Darwin's Four Postulates
Natural selection is a result from the 4 postulates...
The Four Postulates
The main consequence of the four postulates that Darwin presents, is that the characteristics of populations will change slightly with each succeeding generation. With the four postulates also comes the Darwinian evolution, which is the theory that gradual change in populations will occur over time.
Darwin's four postulates are:
- Variation: there is variety among species.
- Inheritance: variation is heritable; offspring resemble parents.
- Differential Survival: overproduction of young.
- Extinction: survival and reproduction is not random; survival of the fittest.
Darwin referred to individuals that make up a greater percentage of the population in the next generation as the fittest. Darwinian fitness is the ability of an individual to survive and reproduce in its environment. It is a trait or characteristic of an organism that increases its fitness relative to individuals without it.
The four postulates and their logical consequence can be verified independently. The ability of individuals to survive and reproduce will lead to a gradual change in the population with favorable traits accumulating over time and may result in the formation of a new species.
Natural selection is a result from these four postulates... Natural selection refers to the process whereby organisms better adapted to their environment tend too survive and reproduce. This is believed to be the main process that brings about evolution and it was first exposed by Darwin.
"It is not the strongest of the species that survive, nor the most intelligent, but the one most responsive to change." Charles Darwin
Is variation heritable (Postulate 2)? The Grants estimated heritability estimated the similarity in the bill length between pairs of relatives and there appeared to be strong correlation.
Is there an excess of offspring so that only some can survive and reproduce (Postulate 3)? In 1977 there was a drought and only the finches who could live in drought survived and continued to reproduce; the others died.
Is survival and reproduction nonrandom (Postulate 4)? In the drought, only those with the deepest beaks survived because these were the only who could survive in the given environment.
Below is a video embedded from YouTube explaining in further details Darwin's four postulates.
Bioserve Ortegaj. Evolution (PCB 4674). (2009). Retrieved April 05, 2016, from http://bioserv.fiu.edu/ortegaj/CHAPTER3_DARWIN_SPR.pdf
Buffalo State Faculty. Ch 3. Darwinian Natural Selection. (2015). Retrieved April 05, 2016, from http://faculty.buffalostate.edu/penaloj/bio405/outline3.html
B. (2011). 12.2.2 Darwin's Principles of Natural Selection. Retrieved April 05, 2016, from https://www.youtube.com/watch?v=jQf1owiEje8
Evansville Faculty. Natural Selection. (2015). Retrieved April 05, 2016, from http://faculty.evansville.edu/de3/b32003/lecture summaries/selection.pdf