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Natural Selection. Or, how did we get here…. Natural Selection. The Theory of Natural Selection is so simple that anyone can misunderstand it…. ( Anonymous ) Charles Darwin (1809-1882) saw three problems in need of a solution. Darwin was not the only one to see these problems BTW

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Natural Selection

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natural selection

Natural Selection

Or, how did we get here….

natural selection1
Natural Selection
  • The Theory of Natural Selection is so simple that anyone can misunderstand it…. (Anonymous)
  • Charles Darwin (1809-1882) saw three problems in need of a solution.
    • Darwin was not the only one to see these problems BTW
    • Other ‘Naturalists’ were struggling with the same issues
problem the first
Problem the First
  • There is change over time in the flora and fauna of the Earth
    • What we would commonly call ‘evolution’ today
    • The fossil record showed this to be pretty clear, even to people in the mid 1800s
    • This was not controversial in Darwin’s time, and is not now.
the second problem
The Second Problem
  • There is a taxonomic relationship among living things
    • People were big into classifying stuff
    • It was pretty obvious that there was a relationship between different species
      • Different birds, different grasses, different cats etc
the third problem
The Third Problem
  • Adaptation
    • Different kinds of teeth for different animals, say carnivore ripping teeth and herbivore grinding teeth
    • Different tissues within species
      • Heart vs. eye etc.
the solution
The Solution!
  • Natural Selection provides a mechanistic account of how these things occurred and shows how they are intimately related.
  • It is one of those ‘oh man is that ever easy, why didn’t I think of that?’ type things.
how s it work
How’s it work?
  • There is competition among living things
    • More are born or hatched or whatever, than survive and reproduce
  • Reproduction occurs with variation
    • This variation is heritable
    • Remember, there was NO genetics back then, Chuck knew, he just knew….
    • Realized that is wasn’t ‘blending’
how s it work1
How’s it Work?
  • Selection Determines which individuals enter the adult breeding population
    • This selection is done by the environment
    • Those which are best suited reproduce
    • They pass these well suited characteristics on to their young
how s it work2
How’s it Work?
  • REPRODUCTION is the key, not merely survival
  • If you survive to be 128 but have no kids, you are not doing as well as I am
  • I have reproduced…
  • Assuming the traits that made me successful will help them then I amore fit NOW than the 127 year old guy
this lecture keeps evolving
This lecture keeps evolving…..
  • Survival of the Fittest (which Chucky D NEVER said) means those who have the most offspring that reproduce
  • So, the answer to the trilogy of problems is:
  • ‘Descent with modification from a common ancestor, NOT random modification, but, modification shaped by natural selection’
different types of selection
Different types of selection
  • Directional Selection
  • What most of us think about when we think about selection
  • An extreme value is selected for
  • Human brain size is a nice example
different kinds of selection
Different kinds of selection
  • Stabilizing or Normalizing selection
  • The middle is selected for
  • Many examples here
    • Symmetry
    • Two eyes
different kinds of selection1
Different kinds of selection
  • Disruptive selection
  • Extremes are selected for
  • Might be where the two sexes come from
  • Trait was probably gamete sized
  • Two ‘mating types’
other evolutionary theories
Other Evolutionary Theories
  • Lamarckism
    • Inheritance of acquired characteristics
      • E.g., giraffes really wanted leaves, so they stretched their necks and…..
      • Sounds crazy, but a lot of people think this way
      • ‘We will all have giant heads and tiny bodies someday’
      • ‘Cave swelling fish don’t use their eyes so they disappear’
      • ‘We don’t use our appendix so it is disappearing’
silly incorrect evolutionary theories and ideas
Silly incorrect evolutionary theories and ideas
  • Orthogenesis
    • There is some plan to evolution.
    • The idea of an ‘evolutionary ladder’ fits in here
    • It is wrong too……
still another silly idea
Still another silly idea
  • Intelligent Design
  • Just Creationism with a fancy name
  • God does not belong in a science class, any more than experiments belong in church