What are the organs called that have a similar appearance and perform similar functions but have different basic structures?

On which of the following plant species has Mendel worked?

Which of the following statements is not true with respect to variation?

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

$A$ 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?

$A$ trait may be inherited, but may not be expressed. Justify this statement with the help of a suitable example.