An Overview of Ncert Books Class 12 Biology Chapter 9 Free Download
FAQs on Ncert Books Class 12 Biology Chapter 9 Free Download
1. What are some of the most frequently asked 5-mark questions from Chapter 9, Strategies for Enhancement in Food Production, for the CBSE Board Exam 2025-26?
For the CBSE Board Exam 2025-26, students should focus on the following expected 5-mark questions:
Explain the various steps involved in breeding a new genetic variety of a crop. This should include details on collection of variability, evaluation and selection of parents, cross-hybridisation, and testing of superior recombinants.
What is Multiple Ovulation Embryo Transfer (MOET) technology? Describe the entire process and explain its significance in modern cattle breeding programs.
Describe the process of plant breeding for developing disease resistance in crops. Mention the steps involved and provide two examples of crop varieties bred for disease resistance.
2. Why has the enhancement of food production become a major necessity, and what are the two main approaches to achieve this?
The enhancement of food production is a major necessity primarily to meet the nutritional demands of the ever-increasing global population. With limited land for agriculture, it is crucial to increase yield per unit area. The two main approaches to achieve this are Animal Husbandry, which deals with the scientific management of livestock for better yield and quality, and Plant Breeding, which involves developing high-yielding and disease-resistant crop varieties.
3. What is biofortification? State its primary objective and provide an important example as per the Class 12 syllabus.
Biofortification is the scientific method of breeding crops to increase their nutritional value. The primary objective is to improve public health by tackling deficiencies of essential micronutrients like vitamins, minerals, and proteins in the population. An important example is the development of Atlas 66 wheat, which has a significantly higher protein content compared to traditional wheat varieties.
4. Differentiate between inbreeding and outbreeding in animal husbandry. What are the major advantages of each technique for a breeder?
Inbreeding and outbreeding are two key strategies in animal husbandry:
Inbreeding refers to the mating of more closely related individuals within the same breed for 4-6 generations. Its main advantage is that it increases homozygosity, which helps in accumulating superior genes and eliminating less desirable genes.
Outbreeding is the breeding of unrelated animals. This can be between individuals of the same breed with no common ancestors (out-crossing), different breeds (cross-breeding), or different species (interspecific hybridisation). Its main advantage is that it helps overcome inbreeding depression and introduces new, desirable traits into the population.
5. How does Multiple Ovulation Embryo Transfer (MOET) technology represent a significant improvement over traditional animal breeding methods for herd improvement?
MOET represents a significant improvement because it allows for the rapid multiplication of desirable genetic traits in a herd. In traditional breeding, a superior female can produce only one calf per year. With MOET, a genetically superior cow is induced to super-ovulate (produce 6-8 eggs instead of one) and is then artificially inseminated. The resulting embryos are collected and transferred to surrogate mothers. This allows a single superior female to produce many offspring in a short time, dramatically accelerating the rate of herd improvement.
6. What is Single-Cell Protein (SCP)? Explain why it is considered an important alternative food source for the future.
Single-Cell Protein (SCP) refers to the biomass or protein concentrate extracted from pure or mixed cultures of microorganisms like algae, fungi, yeast, and bacteria. It is considered an important alternative food source because:
It allows for the high-rate production of protein-rich food in a very small area.
Microorganisms can be grown using inexpensive substrates like agricultural waste, straw, and even sewage, which helps in reducing pollution.
The production is independent of climatic conditions, ensuring a stable food supply.
7. What is meant by 'somatic hybridisation'? What is the key achievement of this technique, even if the resulting plant was not commercially viable?
Somatic hybridisation is the process of fusing protoplasts (cells without cell walls) from two different plant varieties to create a hybrid plant. A key achievement of this technique was the creation of the 'pomato', a somatic hybrid of a potato and a tomato plant. Although the pomato did not have the desired combination of characteristics for commercial use, it was an important scientific milestone that demonstrated the possibility of overcoming natural barriers to hybridization and creating novel plant combinations.
8. From an examination perspective, why is continued inbreeding often considered a double-edged sword for a breeder?
From an examination perspective, this is a classic HOTS (Higher Order Thinking Skills) question. Continued inbreeding is a double-edged sword because while it is essential for developing pure lines and accumulating desirable superior genes, it also exposes harmful recessive alleles. If continued for too long, it can lead to a condition called inbreeding depression, where the fertility and overall productivity of the offspring decrease significantly. Therefore, a breeder must carefully balance the benefits of homozygosity with the risks of reduced fitness.
9. Explain the concept of 'totipotency' and how it forms the basis of plant tissue culture. What is an explant?
Totipotency is the inherent potential of a single plant cell to grow and develop into a whole plant under suitable laboratory conditions. This ability is the fundamental principle behind plant tissue culture. An 'explant' is any part of a plant, such as a piece of leaf, stem, or root, that is taken and grown in a sterile, nutrient-rich culture medium in a test tube. Because of totipotency, the cells of the explant can differentiate and regenerate into a complete, new plant.
