Darwin's Four Postulates

Isabella S. Vela

Potential Increase in Species Numbers and Genetic Variation due to Sexual Reproduction

Species naturally have increases or decreases in population. There are some species that have the potential to increase more than others. For examples, grey squirrels in the UK are increasing in number. This is proving to be an issue because they are an invasive species and the increase in grey squirrels is leading to a decline in red squirrels.

Offspring is genetically unique. It gets traits from both the mother and the father which makes the offspring different from the parents and therefore makes the species more diverse. For example, a child that has a mother with dark hair and green eyes and a father with light hair and blue eyes might have dark hair and blue eyes, light hair and green eyes there are many different combinations.

Darwin's Four Postulates

Competition for Limited Resources and Proliferation of Organisms

When a species gets overcrowded the resources they need to survive can become limited and species have to compete with each other in order to get the resources they need. In order for this not to happen the species the species evolve. For example, different species of finches can coexist because because they vary in some small way like beak size, and this allows them to specialize on one resource.

The species also naturally selects the best example of the species to reproduce because they are old enough or healthy enough to survive and mate. The weak organisms in the species are either killed when they are younger or they cannot attract a mate. For example, birds of paradise dance to attract the female and the male bowerbird builds a huge structure and decorates it while giving the female gifts. The dancing is to show the female that the bird is healthy and strong. The gift-giving is to prove himself as a provider. The birds want to demonstrate their supremacy over other members of their species in order to attract a mate and that is why they are the ones that breed and have stronger children.


Competition. (n.d.). Retrieved April 04, 2016, from http://www.biologyreference.com/Ce-Co/Competition.html

Invasive species threat growing globally, experts warn. (2010). Retrieved April 04, 2016, from http://www.theguardian.com/environment/2010/jan/22/invasive-species-threat

Love in the Animal Kingdom. (n.d.). Retrieved April 04, 2016, from http://www.planet-science.com/categories/under-11s/our-world/2011/02/love-in-the-animal-kingdom.aspx

Superb bird of paradise part 2 | Publish with Glogster! (n.d.). Retrieved April 04, 2016, from http://www.glogster.com/17giferr/superb-bird-of-paradise-part-2/g-6lsr82i30td63t3ts2cvma0