Darwin's Postulates

Bio P.2 --- - --------------------------------- - --- mikelr

The Four Postulates

These are a combination of two sources, put together to make each postulate easier to understand and to fully cover it's meaning.

1. There is variation in individuals within a species or population that are due to genetics, and some are heritable.

2. Individuals in a population differ physically from one another, in many ways since variation ensures that individuals that are better suited to their environment will survive.

3. Individuals with the most favorable traits survive and reproduce more than do individuals with less favorable traits. These traits are passed on the next generation.

4. Individuals produce more offspring than the local resources can support.

Explanation of Postulate #1

In this picture we can see how different genes combine and re combine in different patterns to create many different looking bugs. The almost infinite possibilities for mixing of genes makes variation.
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Visual for Postulate #2

Assuming this is the same species of butterfly, we can see in the picture above that within the same population there is a bonanza of physical characteristics, in this case the design of these butterflies' wings. Some of these will be inherited by the offsprings just like it is likely for humans to have similar skin tone as their parents; some genes, however, wont be passed down and remain recessive.
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Postulate #3 Example

In the picture there are two moths on a tree, one is dark brown and the other is light brown. In this scenario, the trait that will define each moth's survival is their color, not wing shape or antennae length. We can see it is much easier to identify the dark brown month since the other moth blends in with the tree, so any predators such as birds will more likely eat the dark brown moth.
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Example of Postulate #4

Though there are 3 bears, only one is getting the salmon. A prospering species will reproduce without limitation to the point where the population is simply too big and the young or weakest wont get food. This might seem like the top of the spectrum where a species simply stops evolving, but in fact food is always the last line of evolution.


Freeman, S., & Herron, J. C. (2007). Evolutionary analysis (No. 575.8 FRE). Upper Saddle River, NJ: Pearson Prentice Hall.

Gayon, J. (2003). 10 From Darwin to today in evolutionary biology. The Cambridge Companion to Darwin, 240.

Huxley, J. S. (1938). Darwin's theory of sexual selection and the data subsumed by it, in the light of recent research. The American Naturalist,72(742), 416-433.

Kirkpatrick, M., Price, T., & Arnold, S. J. (1990). The Darwin-Fisher theory of sexual selection in monogamous birds. Evolution, 180-193.

Mayr, E. (1991). One long argument: Charles Darwin and the genesis of modern evolutionary thought (Vol. 2). Harvard University Press.