Organisms have a varied body design. Name the property which gives the basic difference in body design.

State the importance of chromosomal difference between sperms and eggs of humans.

Describe sexually transmitted diseases (STDs) and mention the ways to prevent them.

In the process of reproduction as used in $Spirogyra$,the organism splits itself into small pieces.
$(a)$ What is this process of reproduction called?
$(b)$ Will this type of reproduction be asexual or sexual reproduction? Answer with reason.
$(c)$ Is this process same as regeneration? Give reasons.

Draw the diagram of a flower and label the four whorls. Write the names of gamete-producing organs in the flower.

In which type of reproduction do genetic variations occur in the offspring?