Question

Besides the XY system, are there other sex determination systems?

Answer 1

Some animals have a sex determination system different from the XY system.

The X0 system is the sex determination system of many insects. In this system, females are XX and males have only one X chromosome (a condition represented by X0).

In birds, in some fish and in lepidopterae insects (butterflies), sex determination is carried out through the ZW system. In this system, females are ZW and males are ZZ.

In another system, called the haploid-diploid sex determination system, one of the sexes is represented by the fertilized diploid individual and the individual of the opposite sex is formed by parthenogenesis, and is haploid (this occurs in bees and other insects).