Class 12th Biology CBSE Solution
Exercises- Explain in brief the role of animal husbandry in human welfare.
- If your family owned a dairy farm, what measures would you undertake to improve the…
- What is meant by the term ‘breed’? What are the objectives of animal breeding?…
- Name the methods employed in animal breeding. According to you which of the methods is…
- What is apiculture? How is it important in our lives?
- Discuss the role of fishery in enhancement of food production.
- Briefly describe various steps involved in plant breeding.
- Explain what is meant by biofortification.
- Which part of the plant is best suited for making virus-free plants and why?…
- What is the major advantage of producing plants by micropropagation?…
- Find out what the various components of the medium used for propagation of an explant in…
- Name any five hybrid varieties of crop plants which have been developed in India.…
- Explain in brief the role of animal husbandry in human welfare.
- If your family owned a dairy farm, what measures would you undertake to improve the…
- What is meant by the term ‘breed’? What are the objectives of animal breeding?…
- Name the methods employed in animal breeding. According to you which of the methods is…
- What is apiculture? How is it important in our lives?
- Discuss the role of fishery in enhancement of food production.
- Briefly describe various steps involved in plant breeding.
- Explain what is meant by biofortification.
- Which part of the plant is best suited for making virus-free plants and why?…
- What is the major advantage of producing plants by micropropagation?…
- Find out what the various components of the medium used for propagation of an explant in…
- Name any five hybrid varieties of crop plants which have been developed in India.…
Exercises
Question 1.Explain in brief the role of animal husbandry in human welfare.
Answer:The practice of breeding and raising livestock is called animal husbandry. It is very useful for human welfare as it deals with caring and breeding livestock like buffaloes, cows, pigs, horses, cattle, sheep, camels, goats, etc. that are useful to humans.
Animal husbandry plays a vital role in human welfare because it helps to improve the quality and quantity of the products produced by these livestock. Some of the examples are as follows.
(a) Cattle farming helps to increase the production of milk.
(b) Poultry farming helps to increase the production of eggs.
(c) Fish farming helps to improve the quality and quantity of meat.
(e) Animal wastes like dung can be utilized to produce biogas and manure.
(d) Bee keeping helps to produce more honey and bee wax.
Question 2.If your family owned a dairy farm, what measures would you undertake to improve the quality and quantity of milk production?
Answer:Some of the measures I would undertake to improve the quality and quantity of milk production are as follows:
(a) Select good breeds with high-yielding potential and resistance to diseases
(b) Take care of the cattle well by providing them good-quality fodder and a better place to live in.
(c) Maintain cleanliness and hygiene while milking, storage and transport of the milk and its products.
(d) Visit a veterinary doctor regularly.
Question 3.What is meant by the term ‘breed’? What are the objectives of animal breeding?
Answer:A group of animals related by descent and similar in most characters like appearance, features, size, configuration, etc., are said to belong to one breed.
The objectives of animal breeding are as follows:
(a) Animal breeding helps to develop pure lines of cattle by inbreeding. When breeding is between animals of the same breed it is called inbreeding, while crosses between different breeds are called out-breeding.
(b) Sometimes continued inbreeding, usually reduces fertility and even productivity. This is called inbreeding depression. Here, out-crossing helps to overcome the problem of inbreeding depression. Out-crossing is the practice of mating of animals within the same breed, but having no common ancestors on either side of their pedigree up to 4–6 generations. The offspring of such a mating is known as an out-cross.
(c) Outbreeding helps to combine the good qualities of two different breeds.
(d) Outbreeding also helps to combine the desirable characters of two different species by interspecific hybridization.
Question 4.Name the methods employed in animal breeding. According to you which of the methods is best? Why?
Answer:Different methods of animal breeding are: inbreeding, out-breeding, out-crossing, cross-breeding and interspecific hybridisation.
Out of these methods, the best breeding method is of out-crossing because it increases the milk production and growth rate of beef cattle. Even a single outcross often helps to overcome the problem of inbreeding depression.
Question 5.What is apiculture? How is it important in our lives?
Answer:Apiculture is the maintenance of hives of honeybees for the production of honey and bee wax. It is also known as bee-keeping.
Apiculture is of great importance to the human beings in the following ways:
(a) Honey has a high nutritive value. Thus, it is included in our diet.
(b) Honey also has medicinal importance and hence used as laxative, antiseptic and sedative.
(c) Honey is used in the manufacturing of cakes.
(d) Honeybees also produce beeswax, which is used in the preparation of cosmetics and polishes of various kinds.
(e) Honeybees act as pollinating agents and thus help in improving crop production.
Question 6.Discuss the role of fishery in enhancement of food production.
Answer:A large number of our population is dependent on fish, fish products and other aquatic animals such as prawn, crab, lobster, edible oyster, etc., for food. Some of the freshwater fishes which are very common include Catla, Rohu and common carp. Some of the marine fishes that are eaten include – Hilsa, Sardines, Mackerel and Pomfrets.
Fishery plays an important role in enhancement of food production because of the following reasons.
(a) Fishes provide food that is the rich source of animal proteins, fats, good amount of vitamins A and D and iodine.
(b) Fish’s meat is easily digestible than the meat of other animals.
(c) Fish breeding also produces a number of useful by-products like vitamin-rich liver oil.
Question 7.Briefly describe various steps involved in plant breeding.
Answer:Plant breeding is the process by which we produce desired characteristics in a plant. It is done by crossing different varieties to create better crops that are better suited for cultivation, give better yields and are disease resistant. Plant breeding is carried out in a systematic way and involves the following steps:
(i) Collection of variability – This step involves the collection and preservation of all the different wild varieties, species and relatives of the cultivated species. The entire collection (of plant/seeds) having all the diverse alleles for all genes in a given crop is called germplasm collection.
(ii) Evaluation and selection of parents – This step involves the evaluation of the germplasm so as to identify plants with desirable combination of characters.
(a) Selection in self-pollinated crops – The degree of cross-pollination is less than 5%. There is repeated self-pollination of selected plants till superior homozygous genotypes are obtained. The best one is used as new variety. The self-pollinated progeny of homozygous plant constitutes a pure line. (b) Selection in cross-pollinated crops – The cross pollinated crop are heterozygous for most of their genes and their population contains plants of several different genotypes. Superior genotype plants are selected and are allowed to crossbreed (these plants are not allowed to self-breed) so that heterozygosity is also maintained.
(iii) Cross hybridization among the selected parents – This step involves the hybridization i.e., crossing of two or more types of plants for bringing their traits together in the progeny. The procedure of hybridization involves selection of parents with desired characters, selfing, emasculation, bagging, tagging and artificial pollination.
(iv) Selection and testing of superior recombinants – This step involves the selection of the plants, from the progeny of hybrids, which have the desired combined character. The selected plants are then self-pollinated for several generation to get a uniformity i.e., homozygosity.
(v) Testing, release and commercialisation of new cultivars – This step involves the the evaluation of newly selected lines for their yield and other agronomic traits of quality, disease resistance, etc. These selected cultivars are then tested with local best cultivar and then are released for commercial purposes.
Question 8.Explain what is meant by biofortification.
Answer:Biofortification is breeding crops with higher levels of vitamins and minerals, or higher protein and healthier fats. It helps to improve general health of people by improving the quality of crops.
Biofortification is important because of the following reasons.
(a) It improves protein contents and quality in crops.
(b) It improves oil contents and quality in crops.
(c) It improves vitamin contents in crops.
(d) It improves micronutrient and mineral contents in crops.
Question 9.Which part of the plant is best suited for making virus-free plants and why?
Answer:Apical and axillary meristem of plant is free from virus. Thus, we can remove the meristem and grow it in vitro to obtain virus-free plants. Meristems of banana, sugarcane, potato have been cultured to produce virus-free plants.
Question 10.What is the major advantage of producing plants by micropropagation?
Answer:Micropropagation is the method of producing a large number of plants through tissue culture. Each of these plants will be genetically identical to the original plant from which they were grown. Such plants are known as somaclones. Thus, this method helps in producing clones of a plant in large number within a short span of time. Such clones are virus-free also. Many food plants like tomato, banana, apple, etc., are produced on a large scale using this method.
Question 11.Find out what the various components of the medium used for propagation of an explant in vitro are?
Answer:The medium used for propagation of an explant in vitro is called nutrient medium or culture medium. This medium must provide a carbon source such as sucrose and also inorganic salts, vitamins, amino acids and growth regulators like auxins, cytokinins with or without the use of yeast extract or coconut milk or banana pulp. The culture medium can be kept liquid, made semisolid with gelatin or solidified with agar.
Question 12.Name any five hybrid varieties of crop plants which have been developed in India.
Answer:The five hybrid varieties of crop plants which have been developed in India are as follows:
1. Wheat: Sonalika and Kalyan Sona
2. Rice: Jaya and Ratna
3. Maize: Pusa Composite 3 and Jagannath
4. Cowpea: Pusa Komal
5. Mustard: Pusa Swarnim
Explain in brief the role of animal husbandry in human welfare.
Answer:
The practice of breeding and raising livestock is called animal husbandry. It is very useful for human welfare as it deals with caring and breeding livestock like buffaloes, cows, pigs, horses, cattle, sheep, camels, goats, etc. that are useful to humans.
Animal husbandry plays a vital role in human welfare because it helps to improve the quality and quantity of the products produced by these livestock. Some of the examples are as follows.
(a) Cattle farming helps to increase the production of milk.
(b) Poultry farming helps to increase the production of eggs.
(c) Fish farming helps to improve the quality and quantity of meat.
(e) Animal wastes like dung can be utilized to produce biogas and manure.
(d) Bee keeping helps to produce more honey and bee wax.
Question 2.
If your family owned a dairy farm, what measures would you undertake to improve the quality and quantity of milk production?
Answer:
Some of the measures I would undertake to improve the quality and quantity of milk production are as follows:
(a) Select good breeds with high-yielding potential and resistance to diseases
(b) Take care of the cattle well by providing them good-quality fodder and a better place to live in.
(c) Maintain cleanliness and hygiene while milking, storage and transport of the milk and its products.
(d) Visit a veterinary doctor regularly.
Question 3.
What is meant by the term ‘breed’? What are the objectives of animal breeding?
Answer:
A group of animals related by descent and similar in most characters like appearance, features, size, configuration, etc., are said to belong to one breed.
The objectives of animal breeding are as follows:
(a) Animal breeding helps to develop pure lines of cattle by inbreeding. When breeding is between animals of the same breed it is called inbreeding, while crosses between different breeds are called out-breeding.
(b) Sometimes continued inbreeding, usually reduces fertility and even productivity. This is called inbreeding depression. Here, out-crossing helps to overcome the problem of inbreeding depression. Out-crossing is the practice of mating of animals within the same breed, but having no common ancestors on either side of their pedigree up to 4–6 generations. The offspring of such a mating is known as an out-cross.
(c) Outbreeding helps to combine the good qualities of two different breeds.
(d) Outbreeding also helps to combine the desirable characters of two different species by interspecific hybridization.
Question 4.
Name the methods employed in animal breeding. According to you which of the methods is best? Why?
Answer:
Different methods of animal breeding are: inbreeding, out-breeding, out-crossing, cross-breeding and interspecific hybridisation.
Out of these methods, the best breeding method is of out-crossing because it increases the milk production and growth rate of beef cattle. Even a single outcross often helps to overcome the problem of inbreeding depression.
Question 5.
What is apiculture? How is it important in our lives?
Answer:
Apiculture is the maintenance of hives of honeybees for the production of honey and bee wax. It is also known as bee-keeping.
Apiculture is of great importance to the human beings in the following ways:
(a) Honey has a high nutritive value. Thus, it is included in our diet.
(b) Honey also has medicinal importance and hence used as laxative, antiseptic and sedative.
(c) Honey is used in the manufacturing of cakes.
(d) Honeybees also produce beeswax, which is used in the preparation of cosmetics and polishes of various kinds.
(e) Honeybees act as pollinating agents and thus help in improving crop production.
Question 6.
Discuss the role of fishery in enhancement of food production.
Answer:
A large number of our population is dependent on fish, fish products and other aquatic animals such as prawn, crab, lobster, edible oyster, etc., for food. Some of the freshwater fishes which are very common include Catla, Rohu and common carp. Some of the marine fishes that are eaten include – Hilsa, Sardines, Mackerel and Pomfrets.
Fishery plays an important role in enhancement of food production because of the following reasons.
(a) Fishes provide food that is the rich source of animal proteins, fats, good amount of vitamins A and D and iodine.
(b) Fish’s meat is easily digestible than the meat of other animals.
(c) Fish breeding also produces a number of useful by-products like vitamin-rich liver oil.
Question 7.
Briefly describe various steps involved in plant breeding.
Answer:
Plant breeding is the process by which we produce desired characteristics in a plant. It is done by crossing different varieties to create better crops that are better suited for cultivation, give better yields and are disease resistant. Plant breeding is carried out in a systematic way and involves the following steps:
(i) Collection of variability – This step involves the collection and preservation of all the different wild varieties, species and relatives of the cultivated species. The entire collection (of plant/seeds) having all the diverse alleles for all genes in a given crop is called germplasm collection.
(ii) Evaluation and selection of parents – This step involves the evaluation of the germplasm so as to identify plants with desirable combination of characters.
(a) Selection in self-pollinated crops – The degree of cross-pollination is less than 5%. There is repeated self-pollination of selected plants till superior homozygous genotypes are obtained. The best one is used as new variety. The self-pollinated progeny of homozygous plant constitutes a pure line. (b) Selection in cross-pollinated crops – The cross pollinated crop are heterozygous for most of their genes and their population contains plants of several different genotypes. Superior genotype plants are selected and are allowed to crossbreed (these plants are not allowed to self-breed) so that heterozygosity is also maintained.
(iii) Cross hybridization among the selected parents – This step involves the hybridization i.e., crossing of two or more types of plants for bringing their traits together in the progeny. The procedure of hybridization involves selection of parents with desired characters, selfing, emasculation, bagging, tagging and artificial pollination.
(iv) Selection and testing of superior recombinants – This step involves the selection of the plants, from the progeny of hybrids, which have the desired combined character. The selected plants are then self-pollinated for several generation to get a uniformity i.e., homozygosity.
(v) Testing, release and commercialisation of new cultivars – This step involves the the evaluation of newly selected lines for their yield and other agronomic traits of quality, disease resistance, etc. These selected cultivars are then tested with local best cultivar and then are released for commercial purposes.
Question 8.
Explain what is meant by biofortification.
Answer:
Biofortification is breeding crops with higher levels of vitamins and minerals, or higher protein and healthier fats. It helps to improve general health of people by improving the quality of crops.
Biofortification is important because of the following reasons.
(a) It improves protein contents and quality in crops.
(b) It improves oil contents and quality in crops.
(c) It improves vitamin contents in crops.
(d) It improves micronutrient and mineral contents in crops.
Question 9.
Which part of the plant is best suited for making virus-free plants and why?
Answer:
Apical and axillary meristem of plant is free from virus. Thus, we can remove the meristem and grow it in vitro to obtain virus-free plants. Meristems of banana, sugarcane, potato have been cultured to produce virus-free plants.
Question 10.
What is the major advantage of producing plants by micropropagation?
Answer:
Micropropagation is the method of producing a large number of plants through tissue culture. Each of these plants will be genetically identical to the original plant from which they were grown. Such plants are known as somaclones. Thus, this method helps in producing clones of a plant in large number within a short span of time. Such clones are virus-free also. Many food plants like tomato, banana, apple, etc., are produced on a large scale using this method.
Question 11.
Find out what the various components of the medium used for propagation of an explant in vitro are?
Answer:
The medium used for propagation of an explant in vitro is called nutrient medium or culture medium. This medium must provide a carbon source such as sucrose and also inorganic salts, vitamins, amino acids and growth regulators like auxins, cytokinins with or without the use of yeast extract or coconut milk or banana pulp. The culture medium can be kept liquid, made semisolid with gelatin or solidified with agar.
Question 12.
Name any five hybrid varieties of crop plants which have been developed in India.
Answer:
The five hybrid varieties of crop plants which have been developed in India are as follows:
1. Wheat: Sonalika and Kalyan Sona
2. Rice: Jaya and Ratna
3. Maize: Pusa Composite 3 and Jagannath
4. Cowpea: Pusa Komal
5. Mustard: Pusa Swarnim
