Four postulates

Sebastian Domene

Postulate 1: potential increase in number

The first postulate consists of the abilities of species to grow as a population and endure as a whole. This postulate essentially consists in the belief that if a species is to become an easy prey, then an adaption of a larger birth rate will happen. We see this in a number of different species, javelina and rabbits having numerous pregnancies a year in order to keep the population increasing because of the fact that there is a high possibility of being killed by another animal. This also connects to the fact that variations happen in order to keep the birth rate bigger than the death rate or at least diminish the impact of the death rate.
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Postulate 2: variations are heritable

Heritable variation is what allows genes to get passed down through generations in order to change certain aspects of a species. More often they are variations for positive motives since natural selection does its part in eradicating those who are not essentially fit for certain environments. It allows the mutations to be filtered through the generations that passed and it is the fact that the parents can pass it down to a baby.
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Postulate 3: Struggle for survival, and necessarily if the others are satisfied

This postulate refers to the certain competition that there is for survival between animals from the same species. Say for example that a dog just had babies and all of them want to be fed at the same time. The struggle for survival would be the fighting for the mother's milk. Another example could be a battle for food when a pack of lions have just killed a buffalo. This connects very much to the postulate number 4 of survival of the fittest.
puppies fighting for milk

Postulate 4: Survival of the fittest

This postulate is, in my opinion, the most important one by far. It connects and means that those who are eliminated (or killed) in nature are the unfit. In the example that I gave about the lion, both the buffalo and a weak lioness could be the unfit in this situation. This connects to the idea that all species are constantly getting better, us humans included in this with the fact that we have evolved into smarter creatures. Charles Darwin said that "survival of the fittest also implies multiplication of the fittest because of the struggle for survival". All of the three are connected in natural selection and are the main pillars of the thinking of Darwin.
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APA sources

Darwin's Four Postulates. (2016) Retrieved 8 April 2016, from

What is heritable variation important for?. (2016). Biology Q&As. Retrieved 8 April 2016, from

Ch 3. Darwinian Natural Selection. (2016) Retrieved 8 April 2016, from