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Therefore, chromosomes are the base of heredity.

(image will be uploaded soon) Heredity is the study of the transmission of genetic characters and variation from one generation to the other generation. Heredity involves the chromosomes transfer from parents to the progeny or from one person to another person. Therefore,  chromosomes are the base of heredity. The physical basis of heredity is genes while the chemical basis of heredity is DNA. The process of transfer of heredity character from generation to generation is called Genetics. The name genetics was first coined by Watson in 1905. Gregor John Mendel was the first scientist who gave the idea of heredity based on his experiments in 1822- 1884 and is also known as ‘Father of Genetics’.

Both animals and plants have common variations that reproduce by sexual means because sexual reproduction is biparental and involves the process of fertilization and meiosis and traits are received by the progeny from both the parents.

More and more creation of organisms by gradual changes from low categories animals to higher animals is called evolution.

(image will be uploaded soon) Charles Robert Darwin in 1809 -1882, explains the evolutionary principle in his book ‘The origin of species’. The theory proposed by him is popularly known as “Theory of natural selection” or Darwinism. Darwin explained that despite having the enormous potential of fertility, the population of organisms remains within a limit. It is due to the struggle between the members of the same species and different species for food, space, and mate. Struggle eliminates the unfit individuals. The fit organism possesses from a variation which is favorable and they can leave the progeny to continue the favorable variations. The variation which when accumulated for a long time gives rise to the origin of new species with progress in genetics, the source of variation was explained and Darwin’s theory was modified. Now, the most accepted theory of evolution is  ‘Modern synthetic theory’, in which the origin of species is made on the interaction of genetic variation and natural selection. His Main Ideas Include:

Evolution helps in a better understanding of the various aspects of life which includes how a species came into existence, and how it became extinct and several. It also helps to know about the various other factors like their behavior and habitats.  

Example: Paw of cat and hands of a human. (image will be uploaded soon)

Example: Vermiform appendix of the large intestine. (image will be uploaded soon)

Example: Archaeopteryx 2) What are the Other Theories of Evolution?

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