Bihar Board - Class 12 Biology - Chapter 9: Strategies for Enhancement in Food Production Short Answer Question

Q.1. Can gamma rays be used in crop improvement programmes?

A.1. Analysis of plants is carried out in closed chambers. These plants are consequently tested for desired mutations to be induced to breed further. The irradiated plants do not possess any adverse effects of radiation, hence are not harmful and can be used.

Q.2. Why does the mating of two closely related animals after a few generations lead to loss of fertility and vigor in animal husbandry?

A.2. Since recessive alleles tend to get together and express causing harmful effects in the progeny. This is called inbreeding depression.

Q.3. Where and how is a man-made cereal developed? Give an example.

A.3. An example is Triticale. It is developed by a cross of the plants – common wheat (Triticum aestivum) and European rye (Secale cereale). It is used as a substitute for wheat in a few parts of the world.

Q.4. Why are plants derived from protoplast culture named somatic hybrids?

A.4. Since the plants are formed after the fusion of two different varieties of isolated protoplasts, they are known as somatic hybrids. Each protoplast possesses a desirable character to obtain a hybrid protoplast which can further be grown to form a plant.

Q.5. What is protoplast fusion?

A.5. The fusion of isolated protoplasts to form a somatic hybrid is called protoplast fusion. The hybrid thus formed has the characteristics of both protoplasts.

Q.6. Why are culture meristems easier to culture compared to permanent tissues?

A.6. Meristems are undifferentiated cells that divide continuously and they have thin and elastic walls thus suitable for tissue culture as opposed to permanent cells which have to be differentiated to be able to divide. They also possess thick walls.

Q.7. Why are proteins synthesized from single cell proteins, Spirulina?

A 7. Single cell proteins are proteins produced by microorganisms. One such unicellular microbe is the Spirulina. Thus the proteins produced by Spirulina are termed as single-cell proteins.

Q.8. Give one difference between a hybrid and a somatic hybrid.

A.8. A hybrid is obtained by crossing two selected plants of the opposite sex whereas somatic hybrids are obtained by fusion of any protoplasts from two different species of plants which are further cultured.

Q.9. What is emasculation? When is it done and why?

A.9. It is the removal of stamens from the bisexual flower that is used as a female parent in plant hybridization. It is done so as to avoid self-pollination. It is to be done at the bud stage before the anthers dehisce.

Q.10. What are the two main limitations of the plant hybridization programme?

A.10. Limitations:

• Compatibility of parents

• Limited availability of identified disease-resistant genes in crops

• It is a tedious and time-consuming process

Q.12. Why are intergeneric crosses almost unknown and interspecific crosses rare in nature?

A.12. Male and female animals of two varied related species are mated in interspecific crosses and their fertility varies. In a certain case, the progeny may display desirable features of both the parents and may be of economic value. Example – A mule, whereas the female counterparts can breed with the species which is rare in nature. Intergeneric hybridization, on the other hand, is the cross of two different genera which is almost unknown in nature. They never form the complete zygote and are infertile.