CBSE Class 10 Science 2017 · Paper 31/2/1 · Question 12

Regeneration is the ability of a fully differentiated organism to give rise to new individual organisms from its body parts: if the organism is cut into pieces, many of the pieces grow into complete individuals. It is carried out by specialised cells, which multiply and then develop into the various cell types and tissues. An organism that shows regeneration: Planaria (or Hydra). An organism that does not: a human being (or another complex animal, such as a dog). Reason: complex animals have a highly organised body. Their specialised cells form tissues, the tissues form organs and organ systems, and these lie at definite positions in the body. They lack cells that can multiply and develop into all the tissues and organs of a new body, so a cut-off part cannot rebuild the whole organism.