CBSE Class 10 Science 2022 · Paper 31(B)/6 · Question 4

(a) When a Spirogyra filament attains maturity, it simply breaks up into smaller pieces called fragments. Each fragment grows into a new Spirogyra filament, a new individual. This is fragmentation, a method of asexual reproduction. (b) When a Planaria is cut into any number of pieces, each piece grows into a complete Planaria. This is regeneration: specialised cells in each piece proliferate to form a mass of cells, and these cells then change into the various cell types and tissues in an organised sequence called development, rebuilding the parts that are missing.