In humans, there are two pairs of sex chromosomes.

Exchange of genetic material takes place in

In dogs, the barking trait is dominant over the silent trait and erect ears are dominant over drooping ears. Now, find out
$(i)$ What is the expected phenotypic ratio of the offspring when dogs, heterozygous for both the traits are crossed?
$(ii)$ What are different phenotypes observed?
$(iii)$ What is this type of cross known as?

Humans have a genetic basis for sex determination.
$(a)$ Besides humans,which organisms have a genetic basis for sex determination?
$(b)$ Which chromosomes are similar in human males and females?
$(c)$ What is the function of these types of chromosomes?

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

$(a)$ Differentiate between:
$(i)$ Homologous organs and Analogous organs
$(ii)$ Pollination and Fertilisation
$(b)$ What do fossils tell us about the process of evolution?