Question

Describe in brief the various special modes of reproduction. Mention their economic significance.  

Answer 1

Special modes of reproduction include the following:

1. Gemmule formation: In sponges, internal buds called gemmules are formed. Each gemmule can develop into a new sponge when conditions become favourable. This helps the organism survive unfavourable conditions.
2. Parthenogenesis: In this mode, an unfertilised ovum develops into a new individual. It is seen in organisms such as honey bees, ants and wasps.
3. Micropropagation or tissue culture: Small pieces of plant tissue, cells or organs are grown on a sterile nutrient medium under controlled conditions to produce a large number of plantlets.
4. Cloning: Cloning is the production of genetically identical individuals from a single parent, cell or organism.

Economic significance: Micropropagation helps in the rapid production of a large number of uniform and disease-free crop and ornamental plants. Cloning and similar techniques are useful for preserving and multiplying organisms with desirable characteristics. Gemmule formation and parthenogenesis mainly help in survival and reproduction of organisms.

Thus, these special modes of reproduction help in survival, rapid multiplication and the propagation of useful organisms.