By what is the expression of tallness in the pea plant exhibited?

The preserved traces of all living organisms are called fossils.

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?

In peas,a pure tall plant $(TT)$ is crossed with a short plant $(tt)$. The ratio of pure tall plants to short plants in $F_2$ is

$(a)$ When a pesticide is sprayed on a population of insects,all insects do not get killed but few of them survive. Give reason.
$(b)$ When is a recessive trait capable of expressing itself? Write its expression with respect to the height of a plant (genotype).

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