In human males and females, how many pairs of chromosomes are identical?

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

An organism which is a worm,has very simple 'eyes',that are really eye spots which detect light. Name that organism.

$A$ woman having blood group $B$ marries a man having blood group $A$ and they have four offspring. Two children have blood group $O$,one has blood group $B$,and one has blood group $AB$. Now,answer the following:
$(i)$ Which blood group is dominant?
$(ii)$ Which blood group is recessive?
$(iii)$ What are the genotypes of the parents?
$(iv)$ Show the possible genotypes and phenotypes of the offspring.

Give reasons why acquired characters are not inherited.

Exchange of genetic material takes place in