What is produced by the fusion of a male gamete and a female gamete?

Which of the following organs is included in the male reproductive system?

What happens when a mature $Spirogyra$ filament attains considerable length?

For approximately how many days does menstruation last in human females?

In the given figure,label the parts and mention their functions:
$(a)$ Production of egg
$(b)$ Site of fertilisation
$(c)$ Site of implantation
$(d)$ Entry of the sperms

The process of spore formation takes place in many simple multicellular organisms which have certain reproductive parts that can be identified.
$(a)$ Name the organism using this process.
$(b)$ Name the reproductive and non-reproductive parts of such organisms.