Which is the primary sex organ of the male reproductive system?

How does the number of chromosomes in germ cells compare to the number of chromosomes in normal body cells of an animal?

Mention the functions of $(a)$ placenta and $(b)$ fallopian tube in the human female reproductive system.

State whether the following statement is true or false: $A$ thick and spongy lining of the uterus is required for nourishing the embryo if fertilization has taken place.

In females,the period around $45-50$ years of age is known as:

What are the changes seen in girls at the time of puberty?