CBSE Class 10 Science 2017 · Paper 531 · Question 11

(a) Fragmentation is a method of asexual reproduction in which a multicellular organism with a simple body breaks up, on maturing, into two or more small pieces (fragments), and each fragment grows into a new individual. Example: Spirogyra, a filamentous green alga. (b) Regeneration is the ability of an organism to give rise to new individuals from its body parts: when a simple animal such as Planaria or Hydra is cut into pieces, many of the pieces grow into complete organisms. It is carried out by specialised cells, which divide to form a large mass of cells; different cells of this mass then change into the various cell types and tissues in an organised sequence called development. It is not possible in all animals because complex animals have highly specialised cells organised into tissues, organs and organ systems at definite positions in the body, and they do not have the specialised cells that can multiply and develop into a complete new body from a piece; they can at most heal wounds or regrow some lost parts.