Natural SelectionNatural 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
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 FirstProblem 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.
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 ProblemThe 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
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 ProblemThe 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.
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.
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’
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 Work?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
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 Work?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
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’
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 selectionDifferent 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
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 selectionDifferent kinds of selection Stabilizing or Normalizing selection
The middle is selected for
Many examples here Symmetry Two eyes
Stabilizing or Normalizing selection
The middle is selected for
Many examples here Symmetry Two eyes
Different kinds of selectionDifferent 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’
Disruptive selection
Extremes are selected for
Might be where the two sexes come from
Trait was probably gamete sized
Two ‘mating types’
Other Evolutionary TheoriesOther 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’
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. NO WRONG INCORRECT, THANKS FOR PLAYING
The idea of an ‘evolutionary ladder’ fits in here
It is wrong too……
Orthogenesis There is some plan to evolution. NO WRONG INCORRECT, THANKS FOR PLAYING
The idea of an ‘evolutionary ladder’ fits in here
It is wrong too……
Still another silly ideaStill 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
NOT A SCIENTIFIC THEORY
Intelligent Design Just Creationism with a fancy name
God does not belong in a science class, any more than experiments belong in church
NOT A SCIENTIFIC THEORY