Biogeography suggests that physical factors often determine where a population can spread. Placental mammals evolved later. Population Genetics A. Gene mutations are random alterations in DNA sequence, which provides new alleles . Single base pair change. Change in regulatory gene.
Any gene can mutate at any time.
B. Chromosome mutations alter number of chromosomes, arrangement of alleles, or duplicate alleles with change in base sequence in one copy. C. Recombination of alleles and chromosomes. The various alleles at all gene loci in all individuals make up the gene pool of the population. The gene pool is described in terms of gene frequencies. Assuming random mating and known allele frequencies, the ratio of genotype can be predicted for the next generation.