Cbse Class 12 Biology Revision Notes Chapter 9

Class 12 Biology Chapter 9 Notes – Strategies For Enhancement In Food Production

Biology is an essential subject in the field of science and medicine. The principles of Biology are also applied to animal husbandry and plant breeding to increase food production. With the increase in population worldwide, improving food production is a significant need. The Chapter’ Strategies For Enhancement In Food Production’  reveals the importance of Embryo transfer technology and tissue culture techniques for increasing food production.

Extramarks Class 12 Biology Chapter 9 Notes is a perfect guide for students to help them understand and gain complete knowledge of Food Enhancement Strategies. It is based on the CBSE Syllabus and referred from the NCERT textbook. Class 12 Biology Chapter 9 Notes includes all essential study resources for understanding fundamental concepts, step-by-step explanations and complex topics covered in the NCERT textbook syllabus.

Key topics covered in Class 12 Biology Chapter 9 Notes.

Given below are a few of the key topics as covered in our Class 12 Biology Chapter 9 Notes:

• Animal Husbandry
• Plant Breeding
• Single Cell Proteins
• Tissue Culture

Animal Husbandry:

The agricultural practice of breeding animals and raising livestock is called animal husbandry. Animal husbandry includes breeding buffaloes, cows, pigs, horses, etc. Fisheries include rearing, selling of fish, molluscs and crustaceans, etc. Some animals like crabs, fishes, cattle, sheep and camels have been used for essential products like milk, eggs, meat, wool, silk,  honey, etc.  

According to an estimation, more than 70% of the total world livestock population is in India and China. However, the world farm produce contribution is only 2%. Thus, in addition to conventional animal breeding practices, new technologies are required to improve quality and productivity.

For a boost in study preparation, students can visit the Extramarks website for Biology Chapter 9 Class 12 Notes.

Management of Farms and Farm Animals:

As covered in our Class 12 Biology Chapter 9 Notes, a professional approach is required to aid traditional farm management practices and boost farm production. 

Dairy Farm Management:

The management of farm animals for milk and its products to meet human demands is called Dairying. Let us read the critical aspects of Dairy Farm Management:

• Dairy Farm Management deals with processes that increase yield and enhance milk quality.
• Milk yield is mainly dependent on the quality of farm breeds. 
• Under climatic conditions, fine breeds with high yielding potential must combine with  resistance to diseases. 
• For the milk yield potential to be reaped, the cattle must be well looked after and free from disease. 
• Cattle feeding should follow a scientific method, prioritising the quality and quantity of fodder. 
• One must strictly follow the hygiene of both handlers and the cattle while milking, storing, and transporting the milk and milk products. 
• Today, all the above processes are becoming mechanised, and we can see a reduction of direct contact of the handler with the product. 
• Regardless, strict measures such as regular inspections, proper record keeping and regular visits by a veterinarian should be made mandatory.

Poultry Farm Management:

Poultry is a  class of domesticated birds used for food and their eggs. They include chicken, ducks, turkey and geese. Including these birds, the word Poultry may refer to the meat of other birds as well. The fundamental aspects of Poultry Farm Management are similar to dairy farming:

• Selection of suitable and disease-free breeds
• Proper farm conditions
• Good quality feed and water
• Proper Hygiene and Health care 

There are more real-life examples given in our Class 12 Biology Chapter 9 Notes for management of farms and farm animals. Students can visit Extramarks’ website and gain access to these chapter notes. 

Animal Breeding:

Breeding animals to increase the yield is a vital aspect of animal husbandry. We will study different types of breeding in detail such asInbreeding, outbreeding, outcrossing, cross-breeding and interspecific hybridisation.

Inbreeding:

Inbreeding is mating closely related individuals for 4-6 generations within the same breed. The breeding strategy involves superior mating males with superior females in pairs of the same breed. The progeny obtained from such matings undergo evaluation and the selection of superior males and females for further mating. A superior female among cattle is the cow or buffalo that yields more milk each lactation. A superior male is a bull, which gives rise to an outstanding progeny. Inbreeding is essential to evolve a pure line in an animal. However, there arises a chance of inbreeding depression when continued Inbreeding is done especially close inbreeding,  usually reduces fertility and productivity. 

Outbreeding:

The breeding of unrelated animals is called Outbreeding. This occurs between individuals of the same breed but has no common ancestors for 4-6 generations(outcrossing) or between different breeds (cross-breeding) or different species (interspecific hybridisation).

Out-crossing:

Outcrossing is the practice of mating animals for up to 4-6 generations in the same breed, with no common ancestors on their pedigree. The offspring is known as an outcross. It is considered the best breeding method for animals that are below average in milk production. A single outcross helps to control inbreeding depression.

Cross-breeding:

In cross-breeding, superior males are mated with superior females of another species. In this method, the desirable qualities of two different breeds must be combined. The progeny of hybrid animals may either be used for commercial production or may be subjected to some form of inbreeding that may develop new superior breeds. In Punjab, Hisardale is a new breed of sheep developed by crossing Marino rams and Bikaneri ewes.

Interspecific Hybridisation:

In this method, two different related species are mated. In some cases, the progeny may combine desirable features of both the parents and may be of considerable economic value—for Example, the mule.

Controlled Breeding Experiments:

Controlled breeding experiments are carried out by using artificial insemination. The collected semen is carried from the male parent and injected into the female’s reproductive tract. The semen may be used or frozen as desired and can be later transported by the breeder. In this way, desirable matings are carried out. 

Multiple Ovulation Embryo Transfer Technology (MOET):

The success rate of crossing mature males with mature female animals is low. MOET is a programme designed for herd improvement. In this method, hormones such as FSH are administered for follicular maturation and superovulation, where instead of one egg, they will produce 6-8 eggs. High milk-yielding female breeds and good quality meat-yielding bulls have been bred successfully to increase herd production in a short time.

Animal breeding is a vast topic and students often find it difficult to memorise the content. Our team of Biology experts have explained this complex topic in very easy-to-understand terms in our Class 12 Biology Chapter 9 Notes. 

Bee-keeping:

Apiculture is the conservation of beehives for the production of Honey. Bee-keeping should be practised in an area with wild shrubs, fruit orchards and cultivated crops. Honey is high in nutrition and also has medicinal values . Beeswax produced from Honey is used in multiple industries, such as the preparation of cosmetics and polishes. The rise in demand for Honey has led to the practice of apiculture. The most common species is Apis indica.

Bee-keeping requires knowledge, and several organisations teach bee-keeping. Given below are few of the factors to keep in mind while going for bee-keeping:

• Knowledge of nature.
• Habits of bees.
• Selection of suitable location.
• Hiving of swarms.
• Management of beehives in seasons.
• Collection of Honey and beeswax.

Each topic is explained in further detail in our Class 12 Biology Chapter 9 Notes. Students can register on Extramarks website and get access to these notes and other related study material.

Fisheries:

The fishery is an industry that involves the catching, processing or selling of fish, shellfish or other aquatic animals. Aquatic animals include prawns, crab, lobster, edible oysters, etc.; freshwater fish such as Catla, Rohu and common carp; marine fish like Hilsa, Sardines, Mackerel and Pomfrets. 

A few important highlights about the fishery industry as covered in our Class 12 Biology Chapter 9 Notes:

• Fisheries play a significant role in the Indian economy.
• It employs millions of fishers and farmers.
• It is the primary source of living in the coastal areas. 
• Different techniques have been implemented to increase production, such as aquaculture and pisciculture, including freshwater and marine fish. 
• These techniques have led to the fishery industry’s growth and increased the farmers’ incomes.

Plant Breeding:

Traditional farming, as described in the Class 12 Biology Chapter 9 Notes,  can only yield limited food for humans and animals. An increase in land with better management practices may increase yield, but only a little. 

With the introduction of the Green Revolution, Plant breeding as technology has helped increase yields and meet the needs of our country and export.

What is plant breeding?

Plant breeding is a method in which plant species are bred to create desired plant types that are well suited for cultivation, produce better yields, and resist disease.

• The practice of conventional plant breeding has continued since the beginning of human civilisation.
• Evidence of plant breeding records dates back to 9,000-11,000 years before.
• Today, we obtain all our major food crops from domesticated varieties.
• In  classical plant breeding, we see hybridisation of pure lines and artificial selection to produce plants with suitable traits of higher yield, nutrition and  resistance to diseases. 
• Plant breeding uses molecular genetic tools with advancements in genetics, molecular Biology and tissue culture.

Characteristics that the breeders have incorporated into crop plants are:

• Growth in crop yield and improved quality

• Increased tolerance to environmental stresses

• Resistance to pathogens

• Increased tolerance to pests and insects

Plant breeding programmes are carried out in an organised way worldwide. The Class 12 Biology Chapter 9 Notes state the following steps in breeding a new variety of crops:

1. Collection of variability: 

The root of any breeding programme is genetic variability. The preservation of all the different wild varieties of species and relatives of the cultivated species is necessary to utilise natural genes effectively. The entire collection is called germplasm and comprises the diverse alleles for all genes in a given crop collection.

2. Evaluation and selection of parents: 

The germplasm is  examined to select plants with a desirable combination of characters. The selected plants are increased and used in hybridisation and creation of Pure lines.

3. Cross hybridisation among the selected parents: 

The desired characters from two different parent characters are combined; for instance, the high protein quality of one parent is combined with disease resistance traits from another parent. This is only possible by cross-hybridisation, where desired characters are combined in one plant. 

4. Selection and testing of superior recombinants: 

This step selects the progeny of the hybrids with the desired character combination. The selection process is essential to the success of the breeding goals and needs careful scientific evaluation of the progeny. These are self-pollinated until they reach a homozygous state, so the characters will not segregate in the progeny.

5. Testing and commercialisation of new cultivars: 

The selected new lines are estimated for their yield and other agronomic traits. This survey is done by growing them in research and monitoring their performance under ideal fertiliser application, adequate irrigation, and other crop management practices. 

India is an agricultural country where nearly 33% of India’s GDP comes from agriculture and employs approximately 62% of the population. Various plant breeding techniques played a role in increasing food production after India’s independence. This phase is called the Green Revolution. 

Here are some examples as covered in our Class 12 Biology Chapter 9 Notes.

1. Wheat and Rice:

The years 1960 to 2000 saw an increase in wheat production from 11 million tonnes to 75 million tonnes while rice production scaled up to 89.5 million tonnes from 35 million tonnes. This was because of the development of semi-dwarf varieties of wheat and rice. Norman E. Borlaug, a Nobel laureate at the International Centre for Wheat and Maize Improvement in Mexico, evolved semi-dwarf wheat. In 1963, high-yielding and disease-resistant varieties such as Sonalika and Kalyan Sona were introduced in the wheat-growing areas of India. IR-8 and Taichung Native-1 developed Semi-dwarf rice varieties. The derivatives were introduced in 1966. In the following years, better-yielding semi-dwarf varieties such as  Jaya and Ratna were produced in India.

2. Sugar cane:

Saccharum Barberi was produced in north India but had poor sugar content and yield. Tropical canes that grew in south India, Saccharum officinarum, had higher sugar content with thicker stems but did not thrive well in north India. For desired qualities, the two species were successfully crossed to produce sugarcane varieties with greater yield, thick stems, more sugar and the ability to grow in areas of north India.

3. Millets:

Hybrids of maize, jowar and bajra have been developed progressively in India, leading to several wide yielding varieties resistant to water stress.

Plant Breeding for Disease Resistance:

Primarily seen in tropical climates, fungus, bacteria, and viruses alter the yield of cultivated crops. Often, 20-30% of the crop is lost or even total. The breeding and development of crops resistant to disease were focused on enhancing food production to solve this. This helps decrease the dependence on fungicides and bactericides. The ability of a plant to prevent the pathogen from causing disease is determined by the genetic composition of the host plant. Before breeding, it is advisable to know about the organisms that cause diseases and their transmission mode. Some fungal diseases include brown rust of wheat, red rot of sugarcane and late blight of potato. Bacterial diseases include black rot of crucifers; Diseases caused by viruses are tobacco mosaic, turnip mosaic, etc. 

The process and methods of plant breeding for disease resistance are covered in depth in our Class 12 Biology Chapter 9 Notes. Below is a brief summary about it covering a few salient aspects.

Methods of breeding for disease resistance:

Breeding is carried out by conventional breeding techniques for disease resistance and includes hybridisation and selection. Its steps are similar to those for breeding agronomic characters. 

The various stages are in the following sequence: 

• Screening germplasm for resistance sources.

• The hybridisation of selected parents.

• Selection and evaluation of the hybrids

• New varieties are tested and released.

Some crop varieties are bred by hybridisation and selection for disease resistance against fungi, bacteria and viruses. 

Table 9.1

Conventional breeding is limited by the availability of a fixed number of disease resistance genes in several crop varieties. Inducing mutations and screening the plant materials for Resistance sometimes helps identify desirable ones. The process by which genetic variations take place through changes in the base sequence within genes is called a mutation.  

Chemicals or radiation can induce mutations artificially. The selection and usage of the plants with the desired characteristics are called mutation breeding. In mung, Resistance to yellow mosaic virus and powdery mildew were induced by mutations. Moreover, Resistance to the yellow mosaic virus in bhendi resulted in a new variety of A. esculentus called Parbhani Kranti.

Plant Breeding for Developing Resistance to Insect Pests:

Insect and pest infestation also lead to enormous scale destruction of crop plants and crop production. Insect resistance in host crop plants may be due to biochemical, physiological and morphological characteristics—for instance, Resistance to cereal leaf beetles in wheat and jassids in cotton. High aspartic acid, low nitrogen and sugar content in maize lead to resistance to maize stem borers.

The plant breeding for developing resistance to insect pests is explained in further detail in our Class 12 Biology Chapter 9 Notes. 

Table 9.2

Plant Breeding for Improved Food Quality:

More than 840 million people lack adequate food to meet their daily nutritional requirements. Many suffer from micronutrient, protein and vitamin deficiencies because 

fruits, vegetables, legumes, fish and meat are not affordable. Diets lacking essential micronutrients like Iron, vitamin A, iodine and zinc increase the risk for disease and reduce mental abilities.

Biofortification: 

In this process, crops are bred with higher vitamins, minerals, proteins and healthier fats to improve public health. The objectives for improvement are:

• Protein content and quality.
• Oil content and quality.
• Vitamin content.

• Mineral content.

Compared to existing maize hybrids, maize hybrids in 2000 had twice the amount of the amino acids, lysine and tryptophan. Wheat variety with high protein content has been used as a donor for improving cultivated wheat. It is also possible to develop an iron-fortified rice variety containing more than five times the Iron consumed in the regular variety. Various vegetable crops are rich in vitamins and minerals. For instance,  Carrots, spinach, and pumpkin are enriched with Vitamin A ;  Bitter gourd, mustard, tomato and garden peas are full of Vitamin C; Iron and calcium-rich spinach and bathua and Protein-enriched beans.

Single Cell Protein (SCP):

• The population of humans and animals is increasing at an alarming rate. Thus conventional agricultural production of food may not be able to meet the growing demands. 
• A shift from grain to meat diets adds to the demand for cereals. It takes around 3-10 Kg of grain to obtain 1 Kg of meat by animal farming.
• Moreover, more than a quarter of the human population suffers from malnutrition. To solve this problem, we come across Single Cell Protein (SCP), the alternate source of proteins for animal and human nutrition.
• Microbes are being grown in industries as a high biological value protein source. 
• Spirulina, Blue-green algae, can be grown quickly on materials like wastewater from potato processing plants, straw, molasses, animal manure, etc. and produce large quantities of protein, minerals, fats, carbohydrates and vitamins. 
• This method also reduces environmental pollution.
• Certain bacterial species like Methylophilus methylotrophus can be expected to produce 25 tonnes of protein. 
•  The large-scale culture of mushrooms is an expanding industry, there are many people who consume edible mushrooms

Tissue Culture:

• With an increase in demand, traditional breeding techniques failed to keep up. Scientists discovered that whole plants could regenerate. 
• Any plant part can be developed in a test tube under sterile conditions in unique nutrient culture. This ability to grow a whole plant from any cell is called totipotency. 
• The applied methods must provide nutrients and growth regulators for the explants for regeneration; it is possible to obtain the propagation of a large number of plants in a brief period. This method is called micro-propagation.  
• Each plant is genetically identical to its parent plant and is called Somaclones.
• Another significant benefit of the method is the recovery of healthy plants from diseased plants. For instance, if a virus infects the plant, the meristem could be free of the virus. Hence, the meristem can be removed and grown in vitro to gain virus-free plants.
• Scientists have successfully cultured meristems of bananas, sugarcane, etc. 
• Scientists have even isolated protoplasts from two different plant varieties after digesting their cell walls. The protoplast having a desirable character can be used to get hybrid protoplasts, which further develop into a new plant. These hybrids are called somatic hybrids, and the process is called somatic hybridisation. 

Class 12 Biology Chapter 9 is an extensive chapter and many students struggle to understand a few aspects of different types of plant breeding techniques. We recommend students to register on Extramarks’ website and go through our Class 12 Biology Chapter 9 Notes to get a good understanding of the various elements covered in this chapter.

Class 12 Biology Chapter 9 Notes: Exercises & Answer Solutions

Extramarks provides a repository of  study materials for Class 12 students. Students can refer to Class 12 Biology Chapter 9 Notes to learn the importance of food enhancement for food production. Students are advised to register on the Extramarks website to refer to Exercise and Answer solutions for Biology Chapter 9,’ Strategies For Enhancement In Food Production. The answer solutions are based on NCERT Books. 

Students can also view the study materials for the CBSE Syllabus by selecting the links below:

• CBSE Revision Notes
• CBSE Syllabus
• CBSE Sample Papers
• CBSE previous year’s question papers
• CBSE extra questions

NCERT Exemplar for Class 12 Biology Chapter 9 Notes

NCERT Class 12 Biology Chapter 9 Exemplar Notes are fantastic study tools for students. It covers the CBSE Syllabus and consists of several CBSE extra questions, CBSE Revision Notes, CBSE Sample Papers and CBSE previous year’s question papers. This provides a plethora of information for students to increase their knowledge. 

NCERT Exemplar and Chapter 9 Biology Class 12 Notes, both available on the Extramarks website, are excellent study material for thoroughly reviewing all the chapters.

Key Features of Class 12 Biology Chapter 9 Notes

Class 12 Biology Notes Chapter 9 available on the Extramarks’ website forms a significant part in every student’s preparation plan. Here’s why:

• Biology experts prepare the Notes in a pointwise format.
• It consists of summarised content from NCERT textbooks.
• Class 12 Biology Chapter 9 Notes provide a basic understanding of essential concepts in an easy language.
• It covers the CBSE Syllabus and aids students in revision during the  examination.
•  Class 12 Biology Chapter 9 Notes are the most reliable and authentic notes  for  examination preparation.