There is an inbuilt tendency to variation during reproduction,both because of errors in $DNA$ copying,and as a result of sexual reproduction.

In human males and females, how many pairs of chromosomes are identical (in $pairs$)?

Select the incorrect statement.

$(a)$ What are fossils?
$(b)$ Explain the importance of fossils in evolutionary relationships.

What are sex chromosomes? Which sex chromosomes are found in male and female human beings? State the chromosome responsible for the development of a male child in human beings?

In a beetle population, the number of green beetles is more than blue and red beetles. Give a reason behind this situation.