Final answer:
Additive genetic variance is the sum of the effects of individual alleles, and dominance genetic variance involves the masking effect of certain alleles over others. Additive variance contributes more significantly to evolutionary change because it can be acted upon by natural selection, providing a wider range of phenotypes for selection to work on.
Step-by-step explanation:
The difference between additive genetic variance and dominance genetic variance lies in how the alleles at a loci contribute to a phenotype. Additive genetic variance refers to the impact of individual alleles added together, without any interaction between them affecting the phenotype. This type of variance allows for the gradual accumulation of small changes, which can be acted upon by natural selection. Dominance genetic variance, on the other hand, occurs when an allele at one locus masks or suppresses the expression of alleles at the same or different loci, complicating predictions about phenotype.
Additive genetic variance is particularly important for evolutionary change because it provides a broad range of phenotypes for natural selection to act upon. Traits with a high degree of additive variance respond more effectively to selection pressures and therefore contribute more to the evolutionary process. In contrast, dominance genetic variance can hide the expression of alleles, potentially slowing evolutionary change since alleles that are masked do not affect the phenotype and are not subject to selection.