Final answer:
Females determine the gender of their offspring in birds, as they can pass either a Z or W chromosome, in contrast to males who only pass on a Z chromosome. This differs from mammals, where males determine the sex, since they can provide either an X or Y chromosome.
Step-by-step explanation:
In the case of bird sex determination, it is the combination of Z and W chromosomes that decides the gender of the offspring. Since females have the ZW combination and can pass either Z or W to their offspring, it is clear that females determine the gender of their offspring - males will always pass on a Z chromosome. Therefore, if a female passes a Z chromosome, the offspring will be male (ZZ), and if she passes a W chromosome, the offspring will be female (ZW).
History has shown that recognizing the importance of chromosomes in determining sex was a significant scientific discovery made by Nettie Stevens. However, unlike in mammals where males determine the sex of the offspring, in birds, it is the female's W chromosome that is essential for sex determination.
The correct statement is b) Females determine the gender of their offspring.
In birds, females have a Z chromosome and a W chromosome, while males have two Z chromosomes. When a female bird reproduces, she passes on a Z chromosome to her sons and a W chromosome to her daughters.
This means that females determine the gender of their offspring because they are the ones who determine whether they pass on a Z or a W chromosome.