CBSE Class 7 Answered

(a) Nature always wants to get the best set of characters which help it to flourish in adverse conditions. This can only be achieved by having variations in individuals. In self-pollination, there will be fusion of male and female gametes from the same parent plant. Hence, there will no new variant formed and no evolution. However, in cross-pollination, the fusion of two different male and female gametes results in variation in the progeny produced. Hence, nature favours cross-pollination over self-pollination.

(b) Vegetative propagation is quicker than sexual reproduction because only one parent is involved. There is no fusion of gametes involved and hence, comparatively lesser energy is spent in vegetative propagation.

(c) Some plants produce large flowers with a sweet smell so as to attract insects for pollination.