Species
Species is defined as the reproduction of fertile offspring. It is composed of related individuals that take after each other and are able to breed among themselves. It can also be defined as the reproductive isolation. The smallest unit of classification is the species.
Population
Population on the other hand refers to a group of living organisms of the same species that live and interbreed in the same geographical location at the same time. It is basically the total number of inhabitants occupying a given area. It is geographical and behavioral isolation.
Variation
Variation refers to refers to the genetic differences that exist between organisms of the same species. These differences may either be caused by genetics or by environmental factors. The variations are normally evident in a species behavior, fertility, metabolism or mode of reproduction.
Main Sources of Genetic Variation
The main source of genetic variation is meiosis. The main genetic source of variation is from meiosis. Meiosis aids in the division of a sex cell into four daughter cells with half of the chromosome. Since the daughter cells only contain half of the chromosome, the probability of the same chromosome matching together is low. Such occurrences happen on either the egg or sperm. Other sources of variations include; genetic duplication, rapid reproduction and sexual reproduction.
The Role of Genetic Variation in Evolution
Genetic variation plays a very significant role in evolution because it prevents extinction. Variation prevents extinction in evolution. Natural selection allows for individuals that are best suited in a given environment to be selected. These individuals reproduce fertile offspring, which will carry the good gene and pass it on to other generations. Variation also drives evolution. Variation allows the natural to have something to select from. As a result, evolution occurs.
Selective Pressure
Selective pressure basically refers to the extent to which organisms that have certain characteristics are either favored or eliminated by environmental demands. It denotes the degree of intensity of natural selection. Different organisms have different unique characteristics. These unique set of features may make a species better equipped to survive in a particular environment as compared to others. They therefore survive in the environment for longer. Selective pressure therefore refers to the pressure provided by the environment.
Negative and Positive Selective Pressure
Negative selective pressure involves the selective removal of rare alleles that are deleterious. It is also referred to as natural selection. Positive selective pressure on the other hand are variants that increase in frequency until they fix in the relevant population. Positive selective pressure increases the proportion of a given trait whereas negative selection pressure decreases the occurrence of a trait.
Fitness
According to Charles Darwin, fitness refers reproductive success. It is normally measured by the number of off springs that survive to the reproductive age. In contrast, fitness as commonly used refers to the idea of an individual being in good shape in terms of one’s physical attributes such as strength.
Survival of the Fittest
Survival for the fittest does not best describe Charles Darwin’s theory. This is because not always the strongest, fastest or smartest species normally survive to their reproductive age. Darwin meant that the species that are suited for the immediate environment are the ones that mostly survive to their reproductive age. This is actually the basis of the idea of natural selection. However, to most people especially those who do not understand the concept of natural selection, fitness means the best physical specimen of the available species.
