Evolution

One of the fundamental concepts of biology is the idea that the present diversity among organisms developed slowly from earlier, more primitive organisms. The process by which the present day organisms arose or developed from earlier ones is called evolution. It is therefore assumed that by the same present day organisms will give rise to future forms. Evolution can also be said to be a gradual process of changes over a period of geological time. This may result in the origin of new species or the extinction of others. Because evolution is very slow, people may not release that it is happening. Evidence of Evolution Evidence supporting the hypothesis that evolution occurs comes from the various sources including. 1.Fossil records. 2.Comparative Anatomy 3.Comparative Embryology 4.Studies of the geographical distribution of plants and animals Theories of Evolution These theories put forward by Charles Darwin, a British naturalist in 1859. These theories are summarised as follows: 1.Organisms produce far more offspring than can possibly survive. However, the population of any wild organism in any environment remains relatively constant due to high mortality rate. 2.Organisms differ in ways (size, colour, shape, physiology, etc), which affect their ability to survive. 3.Much of the important variation in character among organisms is controlled by genes. Most of the genes are inherited in simple Mendelian fashion. Others depend on the interaction between genes. 4.Natural selection preserves species best adapted to the environment to contribute to successive generations. 5.New species can only arise by genetic isolation aided by natural selection. Isolation can be geographical or ecological. These theories put forward by Jean Baptiste Lamarck, a French professor of zoology in 1809. This theory involves the inheritance of acquired characters. The theory is resolved into three components. 1.individuals of the same species growing and developing under different environmental conditions differ from one another (i.e. influence of the environment) 2.in animals, the use or exercise of certain parts of the body results in development of those parts. New characters are thus acquired in life and it is possible that these may be passed onto the offspring, giving rise to new species (i.e. use and disuse of body parts, inheritance of acquired characters)