Darwin's 4 Postulates

Fernando Llovera

1. Individual organisms within a population vary in the traits they possess

About this postulate

This postulate is basically saying that all organisms within a species are different, since they possess different traits that make each and every one of them unique. For example, within the human species, all human beings will possess different physical characteristics. We won't all be tall or short, or we won't all have blue or black eyes. There are variations, differences, among members of a species. All living species possess different traits, and that's what makes us all different. There are a wide variety of traits that each individual may possess, and it is more than evident that this postulate applies to the real world.

2. The heritable genetic variation of individuals in a species due to sexual reproduction and mutation

About this postulate

Some of the trait differences are heritable, meaning that some of the traits that an organism possesses are passed on to different generations of offspring. As an example, tall parents usually tend to have tall children (although it isn't always the case), or vice versa. In an extremely interactive and fun game we played my Biology class, I learned about how species had dominant and recessive traits, which were passed from generation to generation. For example, there were a couple of mutations for the bunnies in the game, one of which was having long and short teeth. It was clear that bunnies with long teeth survived with much more ease, and this mutation was passed from generation to generation. This game was a perfect example of how a species' dominant heritable traits are indeed passed on, and it is in agreement with Darwin's 2nd postulate.

3. In each generation, more offspring are produced than can possibly survive

About this postulate

Hundreds of species are born each week, and it is true that species do reproduce and get bigger in size. However, there are many causes that can instigate death, and among those are starvation, disease, and predation. There is simply no way that a certain environment is able to withstand so many individuals, and since some are more able to cope with external factors, some survive and others die. It is an inevitable cycle that all species are subject to. In the picture to your right, we can see some of the eggs hatched by fish, and these are just a small fraction of the total. There is no way there's enough space available for all fish to survive, and that's just the way it is. Organisms are born with different traits and adaptations, and the truth is that there's no way all individual organisms survive through the harsh conditions a certain environment presents, which brings me to my next point and the last of Darwin's four postulates.

4. Individuals with certain heritable traits are more likely to survive and reproduce (Natural Selection)

About this postulate

To better explain the concept of Natural Selection, Darwin mentioned how "successful individuals" are those who are more fit and able to cope with the different external factors that may limit their growth and threaten their survival. If a certain organism possesses a certain trait that may help itself reproduce or survive with greater ease, then this organism is much more likely to reproduce and survive in the short and long term. For example, a faster cheetah is much more likely to survive and thrive in a certain environment than a slower cheetah, since the traits it possesses make it easier for the cheetah to hunt and acquire food. Or, in another example, rabbits that have the ability to camouflage and change its skin color depending on the seasons are much more able to cope with the external difficulties of predation, and therefore is more likely to survive than a rabbit who doesn't camouflage. All of this relates back to Natural Selection, and it proves the point Darwin was trying to make: that individuals with certain heritable traits are more likely to survive and reproduce.

APA Bibliography

Buffalo State. (2015, March 26). Chapter 3. Darwinian Natural Selection. Retrieved April 6, 2016, from http://faculty.buffalostate.edu/penaloj/bio405/outline3.html


Freeman, S., Allison, L., Black, M., Podgorski, G., Quillin, K., Monroe, J., & Taylor, E. (n.d.). Biological Science (5th ed.). Pearson.


Nature. (Photographer). (2003). Butterfly Species different, July 2001. Retrieved from http://www.nature.com/scitable/content/ne0000/ne0000/ne0000/ne0000/4308521/10.1038_nrg818-box1_large_2.jpg


New England Complex Systems Institute. (2013, January 2). How Does Evolution Occur? Retrieved April 6, 2016, from http://necsi.edu/projects/evolution/evolution/5parts/evolution_5parts.html


Wallart. (Photographer). White rabbit in snow. Retrieved from http://cdn.pcwallart.com/images/white-rabbit-in-snow-wallpaper-2.jpg