(a) What are homologous structures? Give an example.
(b) "The sex of a newborn child is a matter of chance and none of the parents may be considered responsible for it." Justify this statement with the help of a flow chart showing sex-determination in human beings.

Explanation

The organs having similar origin / structures but performing different functions.
Example : limbs of frog, limbs of lizard, bird and human
(b)
Hence, sex determination is purely a matter of chance.
Detailed Answer:
a) Homologous structures are structures which have a common basic structure but perform different functions. Example, forelimbs of reptiles, amphibians and mammals.
(b) In human beings, the sex of the individual is determined by the genes inherited from the parents. Women have a perfect pair of sex chromosomes i.e, XX whereas men have a mismatched pair of normal sized X and short one Y marking it XY. All children will inherit an X chromosome from their mother regardless of whether they are boys or girls. Thus the sex of children is decided by what they inherit from their father. A child who inherits an X chromosome will be a girl and one who inherits a Y chromosome from him will be a boy. So, there is an equal chance of a girl child as well as a boy child.