ORGANIC EVOLUTION

Concept of evolution was given by Empedocle and Buffon. Trend of evolution was first explained by Lamarck. Lamarck: Father of evolutionary theories. Evolution means: Gradual change from simple to complex forms with the passage of time. Organic evolution of living beings. Term organic evolution is given by Herbert Spencer. Organic evolution can be defined as:' Adaptations through generations'. Inorganic evolution: Means evolutions of Non-living things eg. evolution of rivers, rocks, Mountains etc. Evolution is defined as historical and developmental race of organisms with variation. The main theme of evolution is Descent with modification i.e. docterine of desires. Biological meaning of evolution is gradual changes. The process of evolution is continuous but very slow, taking place even now. Main postulates of organic evolution are: Earlier organism were simpler. They gradually changed in to complex organisms. They are inter related because of common origin. They have common shelter and environment. Evolution is generally slow, continuous, irreversible and progressive. For evolution the most important requirement is variation. The ultimate source of organic evolution is mutation. The evolution of any species can be considered as a sum total of the species Adaptive changes preserved by natural selection. One of the most important factors of the development of a new species is the geographical isolation.