Question

15. (8 points) Answer the following questions about both microevolutionary and macroevolutionary processes. Use no more than 2 sentences or bullet points per subpart. It may help to think about how these subparts are related. (a) In a neutral (no selection) locus, you can experimentally demonstrate that different alleles are fixed in different populations even if they all start at the same allele frequencies. What does this demonstrate about genetic drift? (b) A common paleontologists' phrase for evolution and extinction is that if you could "replay the tape of life," you would end up with a completely different outcome (in terms of extant biodiversity). What does this mean about the process of (background) extinction?

Answer 1

15

(a)Genetic drift unlike natural selection is based on random changes. e.g. If there are equal alleles of black mollies, denoted by 'B' and white mollies denoted by 'b',( here B is the dominant allele, hence having the allele B will exhibit black colour and b is the recessive allele and the phenotype requires to have two 'b's, ie 'bb' to exhibit white colour. ) Due to genetic drift the first five is chosen to reproduce, there is no apparent reason like natural selection, even the bottom 5 may be chosen , as the process continues the 'b' allele is reduced in generation 2 and finally wiping out the 'b' allele out of the population in the third generation.
beneration I не е BB BB B B Be Bg е е BB BB BB Bв вв Ре) / 2 O

Generation II БB Bg Bв вв. на ни я 99 а 18 19 to = bay mab gaf y: b 3c fer 2013

Generate ѕв вBE Bь в ьььь p= 6 gene frequency = 0.5 go 6 gene frequerg=0.5

(b) The alleles that cause non-deleterious phenotypic differences among animals, plants and yeasts indicates that similar phenotypes have often evolved in distinct taxa through independent mutations in the same genes.

The extinction of dinosaurs has various theories attributed to the same like equivocal events in the history, out of which one of them is the asteroid impact which is believed to have led to the extinction of dinosaurs and the subsequent radiation, sixty-five millions of years ago. If the tape of life is replayed and the meteorite did not strike those creatures would not have been extinct, neither the human beings would have evolved.