BIOL 2400 Lecture Notes - Lecture 3: Genetic Drift, Biostratigraphy, Gamete
15 Sep 2017
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Darwin"s theory of descent with modification explained: The non-constancy of species (species change over time) The descent of all organism from common ancestors (branching evolution rather than lineages) The gradualness of evolution (no saltation, no discontinuities) The multiplication of species (the origin of biodiversity) Darwin believed in blending inheritance or pangenesis: inheritance elements act like pigment in paint (black female bear and white male predict only grey cubs) He never completely resolved the relationship between natural selection and the effects of use and disuse (lamarck) He could not answer the criticism, that the initial effects of natural selection (for white fur) would be nullified by crossing between the selected individuals and the rest of the population with black fur. Cross homozygous dominant yellow pea with homozygous recessive green pea, results in all yellow peas (became heterozygous) Crossing the offspring together would result in a 3:1 ratio where: 1 homozygous recessive, 2 heterozygous, 1 homozygous dominant (3 yellow, 1 green)
