(a) Sexual Reproduction
1. It involves both the parent
2. It involves fusion of male and female gametes
3. It results in the introduction of variation in a population as newly formed organisms are not the exact copies of the parent

Asexual Reproduction
1. It involves only a single parentĀ 
2. It does not involve fusion of gametes. The gamete of single parent undergoes division and gives rise to new a individualĀ 
3. It does not bring variation in a population as the newly formed organisms are identical to the parentsĀ 

(b) In case of sexual reproduction, there is marked variation between the parent and offspring due to the following reasons:1. The male and female gametes are formed by meiotic division which allows crossing over and recombination. This generates variation in the genes of offspring.2. Two parents are involved who are different from each other. The fusion of their gametes would produce a distinct individual.