CBSE Class 10 Science 2020 · Paper 31/5/1 · Question 28(b)

(a) (i) Planaria reproduces by regeneration: when its body is cut into pieces, each piece grows into a complete organism, because specialised cells in it divide and develop into the lost parts. (ii) Hydra reproduces by budding: during favourable conditions a bud develops as an outgrowth by repeated cell division at one site on the parent, grows into a tiny complete individual on the parent's body, and then detaches as a new Hydra. (iii) Rhizopus reproduces by spore formation: its sporangia produce many spores, each covered by a thick wall that protects it through unfavourable conditions until it reaches a moist surface and grows into a new individual. (b) Bryophyllum reproduces by vegetative propagation through its leaves: buds are produced in the notches along the leaf margin, and when the leaf falls on moist soil, these buds develop into new plants. (c) Any two: (1) The new plants are genetically similar to the parent plant, so they have all its characteristics. (2) Plants raised by vegetative propagation bear flowers and fruits earlier than those produced from seeds. (3) Plants such as banana, orange, rose and jasmine, which have lost the capacity to produce seeds, can still be propagated. Other correct advantages also earn credit.