Darwin's Postulates

By: Paola Rhon

4 Postulates

1. There is a lot of variety within species

2. Offspring looks like their parents, gets traits from them

3. External conditions can affect survival

4. Some traits are not suited for survival and will lead species to die out


Variation is any difference between cells, an individual organism or any species that is caused either by environmental factors or phenotypic variation. Variation is typically shown in physical appearance. Eye color, body form and disease resistance are all types of variation.

Ex. The rock in the image to the right show variation since they have evolved to having different colors.

Another example of variation is the different breeds of dogs since they are all the same species but throughout time different breeds have been created.


Inheritance is the action of getting traits genetically transmitted from parents to offspring. This is the process in which a child gets a characteristic of its parent cells. Through inheritance variations exist and once they accumulate it causes species to evolve.

Ex. The picture to the right shows an example of inheritance. The offspring inherited both the brown pigment and the white pigment which made her a color in between.

Differential Survival

Differential of survival is an essential part o Charles Darwin's theory of natural selection. It talks about food production always increasing and population increasing exponentially. Since more humans are born each generation that can survive, the excess need to be killed by famine or disease. Limited quantities of space and resources lead to struggle for survival so everyone is competing and a result only the most fit can survive.


Over time, species have become extinct for various reasons. Some species die out because they no longer have the resources they need. Others because they are not the fittest species to survive. This connects with the rest of the postulates because this is eventually what ends up happening to organism if they are not apt for natural selection. One of the species that has recently been extinct is the black rhino. It became extinct due to human activity. The loss of this species makes other species evolve into not needing the rhino in their life.