Evolution is basically the change in the heritable characteristic or traits in living organisms which are passed from one generation to another and gives rise to diversity at every stage of the organism’s biological organisation. The process of evolution was not well understood until 19th century when Charles Darwin proposed the scientific theory of natural selection as a driving tool in evolution.
The process involved both the macroevolution in which organisms went through major evolutionary changes over a long period of time and acquired different traits from different parents or ancestries and the microevolution in which a group of organisms went through minimal changes with time but the traits they acquired were typically from the same ancestor. The history of evolution dates back in the 16th century during the pre-Socratic Greek philosophers who thought that all natural things both dead and living as being imperfect fixed natural possibilities and had an intended role within the environment.
The greatest breakthrough in this understanding came with the theory of natural selection mechanism which was formulated by Charles Darwin. In the 19th century, modern evolution synthesis merged the understanding and the theories of natural selection, mutation and the Mendelian inheritance into a one theory which is currently studied under one branch of biology. Natural selection became the main driving tool through which organisms adapted and evolved. Through natural selection, heritable characteristics within a population either became less or more common due to the interactions between the organism and its environment.
Due to this interaction with the environment, the organisms that were favoured by the environment survived and reproduced more frequently resulting to the occupation of well adapted offspring within the same ecological space. Organisms that became unfavoured by the environment died and their species permanently disappeared from the natural environment . Through this process, the environment has filtered out the poorly suited species of organisms from one ecological niche and left the best suited to occupy that niche.
Natural selection often referred to as self evident mechanisms in such that it relies on the facts such as phenotypic variation which shows that variation within a given population of organisms occurs due to the physiological appearance, morphological organization and behavioural characteristics of the individual organism; differential fitness in which different traits in a population of organisms brings about different survival and reproduction within the population and the heritability of fitness where the selected traits can be passed from one generation to the other.
According to these facts of natural selection, several numbers of offspring are usually reproduced with the capability to survive within a given environment. Since the natural resources are usually limited, the reproduction results to competition for survival by utilizing the scarcely available resources. Species of organisms that posses traits that give them advantage over the others, they usually survive and pass the traits to the next generation unless the others organisms lacking the traits which do not survive the competition.
Thus the process of natural selection is determined by the organism’s evolutionary fitness which shows the ability of an organism to survive and reproduce and determines the amount of genetic traits to be passed to the next generation. Evolution occurs through the change in heritable particular characteristics of an organism which makes up a complete structure of the organisms behavioural and observable traits and comes about due to the interaction of the organism and its environment.
Only the heritable traits are usually passed from one generation to the other through genetic exchange during breeding. Natural selection filter out the weak species within the population and allows only the best species to survive and pass the traits to the next generation during breeding resulting to the occupation of a certain group of organisms within a certain ecological niche and not any other group.