Brief about female heterogamety.

Explanation

Heterogametic Females: In this method of sex determination, the homogametic male possesses two 'X' chromosomes as in certain insects and certain vertebrates like fishes, reptiles and birds producing a single type of gamete, while females produce dissimilar gametes.
The female sex consists of a single 'X' chromosome or one 'X' and one 'Y' chromosome. Thus the females are heterogametic and produce two types of eggs. Heterogametic females are of two types, ZO-ZZ type and ZW-ZZ type.
(i) ZO-ZZ Type: Eg. Certain moths, butterflies and domestic chickens. In this type, the female possesses single 'Z' chromosome in its body cells and is heterogametic (ZO) producing two kinds of eggs some with 'Z' chromosome and some without 'Z' chromosome, while the male possesses two 'Z' chromosomes and is homogametic (ZZ).

(ii) ZW-ZZ type: Eg. Insects (gypsy moth) and in vertebrates such as fishes. In this method the female has one 'Z' and one 'W' chromosome (ZW) producing two types of eggs, some carrying that Z chromosomes and some carry the W chromosome. The male sex has two 'Z' chromosomes and is homogametic (ZZ) producing a single type of sperm.