Evolution and Natural Selection:

Evolution and Natural Selection:

The ideologiest of evolution were considered those great Greek philosophers. Aristotle speculated ‘more perfect types not only followed less perfect ones but actually had developed from them’. First complete theory on this matter came from Lamarch as he went as – modifications due to environment, if constant and lasting, would be inherited and produced a new type. This had no evidence but gave working hypothesis to others to work on.

Malthus proposed- the english people were increasing rapidly, the human race tends to run-out its means of subststance unless the redundant individuals are eleminated. Darwin’s favorable variations were preserved and unfavorable oned destroyed, resulting to formation of new species. The origin of Species, survival of existence or the survival value or natural selection are all dedicated to Mr Darwin.

Weismann after Darwin in 1890 studied somatic and germ cells in body. Somatic cells reproduce cells like themselves whilst germ cells give germ cells of a new individual plus many types of cells.

Germ cells descend from germ cells in apure line of germplasm but somatic cells trace their origin to germ cells. From this point of view, the body of each individual is an unimportant by-product of his parents’ germ cells. The body dies, leaving no offspring, but the germ plasms show an unbroken continuity. The products of the germ cells are likely to be affected by the changes in the body. This was the Weismann’s explanation of the apparent non-inheritance of acquired characters.

Darwin’s causin Francis Galton in 1869 studed mental qualities during which Darwin’s propoganda was welcomed by public but not by breeders and horticulturalists. Inheritance of ability is certain- Galton propounded that the chance of the son of a judge showing great ability was about 500 times as high as that of a man taken at random.