$(a)$ List any two methods of asexual reproduction.
$(b)$ Explain how $Spirogyra$ reproduces.

(N/A) Two methods of asexual reproduction are:
$(i)$ Budding (e.g.,in $Hydra$ and yeast).
$(ii)$ Spore formation (e.g.,in fungi).
$(b)$ $Spirogyra$ reproduces by a method called fragmentation. Upon maturation,the filamentous body of $Spirogyra$ simply breaks up into smaller pieces or fragments. Each of these fragments then grows and develops into a new individual.