BIOL 400 Lecture Notes - Lecture 15: Hugo De Vries, Oenothera, Richard Goldschmidt
Document Summary
Blending inheritance suggests that blending would lessen the variation in a population and darwin"s evolution would occur to slowly to act on this variance. Darwin thought maybe variation was being introduced but he didn"t know about mutation and so couldn"t explain it: all new genetic variants must be deleterious (as the appearance of mutants in labs seemed to suggest). Natural selection does not have any directionality, apart from continuous selection in one direction. This suggested a step-wise evolution which was not what was suggested in natural selection. Kelvin suggested this and had estimates based in gravitational collapse. When he self-pollinated them they bred true, but when he crossed them they produced offspring of different sizes. The o spring had large size di erences, so he thought that he had created a new species that could not be back crossed to produce parents. He called mutation in the sense of these one generation transformations.
