(a) Fragmentation is a form of asexual reproduction or cloning where an
organism splits into fragments and each fragment develops into a new
individual. Spirogyra multiplies by fragmentation.

(b) Regeneration is the ability of organisms to generate lost or damaged parts
of the body and is carried out by specialised cells. These cells form a mass
of cells which undergoes changes to form cells specialised in different
functions.

Regeneration is not possible in all animals because the pluripotent stem cells
have different properties in different animals. For example, each tissue—
such as muscle, nerve or skin—has its own set of stem cells which makes
the different types of cells in that particular tissue. So, a muscle stem cell
cannot make skin and skin stem cells cannot make muscle.