Explain the mechanism of 'sex determination' in birds. How does it differ from that of human beings?
The sex chromosomes in birds are determined as Z and W. The male is homomorphic (ZZ) and the female is heteromorphic (ZW). W chromosome carries female sex-determining genes and duplication of Z chromosome indicates male sex. So, in case of chicks, the sex is determined by the egg and not by the sperms.
The difference between sex mechanisms of humans and birds is that the male is homomorphic (ZZ) and the female is heteromorphic (ZW) in birds, whereas the male is heteromorphic (XY) and female is homomorphic (XX) in humans.