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

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

$(a)$ What is vegetative propagation?
$(b)$ Write any two advantages of practising this method.

Which among the following statements are true for unisexual flowers?
$(i)$ They possess both stamen and pistil
$(ii)$ They possess either stamen or pistil
$(iii)$ They exhibit cross pollination
$(iv)$ Unisexual flowers possessing only stamens cannot produce fruits

How are general growth and sexual maturation different from each other?

Where are the ovaries located in a female?