Developing the theory of natural selection
&
What is natural selection?

Influences
 Hutton 1785 and Lyell 1833
 Geologic processes—slow, changes over time, old earth
 Malthus 1798
 Population Study—checks on population growth, limiting factors

 Alfred Wallace 1858
 Studies 1000’s of Beetles
 Sends letter to Darwinproposes a process by which organisms change over time

 Artificial Selection –nature manipulated by humans
 Examples – farmer breeds his best livestock
 Darwin artificially selected pigeons to test and demonstrate how his mechanism for evolution worked.
 Artificially in a short amount of time—nature could certainly do over millions of years
OTHER EXAMPLES???

 Darwin publishes book “On the Origin of Species” in 1859 and
scoops Wallace
 In it: he proposes a mechanism (process of how) for evolution

the mechanism
 Struggle for existence
 Competition for resources: food, living space, and mates
 Survival of the Fittest
 Better suited (most fit) survive and reproduce
 Pass on traits that are better adapted to environment
 Less suited (least fit) die out or reproduce less
 Genes become less common in gene pool

 Fitness: an organisms ability to survive and reproduce
 Adaptation: an inherited characteristic that increases an organism’s chance of survival
 Can be anatomical, structural, physiological, behavioral
SO…adaptations enable higher fitness!
http://www.pbs.org/wgbh/evolution/library/01/1/l_011_03.html
OR http://www.youtube.com/watch?v=KzDGs5WAuDE

Summary of Darwin’s Theory of Evolution
 Individual organisms differ
 Some of this variation is heritable
 Organisms produce more offspring than can survive
 Many that do survive do not reproduce
 More organisms are produced than can survive
 Organisms must compete for limited resources
 Each unique organism has unique advantages and disadvantages in the struggle for existence
 Process of natural selection causes species or population to change over time
 Species alive today are descended with modification from ancestral species
 Unites all organisms on Earth into a single tree of life

Who’s theory is it?
A. B.