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Q1. (i) What are the features of plants which will prevent insect and pest infestation? (ii) Name a man-made cereal and where it is used.

Solution

(i) The features of plants which will prevent insect and pest infestation are (a) Turning flowers nectarless. (b) To have intensive hair on the above ground parts of plants. (c) Toxins released by plants. (ii) A man-made cereal is Triticale, and it is used as fodder.

Q2. (i) Name the chemical used for doubling the chromosome number. (ii) Name the improved variety of wheat which was developed through hybridisation that took 12 years.

Solution

(i) Colchicine is used for doubling the chromosome number. (ii) HUW 468 is an improved variety of wheat which took 12 years to develop through hybridisation.

Q3. (i) What is plant breeding? List the two steps which classical plant breeding involves. (ii) How has mutation breeding helped in improving crop varieties? Give one example where this technique has helped. (iii) How has the breeding programme helped in improving public nutritional health? State two examples in support of your answer.

Solution

(i) Plant breeding is the manipulation of plant species to create desired plant types which are better suited for cultivation, give better yields and are disease resistant. Classical plant breeding involves the following steps: (a) Hybridisation of pure lines (b) Artificial selection to produce plants with desirable traits (ii) Inducing mutation in plants helps in producing desirable genes for disease resistance. Plants having desirable genes can either be multiplied directly or can be used in breeding. For example, in mung bean, resistance to yellow mosaic virus and powdery mildew were induced by mutations. (iii) Biofortification is the technology which has helped in improving public nutritional health by breeding crops with higher levels of vitamins and minerals or higher protein and healthier fats. In biofortification, protein, oil, vitamin, micronutrient and mineral content and their qualities are improved. For example, (a) Maize hybrids with more quantity of amino acids such as lysine and tryptophan were developed. (b) To increase wheat cultivation, an improved variety, Atlas 66, has been used as the donor for having a high protein content.

Q4. Describe the technology which has successfully increased the herd size of cattle in a short time to meet the increasing demands of growing human population.

Solution

Multiple Ovulation Embryo Transfer Technology (MOET) has successfully increased the herd size of cattle. The cow is administered with follicle-stimulating hormone (FSH) to induce follicular maturation and superovulation to produce 6 to 8 eggs. It is then mated or artificially inseminated. The fertilised eggs are recovered non-surgically and transferred to a surrogate mother, where they develop into an improved variety.

Q5. Rohit is a milkman. He asked his father that he has heard about high-milk-yielding cows but has no idea from where he can procure such a variety of cow. Rohit’s father, being an agricultural scientist, solved his son’s problem. Based on the above passage, answer the following questions: (i) What is artificial insemination? (ii) Name two superior varieties of cows. (iii) How did Rohit’s father help him?

Solution

(i) The collection of semen from the desired male parent and its injection into the reproductive tract of the selected female is called artificial insemination. (ii) Two superior varieties of cows are Jersey and Holstein. (iii) Rohit’s father advised him to get his cows artificially inseminated.

Q6. Define the terms somatic embryos and somatic hybrids. 

Solution

The embryos which develop from somatic cells of a callus culture are called somatic embryos. Fusion of two somatic cells of different varieties is called somatic hybrids.

Q7. Describe two main components of cattle feed.

Solution

Two main components of cattle feed are roughage and concentrate. Roughage includes the straw of cereals such as wheat, rice and jowar. Sudan grass and Napier grass are common fodder grasses which are highly nutritive but contain less minerals and proteins. Concentrate is also an animal feed which is rich in proteins and minerals. It is obtained from cottonseeds, oil cakes and cereal grains.

Q8. State the importance of biofortification. 

Solution

The main importance of biofortification is the nutritional quality which is better improved due to breeding of crops.

Q9. Explain the process of emasculation and bagging of flowers. State their importance in breeding experiments.

Solution

(i) The removal of anthers from the flower bud before the anther splits apart in bisexual flowers is called emasculation. It is done by using a pair of forceps. (ii) The emasculated flower is covered with a bag of suitable size, generally made of butter paper to prevent contamination of its stigma with unwanted pollen. This process is called bagging.   To obtain superior varieties, artificial hybridisation is one of the major approaches of crop improvement programmes. It is important that only the desired pollen grains are used for pollination and the stigma is protected from contamination.

Q10. Explain the efforts which must be put in to improve health, hygiene and milk yield of cattle in a dairy farm.

Solution

The efforts are as follows: (i) The cattle in the dairy farm must be housed and fed properly. (ii) Cleanliness should be maintained in the milking area. (iii) The health of the dairy cattle should be of utmost importance, and a veterinary doctor must visit regularly. (iv) Regular inspections of the farm, maintaining records, identification and rectification of problems should be done along with maintaining precautionary measures. (v) High-yielding and disease-resistant breeds can be selected to maximise benefits.

Q11. (i) Mention the property which enables explants to regenerate into a new plant. (ii) A banana herb is virus-infected. Describe the method which will help in obtaining healthy banana plants from this diseased plant.

Solution

(i) The property which enables the explants to regenerate into a new plant is called totipotency.   (ii) Healthy banana plants can be obtained from diseased plants by meristem culture. We select the apical and axillary meristem because it is free of virus. The meristem is taken out and is cultured in vitro by micropropagation in which virus-free plants are produced.

Q12. Write four objectives of animal breeding. 

Solution

Four objectives of animal breeding are (i) To produce more milk-yielding cows with longer lactation period. (ii) To produce pure lines through inbreeding. (iii) To combine good characters of different breeds or species of animals to produce cross-breeds. (iv) To produce animals of higher physical strength.

Q13. What is the main difference between layers and broilers? 

Solution

Layers are egg-laying birds, whereas broilers are meat-yielding birds.

Q14. In animal husbandry, if two closely related animals are mated for a few generations, it results in loss of fertility and vigour. Why is this so? 

Solution

Loss of fertility and vigour is referred to as inbreeding depression. This happens because the recessive alleles tend to get together and express harmful effects in the progeny.

Q15. State any one significance of interspecific hybridisation in plants.

Solution

It is important for breeding disease-resistant plant varieties.

Q16. What is dedifferentiation and redifferentiation?

Solution

Dedifferentiation is a process where the mature cells are transformed to meristematic cells leading to the formation of a callus. Redifferentiation is the development of entire plants from the cells of a callus.

Q17. Scientists have succeeded in recovering healthy sugarcane plants from a diseased one. (a) Name the part of the plant used as explants by scientists. (b) Describe the procedure which scientists follow to recover healthy plants. (c) Name the technology used for crop improvement.          

Solution

(a) The stem of Saccharum barberi and Saccharum officinarum is used as explants by scientists. (b) Under aseptic conditions, the explant is grown in a nutrient medium. The tissue proliferates to form undifferentiated mass. This mass is transferred to a medium containing growth hormones. (c) The technology used for crop improvement is plant breeding. 

Q18. What are the physical barriers of a cell in the protoplast fusion experiment? How are the barriers overcome?

Solution

The cell wall is an important physical barrier in the protoplast fusion technique of tissue culture. The barriers can be overcome by treatment of enzymes such as hemicellulase, cellulose and pectinase which digest the cell wall and release the protoplast surrounded by the cell membrane.

Q19. Give a brief account of tissue culture. Also give the advantages of micropropagation.

Solution

The production of whole plants from an explant by growing them on a suitable culture medium under sterile conditions in vitro is called tissue culture. The culture medium must be rich in vitamins, nutrients and growth regulatory hormones such as auxins and cytokinins. The plants which are produced by micropropagation are genetically identical and constitute somaclones.   The advantages of micropropagation are (i) Healthy disease-free plants can be grown by meristem culture. (ii) Somatic hybrids can be produced by tissue culture.

Q20. Why is the Italian bee preferred for beekeeping rather than the Indian bee? 

Solution

The Italian bee (Apis mellifera) is docile, less swarming and produces a high yield of honey.

Q21. Give an example of a somatic hybrid produced.

Solution

Pomato is a somatic hybrid of potato and tomato.

Q22. Name two growth regulators commonly used in plant tissue culture.

Solution

2,4-dichlorophenoxy acetic acid (2,4-D) and benzylaminopurine (BAP) are two growth regulators which are used in plant tissue culture. 

Q23. What is meant by the term ‘breed’? What are the objectives of animal breeding? 

Solution

The group of animals having same ancestry characters, general appearance and size is called ‘breed’. They have been developed as a result of animal breeding which aims at increasing the yield of animals and improving the desirable qualities of the progeny.

Q24. Expand SCP and PEG. What are their uses?

Solution

SCP stands for Single Cell Protein. Single cell protein is rich in protein and helps to reduce environmental pollution. PEG stands for Polyethylene Glycol. In protoplast fusion, the protoplasts are fused in a solution of polyethylene glycol and allowed to grow in a culture medium which gives rise to the callus.

Q25. Why does the pure line represent the progeny of homozygous plants?

Solution

Self-pollinated crops gradually become homozygous. Best homozygous individuals can be isolated from such crops. Pure lines are then produced by selection.

Q26. What is somatic hybridisation? Explain the various steps involved in the process. Mention any two uses of somatic hybridisation.

Solution

The process of fusion of protoplasts of somatic cells obtained from different varieties or species of plant on a suitable nutrient medium in vitro to develop a somatic hybrid is called somatic hybridisation. Various steps involved in somatic hybridisation are (i) Single cells are isolated from a single plant. (ii) The cell walls are digested by enzymes such as pectinase and cellulose to liberate the protoplasts. (iii) Naked protoplasts surrounded only by plasma membranes are isolated. (iv) The isolated protoplasts are fused to obtain hybrid protoplasts under sterile conditions in a nutrient medium. (v) The hybrid protoplasts are cultured in a suitable media to form new plants. Two uses of somatic hybridisation are (i) Somatic hybrids may be produced. (ii) Healthy plants can be recovered from diseased plants.

Q27. IARI has released several varieties of crop plants which are biofortified. Give three examples of such crops and their biofortification.

Solution

(i) IARI released Vitamin A-enriched carrots, spinach and pumpkin. (ii) Vitamin C-enriched bitter gourd, mustard and tomato. (iii) Iron- and calcium-enriched spinach.

Q28. How are somaclones cultured from explants in in vitro conditions? Why are somaclones so called?

Solution

The explant from the plant is grown in a culture medium which is rich in inorganic nutrient, vitamins and growth regulators such as auxins and cytokinins. This method of producing plants through tissue culture is called micropropagation. The plants produced from the original plant are genetically identical, so they are called somaclones.

Q29. Give four examples of microorganisms which help in the production of single cell protein.

Solution

Spirulina maxima, Methylophilus methylotrophus, Candida utilis and Paecilomyces variotii are helpful for production of single cell protein.

Q30. (i) Give two important contributions of Dr M. S. Swaminathan. (ii) Interspecific crosses are rare in nature and intergeneric crosses are almost unknown. Why?

Solution

(i) Two important contributions of Dr M. S. Swaminathan are  (a) Development of high-yielding varieties in rice. Example: Basmati rice  (b) Development of light-coloured wheat variety of Sharbati Sonora and Pusa Lerma from red-coloured Mexican wheat by gamma irradiation. (ii) Unrelated chromosomes in interspecific crosses and intergeneric crosses differ considerably and fail to pair during gametogenesis.