Introduction To Evolution

Introduction To Evolution

Evolution is the process of change in all forms of life over generations, and evolutionary biology is the study of how evolution occurs. Life evolves by means of mutations (changes in an organism's hereditary information), genetic drift (random change in the genetic variation of a population from generation to generation), and natural selection (the non-random and gradual process of natural variation by which observable traits (such as eye color) become more or less common in a population).

All individuals have hereditary material in the form of genes that are received from their parents, then passed on to their offspring. Among offspring there are variations of genes due to the introduction of new genes via random changes called mutations or via reshuffling of existing genes during sexual reproduction. The offspring differs from the parent in minor random ways. If those differences are helpful, the offspring is more likely to survive and reproduce. This means that more offspring in the next generation will have that helpful difference and individuals will not have equal chances of reproductive success. In this way, traits that result in organisms being better adapted to their living conditions become more common in descendant populations. These differences accumulate resulting in changes within the population. This process is responsible for the many diverse life forms in the world.

The forces of evolution are most evident when populations become isolated, either through geographic distance or by other mechanisms that prevent genetic exchange. Over time, isolated populations can branch off into new species.

The majority of genetic mutations neither assist, change the appearance of, nor bring harm to individuals. Through the process of genetic drift, these mutated genes are neutrally sorted among populations and survive across generations by chance alone. In contrast to genetic drift, natural selection is not a random process because it acts on traits that are necessary for survival. Natural selection and random genetic drift are constant and dynamic parts of life and over time this has shaped the branching structure in the tree of life.

The modern understanding of evolution began with the 1859 publication of Charles Darwin's On the Origin of Species. In addition, Gregor Mendel's work with plants helped to explain the hereditary patterns of genetics. Fossil discoveries in paleontology, advances in population genetics and a global network of scientific research have provided further details into the mechanisms of evolution. Scientists now have a good understanding of the origin of new species (speciation) and have observed the speciation process in the laboratory and in the wild. Evolution is the principal theory that biologists use to understand life and is used in many disciplines, including medicine, psychology, conservation biology, anthropology, forensics, agriculture and other social-cultural applications.