lost their eyes; barnacles are basically shrip on their backs
    • neogony = retention of juvenile traits into adulthood
• -The leafy seadragon is a fish that has evolved to look like a seaweed in order to avoid being eaten by predators.-
  • The ancestors of the leafy seadragon that looked more like seaweed contributed more genes to the next generation.
• Natural selection does not have a design to fit things into as would a designer. So the flatfish is a good example of evidence of natural selection being better than designer theory.
• "Blind Watchmaker" argues that fudged design supports there not being a designer.
• Most selective pressures are between two or three species
  • Water is static but other species are not.
• Directional selection pushes the entire population toward one solution to a challenge
• Stabilizing selection keeps wildtype most popular, selects agains variants
• Disruptive selection splits a population with more than one solution to a single challenge
• Frequency dependent selection: a phenotype's selective advantage is related to its frequency in the population.
  • Often ends in waves, sin curves, etc.
  • Perhaps new colors?
• Argument that says 2^nd^ law of thermodynamics forbids evolution" is wrong in two ways

1. 2^nd^ law is about closed systems; organisms aren't closed systems
2. assumes evolution requires increase in complexity, however, it does not

• The word evolution comes from the Latin word _evolvere_ which means to "unroll". Darwin didn't use it because it had been connected to an idea of increasing complexity by developmental biologists.