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

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

$A$ cross was carried out between a pure-bred tall pea plant and a pure-bred dwarf pea plant,and $F_{1}$ progeny was obtained. Later,the $F_{1}$ progeny was selfed to obtain $F_{2}$ progeny. Answer the following questions:
$(a)$ What is the phenotype of the $F_{1}$ progeny and why?
$(b)$ Give the phenotypic ratio of the $F_{2}$ progeny.
$(c)$ Why is the $F_{2}$ progeny different from the $F_{1}$ progeny?

Exchange of genetic material takes place in

Mendel crossed a pea plant having inflated green pod with a constricted yellow pod.
$(a)$ What type of a cross is it?
$(b)$ What type of plants are obtained in $F_{1}$ generation?
$(c)$ In $F_{2}$ generation the phenotype ratio is $9:3:3:1$. State the rule for the inheritance of traits observed by Mendel.

Who was the first scientist to perform a series of experiments to study acquired and inherited traits?