In Spirogyra, asexual reproduction takes place by a breaking up of filaments into smaller bits.
Explanation:
Asexual reproduction in Spirogyra occurs through a process called fragmentation. The filaments of Spirogyra break into smaller pieces, and each fragment can grow into a new individual filament.
Why other options are incorrect:
b division of a cell into two cells:
While Spirogyra cells do divide, this is not the primary mechanism for asexual reproduction. Fragmentation is the dominant method.
c division of a cell into many cells:
This is not the typical process of asexual reproduction in Spirogyra. Fragmentation involves breaking down the existing filament, not dividing a single cell into many.
d formation of young cells from older cells:
This describes a form of reproduction in some organisms, but Spirogyra reproduces primarily through fragmentation. There isn’t a distinct formation of young cells from older cells in Spirogyra.