Question

(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?

Answer 1

(a) Tissue culture is the process of propagating new plants, in a suitable growth medium, from a small piece of a plant's tissue, that is obtained from the growing tip of that plant.

(b) Orchids, Dahlia, carnation and Chrysanthemum are propagated by the method of tissue culture.

(c) DNA copying refers to the replication of DNA at the time of cell division. It is important for transfer of genes of parent(s) to the progeny. This ensures continuity of existence of a species. It also plays a very important role in giving rise to slight variations in offsprings from the parents. During replication, some variations are incorporated in the DNA, as no biochemical process is 100 % efficient. 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: Suppose there is some species of bacteria that is capable of surviving in temperate water. Now, consider a situation in which, due to global warming, the temperature of the temperate water bodies raises. If all the bacteria would have been identical, then all of them would have died because of this rise in temperature. However, it does not happen in nature. Due to slight variation in the DNA of progeny, not all the individuals of a species are identical, 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.

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

(e) 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.