Sexual reproduction involves two individuals .That means the charecetrs of two individuals are coming togetehr.This produces more variety in the population.Variety in the population helps in adaptations.It also allows the population to evolve. So moroe vaariations and ability to adapt and evolve are the advantages of sexual reproduction.
In asexula reproduction only one parent is involved and the off springs are mostly like the parent. So variety in th epoulation will be less and hence population cant adapt and evolve.