The life of all organisms is explained using the evolution theory, which identifies four forces that are responsible for the survival or extinction of organisms. However, it is important to understand the common terms used in the theory of evolution, among them species and population.
Species is the term used to represent the lowest taxonomic rank, or the lowest category of an organism during classification. In addition, the term is used to represent an organism as belonging to a group of other organisms with shared biological characteristics. When the term is used within such context, it means that all the organisms within the group have the capacity of reproducing with another member of the group. Organisms of the same species are therefore capable of reproducing due to their similar biological characteristics.
A population is a term used to describe several organisms sharing a common place. In most cases, a population represents similar species inhabiting a common place at the same time.
The four forces of evolution are natural selection, mutations, gene flows and genetic drift. Natural selection is explained as the process that favors the best-adapted organisms by allowing for more offspring, better feeding sites and giving advantage against attack by other organisms. This process is based on the argument that the strongest, intelligent, fastest and cunning organisms always possess an advantage over the weaker organisms, hence having the opportunity to multiply in numbers. Similarly, the process adapts the slogan of ‘survival for the fittest’. Organisms that are best-adapted pass-on the traits to their offspring, and these characteristics provide the species with an upper edge over other organisms.
Genetic drift is the process by which organisms acquire specific genetic traits based on the genetic variants that survive. Unlike natural selection, which offers specific organisms an advantage, gene drift depends on chances and probabilities on which gene variant, survives and which dies. The genes which survive develop to form new species, which gradually adapts to their environments according to their specific traits.
Gene flow is the process by which genes from one organism are transferred to another organism, mostly belonging to a different population, to form a new species. This process is mainly common in plants, especially during pollination when pollens are carried from one plant to another. The process of mixing up genes from different species forms a new organism with unique characteristics.
Mutations are other processes that involve changes in an organism’s DNA structure. Mutations occur when the offspring differs from its parent in its DNA structure. Since the DNA structure dictates an organism’s character, behavior and physiology, changes to the structure lead to similar changes in an organism’s physiology, character and general behavior.
Variation in evolution is defined as the dissimilarity between organisms in terms of behaviors, genetic composition and physiology. Variation within population refers mostly to the genetic differences between two similar species, for example spiders, which may hinder reproduction. Variation can occur if organisms differ in terms of physiological characteristics and behavioral adaptations. This difference is referred to as variation between populations.
Isolation mechanisms are the longstanding hindrances that prevent organisms from reproduction. They may be influenced by mechanical problems, ecology, behaviors, gametic incompatibility, sterility and zygotic mortality among others.
Specification represents the process of forming a new organism after parents come together either sexually or asexually. Speciation can be allopatric, sympatric or parapatric.