Speciation is the method of formation of new species. A species can be defined as one or more populations of interbreeding organisms that are reproductively isolated in nature from all other organisms. As natural selection adapts populations occupying different environments, they will diverge into races, subspecies, and finally separate species. When populations no longer interbreed, they are thought to be [...]
The theory of organic evolution seems to be the most acceptable explanation of the occurrence of varied forms of plants and animals on Earth. Evolution, which started out as a hypothesis, is now supported by evidence from many fields of science. The various convincing evidences for the occurrence of descent with modification is summarised in the Fig. 15. 1. Evidence [...]
Jean Baptiste Lamarck put forth the theory of inheritance of acquired characters, which is also known as Lamarckism. It was published in 'Philosophie Zoologique' in the year 1809. The four propositions of Lamarckism are as follows: a. Living organisms and their parts tend to increase in size continuously due to internal forces of life. b. New organs are formed in [...]