Darwin's Four Postulates

Mauricio Guzman

First Postulate: Variation

The first postulate that Darwin wrote about is that there is variation within a species. Variation occurs within a species because evolution needs variation to occur. Without variation, no evolution will occur because the phenotypes would always be the same. Charles Darwin wrote about this postulate when he looked at the finches in the Galapagos Islands, observing that different traits and sizes of the beaks of the finches changed in size depending on the island that they were in. These beaks form different types of finches, evolved from one type of finch but because of the scarcity of food and different availability in food, forcing evolution to occur so these finches would survive.
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Second Postulate: Inheritance

The second variation is inheritance, which means that all offsprings from different species look like their creators or their parents. This postulate was the one that confused or angered Darwin the most because he had no knowledge of the dominant and recessive traits of the DNA and the offsprings so he could not come to a certain conclusion. We can say that inheritance maintains a species alive because of inheritance would not exist, all species would look very different, meaning that for evolution to occur, there has to be consistency in traits and phenotypes so they can be naturally changed.
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Third Postulate: Differential Survival

Differential survival states that from a generation that was born, some of them have stronger traits than others which help them survive longer and reproduce. The selection of who lives longer than others and who gets to reproduce is not random, it depends on the stronger traits that that specific progeny has compared to others. If a generation of a certain type of animal turns out to have 3 unhealthy offsprings and 10 healthy offsprings, the strongest, or the healthy ones should survive because they have stronger traits and a more healthy body to get them through rough situations and eventually reproduce and produce upcoming generations, which will also have strong and weak offsprings.
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Fourth Postulate: Survival of the Fittest

This fourth postulate means that in an ecosystem, the strongest and most "fit" animals are the ones who survive longer and reproduce much more. Survival of the fittest is crucial in the study of evolution because survival of the fittest causes the weaker organisms to evolve and protect themselves form the stronger, bigger organisms. For example, some reptiles like lizards and some snakes have evolved to grow another tail when theirs has been eaten off. The tail serves as a defensive mechanism so predators think they have eaten the lizard while the lizard is really escaping form danger. While the lizard may not be the "fittest" animal in an ecosystem, the disadvantage of being a small animal has lead to evolutionary traits like the removable tail.
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Works Cited

Benson, A. (Nd) Survival of the fittest. Encyclopaedia Britannica, Inc. Retrieved: Apr 4, 2016.


Contributors, K. (Feb 6, 2016) Natural selection: Darwin’s four postulates. wordpress.com. Retrieved Apr 4, 2016.


Pujari, S. (Nd) 4 Main Theories of Evolution (explained with diagram and tables). YourArticleLibrary. Retrieved: Apr 4, 2016.


Thompson, E. (Jul 26, 2014) DARWIN’S POSTULATES & FIREMOUTH CICHLIDS. wordpress.com. Retrieved: Apr 4, 2016.