Darwin's Four Postulates

The Key to Evolution


Darwin's First postulate is Variation. Variation means that in a population of organisms, some traits such as the genotypes and phenotypes of the population can vary. These variations can be beneficial, detrimental or have no impact on the specific organism.

An example of this can be seen with the harlequin ladybirds shown in the picture below.

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Darwin's second postulate speaks of inheritance. This means that some of the traits in the population were passed on by the parents to their offspring. This can account for some part of the first postulate, variation.

An example of this postulate is parents passing on their eye colour to their children.

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Darwin's third postulate is one of survival. This means that not every member of the population will survive. This can be due to external factors such as natural disasters like a typhoon or a volcanic eruption. Regardless of how suited an organism is to an environment, it can always die suddenly.

An example of this is a tiger being hunted or poached by humans. Despite the tigers being the biggest member of their own food chain they can still die to external factors.

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Natural Selection

Darwin's fourth and final postulate consists of natural selection. This means that the organisms who will survive are the ones who are able to adapt. The one who are able to evolve to the point where they are suited to their environment. Only the fastest, strongest, more agile, or the ones who are the most capable to hide or fight off predators will live in an ecosystem.

An example of this is the giraffe who has very long necks to reach the fruit in the trees. They evolved this long neck because they could not obtain food otherwise.

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