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