3 Types of Natural Selection
1. Directional Selection a. Favors those w/extreme variations in traits w/in a population b. breeding of the greyhound dog -bred for speed - selected those who ran the fastest - Egypt 3BC: used to hunt fastest game (fox, deer) http://images.google.com/images?um=1&hl=en&q=greyhound
c. Wolves from Minn migrate to N. Canada for food -thicker coats are more fit -better chance of passing traits on http://news.google.com/news?hl=en&q=wolves&um=1&ie=UTF-8&sa=X&oi=news_result&resnum=1&ct=title
2. Stabilizing Selection a. Favors the norm/average traits b. Siberian Husky bred for working in snow -medium dog w/ strong leg muscle -if heavier sink in snow -if lighter cannot pull sleds http://images.google.com/images?um=1&hl=en&q=siberian+husky+pulling+sleds
-small enough to hide from predators c. Mice survival -small enough to hide from predators -large enough to fight rats for food -medium size best http://www.wildaboutbritain.co.uk/files/mammals/Wood%20Mouse%20-%20Apodemus%20sylvaticus.jpg
a. Also favors the extreme traits b. Crabs live on shoreline 3. Disruptive Selection a. Also favors the extreme traits b. Crabs live on shoreline -brown blend in better in water -lighter blend in better on land -medium more easily spotted & picked off in predation http://www.the-islander.org.ac/oldsite/landcrabs.gif
http://upload.wikimedia.org/wikipedia/en/c/c6/Selection_Chart.PNG