Answer:
1.) The two gametes found in humans are the sperm and the ova.
2.) Variation, in biology, any difference between cells, individual organisms, or groups of organisms of any species caused either by genetic differences (genotypic variation) or by the effect of environmental factors on the expression of the genetic potentials (phenotypic variation).
3.) Because the alleles that the mother and the father carry are mixed together in the offspring.
4.) Because it only introduces genetic variation into the population if a random mutation in the organism's DNA is passed on to the offspring.
Please this is all I can answer