"The chromosome number of the sexually reproducing parents and their offspring is the same." Justify this statement.

It is a commonly held misconception that the mother's egg is responsible for determining whether the baby will be a boy or a girl. But actually,it is the father's sperm that decides this. Which of the following makes the sperm the decisive factor?

There is an inbuilt tendency to variation during reproduction,both because of errors in $DNA$ copying,and as a result of sexual reproduction.

Mention three important features of fossils which help in the study of evolution.

$A$ child who inherits an $X-$chromosome from her father will be a boy.

New species may be formed,if $......\,.$
$(i)$ $DNA$ undergoes significant changes in germ cells.
$(ii)$ there is no change in the genetic material.
$(iii)$ mating does not take place.