Natural Selection is defined as "any consistent difference in fitness among phenotypically different classes of biological entities".
There are three general components of fitness: probability of survival to reproductive age, average number of offspring produced through female reproductive function (ex. eggs, seeds), or male reproductive function.
These areas of fitness refer to the whole group, not individual specie because the terms probablity and average are used.
Futuyma, F.J. (2009). Evolution. 2nd Ed. Chapter 11. Retrieved from http://ncse.com/files/pub/evolution/Evolution--Futuyma--chap11.pdf
10 examples of Natural Selection[]
Discovery Channel: 10 Examples of Natural Selection by Diana Bocco
http://dsc.discovery.com/tv-shows/curiosity/topics/10-examples-natural-selection.htm
What Not to Expect[]
Misconceptions & misguided inferences
Darwin stated in The Origin of Species, "natural seelction will not produce absolute perfection, nor do we always meet, as far as we can judge, with this high standard in nature" (Futuyma, 2009).
Natural selection is not goal oriented. There are two misconceptions here: organisms intentionally try to become a new specie and organisms intentionally try to change genetically. (Anderson, et al., 2002).
Anderson, D. L., Fisher, K. M., & Norman, G. J. (2002). Development and evaluation of the conceptual inventory of natural selection. Journal of research in science teaching, 39(10), 952-978.
Futuyma, F.J. (2009). Evolution. 2nd Ed. Chapter 11. Retrieved from http://ncse.com/files/pub/evolution/Evolution--Futuyma--chap11.pdf