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.

"It is not the strongest of the species that survive, nor the most intelligent, but the one most responsive to change." Charles Darwin

Testing Postulates

Are populations variable (Postulate 1)? The Grants measured a number of morphological variables from populations of Geospiza fortis, including beak width depth and length; these data were plotted and the data formed a bell-shaped curve, proving reliability.

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.

12.2.2 Darwin's Principles of Natural Selection

Bibliography

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