a) List any three distinguishing features between sexual and asexual types of reproduction.
b) Explain why variations are observed in the offspring of sexually reproducing organisms.

Hint:Organisms reproduce in different manners. They reproduce in both sexual and asexual manner. We know that organisms may look similar to their parents and it is known as heredity. The degree by which the progenies differ from them is called variation.

Complete answer:
a) We know that in sexual reproduction, the male gametes are produced by male parent which fuses with the female gamete from the female parent. Formation of zygotes and the process of embryogenesis are seen only in sexual reproduction. Male and female gametes fuse together to form a zygote. The zygote undergoes differentiation and maturation to form an embryo. The process of variation which is the degree by which an offspring differs from their parent is only seen in sexual reproduction.
In asexual reproduction, all the young ones are alike. Know that they are called clones. Here, young ones are formed from a single parent and no involvement of fertilisation can be seen. Process of variation is absent. Embryogenesis and zygote formation will be absent in this mode of reproduction.

b) In sexual reproduction, male and female characters of the parents will be seen along with some variations. We know that male and female gametes are produced by meiosis from the gamete mother cells in sexual reproduction. Characters are assorted independently to both of the gametes during gamete formation. During gamete formation, a process called crossing over takes place in the chromosomes. Here, segments of chromosomes are transferred between paired homologous chromosomes. This leads to a recombination in the genetic material and the expression of a new character in the progeny that are absent in the parents.

Note: We can see that in some species, the female gamete doesn’t undergo fertilisation with the male gamete. They skip the step of fertilisation and grow into a new organism. This phenomenon is called parthenogenesis and is seen in many plants.