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Mechanisms of Evolution
How does this all work?
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.
The First Problem There is change over time in the flora and
fauna of the Earth
The Second Problem There is a taxonomic relationship among living
things
The Third Problem Adaptation
The Solution!Processes that drive evolution
1. Natural Selection
2. Gene Flow3. Sexual Selection4. Mutation
1. Natural Selection * Survival of the fittest.......
What is Fitness?Physical traits and behaviors
that enable organisms to survive
and reproduce in their environment
How’s it work? 1. OVERPRODUCTION
More are born or hatched or whatever, than survive and reproduce
How’s it work?2. VARIATION
This variation can be inheritedRemember, there was NO genetics back then, Chuck knew, he just knew….Realized that is wasn’t ‘blending
How’s it Work? 3. 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 it works? 4. Adaptation
* Over time – those traits that improve fitness will become more common.
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 my kids then I am more fit NOW than the 127 year old guy
This lecture keeps evolving….. 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’
The Origin of Species How did Darwin say it?
“As many more individuals of each species is born than can possibly survive, and consequently there is a frequently recurring struggle for existence, it follows that any being, if it vary in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance for survival and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form.”
One Year
Many Years…
1
2
2. Gene Flow
also called migration—is any movement of genes from
one population to another.
3. Sexual Selection
= random, heritable changes in DNA sequences that introduce new alleles into a gene pool
4. Mutation