Darwin's Postulates

Fabiana Garza


Darwin's greatest achievement was discovering the truth about Natural Selection, which is the mechanism of evolution. The way living organisms can survive and reproduce in order to create more genetic variation and a change in the population is due to these four postulates. This led some specific species not only into changing within each generation, but in time, to actually begin forming other sorts of species never before seen.

Postulate #1- VARIATION

The first postulate indicates that within each species, there is variation among individuals in order for natural selection to be able to act upon resulting in evolution. This means that each individual differs from each other, and this is why every single organism is different from one another. In the image below, you can see that even though these are all bird beaks, they don't look at all the same, this is because of variation among species.
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Postulate #2- INHERITANCE

The second postulate states that some of the variation created among the same species are inheritable which means that traits were passed down from past generations, therefore causing the offspring to have a resemblance of their parents. This can vary from skin, eye or hair color and other physical characteristics. Or they can also be diseases that you get from your descendants and have to live with your whole life. This is called inheritance.
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The third postulate indicates that some living organisms are more fitted to survive than others, this is not chosen randomly. These individuals with the more desirable and better suited traits are the ones that increase and live on to later on reproduce. This is why generations later these organisms are more convenient to their environment and surroundings.
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Postulate #4- EXTINCTION

The fourth and last postulate states that the way species survive and reproduce is because of Natural Selection, it is not random. The traits that are not well suited for the organism to survive in their specific environment, will start to die, eventually leading them to extinction. The ones with the most favorable traits increase in population, and these traits are passed down through generations resulting in evolutionary change.
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Road, T. (n.d.). Introduction to Ecological Genetics. Retrieved April 07, 2016.