Heritable traits that enable particular organisms to survive and reproduce successfully tend to become common in a population for generations to come. This happens in the process of natural selection: a process responsible for evolution. In natural selection, nature selects the ‘most’ fit organisms allowing them to reproduce successfully while eliminating the unfit organisms. As a result, the traits of these fit organisms become common over time in a given population while the traits of the unfit organism diminish in that particular population with time.
Take for instance the dark and white peppered moth (Biston betularia). These months are in the same population, that is, an assembly of interbreeding organisms in a given species (Menton, 1991). Offsprings are not identical to their parents but are similar. This implies that every set of offspring has a given range of genetic variations. Since these offsprings interbreed, the successive offsprings have characteristics that their parents do not have (Harding, 1999). The trait under study here is color. White and dark moths came to being under these genetic variations. The population of these moths will have both dark and white moths at the starting point.
After a long time, changes in the environment like the effects of industrial evolution catch up with this population exposing it to selective pressures. Selective pressure in this context refers to any cause that minimizes successful reproduction in some species in a given population. Industrial soot from industries covers trees and this offers the dark moths camouflage that enables them to evade predation from birds. The selective pressure in this population is predation from birds. Birds can only see and eat the white moths due to lack of camouflage. Consequently, the dark moths survive predation and increase in number as the white moths diminish under predation. These occurrences lead to differential reproduction in this population with dark moths having a great chance of successful reproduction as predation reduces the successful reproduction chances of white moths.
It is important to note at this point that, in natural selection and evolution, individuals do not change instead it is the environment that changes.
After several years, the surviving dark moths will have more baby moths compared to the white moths. This is because the dark color (trait) has a genetic orientation. With repeated cycles of these occurrences, this population portrays the effects of natural selection. Due to its advantage, dark coloration becomes more common because it allows dark moths to have more offspring. The result may be a population with dark moths without any white moths. This is the process of natural selection.
Evolution occurs through natural selection in presence of the following: variation, differential reproduction, and inheritance of genetic materials (‘Understanding Evolution’, 2009). In the beginning, the moths had color variations. Thereafter, the population faced selective pressures from predation by birds. The white moths could not survive to reproduce successfully due to predation. The dark moths reproduced successfully due to lack of predation. This is the differential reproduction part of natural selection. Dark baby beetles inherited dark colors from their parents increasing their chances of survival.
Nature selected the fit moths that could stand predation and reproduce successfully. In this case, the industrial revolution that occurred in the environment caused dark moths to survive predation as white moths became extinct from the population.
Reference List
Harding, K. (1999). Evolution for Beginners. Web.
Menton, D. (1991). The Peppered Moth Shows Evolution in Action. Web.
‘Understanding Evolution’. (2009). Natural Selection: Evolution 101. Web.