Question

how may mutations contribute to variation in the population?

Answer 1

Mutations produce random changes in an organism's genetic code. Mutations can occur in non-reproductive cells and then they will not be passed to the next generation, thereforу will not contribute to genetic variation. Only mutations that occur in reproductive cells are passed on to the next generations and contribute to genetic variation in a population. -konus OS

Answer 2

like the mutation of human, asian + white = half asian half white
asian + mexican = half asian half mexican
etc...
(barely black + white though)

Answer 3

Refer to allopatric speciation.
Even if a mutation occurs and if the organism is yet allowed to mate with the others, the chance of variation could be 25% or 50% as only one parent would have the carrier mutated gene.
In the case of allopatric speciation, where the same organisms are divided by a physical barrier and are longer allowed to mate whilst after a mutation. The population at two geographical ends would then produce two completely different species with evident variation.

I couldnt explain it better. Hope you understood :P