Darwin's Four Postulates
The Origin of Species
In All Species There Is Heritable Variation
More Progeny Are Produced Than Can Survive
Their fur by itself allows them to survive in the cold weather, but they must also acquire other abilities, such as swimming and climbing, in order to do so.
They are exposed to one of the quickest predators alive. If they are quick enough, they will survive, but it is not uncommon for them to be ultimately preyed on.
Darwin believed that the organisms that exhibited the most "desirable" qualities would be those that ultimately mated and procreated.
Survival And Reproduction of Individuals Is Not Random
One of the many mechanisms that are seen throughout the Animal Kingdom.
These animals release toxic chemicals that are extremely harmful to anyone that touches them, humans included.
Snakes like this may seem defenceless and puny... but looks are truly deceiving.
More Fit Phenotypes Are Present In Subsequent Generations
Developed long necks to reach food and be on the lookout for predators.
Their fur makes them almost invisible in the snowy mountains where they are found.
They can jump from tree to tree by gliding, gracefully escaping from predators.
Buffalo State University. (n.d.). Chapter 3: Darwinian Natural Selection. Retrieved April 7, 2015, from:
Evansville University. (n.d.). Natural Selection. Retrieved April 7, 2015, from:
University of California Berkeley. (n.d.). Introduction to Ecological Genetics. Retrieved April 7, 2015, from:
University of Georgia. (n.d.). Natural Selection. Retrieved April 7, 2015, from:
University of Michigan. (2010, October 10). Evolution and Natural Selection. Retrieved April 7, 2015, from: