The theory of natural selection simply suggests that only the strong survive as the weak ones are eliminated, because they cannot be able to compete competitively with the strong ones. The primary idea is that when change takes place only the organisms that are best adapted to the new conditions will survive, while those that fail to be favored by the new circumstances will eventually be eliminated naturally. This principle was proposed by Charles Darwin after making some observations on some bird’s population variations. Charles was able to notice that birds within the species had traits that varied slightly, and that different traits were better suited to some circumstances than others (Darwin, pp 109)
In his theory, Darwin suggested that over time, the birds that were better thrived better as compared to those birds which had traits that were not well suited for the conditions they were living in, and they eventually died out completely. The resulting bird’s population was composed entirely of those birds with the trait that was better suited for the conditions. With time Darwin reasoned that a species could alter its traits significantly making it look totally different from the original organism and this would then constitute evolution (Darwin, & Burrow, pp 64)
Theory of natural selection of birds and moths
Concerns have been raised about the real meaning of natural selection theory. It is not in doubt that the variations taking place in a species will make some of its members to be suited better in terms of handling diverse conditions. A good example is the popular story in Science books about moths. They inhabited cities during the period of industrial revolution and were faced with the challenge of living in highly polluted environment. The moths that were lighter in color stood on the buildings and trees which were stained with black suit, this made their predators to easily spot them and feed on them thus threatening their survival. The moths that were dark in color thrived in the darkened environment in which they easily blended thus they could not be easy targets for their predators as compared with the lighter ones. The population of the lighter moths decreased significantly and the species was dominated by the dark moths, this is a good case of natural selection (Darwin, Glick, & Kohn, pp 220).
A very important point in natural selection is that, when conditions finally return to the normal state the balance of the species whose population had dwindled will return to normal as well. The birds which have heavy strong beaks will easily break hard nut shells and peel off barks of trees during periods of prolonged drought and therefore will be more dominant in such periods as compared with the birds with weak small beaks, which will struggle to survive in the harsh environmental conditions and might die of hunger. But once the drought period is finally over the population of the birds with the normal beaks will return back to normal. The same case applies to the moths, their population was mainly composed of the dark moths, but once pollution declined and the black stains faded, the population of the moths returned to its normal state as both the lightly and the dark colored moths stood equal chance of being fed by their predators (O’Neil, Dennis, Para 2).
All species are stable genetically as various studies have shown. The genetic defects that alter the function or form of organisms, in most cases result to their death. The birds and the moths examples discussed above demonstrate that there are some variations in each species; the species can be favored by diverse variations at dissimilar times. However, studies have also shown that these variations are possible in subsequent generations of the species and this explains why the populations of various species are capable of returning to their original status. No new variations or species are produced, but are similar to those already existing (Darwin, ; Burrow, pp 98)
Scientifically, no permanent alteration has been observed in species. There are several cases which have been proven on adaptation, it involves changes which are non genetic. Examples of natural selection altering the population balance within a species exist, but there are no examples on natural selection, permanently changing the population of species. Genetic mutations that have been observed in nature are in most cases fatal and result to death. Although, the effects of the short term effects of natural selection are not in doubt, their effects in the long run are not yet understood fully up to date. Most scientists prefer referring to the cases of the birds and the moths to proof the natural selection theory; they adamantly refuse to view these examples as contradicting evolution (O’Neil, Dennis, Para 4-5).
The theory of natural selection shows that the organisms that are better adapted to a certain environment will survive better than those ones that are less suited for the conditions prevailing in their environment. It shows that that the most fit will survive while the least will be eliminated, in this theory the term fit does not only refer to the physical strength of the organisms but certain traits possessed by the organism and lacking in others within the same species that will help them to survive better. This therefore, means that the resulting population will be composed of the organisms with the trait that enables them to survive in the prevailing conditions.
Darwin, Charles & Burrow, John Wyon; The origin of species by means of natural selection, or, The preservation of favored races in the struggle for life, (1985): Penguin Classics, ISBN 0140432051.
Darwin, Charles; On Natural Selection, (2004): Penguin Books, Limited, ISBN 0141018968.
Darwin, Charles, Glick, Thomas F. & Kohn, David; on evolution: the development of the theory of natural selection, (1996): Hackett Publishing, ISBN 0872202852.
O’Neil, Dennis; Darwin and Natural Selection (1998): Retrieved on 4th May from,