(i) Variation is 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).
(ii) Sexual reproduction has more chances of variation than asexual reproduction. Because in sexual reproduction, genetic material from both the parents mixed (recombination of parent chromosomes) by fertilization. Hence offsprings get both the information and produce mixed characters which are not exactly the same as only mother or father. While in asexual reproduction, the single parent is involved and thus there is no recombination of chromosomes. Hence, offsprings that produced are the excat copy of their parent.