Samacheer Class 11 Bio Zoology - Trends in Economic Zoology

• Vermicomposting provides excellent organic manure for sustainable agro-practices.
• Marketing of vermicompost can provide a supplementary income.
• Vermicompost is rich in essential plant nutrients.
• It improves soil structure, texture, aeration, and water holding capacity and prevents soil erosion.
• It is rich in nutrients and an eco-friendly amendment to soil for farming and terrace gardening,
• It enhances seed germination and ensures good plant growth.

Each worker has to perform different types of work in her lifetime. During the first half of her life, she becomes a nurse bee attending to indoor duties such as secretion of royal jelly, prepares bee- bread to feed the larvae, feeds the queen, takes care of the queen and drones, secretes beeswax, builds combs, cleans and fans the beehive. Then she becomes a soldier and guards the beehive. In the second half of her life lasting for three weeks, she searches and gathers the pollen, nectar, propolis, and water.

• The rearing of silkworm on a commercial scale is called sericulture.
• It is an agro-based industry comprising of
• Cultivation of food plants for the silkworms.
• Rearing of silkworms.
• Reeling and spinning of silk.
• Silk fibers are utilized in preparing silk clothes.
• Silk is used in industries and for military purposes.
• Silk is used in the manufacture of fishing fibres, parachutes, cartridge bags, insulation coils for telephone, wireless receivers, tyres of racing cars, filter fibres, in medical dressings and suture materials.

Economic importance of fish:-
Fishes form a rich source of protein food and provide a good staple food to tide over the nutritional needs of man. Fish species such as sardines, mackerel, tuna, herrings have high amino acids concentration particularly histidine which is responsible for the meaty flavor of the flesh. It is rich in fat such as omega 3 fatty acids. Minerals such as calcium, magnesium, phosphorus, potassium, iron, manganese, iodine and copper.
Some of the fish by-products are: Fish oil is the most important fish by-product. It is derived from fish liver and from the fish body.
Fish liver oil is derived from the liver which is rich in vitamin A and D, whereas fish body oil has high content of iodine, not suitable for human consumption, but is used in the manufacture of laundry soaps, paints and cosmetics. Fish meal is prepared from fish waste after extracting oil from the fish.
The dried wastes are used to prepare food for pig, poultry and cattle. The wastes obtained during the preparation of fish meal are widely used as manure.
Isinglass is high-grade collagen produced from dried air bladder or swim bladder of certain fishes viz. catfish and carps. The processed bladder which is dissolved in hot water forms gelatin having adhesive property. It is primarily used for clarification of wine, beer and vinegar.

Economic importance of Lac:
* Lac is largely used as a sealing wax and adhesive for optical instruments.
* It is used in the electric industry, as it is a good insulator.
* It is used in preparations of shoe and leather polishes and as a protective coating of wood.
* It is used in laminating paper board, photographs, engraved materials and plastic moulded articles.
* Used as a filling material for gold ornaments.

• Shellac with denatured alcohol is used to remove dust on the walls.
• Coating of metals with shellac prevents rusting.
• Shellac coating on citrus fruits increases their shelf life.

Advantages of artificial insemination:
* It increases the rate of conception
* It avoids genital diseases
* Semen can be collected from injured bulls which have desirable traits
* Superior animals located apart can be bred successfully.

There are two methods of animal breeding, namely inbreeding and outbreeding.
1. Inbreeding:
Breeding between animals of the same breed for 4-6 generations is called inbreeding.
2. Outbreeding:
The breeding between unrelated animals is called outbreeding. It is done in three ways;
* Outcrossing: It is the breeding between unrelated animals of the same breed but having no common ancestry. The offspring of such a cross is called an outcross.
* Crossbreeding: Breeding between a superior male of one breed with a superior female of another breed. The cross-bred progeny has superior traits (hybrid vigour or heterosis).
* Interspecific hybridization: In this method of breeding mating is between male and females of two different species.

Multiple Ovulation Embryo Transfer Technology (MOET) is a method of propagation of animals with desirable traits. This technology is used to produce high milk-yielding females and high-quality meat-yielding bulls in a short time.

The peculiarity of ducks:
The ducks body is fully covered with oily feathers. They have a layer of fat under their skin which prevents it from getting wet. They lay eggs at night or in the morning. The ducks feed on rice bran, kitchen wastes, waste fish and snails.
Part – II
11th Bio Zoology Guide Trends in Economic Zoology Additional Important Questions and Answers
I. Choose The Best Options

• Vermi wash is a liquid collected after the passage of water through a column of vermibed.
• It is useful as a foliar spray to enhance plant growth and field.

The process of soaking cocoons in hot water (95° – 97°) for 10 – 15 minutes to soften the gum that binds the silk threads together is called cooking.

The cocoons are soaked in hot water at 95° – 97°c for 10 -15 minutes to soften the gum that binds, the silk threads together are called cooking.

* To improve growth rate
* enhancing the production of milk meat egg etc.
* Increasing the quality of the animal products
* Improved resistance to disease.
* Increased reproductive rate.
3 marks
III. Short answers

Characteristics of cultivable fishes.
The special characteristic features of cultivable fishes are:
* Fishes should have a high growth rate in a short period of culture.
* They should accept a supplementary diet.
* They should be hardy enough to resist some common diseases and infections of parasites.
* Fishes proposed for polyculture should be able to live together without interfering or attacking other fishes.
* They should have high conversion efficiency so that they can effectively utilize the food.

External factors affecting fish culture. The factors that affect fish culture are temperature, light rain, water, flood, water current, turbidity of the water, pH hardness, salinity and dissolved O 2. Light and temperature also play an important role in fish breeding.

Uses of Silk:-
1. Silk fibers are utilized in preparing silk clothes. Silk fibers are now combined with other natural or synthetic fibers to manufacture clothes like Teri-Silk, Cot-Silk etc. Silk is dyed and printed to prepare ornamented fabrics. They are generally made from Eri-silk or spun silk.
2. Silk is used in industries and for military purposes.
3. It is used in the manufacture of fishing fibers, parachutes, cartridge bags, insulation coils for telephone, wireless receivers, tyres of racing cars, filter fibres, medical dressings, and suture materials.

• The house of honey bees is a beehive.
• The hive consists of hexagonal cells made up of wax secreted by the abdomen of a worker bee.
• These hives are found hanging vertically from the rocks. building or branches of trees.
• The young stages of the honey bee accommodate the lower and central cells of the hive.
• In the rock beehives, there are separate cells for queens, workers, and drones.

Types of prawn fishery
* Shallow water prawn fishery – located on the west coast restricted to shallow waters.
* Estuaries and backwaters or saline lake prawn fishery – The area of production of prawns are the backwaters seen along the Western coast, Ennur, Pulicat, Chilka lake, and Estuaries of Ganga and Brahmaputra rivers.
* Freshwater prawn fishery – Prawns are caught from the rivers and lakes throughout India.
* Marine prawn fishery – Most of the marine prawns are caught along the Indian coast belonging to the family Penaeidae.

Breeding between animals of the same breed for 4 – 6 generations is called inbreeding.
Effects:
* It increases homozygosity.
* Exposes the harmful recessive genes.
* Reduces fertility.
* It produces inbreeding depression.

First group:
* The humus formers dwell on the surface and feed on organic matter.
* They are darker in colour.
* These worms are used for vermicomposting.
Second group:
The humus feeders are burrowing worms that are useful in making the soil porous and mixing and distributing humus throughout the soil.

• It is used for making candles.
• It is used for making waterproofing materials.
• It is used for making home appliances polishes for leather.
• It is used in pharmaceutical industries.

• It is used as sealing wax.
• It is used as a good insulator.
• It is used in the preparation of shoes and leather polishes.
• It is a protective coating of wood.
• It is used in the preparation of plastic moulded articles.
• It is used as a filling material for gold ornament.

• It does not require high capital for the construction and maintenance of poultry farming.
• It does not require a big space.
• It ensures a high return on investment.
• It provides fresh and nutritious food and has a huge global demand.
• It provides employment opportunities for the people.

• Milk is a rich source of vitamin A, B 2, B 1
• It is a complete food for infants.
• Dairy products such as yoghurt cheese butter ice cream condensed milk, milk powder are produced from milk.

Types of Movements:
* Vermicompost is the compost produced by the action of earthworm in association with all other organisms in the compost unit.
* Vermicompost bed may be selected on upland or an elevated level.
* We have to construct a cement pit of 3 x 2 x 1m size over the ground surface using bricks.
* The vermibed should not be exposed to direct sunlight.
* The first layer of vermibed contains gravel at about 5 cm in height followed by coarses and to a thickness of 3.5 cm which will facilitate the draniage of excess water.
* The unit can now be loaded with digested biomass or animal dung.
* Earthworms such as periyonyx excavatus Eisenia fetida or Eudrilus eugeniae are introduced on the top.
* Earthworms release their castings on the surface.
* Vermiwash is a liquid collected after the passage of water through a column of vermibed. It is useful as a foliar spray to enhance plant growth.

• This moth is unisexual.
• Just after emergence male moth copulates with females for 2-3 hours.
• Just after copulation female starts laying about 400-500 eggs.
• The eggs after ten days of incubation hatch into larva called a caterpillar.
• The newly hatched caterpillar is about 3mm in length and is pale yellowish-white colour.
• The mandibulate type of mouthparts adapted to feed easily on the mulberry leaves.
• After 1st, 2nd, 3rd and 4th moulting caterpillars get transformed into 2nd, 3rd, 4th and 5th instars respectively.
• It develops salivary glands, stops feeding and undergoes pupation.
• The cafter pillars stop feeding and moves towards the comer among the leaves and secrete a sticky fluid through their silk gland.
• The secreted fluid comes out through spinnerret which hardens on exposure to air and is wrapped around the body of cater pillar in the forms of a covering called a cocoon.
• The length of continous thread secreted a caterpillar for the formation of cocoon is about 1000 -1200 metres.
• The pupal period lasts for 10-12 days and the pupae cut through the cocoon and emerge into adult moth.
• In larvel stages the larvae moults for 3 or 4 times or 5 times and become a matured moth.

• Vermicompost is rich in essential plant nutrients.
• It improves soil structure texture aeration and water holding capacity and prevents soil erosion.
• Vermicompost is rich in nutrients and an eco-friendly amendment soil for farming and terrace gardening.
• It enhances seed germination and ensures good plant growth.

Following steps are taken for the insertion of the nucleus:
a. Fitness of oyster for operation:
The selected oysters for the insertion of the nucleus should be healthy and strong enough to overcome the stress during operation.
b. Preparation of graft tissues:
The piece of tissue which is inserted inside the mantle is called as ‘GRAFT’ tissue. The outer edges of these graft squares must be known because nacre secreting cells are found only on the outer surface of the mantle so it is essential to keep the outer surface in contact with the inserted nucleus.
c. Preparation of the nucleus:
Any small particle may function as a nucleus to initiate the pearl formation but it is reported that the calcareous nucleus is the best because the deposition of nacre was found to be more on the calcareous nucleus.
d. Insertion of the nucleus:
For the insertion of the nucleus, oysters are fixed in a desk clamp in the position of the right valve facing upward. Mantle folds are smoothly touched to expose the foot and the main body mass, followed by an incision into the epithelium of the foot and a slender channel into the main mass of one graft tissue which functions as a bed for the nucleus.
e. Post-operation care:
Nucleated oysters are placed into cages and suspended into seawater and attached with floating rafts to a depth of 2 to 3 meters for about 6 to 7 days to recover from the shocks due to operation. This period of 6 to 7 days is known as the ‘Recovery period’. About 3000 to 3600 nucleated oysters are kept in different cages suspended in seawater at 2 to 3 meters depth for 3 to 6 years and undisturbed except at the time of clearing and inspection.
f. Harvesting of pearl:
Pearls are harvested in the month of December to February which may slightly vary according to climatic conditions. After the completion of 3 years of the insertion of the nucleus, pearl oysters are harvested from the sea and the pearls are taken out from the shell.
g. Clearing of pearls:
After taking out the pearls from the oyster’s shell they are washed properly, cleared with the soap solution.

• Silk fibres are utilized in preparing silk cloths.
• Silk fibres are combined with natural or synthetic fibres to manufacture Teri – silk and cot silk.
• Silk is dyed and printed to prepare ornamental fabrics.
• Silk is used in industries and for military purposes.
• It is used in the manufacturing of fishing fibres, parachutes insulation coils for telephones.
• They are used in the preparation of tyres for racing cars, filter fibres in medical dressings and as suture materials.

1. Predators:
They feed on silkworms.
* Birds
* ants
* crows
* kites
* rats.
2. Diseases:
* Pebrin – It is a disease caused by protozoa Nosema bombycis.
* Flacherie – It occurs in the mature larvae caused by bacteria like streptococcus and staphylococcus.
* Grasserie – It is aviral disease caused by Bombyx mori nuclear polyhedrosis virus.
* White Muscardine – It is caused by the fungus Beauveria bassiana.

* In the honey bee, a highly organized division of labour is found.
* There are three types of honey bees seen in the colony.
* There are one queen 10000 – 30000 workers and a few hundred drones in a colony.
Queen bee:
* It feeds on royal Jelly.
* It is only function is to lay eggs throughout its life span.
* During breeding season in winter, a unique flight takes place by the queen bee followed by several drones is called nuptial flight.
* After mating the queen bee lays about 15 lakh eggs in two to four years.
Worker bee:
* These are sterile females.
* Worker bee lives in a worker well and it takes, about 21 days to develop from the egg to adult, and its life span is about six weeks.
Works:
* It secretes royal Jelly.
* Prepares bee – bread to feed the larvae.
* Takes care of the queen and drones.
* Secretes bee wax.
* In the last three weeks, she searches and gathers the pollen nectar.
Drones:
* The drone develops from an unfertilized egg.
* It lives in a chamber called a drone cell.
* The only duty of the drone is to fertilize the queen and it is called the king of the colony.

• Stand – It is a basal part of the hive and is adjusted to make a slope for rainwater to drain.
• Bottom board – It is situated above the stand. It has two gates one gate is an entrance the other acts as an exit.
• Brood chamber – It is an important part of the hive. It is provided with 5 to 10 frames arranged one above the other through which the workers can easily pass.
• The frame is composed of a wax – sheet which is held in a vertical position up by a couple of wires.
• It is strong that can be used repeatedly.
• Super – It is a chamber without cover and base. It is provided with many frames to provide additional space for expansion of the hive.
• Inner cover – It is a wooden piece used for covering the super with many holes for proper ventilation.
• Top cover – It is meant for protecting the colonies from rains. It is covered with a sheet which is plain and sloping.

Methods of Animal breeding:
There are two methods of animal breeding, namely inbreeding and outbreeding:
1. Inbreeding:
Breeding between animals of the same breed for 4-6 generations is called inbreeding. Inbreeding increases homozygosity and exposes the harmful recessive genes.
Continuous inbreeding reduces fertility and even productivity, resulting in “inbreeding depression”. This can be avoided by breeding selected animals of the breeding population and they should be mated with superior animals of the same breed but unrelated to the breeding population. It helps to restore fertility and yield.
2. Outbreeding:
The breeding between unrelated animals is called outbreeding. Individuals produced do not have common ancestors for 4-6 generations.
Outbreeding helps to produce new and favourable traits, to produce hybrids, with superior qualities, and helps to create new breeds. New and favourable genes can be introduced into a population through outbreeding.

• A typical rearing house 6 m x 4m x 3.5m is constructed on an elevated place under shade to accommodate 100 days.
• The windows and ventilators should be covered with a nylon net to restrict the entry of uziflies and other insects.
• The selected healthy silk moths are allowed to mate for 4 hours.
• The female moth is kept in a dark plastic bed it lays about 400 eggs in 24 hours.
• The small larvae hatch between 7 – 10 days.
• The larvae are kept in trays at a temperature of about 20°C-25°C.
• As the larvae grow they are transferred to fresh leaves on clean trays.
• Their maturity is achieved in about 45 days.
• At this stage, the salivary glands start secreting silk to spin cocoons.

1. Deepwater culture – Aquaponics is a technique which is a combination of aquaculture and growing plants in non – soil media.
* It is a raft-based method.
* In this method, the raft floats in water plants are kept in the holes of the raft, and the root floats in water. Fast-growing plants are cultivated.
2. Media-based method – It involves growing plants in inert planting media likely pellets or shales.
This method is applicable for home and hobby scale systems. A large number of fruiting plants leafy green plants herbs can be cultivated.
3. Nutrient film technique – It involves the passage of nutrient-rich water through a narrow trough or pvc pipe.
Plants are kept in the holes of the pipe to allow the roots to be in free contact with the water stream.
4. Aquavertica or vertical aquaponics – Plants are stacked in top of each other in tower systems.
This method is suitable for growing leafy green, strawberries and crops that do not need supporting solid substratum to grow.

(I) Dairy breeds or Milch breeds:
They are high milk yielders with extended lactation. Eg., Sindhi, Gir, Sahiwal, Jersy, Brown Swiss, Holstein cattle.
(II) Draught purpose breeds:
Bullocks are good for draught purposes. Eg. Kangayam, Malvi.
(III) Dual Purpose breeds:
Cows are meant for yielding more milk and bullocks are used for better drought purposes Eg. Ongole, Hariana.

Natural breeding (Bundh breeding): These are special types of ponds where natural riverine conditions or any natural water resources are managed for the breeding of culturable fishes. These bundhs are constructed in large low-lying areas that can accommodate large quantity of rainwater. The shallow area of such bundhs is used as a spawning ground.

Milk products:
Milk is produced by dairy animals which is an emulsion of fat and lactose. Milk also contains enzymes which are destroyed during pasteurization.
Milk is a rich source of vitamin A, B„ Bp and deficient in Vitamin C. Due to its high nutrition value, it serves as a. complete food for infants. Dairy products such as yoghurt, cheese, butter, ice cream, condensed milk, curd, and milk powder processed from milk make dairy, a highly farming attraction.

• Feed on zooplankton and phytoplanktons decaying weeds debris and other aquatic plants.
• They can survive in turbid water with slightly higher temperatures.
• Can tolerate O 2 variations in water.
• Can be transported from one place to another easily.
• They are highly nutritive and palatable.

• To improve the quality of fish seed by the artificial method of fertilization is developed.
• The gonadotrophin (FSH+ LH) secreted by the pituitary gland influences the maturation of gonads and spawning in fishes.
• The pituitary gland is removed from a healthy mature fish.
• The pituitary extract is prepared by homogenizing in 0.3% saline and centrifuged for 15 minutes at 8000rpm.
• The supernatant is injected at the base of the caudal fin.
• Male and Female fishes start to releasing gametes and are fertilized.

(I) Game breeds:
Since ancient times, special breed of roosters have been used for the sport of cockfighting.
(II) Aseel:
This breed is white or black in colour. The hens are not good egg layers but are good in the incubation of eggs. It is found in all states of India. Aseel is noted for its pugnacity, high stamina, and majestic gait and dogged fighting qualities. Although poor in productivity, this breed is well-known for its meat qualities.

• Macrobrachium rosenbergii is seen in rivers fields and low – saline estuaries.
• For fertilization, one pair of prawn are kept in a separate tank.
• After mating the eggs are laid.
• Temperature 24°C – 30°C and PH 7-8 should be maintained in the hatching tank.
• The hatched larvae are supplied with artificial feed.
• Young ones 5cm length can be reared in fresh or slightly brackish water ponds and harvesting of prawns can be done twice a year.

The benefits of Poultry farming are:
* It does not require high capital for the construction and maintenance of poultry farming.
* It does not require a big space.
* It ensures the high return of investment within a very short period of time.
* It provides fresh and nutritious food and has a huge global demand.
* It provides employment opportunities for the people.

Types of Cultivable fishes:
* Indigenous / Native freshwater fishes, (eg) Major Carps Catla Labeo Clarias.
* Saltwater fishes acclimatized for freshwater. (eg)Chanos, Mullet
* Exotic fishes. Imported from other countries, (eg) Common Carps.
Characteristic features of Carps:
* Feed on Zooplanktons and phytoplanktons decaying weeds debris and other aquatic plants.
* They can survive in turbid water with slightly higher temperatures.
* Can tolerate 0 2 variations in water.
* Can be transported from one place to another.
* They are highly nutritive and palatable easily

To culture fish, one should have an idea about different stages of fish culture such as topographic situation quality source physical-chemical and biological factors of water.
Stages of fish farming:
Breeding Pond:
The first step in fish culture is the breeding of fishes therefore for proper breeding special types of ponds are prepared called breeding ponds. These ponds are prepared near the rivers of natural water resources.
a) Natural breeding:
These bundhs are constructed in large low-lying areas that can accommodate a large quantity of rainwater.
b) Induced breeding:
* This involves the removal of ova and sperm from female and male by artificial mechanical process and the eggs are fertilized.
* The fertilized eggs are removed from the spawning place and kept in hatching hapas. Fish seeds: The fish seed is collected from breeding ponds and transferred to the hatching pits.
3. Hatching Pit:
The fertilized eggs are kept in hatching pits. The hatching pits should be nearer to the breeding grounds should be smaller in size with good quality water.
There are two types of hatching pits:
* Hatcheries: These are small-sized ponds in which unfertilized eggs are transferred and hatching happens.
* Hatching hapas: These are rectangular trough-shaped tanks made up of mosquito net cloth supported by bamboo poles and fixed in the river.
4. Nursery Pond:
The newly hatched fries are transported from the hatching happa to nursery ponds where they grow into fingerlings.
5. Rearing Pond:
This pond is long and narrow and this pond should be free from toxicants and predators. The fingerlings are transferred to the stocking ponds.
6. Stocking Ponds:
* This pond should be devoid of weeds and predatory fishes.
* Proper organic manuring should be done to the production with cow dung.
7. Harvesting:
* Well-grown fishes are taken out for marketing is harvesting.
* Small-sized fishes are again released into the stocking ponds for further growth.
* The harvested fishes are preserved and then marketed.

a. Composite fish farming: Few selected fishes belonging to different species are stocked together in proper proportion in a pond is called composite fish farming.
b. Merits:
* All available niches are fully utilized.
* Compatible species do not harm each other.
* No competition among different species is found.
c. Fishes that are cultured:
* Catla Catla
* Labeo rohita
* Cirrhinus mrigala

1. Fishes form a rich source of protein food the sardines, mackerel tuna herrings have high amino acid concentrations.
2. These fishes have histidine and omega fatty acids.
3. Minerals such as calcium magnesium phosphorus potassium and copper and present.
a) Fish Oil:
* It is an important fish product it is derived from fish liver and from the fish body.
* This is rich in vitamin A and O and iodine.
* It is used in the manufacture of laundry soap paints and cosmetics.
b) Fish Meal:
* It is prepared from fish waste after extracting oil from the fish.
* These dried wastes are used to prepare food for pigs, poultry, and cattle.
* The wastes obtained during the preparation of fish meals are used as manure.
c) Ising glass:
* It is high-grade collagen produced from the dried air bladder of catfish and carps.
* It is used for clarification of wine beer and vinegar.

a) Pearl Culture:
* Pearl is a white shining globular concretion found within the shell of an oyster.
* In India, it was cultured for the first time in 1973 at Thoothukudi.
* High-quality pearls are obtained from Genus Pinctada that can be cultured in the salinity range of 30 ppt in racks raft and long-line method.
* The pearl oysters inhabit the ridges of rocks or dead coral forming the best quality pearl.
b) Pearl Formation:
* When a foreign particle accidentally enters into the space between the mantle and shell of the oysters it adheres to the mantle.
* The mantle epithelium encloses its likes sac and starts to secrete concentric layers of nacre around it as a defensive mechanism.
* The repeated layers of calcium carbonate make the hard and glossy pearl that are separated and graded.

* Oysters are caught by a special type of cages.
* This cage is dipped into a sand cement mixture providing a rough surface to the cages and are suspended at a depth of 6 meters.
2. Rearing of oysters:
* The collected oysters are placed into the culture cages for a period of 10 – 20 days.
* These cages are protected from enemies like octopus, Eel, and devil fishes.
3. Insertion of the nucleus:
a) Fitness of oysters for operation:
The selected oysters for the insertion of the nucleus should be healthy and strong enough to overcome the stress during operation.
b) Preparation of graft tissues:
* The piece of tissue which is inserted inside the mantle is called “graft” tissue.
* It is essential to keep the outer surface in contact with the inserted nucleus as nacre secreting cells are found only on the outer surface.
c) Preparation of nucleus:
* Any small particle may function as a nucleus to initiate pearl formation.
* If it is calcareous the deposition of nacre was found to be more on the calcareous nucleus.
d) Insertion of the nucleus:
For the insertion of the nucleus, oysters are fixed in a desk clamp and mantle folds are smoothly touched to expose the foot followed by an incision into the epithelium of the foot and the nucleus is inserted.
e) Post Operation Care:
* Nucleated oysters are placed into cages and suspended into 2-3 metres of depth for 6-7 days.
* These periods are known as the “Recovery Period”.
* These oysters are kept for 3-6 years undisturbed.
f) Harvesting of Pearl:
After the completion of 3 years, pearl oysters are harvested. It is usually done from December to February.
g) Clearing of Pearls:
After taking out the pearls from the oyster’s shell. They are washed properly cleared with the soap solution.

Breeding between animals of the same breed for 4-6 generations is called inbreeding.
Merits:
* It increases homozygosity.
* It exposes the harmful recessive genes. Demerits:
1. Continuous inbreeding reduces fertility
2. And results in inbreeding depression. Avoiding inbreeding depression:
This can be avoided by breeding selected animals be mated with superior animals of the same breed but unrelated to the breeding population.

Dairying is the production and marketing of milk and its products. The dairy operation consists of proper maintenance of cattle, the collection, and processing of milk, and its by-products.

1. Out Crossing:
It is the breeding between unrelated animals of the same breed but having no common ancestry.
Out Cross: This method is suitable for breeding animals that are below average in productivity.
2. Crossbreeding:
* Breeding between a superior male of one breed with a superior female of another breed.
* The cross-breed progeny has superior traits. This is called hybrid vigour or heterosis.
3. Interspecific hybridization:
* Mating between male and female of two different species.
* The progeny obtained from such crosses are different from their parents.
* Mule is produced by the crosses between a male donkey and a female horse.

MOET:
* This method is applied when the success rate of crossing is low even after artificial insemination.
* In this method, the follicle-stimulating hormone is administered to cows for inducing follicular maturation and superovulation.
* Instead of one egg per cycle, 6-8 eggs can be produced.
* The eggs are carefully recovered non-surgically from the genetic mother and fertilized artificially.
* The embryos at the 8 – 32 celled stage are recovered and transferred to a surrogate mother.
* This technology can be applied to cattle sheep and buffaloes.
* It can produce high milk-yielding females and high-quality meat-yielding bulls in a short time.

a) Dairying:
* It is the production and marketing of milk and its products.
* The dairy operation consists of maintenance of cattle the collection, processing of the milk, and its by-products.
* These are 26 well-defined breeds of cattle and 6 breeds of buffaloes in India.
b) Classification of Cattle
* Dairy breeds: They are high milk yielder with extended lactation, (eg) Sindhi, Jersey Sahiwal
* Drought breed: Bullocks are good for draught purposes, (eg) Kangeyam Malvi.
* Dual-purpose breeds: Cows are meant for yielding more milk and bullocks are used for better drought purposes (eg) Ongole Hariana.
c) Uses of dairy product:
1. Milk: Milk is a rich source of vitamin A, B2, B and deficient in Vitamin C.
Dairy products such as yoghurt cheese butter ice cream condensed milk powder are produced from milk.
2. Meat: Meat is rich in protein and also contains minerals like iron zinc vitamins and selenium.
3. Land Management: Grazing of live stocks sometimes used as a way to control weeds.
4. Manure: Manure can be spread on agriculture fields to increase crop yields.

1. Egg layers: These are farmed mainly for the production of eggs.
Leghorn:
* It is originated in Italy. They are small compact with a single comb.
* They mature early and begin to lay eggs at the age of 5 or 6 months.
Chittagong:
* They are good egg layers and are delicious.
* They are found in West Bengal.
2. Selection of eggs for hatching:
Eggs should be fertile medium-sized dark brown shelled and freshly laid eggs are preferred for rearing.
3. Incubation and hatching:
* The maintenance of newly laid eggs in optimum condition till hatching is called incubation.
* The fully developed chick emerges out of egg after an incubation period of 21 – 22 days.
* There are two types of incubation namely natural incubation and artificial incubation.
* In the Natural incubation method, only a limited number of eggs can be incubated by a mother hen.
* In artificial incubation, more eggs can be incubated.
4. Brooding:
* Caring and management of young chicks for 4 – 6 weeks immediately after hatching is called brooding.
* They are natural and artificial brooding. The housing of Poultry:
* To protect the poultry from the sun.
* Rain and predators it is necessary to provide housing to poultry.
* A poultry house should be moisture-proof rat-proof and it should be easily cleanable and durable.
5. Poultry feeding:
The diet of chicks should contain an adequate amount of water carbohydrates proteins fats vitamins and minerals.
Poultry Products:
* The main products of poultry farmings are eggs and meat.
* The primary aim of poultry farming is to obtain eggs.
C. Poultry by-products:
* The feathers: They are used for making pillows and quilts.
* Droppings: The droppings are rich in nitrogen potash and phosphates.
* The by-products of poultry are used as good sources of nutrients for meat-producing animals and poultry.
* These by-products supply proteins fats Vitamins and minerals.
Poultry diseases: Ranikhet coccidiosis Fowl Pox is a common poultry disease.
Merits:
* They can adapt themselves to all types of environmental conditions.
* And for the breed for feed efficiency.
* Growth rate and resistance to diseases.
* They are exhibited in poultry shows they are calm friendly and can be maintained as pets.

Types:
* Organic method
* Yarding method
* Battery cage method
* Furnished cage method.
Stages involved in rearing:
1. Selection of the best layer.
* An active intelligent-looking bird with a bright comb not obese should be selected.
* They are golden or light yellow coloured.
2. Broiler type:
* White Plymouthrock is a fast-growing breed and soft quality meat.
* They have white plumage throughout the body. This is an American breed. It is a fast-growing breed.
3. Dual Purpose breed:
It is known for its massive body having heavy bones. Well feathered and Peacomb is one of the important breed characters.
4. Game breeds:
Aseel:
* The hens are not good egg layers but are good in the incubation of eggs.
* Aseel is noted for its pugnacity high stamina majestic gait.
* This breed is well known for its meat qualities.
5. Ornamental breeds:
Silkie:
* They are reared as pets and for egg production and meat.
* The chicken has a fluffy plumage which is said to feel like silk and satin.
* It has black skin and bones blue ear lobes and five toes on each foot.

Milk products:
Milk is produced by dairy animals which is an emulsion of fat and lactose. Milk also contains enzymes which are destroyed during pasteurization.
Milk is a rich source of vitamin A, B„ Bp and deficient in Vitamin C. Due to its high nutrition value, it serves as a complete food for infants. Dairy products such as yoghurt, cheese, butter, ice cream, condensed milk, curd, and milk powder processed from milk make dairy, a highly farming attraction.

(a) Light is an important aspect of poultry production. Light stimulates the secretion of FSH and LH. A wavelength between 400 and 700 nm is required. The decrease in the photoperiod will affect egg production.
(b) A few selected fishes belonging to different species are stocked together in proper proportion in a pond. This mixed farming is termed composite fish farming or polyculture. It is of great importance because
* All available riches are fully utilized
* Compatible species do not harm each other
* There is no competition among different species