Darwins 4 Postulates

Mauricio Torres

Why do species evolve?

Species evolve to become fitter to their environment and reproduce more effectively. Not all mutations are beneficial, but those that are beneficial are much more likely to get passed on. This is because it might mean that a mutation helped the organism survive and reproduce so the mutation will end up in more offsprings.


Individuals within a population are variable.

Offsprings are of the same parents are not identical, even if some seem to be identical we now know they are different because we can compare DNA. Sexually reproducing organisms get genes from 2 different parents and this creates variation. So organisms of the same species may still have different colours, shapes, etc.

Variations are hereditable.

Some differences in traits are passed on from parents to their offsprings. Parents with long tails may produce an offspring that also carries that trait. Traits may change because of mutations but they are also passed down to later generations.

Differential Survival

Individuals vary in survival and reproductive success.

Not all organisms are equally likely of surviving and reproducing.


Survival and reproduction are NOT random.

Some variations between organisms make them more or less likely to survive and reproduce. This is not random because some traits are responsible for an organisms survival or reproductive success. Organisms that are not well enough suited to their environment will go extinct because they won't be able to adapt.


Charlesworth, B., and D. Charlesworth. "Darwin And Genetics". Genetics 183.3 (2009): 757-766. Web. 6 Apr. 2016.


M. (n.d.). Phenotypic Variation Explained. Retrieved April 04, 2016, from http://nov79.com/mr/exph.html

Phillip, M. (1997). “Evolutionary Genetics”. Population and Evolutionary Genetics. North Dakota State University. Accessed on 2016, April 4. Retrieved from https://www.ndsu.edu/pubweb/~mcclean/plsc431/popgen/popgen4.htm