What could be the reasons for adopting contraceptive method?

Why does menstruation occur?

(a) “The sex of the children is determined by what they inherit from their father and not their mother.” Justify.

(b) Give an example where environmental factor like temperature determined the sex of the offspring.

What are chromosomes? Explain how in sexually reproducing organisms the number of chromosomes in the progeny is maintained.

The germ cell A produced by a person X is round in shape and it fuses with another germ cell B having a long tail and produced by a person Y. The fusion of A and B produces a new cell C. The cell C divides repeatedly and grows inside the organ D of person X to form E in which the body features of the unborn baby are not much developed. E grows further 'to form Fin which the various body features of the unborn baby (like hands, legs, head, eyes, and ears, etc.) can be identified. F grows further and ultimately forms a baby. What are A, B, C, D, E and F ? Out of the two persons X and Y, which one is male and which one female?

How many pairs of chromosomes are present in human beings? Out of these how many are sex chromosomes? How many types of sex chromosomes are found in human beings? "The sex of a newborn child is a matter of chance and none of the parents may be considered responsible for it". Draw a flow chart showing determination of sex of a newborn to justify this statement.

Draw a diagram of human female reproductive system and label the part

(i) that produces eggs.

(ii) where fusion of egg and sperm takes place.

(iii) where zygote is implanted.

What happens to human egg when it is not fertilized?

How does a growing embryo get nutrition from the mother's blood?

What is placenta? Explain its function in human female.