(a) What is tissue culture? (b) Name any four types of ornamental plants which are being produced by tissue culture technique. (c) What is the importance of DNA copying in reproduction? Explain with an example. (d) How does reproduction help in providing stability to population of species? (e) Why is variation during reproduction beneficial to the species but not necessarily for the individual?

• The process of propagating new plants, from a small piece of a plant's tissue obtained from the growing tip of that plant in a suitable medium is called tissue culture.

• Orchids, Dahlia, carnation and Chrysanthemum are propagated by the method of tissue

• DNA copying refers to the replication of DNA at the time of cell It is important for transfer of genes of parent(s) to the next species of same kind. The continuity of existence of species is based on this factor. This process becomes specifically important in the organisms that reproduce asexually, as in such organisms, only one parent is involved and there is no other source of variation in the DNA of the progeny from the parent.

Example: If a species is able to survive in a suitable water at some temperature. But due to climatic changes, there would be change in water temperature so the species may die and become extinct. But this does not happen in nature as there is always some change in DNA replication is present and some identical species but they although they are similar. Some individuals of this species of bacteria, due to this little variation in their DNA, will be capable of surviving in warmer water, thereby ensuring the continuity of species. This is how variations incorporated in DNA during replication are important. .

• Reproduction ensures that new offsprings are produced continuously to replace the dying individuals of the Thus, it ensures continuity of life and provides stability to the population.

• Variation during reproduction ensures that a species can survive and flourish even in adverse conditions. However, these adverse conditions might or might not appear during the life cycle of a specific individual. Thus, it is beneficial to the species but not necessarily for an individual.