Introduction to Evolution
All living organisms show diversity in their structures, living habitat, mode of life etc. But all of them will have some common characters and fundamental similarities. If we examine the origin of life on the earth, we come to know that the earliest forms of life must have been formed from the chemical reaction in ocean. The earliest forms of life were simpler forms. The present diversity of life is due to gradual change from simpler ones.
Evolution is defined as the formation of more and more complex organisms from the pre-existing simpler ones over a period of time. The basic idea of organic evolution means that generation after generation the offsprings of a species modify in accordance with the environmental requirements and after continuous modifications turn into better organised and more complex species.