Biology

Learninsta presents the core concepts of Biology with high-quality research papers and topical review articles.

Lac Culture and its Importance

The culture of lac insect using techniques for the procurement of lac on large scale is known as Lac culture. Lac is produced by the lac insect Tachardia lacca previously known as Laccifer lacca. It is a minute, resinous crawling scale insect which inserts its probosics into the plant tissues and sucks juice, grows and secretes lac from the hind end of the body as a protective covering for its body.

Moreover the insect is a parasite on host plants i.e., Karanagalli (Acacia catechu), Karuvelai (Acacia nilotica) and Kumbadiri (Schleichera oleosa). The quality of lac depends upon the quality of the host plant. The female lac insect is responsible for large scale production of lac, which is larger than the male lac insect.

Economic Importance of Lac

• Lac is largely used as a sealing wax and adhesive for optical instruments. It is used in 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 filing material for gold ornaments.

Lac is a natural resin of animal origin. It is secreted by an insect, known as lac-insect in order to obtain lac, these insects are cultured and the technique is called lac-culture. It involves proper care of host plants, regular pruning of host plants, propagation, collection and processing of lac.

Lac is used in ammunition, airplanes, furniture polish and perfumes, and in making bangles, imitation fruits and flowers. The ‘scientists’ motive was to give lac farmers a host plant that grows faster and reduces tree based farming. Ninety per cent of lac is produced on palash, ber and kusum trees.

Lac cultivation has its roots in India and Bangladesh, the two main Asian countries in the world and was a major source of economy to the local populace. Natural red color obtained on purification of this resin was used in coloring of items like wood and textiles.

Lac is a thick semi-solid gummy substance acquired from a female insect (bug) named ‘Tachardia lacca’ on trees in the forests of India and Thailand. The process of making Lac jewelry is complex and requires high degree of precision.

Lac is actually secreted for protection by females. It generally infests about 400 plant species and feed on the host tissues. The females are degenerated in form and feeds on the sap of its host plants. Male undergoes complete metamorphosis while female undergoes degeneration.

Lac is a natural resin secreted by the tiny insects, mainly K. lacca. The insects are cultured on tender shoots of several plants called hosts. However in costal region of West Bengal and Odisha, a tri-voltine insect, Kerria sharda is found which produce three crops in a year.

Learninsta presents the core concepts of Biology with high-quality research papers and topical review articles.

Apiculture Methods Definition and Its Structure

Ever since the beginning of civilization, man has been trying to make use of organisms around him for various purposes and to rear them for increasing their number. One of the finest discoveries is our knowledge regarding the procurement of honey collected by honey bees. Care and management of honey bees on a commercial scale for the production of honey is called Apiculture or Bee Keeping.

The word ‘apiculture’ comes from the Latin word ’apis’ meaning bee. Bees are reared in apiaries that are areas where a lot of bee hives can be placed. There are fie well recognized types of bees in the world. They are Apis dorsata (Rock bee), Apis florea (Little bee), Apis indica (Indian bee), Apis mellifera (European bee) and Apis adamsoni (African bee).

Social Organization of Honey Bees

In honey bees, a highly organized division of labour is found. A well developed honey bee colony consists of the Queen, Drones and Workers (Figure 12.4). All the three types depend on each other for their existence. There is normally one queen, 10,000 to 30,000 workers and few hundred drones (male bees) in a colony.

Queen bee is a functional female bee present in each hive and feeds on Royal Jelly. Its sole function is to lay eggs throughout its life span. The virgin queen bee mates only once in her life. During the breeding season in winter, a unique flight takes place by the queen bee followed by several drones. This flight is called “nuptial flight”. The queen bee produces a hormonal chemical substance called pheromone.

The drones in the area are attracted to the pheromone and mating takes place. During mating, the drone releases large number of sperms for sufficient fertilization. In a life span of two to four years, a queen bee lays about 15 lakh eggs. When the queen bee loses its capacity to lay eggs, another worker bee starts feeding on the Royal Jelly and develops into a new queen.

Among the honey bees, workers are sterile females and smallest but yet function as the main spring of the complicated machinery in the colony. Worker bee lives in a chamber called ‘Worker Cell’ and it takes about 21 days to develop from the egg to adult and its lifespan is about six weeks.

Each worker has to perform different types of work in her life time. 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 bees wax, builds combs, cleans and fans the bee hive.

Then she becomes a soldier and guards the bee hive. In the second half her life lasting for three weeks, she searches and gathers the pollen, nectar, propolis and water.

The drone is the functional male member of the colony which develops from an unfertilized egg. It lives in a chamber called drone cell. Drones totally depend on workers for honey. The sole duty of the drone is to fertilize the virgin queen hence called “King of the colony”. During swarming (the process of leaving the colony by the queen with a large group of worker bees to form a new colony) the drones follows the queen, copulates and dies after copulation.

Structure of a Bee Hive

The house of honey bee is termed as bee hive or comb. The hive consists of hexagonal cells made up of wax secreted by the abdomen of worker bees arranged in opposite rows on a common base. These hives are found hanging vertically from the rocks, building or branches of trees.

The young stages of honey bees accommodate the lower and central cells of the hive called the brood cells. In Apis dorsata, the brood cells are of similar in size and shape but in other species, brood cells are of three types viz., queen cell for queens, worker cell for workers and drone cells for drones (Figure.12.5). The cells are intended for storage of honey and pollen in the upper portion of the comb whereas the lower portions are for brood rearing.

Methods of Bee Keeping

The main objective is to get more and more quality honey. There are two methods used by apiculturists. They are indigenous method and the modern method. In indigenous method, the honey extracted from the comb contains wax.

To overcome the drawbacks of the indigenous method, the modern method has been developed to improve the texture of hives. In India, there are two types of beehives in practice namely, Langstroth and Newton.

The Langstroth bee hive is made up of wood and consists of six parts (Figure 12.6) namely Stand, Bottom board, Brood chamber, Super, Inner cover and Top cover. Besides the above primary equipments, other accessory equipments are used in beekeeping. They are Queen Excluder, Comb foundation, Bee gloves, Bee veil, Smoker, Hive Tool, Uncapping knife, Bee brush, Queen introducing cage, Feeder, Honey Extractor and Hive Entrance Guard.

Products of Bee Keeping and Their Economic Importance

The chief products of bee keeping industry are honey and bee wax. Honey is the healthier substitute for sugar. The major constituents of honey are: levulose, dextrose, maltose, other sugars, enzymes, pigments, ash and water.

It is an aromatic sweet material derived from nectar of plants. It is a natural food, the smell and taste depends upon the pollen taken by the honey bee. It is used as an antiseptic, laxative and as a sedative. It is generally used in Ayurvedic and Unani systems of medicine.

It is also used in the preparation of cakes, breads and biscuits Bee wax is secreted by the abdomen of the worker bees at the age of two weeks. The wax is masticated and mixed with the secretions of the cephalic glands to convert it into a plastic resinous substance.

The resinous chemical substance present in the wax is called propolis which is derived from pollen grains. The pure wax is white in colour and the yellow colour is due to the presence of carotenoid pigments. It is used for making candles, water proofing materials, polishes for floors, furniture, appliances, leather and taps. It is also used for the production of comb foundation sheets in bee keeping and used in pharmaceutical industries.

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Sericulture – Diseases and Pests of Silkworm

Silk is Nature’s gift to mankind and a commercial fiber of animal origin other than wool. Being eco-friendly, biodegradable and self-sustaining material; silk has assumed special relevance in present age. Sericulture is an agro – based industry, the term which denotes commercial production of silk through silkworm rearing. Historical evidence reveals that sericulture was practiced in China long back and they preserved the secret for more than 3000 years and maintained monopoly in silk trade with the rest of the world.

According to Western historians, mulberry cultivation spread to India about 140BC from China through Tibet. The fabulous silk from China and India were carried to European countries. The 7000 mile lengthy road, historically called the “Silk road” passing through Baghdad, Tashkent, Damascus and Istanbul was used for silk transport. Today more than 29 countries in the world are practicing sericulture and producing different kinds of silk. India stands second in silk production next to China.

Production of silk from the silk worm, by rearing practices on a commercial scale is called sericulture. It is an agrobased industry comprising three main components:

• Cultivation of food plants for the silkworms
• Rearing of silkworms, and
• Reeling and spinning of silk.

The first two are agricultural and the last one is an industrail component. Only few species of silkworms are used in the sericulture industry (Table 12.1 and Figure 12.2).
Table 12.1: Different Types of Silkworm

Life Cycle of Bombyx Mori

The adult of Bombyx mori is about 2.5 cm in length and pale creamy white in colour. Due to heavy body and feeble wings, flight is not possible by the female moth. This moth is unisexual in nature and does not feed during its very short life period of 2-3 days. Just after emergence, male moth copulates with female for about 2-3 hours and if not separated, they may die after few hours of copulating with female.

Just after copulation, female starts egg laying which is completed in 1-24 hours. A single female moth lays 400 to 500 eggs depending upon the climatic conditions. Two types of eggs are generally found namely diapause type and non-diapause type.

The diapause type is laid by silkworms inhabiting the temperate regions, whereas silkworms belonging to subtropical regions like India lay non-diapause type of eggs. The eggs after ten days of incubation hatch into larva called about 3 mm in length and is pale, yellowishwhite in colour. The caterpillars are provided with well developed mandibulate type of mouth-parts adapted to feed easily on the mulberry leaves.

After 1^st, 2^nd, 3^rd and 4^th moultings caterpillars get transformed into 2^nd, 3^rd, 4^th and 5^th instars respectively (Figure 12.3). It takes about 21 to 25 days after hatching. The fully grown caterpillar is 7.5 cm in length.

It develops salivary glands, stops feeding and undergoes pupation. The caterpillars stop feeding and move towards the corner among the leaves and secretes a sticky fluid through their silk gland. The secreted fluid comes out through spinneret (a narrow pore situated on the hypopharynx) and takes the form of long fie thread of silk which hardens on exposure to air and is wrapped around the body of caterpillar in the forms of a covering called as cocoon.

It is the white coloured bed of the pupa whose outer threads are irregular while the inner threads are regular. The length of continuous thread secreted by a caterpillar for the formation of cocoon is about 1000-1200 metres which requires 3 days to complete. The pupal period lasts for 10 to 12 days and the pupae cut through the cocoon and emerge into adult moth.

On the basis of the moults which they undergo during their larval life, B. mori is divided into three races – tri-moulters, tetramoulters and pentamoulters. Based on voltinism (the number of broods raised per year), three kinds of races are recognized in mulberry silkworm – univoltines (one brood only), bivoltines (two broods only) and multivoltines (more than two broods).

Cultivation of Food Plants for the Silkworms

The first component, is to grow the food plants for the silkworms. Mulberry leaves are widely used as food for silkworm Bombyx mori and the cultivation of mulberry is called as Moriculture. Presently improved mulberry varieties like Victory1, S36, G2 and G4 which can withstand various agro – climatic and soil conditions are used for planting.

The favourable season for cultivating of the mulberry plants is June, July, November and December. The mulberry crop production technology includes land preparation, preparation of cutting, planting techniques, maintenance of mulberry nursery, disease and pest management and uprooting for raising new mulberry gardens. Mulberry is also being grown as tree plant at an height of 123-152 cm with 20 x 20 cm or 25 x 25 cm spacing to harvest better silkworm cocoon crops.

Rearing of Silkworms

The second component is the rearing of silkworm. A typical rearing house (6m x 4m x 3.5m) is constructed on an elevated place under shade to accommodate 100 dfls (disease free layings). Space of 1m should be provided surrounding the rearing house. Sufficient windows and ventilators should be provided for free circulation of air inside the rearing house.

The windows and ventilators should be covered with nylon net to restrict the entry of uzi flies and other insects. Apart from the specified area of the rearing house; the following appliances such as hygrometer, power sprayers, rearing stands, foam pads, wax coated paraffin papers, nylon nets, baskets for keeping leaves, gunny bags, rotary or bamboo mountages and drier are needed for effective rearing of silkworms. The steps involved in rearing process of silkworm are disinfection of rearing house, incubation of eggs, brushing, young larval rearing and late age larval rearing.

The selected healthy silk moths are allowed to mate for 4 hours. Female moth is then kept in a dark plastic bed, it lays about 400 eggs in 24 hours; the female is taken out, crushed and examined for any disease, only certified disease-free eggs are reared for industrial purpose. The eggs are incubated in an incubator. The small larvae (caterpillars) hatch between 7-10 days.

These larvae are kept in trays inside a rearing house at a temperature of about 20°C – 25°C. These are first fed on chopped mulberry leaves. After 4-5 days fresh leaves are provided. As the larvae grow, they are transferred to fresh leaves on clean trays, when fully grown they spin cocoons. Their maturity is achieved in about 45 days. At this stage the salivary glands (silk glands) starts secreting silk to spin cocoons.

Post Cocoon Processing

The method of obtaining silk thread from the cocoon is known as post cocoon processing. This includes stifling and reeling. The process of killing the cocoons is called stifling. The process of removing the threads from the killed cocoon is called reeling. For reeling silk the cocoons are gathered about 8 – 10 days after spinning had begun. The cocoons are first treated by steam or dry heat to kill the insect inside.

This is necessary to prevent the destruction of the continuous fibre by the emergence of the month. The cocoons are then soaked in hot water (95° – 97°C) for 10-15 minutes to soften the gum that binds the silk threads together. This process is called cooking.

The “cooked” cocoons are kept in hot water and the loose ends of the thread are caught by hand. Threads from several cocoons are wound together on spinning wheels (Charakhas) to form the reels of raw silk. Only about onehalf of the silk of each cocoon is reelable, the remainder is used as a silk waste and formed into spun silk. Raw silk thus obtained is processed through several treatments to bring about the luster on the thread.

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, in medical dressings and as suture materials.

Diseases and Pests of Silkworm:

The profitable silk industry is threatened by various diseases caused by the virus, fungal, bacterial and protozoan infections but also by insect predators, birds and other higher animals. Ants, crows, kites, rats, feed upon silk worms thereby causing a great loss to silk industry.

Pebrine, is a dangerous disease to in silkworms and the causative organism is Nosema bombycis, a protozoan. This silkworm disease is transmitted through the egg of the mother silkworm and also through ingestion of contaminated food.

Flacherie generally occurs in the mature larvae and is caused mainly by bacteria like Streptococcus and Staphylococcus. Grasserie is a most dominant and serious viral disease. It is caused by Bombyx mori nuclear polyhedrosis virus (BmNPV) a Baculovirus, which belongs to sub group ‘A’ of the Baculoviridae. Among the fungal diseases, white muscardine is common. This disease is caused by fungus Beauveria bassiana.

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Vermiculture Definition and its Advantages

Vermiculture is the process of using earthworms to decompose organic food waste, into a nutrient-rich material capable of supplying necessary nutrients which helps to sustain plant growth. The aim is to continually increase the number of worms to have a sustainable harvest.

The excess worms can either be used to expand a vermicomposting operation or sold to customers. Vermicompost is the primary goal of vermiculture. Technically the worm castings are pure worm waste and are fine and nutrient rich organic soil amendment.

Vermicompost on the other hand, is comprised of the castings, bits of bedding and other organic matter. Essentially, though the terms are used interchangeably, they are both worm manure and are valuable for improving soil health. Applications of earthworm in technology of composting and bioremediation of soils and other activities is called Vermitech (Sultan Ismail, 1992).

The disposal of solid wastes (biodegradable and non – biodegradable) remains a serious challenge in most of the countries. Earthworms play a vital role in maintaining soil fertility; hence these worms are called as “farmer’s friends”.

These are also called as “biological indicators of soil fertility”. The reason is that they support bacteria, fungi, protozoans and a host of other organisms which are essential for sustaining a healthy soil.

The breakdown of organic matter by the activity of the earthworms and its elimination from its body is called vermicast. It is a finely divided granular material and is noted for its porosity, aeration, drainage and moisture holding capacity and serves as rich organic manure. Earthworms are divided into two major groups. The first group, the humus formers, dwell on the surface and feed on organic matter.

They are generally darker in colour. These worms are used for vermicomposting. The second group, the humus feeders, are burrowing worms that are useful in making the soil porous, and mixing and distributing humus through out the soil.

There are different endemic (native) species of earthworms cultured in India for vermicomposting such as Periyonyx excavatus, Lampito mauritii, Octochaetona serrata. Some earthworm species have been introduced from other countries and called as exotic species Eg. Eisenia fetida, Eudrilus eugeniae.

Vermicomposting

Vermicompost is the compost produced by the action of earthworms in association with all other organisms in the compost unit. Vermicompost bed may be selected on upland or an elevated level as it prevents the stagnation of water. You may construct a cement pit of 3x2x1m size (LxWxD) over ground surface using bricks. The size of pit may vary as per availability of raw materials.

Cement pot or well rings are practically good. Provision should be made for excess water to drain. The vermibed should not be exposed to direct sunlight and hence shade may be provided (Figure. 12.1). The first layer of vermibed contains gravel at about 5 cm in height, followed by coarse sand to a thickness of 3.5 cm, which will facilitate the drainage of excess water.

Earthworms collected from native soil prefer a layer of local soil in their compost beds. If local soil earthworms are used, add a layer of native loamy soil for about 15 cm on top of the gravel sand layer and introduce earthworms into it.

For exotic species such as Eisenia fetida and Eudrilus eugeniae, the layer of soil is not needed. The unit can now be loaded with digested biomass or animal dung such as cow dung that has lost its heat.

The number of earthworms to be introduced in an unit depends on the size of the vermibed prepared. Earthworms such as Periyonyx, Excavatus, Eisenia fetida or Eudrilus eugeniae are introduced on the top. Jute bags or cardboards or broad leaves are used to cover the unit. As worms require moisture, water management is most important for the survival of the earthworms. Too little or too much of water is not good for the worms.

Earthworms release their castings on the surface. One can start harvesting this from the surface on noticing the castings on the surface. It may take several days for the entire biomass to be composted depending on the amount of biomass.

When all the compost is harvested, earthworms can be handpicked by creating small conical heaps of harvested compost and leaving in sunlight for a few hours. The earthworms then move down and settle at the bottom of the heap as a cluster.

Earthworms from the lower layers of the compost can be recovered and the worms can be transferred to new composting units. 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 and yield. It is obtained from the burrows or drilospheres formed by earthworms. Nutrients, plant growth promoter substances and some useful microorganisms are present in vermiwash.

Earthworms can be used for recycling of waste food, leaf, litter and biomass to prepare a good fertilizer in container known as wormery or wormbin. Earthworm Pests and Diseases Earthworms are subjected to attack by a variety of pests.

Most outbreaks are the result of poor bed management. Earthworm enemies include ants, springtails, centipedes, slugs, mites, certain beetle larvae, birds, rats, snakes, mice, toads, and other insects or animals which feed on worms.

The earthworm has a number of internal parasites including numerous protozoa, some nematodes, and the larvae of certain flies. Larger predators can be excluded from worm beds by proper construction of the bins, and by use of screens or gratings at the bottom and top of the beds.

Advantages of Using Vermicompost

People are aware about benefits of organic inputs in farming. Vermicompost is excellent organic manure for sustainable agropractices. So, marketing vermicompost is now a potential and flurishing industry. Retail marketing of vermicompost in urban areas is most promising.

Vermicompost is neatly packed in designed and printed packets for sale. People of different age groups are involved in the production and selling of vermicompost. Marketing of vermicompost can provide a supplementary income.

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

Learninsta presents the core concepts of Biology with high-quality research papers and topical review articles.

Scope of Zoology Science and its Importance

Studying Zoology can provide self employment opportunities and you can become an entrepreneur. Economic Zoology is a branch of science that deals with economically useful animals. It involves the study of application of animals for human welfare.

The need of Zoology is not just to improve our economic condition but also to provide food security and provide employment opportunities. Based on the economic importance, animals can be categorized as:

• Animals for food and food products
• Economically beneficial animals
• Animals of aesthetic importance
• Animals for scientific research

Zoology offers immense scope to a candidate who has done master’s degree in the subject. They can work as Animal Behaviourist, Conservationist, Wildlife Biologist, Zoo Curator, Wildlife Educator, Zoology faculty, Forensic experts, lab technicians, and Veterinarians.

Tools and Techniques in Biology:
Animal Physics

Structure and Function of Genes:
Animal Behaviour

Genetics Evolution:
Ecology

Cell and Molecular Biology:
Embryology

There are generally not a plethora of employment opportunities with a zoology degree, unless you have some connections and experience that have you ready to go. It is also not a lucrative field. However, if you have a passion to study animals or do related research, it’s a pathway.

B.Sc Zoology and B.Sc Botany are the two most popular B.Sc courses under Life Science. The scope of both B.Sc Zoology and B.Sc Botany is wide and can be a good option for candidates who want to go for research work in future that involves the study of living forms in the ecosystem.

Zoologists are also hired for zoos, wildlife services, botanical gardens, conservation organizations, national parks, nature reserves, universities, laboratories, aquariums, animal clinics, fisheries and aquaculture, museums, research, pharmaceutical Companies, veterinary hospitals, etc.

Chemistry has more scope than zoology and botany. If you want to pursue your career in teaching and in research then go for zoology and botany whereas in chemistry you have other scopes to work with Food manufacturing industries, chemical industries, pharmaceutical industries also teaching and research.

They are both “hard”. There is a lot of science and math in each. However, both botany and zoology are broad topics covering many sub-subjects. If you enter university to study one or the other of these, you will probably narrow your interests, and probably your career, by the time you graduate.

Designing and conducting research projects and studies of animals. Studying the characteristics of animals and their behaviors. Collecting and analyzing biological data and specimens. Writing papers, reports, and articles that explain research findings.