Question

how are equal contribution of male and female parents ensured in progeny

Answer 1

Equal genetic contribution of male and female parents ensured in the progeny is ensured during sexual reproduction, where a unipoloid female gamete fuses with a uniploid male gamete to produce a zygote, which is diploid and gives rise to the progeny. The female gamete contais 23 chromosomes and the male gamete also contains 23 chromosomes. So the zygote that is formed contains a full normal set of 46 chromosomes.

Answer 2

How are equal genetic contribution of male and female parents ensured in the progeny?

During the formation of gametes as a result of reductional division (meiosis), sperms - XY & eggs - XX receive only single genome of a parent.

When fertilization occurs, one genome each from sperm & egg reaches the zygote.

It means both male & female parents contribute exactly equal amount of genetic material to the offspring.