Given the assumptions of the theory of natural selection and the diverse population of species around the globe, changes could occur to every member of a given group. Take for example, the Rattus norvegicus or the rat to illustrate the theory.
Rats can travel to different parts of the world by variety of means and they are known to be associated with humans (Maust, 2002). Say, from the cities, they went to the hot place of African bushes and demonstrate their ability to rapidly increase in number. With the change in environment, resources, human and animal actions, the rats become adaptive with the situation, having their chance to survive and reproduce successfully while others do not.
Postulate 4 states that the “fate of individuals is not determined by luck. Instead, an individual’s likelihood of survival and reproduction depends on its characteristics. Individuals with advantageous traits survive longest and leave the most offspring…” The ‘survival of the fittest’ is determined by the individual’s ability to adapt above all other members of the population.
With the change of environmental setting and resource scarcity, which are mostly given by nature, members learn to survive in the place. By eating flesh of other animals, they develop leaner body and sharper teeth. Some other members prefer to eat plants since others can’t adjust to eating meat.
This causes diversity of species and change in traits. By looking at these possibilities, evolution of characteristics is likely to occur, and as different individuals tend to travel farther than anybody, they become acquainted with other species making them adapt to living and acquisition of unique genetic traits that are passed from parents to offspring by the most adaptive and fittest individual surpassing other generations of species that could constitute a new population through time.
Darwin, C. 1958. On the Origin of Species by Means of Natural Selection, or, the Preservation of Favoured Races in the Struggle for Life. London: J. Murray.
Maust, Maria. (2002). Introduced species summary project: Norway rat (Rattus norvegicus). Retrieved October 28, 2008, from http://www.columbia.edu/itc/cerc/danoff-burg/invasion_bio/inv_spp_summ/Rattus_norvegicus.html