Ecology is the study of the relationships of organisms with each other and with their surroundings. The term was coined by Ernst Haeckel (1866). This topic covers ecological factors, population characteristics and growth, animal interactions, the structure and function of an ecosystem, food chains, ecological pyramids, biogeochemical cycles and environmental pollution.
महत्त्वाचे मुद्दे
Ecology (परिस्थितिकी) – oikos = house, logos = study. Coined by Ernst Haeckel (1866).
Levels of organisation: individual → population → community → ecosystem → biome → biosphere.
Abiotic factors: temperature, light, water, humidity, soil, pH, salinity. Animals may be eurythermal (tolerate a wide temperature range) or stenothermal (narrow range).
Liebig's law of minimum and Shelford's law of tolerance explain how limiting factors control distribution.
Population attributes: density, natality (birth rate), mortality (death rate), age structure (pyramids), sex ratio, dispersion.
Population growth:exponential (J-shaped curve) when resources are unlimited; logistic (S-shaped / sigmoid curve) when resources are limited and growth levels off at the carrying capacity (K).
Energy flow is one-way; Lindeman's 10% law – about 10% of energy passes to the next trophic level.
Ecological pyramids: number, biomass and energy (pyramid of energy is always upright).
Biogeochemical cycles: gaseous (carbon, nitrogen, oxygen) and sedimentary (phosphorus, sulphur).
महत्त्वाच्या संज्ञा
Habitat – the place where an organism lives.
Niche – the role and position of a species in its community.
Carrying capacity (K) – maximum population an environment can support.
Keystone species – a species with a very large effect on its community (e.g. tiger as top predator).
Biomagnification – increase in concentration of a non-degradable toxin (e.g. DDT, mercury) at higher trophic levels.
Eutrophication – nutrient enrichment of water bodies leading to algal blooms and oxygen depletion.
BOD – biochemical oxygen demand; a measure of organic pollution in water.
सूत्रे
Exponential growth: dN/dt = rN (r = intrinsic rate of natural increase, N = population size).
Logistic growth: dN/dt = rN (K − N)/K.
Population density = number of individuals ÷ area (or volume).
Example: 600 deer live in a 30 km² forest. Density = 600 ÷ 30 = 20 deer per km².
Growth rate example: a population of 1000 has 80 births and 30 deaths in a year (no migration). Net increase = 50; growth rate = 50/1000 = 0.05 per individual per year (5%).
५ महत्त्वाचे प्रश्न
Q1. Give two examples of mutualism.
Lichen (alga and fungus), and the termite with flagellate protozoa in its gut that digest wood. Both partners benefit in each case.
Q2. What is biomagnification?
Biomagnification is the increase in the concentration of a persistent toxic chemical, like DDT, at each higher level of a food chain. Top predators such as fish-eating birds get the highest amounts, which can thin their egg shells.
Q3. Compare exponential and logistic growth of a population.
Exponential: unlimited resources; J-shaped; dN/dt = rN; no upper limit.
DNA replication is the process by which a DNA molecule makes an exact copy of itself before cell division. Each new DNA molecule keeps one old strand and gets one new strand, so replication is semi-conservative. This topic covers the models of replication, the Meselson–Stahl experiment, the enzymes involved, and the steps of replication in prokaryotes with notes on eukaryotes.
महत्त्वाचे मुद्दे
Replication (प्रतिकृती) takes place in the S phase of interphase.
Three possible models: conservative (old molecule stays intact, new one fully new), semi-conservative (each daughter has one old and one new strand) and dispersive (old and new pieces mixed). Watson and Crick predicted the semi-conservative model.
Meselson and Stahl (1958) proved semi-conservative replication in E. coli using heavy nitrogen (¹⁵N), light nitrogen (¹⁴N) and caesium chloride density-gradient centrifugation.
Replication starts at a fixed point called the origin of replication (ori). E. coli has one origin; eukaryotic chromosomes have many.
Unwinding forms a Y-shaped replication fork; replication usually proceeds in both directions (bidirectional) from the origin.
Helicase unwinds the double helix by breaking hydrogen bonds; single-strand binding (SSB) proteins keep the strands apart; topoisomerase (DNA gyrase) relieves the tension ahead of the fork.
Primase lays down a short RNA primer, because DNA polymerase cannot start a new chain by itself.
DNA polymerase III (main enzyme in E. coli) adds nucleotides to the 3' end, so new DNA always grows in the 5' → 3' direction.
The leading strand is made continuously towards the fork. The lagging strand is made discontinuously in short pieces called Okazaki fragments (discovered by Reiji Okazaki, 1968).
DNA polymerase I removes RNA primers and fills the gaps with DNA; DNA ligase joins the fragments.
DNA polymerases proofread (3' → 5' exonuclease activity) and remove wrong bases, so replication is very accurate.
In eukaryotes the ends of linear chromosomes are completed by telomerase.
महत्त्वाच्या संज्ञा
Template strand – the old strand read to make the new strand.
Replicon – a unit of DNA replicated from one origin.
Replication bubble (eye) – opened region between two forks.
Primer – short RNA piece that provides a free 3'-OH end.
Okazaki fragments – short DNA pieces of the lagging strand (about 1,000–2,000 nucleotides in bacteria).
महत्त्वाची माहिती
Enzyme / protein
Role
Helicase
Unwinds DNA
SSB proteins
Keep strands separate
Topoisomerase (gyrase)
Removes supercoils
Primase
Makes RNA primer
DNA polymerase III
Main synthesis
DNA polymerase I
Removes primer, fills gaps
DNA ligase
Joins fragments
Meselson–Stahl results: parent DNA (¹⁵N) = heavy band; after 1 generation in ¹⁴N = only hybrid (intermediate) band; after 2 generations = half hybrid, half light. This matches only the semi-conservative model.
५ महत्त्वाचे प्रश्न
Q1. Why is DNA replication called semi-conservative?
Because each daughter DNA molecule has one parental (old) strand and one newly made strand. Half of the original molecule is conserved in each daughter.
Q2. Why is the lagging strand made in pieces?
DNA polymerase can add nucleotides only in the 5' → 3' direction. On the lagging strand this direction is away from the fork, so short Okazaki fragments are made one by one and joined later by ligase.
Q3. Describe the Meselson–Stahl experiment.
Growth of E. coli in ¹⁵NH₄Cl for many generations.
Transfer to ¹⁴N medium.
DNA extraction and CsCl centrifugation after each generation.
Band positions and their interpretation.
Diagram of the bands.
Q4. Explain the mechanism of DNA replication in prokaryotes.
Initiation at oriC; unwinding by helicase; SSB and gyrase.
Primer synthesis by primase.
Elongation by DNA pol III; leading and lagging strands.
Primer removal by pol I; joining by ligase.
Termination; proofreading.
Labelled diagram of replication fork.
Q5. Write a note on the enzymes of DNA replication.
List each enzyme with its function (table above).
Directionality of polymerases; proofreading.
Telomerase in eukaryotes and its importance.
परीक्षेसाठी टीप
A neat replication fork diagram with leading strand, lagging strand, Okazaki fragments and enzymes labelled answers most questions on this topic.
Protein synthesis is the process by which the information in DNA is used to build proteins. It happens in two stages: transcription (DNA → mRNA) in the nucleus and translation (mRNA → protein) on ribosomes. This topic covers the central dogma, the genetic code, transcription and RNA processing, and the steps of translation.
महत्त्वाचे मुद्दे
Central dogma (Francis Crick, 1958): DNA → RNA → protein. Information flows from DNA to RNA by transcription and from RNA to protein by translation. In some viruses RNA → DNA by reverse transcription.
Transcription is carried out by RNA polymerase, using one DNA strand (the template or antisense strand) and making RNA in the 5' → 3' direction.
In bacteria, the sigma (σ) factor of RNA polymerase recognises the promoter (the −10 Pribnow box TATAAT and the −35 region). Termination is either rho-dependent or rho-independent (hairpin loop).
Eukaryotes have three RNA polymerases: I (rRNA), II (mRNA), III (tRNA and 5S rRNA).
Processing of eukaryotic mRNA: a 5' cap (methyl guanosine) is added, a poly-A tail is added at the 3' end, and introns are removed while exons are joined (splicing).
Genetic code: a triplet of bases (codon) codes for one amino acid. There are 64 codons: 61 code for amino acids and 3 are stop codons (UAA, UAG, UGA). AUG is the start codon (methionine).
Properties of the code: triplet, non-overlapping, commaless, degenerate (most amino acids have more than one codon), universal (with a few exceptions), unambiguous.
Nirenberg and Matthaei (1961) cracked the first codon: poly-U gave polyphenylalanine, so UUU = phenylalanine.
Translation – activation: each amino acid is attached to its tRNA by aminoacyl-tRNA synthetase using ATP.
Initiation: small ribosomal subunit binds mRNA; initiator tRNA (carrying formyl-methionine in bacteria, methionine in eukaryotes) pairs with AUG; large subunit joins.
Elongation: the next aminoacyl-tRNA enters the A site; peptidyl transferase (an RNA enzyme, ribozyme) forms a peptide bond; the ribosome moves one codon (translocation); the empty tRNA leaves from the E site.
Termination: a stop codon in the A site is recognised by release factors; the polypeptide is released and the ribosome separates.
महत्त्वाच्या संज्ञा
Codon – three-base sequence on mRNA.
Anticodon – complementary three-base sequence on tRNA.
Exon / intron – coding / non-coding parts of a gene.
Polysome – several ribosomes translating one mRNA at the same time.
Wobble hypothesis (Crick, 1966) – the third base of a codon can pair loosely, so one tRNA can read more than one codon.
Cells do not use all their genes all the time; they switch genes on and off as needed. This control of gene expression is called gene regulation. In bacteria, groups of related genes are controlled together as an operon. This topic covers the operon concept, the lac operon of E. coli with negative and positive control, a brief note on the trp operon, and an outline of gene regulation in eukaryotes.
महत्त्वाचे मुद्दे
The operon model was proposed by François Jacob and Jacques Monod (1961), working on E. coli; they received the Nobel Prize in 1965.
An operon is a group of structural genes with one promoter and one operator, transcribed together into one mRNA (polycistronic).
Parts of the lac operon:
Regulator gene (i / lacI) – makes the repressor protein; it has its own promoter and is always active.
Promoter (p) – site where RNA polymerase binds.
Operator (o) – site where the repressor binds; acts as an on–off switch.
Structural genes:z (β-galactosidase – splits lactose into glucose and galactose), y (permease – brings lactose into the cell) and a (transacetylase).
The lac operon is an inducible operon: it is normally off and turned on when lactose is present.
Without lactose: the repressor binds the operator, blocks RNA polymerase, and the structural genes are not transcribed.
With lactose: lactose (converted to allolactose, the true inducer) binds the repressor and changes its shape. The repressor can no longer bind the operator, so RNA polymerase transcribes z, y and a.
When lactose is used up, the repressor becomes active again and the operon switches off. This is negative control.
Positive control: when glucose is low, cAMP level rises; cAMP binds CAP (catabolite activator protein), and the CAP–cAMP complex helps RNA polymerase bind the promoter. When glucose is present, cAMP is low and the lac operon is weakly expressed even with lactose – catabolite repression. So E. coli uses glucose first.
trp operon is a repressible operon: normally on; when tryptophan (the co-repressor) is plentiful it binds the inactive repressor, which then binds the operator and switches the operon off.
Eukaryotic regulation works at many levels: chromatin packing, transcription factors, enhancers and silencers, RNA processing, mRNA stability and translation.
महत्त्वाच्या संज्ञा
Inducer – small molecule that switches on an inducible operon (allolactose).
Co-repressor – small molecule that activates a repressor (tryptophan).
Polycistronic mRNA – one mRNA carrying information for several proteins.
Constitutive gene – gene expressed all the time (housekeeping gene).
Catabolite repression – glucose preventing use of other sugars.
महत्त्वाची माहिती
Condition
Repressor
Lac genes
No lactose
Binds operator
Off
Lactose, no glucose
Inactivated; CAP–cAMP present
Strongly on
Lactose + glucose
Inactivated; little cAMP
Weakly on
Feature
Lac operon
Trp operon
Type
Inducible
Repressible
Normal state
Off
On
Small molecule
Inducer (allolactose)
Co-repressor (tryptophan)
Pathway
Breakdown (catabolic)
Synthesis (anabolic)
५ महत्त्वाचे प्रश्न
Q1. What is an operon?
An operon is a unit of gene expression in bacteria consisting of a promoter, an operator and a group of structural genes that work together and are transcribed as one mRNA.
Q2. What is the role of the repressor in the lac operon?
The repressor, made by the regulator gene, binds to the operator when lactose is absent and blocks RNA polymerase, so the structural genes stay switched off.
Q3. Describe the lac operon with its negative control.
Proposers and organism.
Parts and their roles.
Absence and presence of lactose (with diagrams).
Switching off when lactose is used.
Q4. Explain positive control of the lac operon.
Role of glucose, cAMP and CAP.
CAP–cAMP binding site near the promoter.
Catabolite repression and diauxic growth.
Table of conditions.
Q5. Distinguish between inducible and repressible operons with examples.
Definitions.
Lac operon as inducible; trp operon as repressible with diagrams.
Table of differences.
परीक्षेसाठी टीप
Draw two diagrams for the lac operon: "lactose absent" and "lactose present". Label repressor, operator, promoter and the three structural genes.
Animal biotechnology uses animal cells, genes and reproductive techniques to make useful products and improve animals and human health. This topic covers animal cell culture, recombinant DNA technology, transgenic animals, cloning (Dolly), artificial insemination and embryo transfer, monoclonal antibodies, gene therapy, DNA fingerprinting and ethical issues.
महत्त्वाचे मुद्दे
Animal cell culture: growing animal cells outside the body in a sterile, nutrient medium at about 37 °C with 5% CO₂, in a CO₂ incubator. The medium has salts, glucose, amino acids, vitamins and usually serum (e.g. foetal bovine serum). Work is done in a laminar air flow cabinet.
Primary culture comes directly from tissue; a cell line can be sub-cultured many times. HeLa cells (from Henrietta Lacks, 1951) were the first continuous human cell line.
rDNA technology tools: restriction enzymes, DNA ligase, vectors (plasmids, viruses), host cells; gene products like human insulin (Humulin, made in E. coli; Eli Lilly, 1983), growth hormone, interferons and vaccines (hepatitis B vaccine made in yeast).
Transgenic animals carry a foreign gene. Example: Rosie, the first transgenic cow (1997), produced milk with human alpha-lactalbumin. Transgenic mice are used as disease models.
Cloning:Dolly the sheep (born 1996, announced 1997) was the first mammal cloned from an adult cell by somatic cell nuclear transfer, by Ian Wilmut and team at the Roslin Institute, Scotland.
Artificial insemination (AI): semen from a superior bull is collected, stored frozen in liquid nitrogen (−196 °C) and placed into the female's tract. Widely used for cattle and buffalo improvement in India.
MOET (Multiple Ovulation Embryo Transfer): a cow is given FSH-like hormones for superovulation, mated or inseminated, embryos (8–32 cell stage) are collected and transferred to surrogate mothers.
Monoclonal antibodies: made by hybridoma technology (Köhler and Milstein, 1975) – fusing an antibody-making B-cell with a myeloma (cancer) cell.
Gene therapy: correcting a defective gene by inserting a normal gene. The first clinical gene therapy (1990) was for ADA (adenosine deaminase) deficiency.
DNA fingerprinting: developed by Alec Jeffreys (1984–85); based on VNTRs (variable number tandem repeats). In India, Dr. Lalji Singh (CCMB, Hyderabad) is called the father of Indian DNA fingerprinting.
महत्त्वाच्या संज्ञा
Transgenic – organism with a foreign gene in its genome.
Somatic cell nuclear transfer – putting a body-cell nucleus into an enucleated egg.
Hybridoma – fused cell that makes one specific antibody and divides endlessly.
Southern blotting – technique to detect specific DNA sequences (E. M. Southern).
Stem cells – unspecialised cells that can divide and form many cell types (embryonic and adult).
Biopiracy – use of biological resources or traditional knowledge without permission or fair payment (e.g. patent disputes on turmeric and neem).
महत्त्वाची माहिती
Technique
Key name / year
Use
Recombinant insulin
1982–83
Diabetes treatment
Hybridoma
Köhler and Milstein, 1975
Diagnosis, therapy
DNA fingerprinting
Jeffreys, 1984–85
Crime, paternity
Cloning (Dolly)
Wilmut, 1996
Research, conservation
Gene therapy
1990, ADA deficiency
Genetic disease
Ethical issues: animal welfare, safety of GM products, misuse of cloning, gene patenting. In India, the GEAC (Genetic Engineering Appraisal Committee) checks the safety of GM research and products.
५ महत्त्वाचे प्रश्न
Q1. What is a transgenic animal? Give an example.
A transgenic animal has a foreign gene deliberately inserted into its genome and passes it to offspring. Example: Rosie, a transgenic cow whose milk contained human alpha-lactalbumin.
Q2. What are monoclonal antibodies?
Monoclonal antibodies are identical antibodies made by a single clone of hybridoma cells. They bind one specific antigen and are used in pregnancy tests, diagnosis and cancer treatment.
Q3. Explain how Dolly the sheep was cloned.
Udder (mammary) cell taken from a Finn Dorset ewe; grown in low-nutrient culture.
Egg taken from a Scottish Blackface ewe; nucleus removed.
Udder cell fused with the empty egg by an electric pulse.
Embryo grown and placed in a surrogate ewe.
Dolly born genetically identical to the udder-cell donor.
Q4. Describe DNA fingerprinting and its applications.
Isolate DNA from blood, hair roots, semen etc.; amplify by PCR if needed.
Cut with restriction enzymes; separate by gel electrophoresis.
Southern blotting onto a membrane; hybridise with labelled VNTR probes.
Autoradiography shows a band pattern unique to each person (except identical twins).
Helminths are parasitic worms belonging to flatworms (Platyhelminthes) and roundworms (Nematoda). Many of them live in the human body and cause serious diseases, especially where sanitation is poor. This topic covers the host–parasite relationship and parasitic adaptations, followed by important helminths of man – Wuchereria, Ancylostoma, Enterobius, Dracunculus, Echinococcus and Fasciola – with their mode of infection, disease and control.
महत्त्वाचे मुद्दे
Parasitism: a close relationship in which one organism (parasite) lives on or in another (host) and harms it.
Definitive host – where the parasite becomes adult and reproduces sexually; intermediate host – where larval stages develop.
Adaptations of endoparasites: loss or reduction of locomotory and sense organs; thick cuticle or tegument resistant to digestive enzymes; hooks and suckers for attachment; anaerobic respiration; very high reproductive capacity; often hermaphrodite (flatworms); complex life cycles with more than one host.
Wuchereria bancrofti (filarial worm): adults live in lymph vessels and nodes. Female releases microfilariae that circulate in blood mostly at night (nocturnal periodicity). Vector: **female Culex mosquito. Disease: filariasis, leading to elephantiasis** (swelling of legs, scrotum) and hydrocele. Many districts of Vidarbha are endemic.
Ancylostoma duodenale (hookworm): lives in the small intestine, attaching by cutting plates and sucking blood. Infection: filariform larvae penetrate the skin of bare feet ("ground itch"). Causes severe anaemia and weakness.
Enterobius vermicularis (pinworm/threadworm): common in children; lives in the large intestine. Female lays eggs at night around the anus, causing itching; scratching leads to autoinfection.
Dracunculus medinensis (guinea worm): infection by drinking water with infected Cyclops. The female emerges from a painful blister on the leg. India was declared guinea-worm free in 2000.
Echinococcus granulosus (dog tapeworm): adult in dog's intestine; man gets eggs from dog faeces and becomes an accidental intermediate host, developing hydatid cysts in the liver or lungs.
Fasciola hepatica (liver fluke): mainly in sheep and cattle, occasionally in man; snail (Lymnaea) is the intermediate host; infection by eating aquatic plants with metacercariae.
महत्त्वाच्या संज्ञा
Vector – organism that carries a parasite from one host to another.
Microfilaria – larva of the filarial worm in blood.
Autoinfection – reinfection of the same host by its own parasite's eggs.
Hydatid cyst – fluid-filled larval cyst of Echinococcus.
Zoonosis – disease passed from animals to humans.
महत्त्वाची माहिती
Parasite
Site in man
Infection
Disease
Wuchereria bancrofti
Lymphatics
Bite of Culex
Filariasis, elephantiasis
Ancylostoma duodenale
Small intestine
Larvae through skin
Hookworm anaemia
Enterobius vermicularis
Large intestine
Eggs swallowed
Enterobiasis
Dracunculus medinensis
Under skin
Cyclops in water
Dracunculiasis
Echinococcus granulosus
Liver, lungs
Eggs from dog faeces
Hydatid disease
५ महत्त्वाचे प्रश्न
Q1. What is nocturnal periodicity?
It is the appearance of microfilariae of Wuchereria in the peripheral blood mainly at night (about 10 pm to 2 am), the time when the Culex vector bites. Blood samples for diagnosis are therefore taken at night.
Q2. How does hookworm infection occur?
Hookworm eggs pass out in faeces and hatch in moist soil. Their filariform larvae penetrate the skin of a person walking barefoot, travel through blood and lungs, and reach the small intestine.
Q3. Describe parasitic adaptations in helminths.
Morphological: cuticle/tegument, hooks, suckers, loss of organs.
Sericulture is the rearing of silkworms for the production of raw silk. India is the second largest producer of silk in the world after China, and the only country that produces all four commercial kinds of silk: mulberry, tasar, eri and muga. This topic covers types of silkworms, the life cycle of Bombyx mori, mulberry cultivation, rearing methods, cocoon processing, diseases and the economic value of sericulture.
महत्त्वाचे मुद्दे
The word comes from "sericos" (Greek for silk). Sericulture is रेशीम उद्योग in Marathi.
Silk is a natural protein fibre made of fibroin (inner core) and sericin (outer gum).
Types of silk and silkworms:
Mulberry silk – Bombyx mori; feeds on mulberry (Morus alba). Most important (bulk of India's silk).
Tasar (tussar) silk – Antheraea mylitta (tropical tasar) on Terminalia (arjun, ain) and Shorea robusta (sal). Grown in forest areas including Vidarbha (Bhandara, Gondia, Chandrapur, Gadchiroli).
Eri silk – Samia ricini (Philosamia ricini) on castor leaves. Eri is spun from opened cocoons, so it is called "ahimsa silk".
Muga silk – Antheraea assamensis on som and soalu trees; golden-yellow silk found only in Assam.
Bombyx mori is a fully domesticated insect; it cannot survive in the wild.
Larva grows through five instars with four moults; the final instar stops feeding and spins a cocoon.
Silk is secreted by a pair of silk glands (modified salivary glands) and comes out through the spinneret.
One cocoon has a single continuous filament, often about 1000–1500 m long (varies with breed).
महत्त्वाच्या संज्ञा
Moriculture – cultivation of mulberry plants.
Instar – larval stage between two moults.
Spinning – making the cocoon by laying silk thread in a figure-of-eight pattern.
Stifling – killing the pupa inside the cocoon by heat (sun drying, steam or hot air) to keep the filament unbroken.
Reeling – unwinding silk filaments from cooked cocoons to make raw silk.
Degumming – removing sericin to make silk soft and shiny.
Disease-free layings (DFLs) – eggs from tested, healthy moths.
Voltinism – number of generations per year: univoltine (one), bivoltine (two), multivoltine (many).
महत्त्वाची माहिती
Rearing: chawki (young-age) rearing of 1st–2nd instars with tender leaves; late-age rearing on mature leaves; temperature about 23–28 °C and humidity about 70–85% (varies by stage); mountages (chandrikes) for spinning.
Diseases of silkworm:pebrine (protozoan Nosema bombycis; studied by Louis Pasteur), flacherie (bacteria/virus; flaccid larvae), grasserie (nuclear polyhedrosis virus; milky fluid, swollen body), muscardine (fungus Beauveria bassiana; larva becomes hard and chalky).
Pest: uzi fly (Exorista bombycis) lays eggs on larvae.
By-products: silk waste for spun silk, pupae as poultry/fish feed and oil, mulberry for fodder.
Central Silk Board (Bengaluru) oversees sericulture in India; Karnataka is the leading mulberry silk state.
५ महत्त्वाचे प्रश्न
Q1. What are fibroin and sericin?
Fibroin is the insoluble protein forming the inner core of the silk filament. Sericin is the gummy protein coating that sticks the filaments together; it is removed by degumming.
Q2. Name the four types of silk produced in India with their silkworms.
Mulberry (Bombyx mori), tasar (Antheraea mylitta), eri (Samia ricini) and muga (Antheraea assamensis).
Q3. Describe the life cycle of Bombyx mori.
Egg: laid in clusters on mulberry leaves or paper; hatches in about 10 days (non-hibernating).
Larva: five instars, four moults; voracious feeding on mulberry leaves.
Spinning: mature larva secretes silk from silk glands; cocoon formed in 2–3 days.
Pupa: inside cocoon.
Adult: moth comes out by softening cocoon with alkaline fluid; does not feed; mates and lays eggs.
Draw labelled stages.
Q4. Explain the processing of cocoons.
Harvest and sorting of cocoons.
Stifling to kill pupae.
Cooking in hot water to soften sericin.
Reeling: filaments of several cocoons combined into one raw silk thread.
Apiculture (bee-keeping) is the rearing and management of honey bees for honey, wax and other products, and for pollination of crops. Honey bees are social insects that live in colonies with clear division of labour. This topic covers Indian species of honey bees, the bee colony, life cycle, communication, modern bee-keeping methods, bee products, enemies and diseases.
महत्त्वाचे मुद्दे
Apiculture comes from Apis (bee). Bee-keeping is मधुमक्षिका पालन in Marathi.
Honey bees of India:
Apis dorsata – rock bee; largest; builds a single huge comb in the open on trees, cliffs and buildings; aggressive; gives the most honey per comb but cannot be domesticated.
Apis cerana indica – Indian hive bee; builds several parallel combs in dark cavities; gentle; domesticated in boxes.
Apis florea – little bee; smallest; single small comb on bushes; little honey.
Apis mellifera – European (Italian) bee; introduced; high yield; gentle; widely kept in modern apiaries.
Stingless bees (Trigona) also give small amounts of honey.
Castes in a colony:
Queen – one fertile female; largest; lays eggs (up to about 1500–2000 eggs a day in peak season); develops from a fertilised egg fed only royal jelly.
Drones – fertile males from unfertilised eggs (parthenogenesis); die after mating; do no other work.
Workers – sterile females; do all work: cleaning, feeding larvae (nurse bees), building comb, guarding, collecting nectar and pollen (foragers).
Life cycle: complete metamorphosis – egg → larva → pupa → adult. Development time is about 16 days for the queen, 21 days for the worker and 24 days for the drone.
Nuptial flight – the queen mates with several drones in the air and stores sperm for life.
Communication (dance language) was explained by Karl von Frisch (Nobel Prize 1973): the round dance shows food near the hive; the waggle (tail-wagging) dance shows direction and distance of distant food.
महत्त्वाच्या संज्ञा
Royal jelly – protein-rich secretion of the hypopharyngeal glands of young workers.
Swarming – old queen leaves with part of the colony to form a new colony.
Absconding – whole colony leaves the hive due to disturbance, disease or lack of food.
Propolis – sticky resin collected from plants; used to seal gaps in the hive.
Bee venom – secretion from the sting gland; used in some medicines.
Honey extractor – machine that removes honey from combs by centrifugal force without damaging them.
महत्त्वाची माहिती
Modern (movable-frame) hive, based on Langstroth (1851), has: stand, bottom board, brood chamber with frames, queen excluder, super chamber (honey frames), inner cover and top cover. Comb foundation sheets of beeswax help bees build straight combs.
Products: honey (mainly fructose and glucose with water, enzymes and minerals), beeswax (from wax glands on the worker's abdomen; used in cosmetics, candles, polishes), royal jelly, propolis, pollen, venom.
Pollination: bees greatly increase yield of crops like sunflower, mustard, apples and many fruits.
Royal jelly is a creamy, protein-rich food secreted by the glands of young worker bees. All larvae get it for the first few days, but only the queen larva is fed on it throughout, which makes her develop into a fertile queen.
Q2. Why is the drone called the son of an unmarried mother?
A drone develops from an unfertilised egg laid by the queen (parthenogenesis). So it has a mother (the queen) but no father.
Q3. Describe the social organisation of a honey bee colony.
Queen: egg laying; controls colony with pheromones.
Q4. Describe the structure of a modern bee hive (Langstroth type).
Stand and bottom board with entrance.
Brood chamber with movable frames for egg laying.
Queen excluder to keep queen out of the super.
Super chamber for honey storage.
Inner cover and top cover (roof).
Advantages: easy inspection, honey extraction without killing bees, reuse of combs.
Q5. Give the economic importance of apiculture.
Honey as food and medicine.
Beeswax for cosmetics, candles, polish, foundation sheets.
Royal jelly, propolis, pollen, venom.
Pollination increases crop yield and quality.
Self-employment for rural people; low investment (supported by KVIC and the National Bee Board).
परीक्षेसाठी टीप
Learn the four Apis species and the castes with their origin (fertilised or unfertilised eggs). The waggle dance by von Frisch is a favourite short note.
Lac culture is the rearing of the lac insect on host trees to obtain lac, a natural resin. Vermiculture is the rearing of earthworms to turn organic waste into rich manure called vermicompost. Both are low-cost, eco-friendly rural industries suited to Vidarbha and other parts of Maharashtra. This topic covers the lac insect, its life cycle, host plants, cultivation and products, and the species, method and benefits of vermicomposting.
महत्त्वाचे मुद्दे
Lac insect:Kerria lacca (earlier Laccifer lacca), a scale insect of order Hemiptera. Lac is लाख in Marathi.
Lac is a resin secreted by the female through glands on its body as a protective covering. Females are degenerate, sac-like and stay fixed on twigs; males are smaller and some are winged.
Life cycle: eggs hatch inside the female's cell (it is ovoviviparous) → red crawlers (nymphs) come out in large numbers (swarming) → settle on tender twigs and suck sap → secrete lac → moult and become adults → mating → each female produces a few hundred young. Two generations a year.
Host plants:kusum (Schleichera oleosa), palas (Butea monosperma), ber (Ziziphus mauritiana), and others.
Strains and crops:Kusmi strain (on kusum) gives the Aghani and Jethwi crops; Rangeeni strain (on palas, ber) gives the Katki and Baisakhi crops.
Cultivation steps: pruning of host trees → inoculation by tying brood lac (twigs with mature females about to release crawlers) on fresh shoots → removal of brood lac after swarming → crop care → harvesting by cutting lac-encrusted twigs (stick lac).
Processing: stick lac → scraping and crushing → washing → seed lac → melting and filtering → shellac.
Uses: varnishes and polishes, sealing wax, electrical insulation, printing inks, coating of fruits and tablets, cosmetics, bangles, and lac dye.
Enemies: predator moths such as Eublemma amabilis, and chalcid parasitoids.
India is the world's leading lac producer (Jharkhand, Chhattisgarh, Madhya Pradesh, and Gondia–Bhandara belt of Maharashtra). The ICAR–Indian Institute of Natural Resins and Gums, Ranchi (founded 1925 as the Indian Lac Research Institute) guides lac research.
Vermiculture: surface-living earthworms are used – Eisenia fetida (red wiggler), Eudrilus eugeniae (African nightcrawler) and Perionyx excavatus.
Vermicomposting method: shaded pit, tank or bed → bottom layer of bricks or coarse material for drainage → bedding of dry leaves and soil → half-decomposed cow dung and organic waste → release of earthworms (about 1 kg per square metre) → cover with gunny bag → keep moist (about 50–60%) and cool (about 20–30 °C) → compost ready in about 45–60 days → stop watering, worms move down, harvest the upper compost and sieve.
महत्त्वाच्या संज्ञा
Brood lac – lac-bearing twigs used as "seed" for new infection.
Swarming – mass emergence of crawlers from the mother cells.
Shellac – purified, flaked form of lac.
Vermicompost – earthworm castings mixed with decomposed organic matter.
Vermiwash – liquid collected from a vermicompost unit, used as a foliar spray.
महत्त्वाची माहिती
Product
Benefit
Vermicompost
Rich in N, P, K and micronutrients; improves soil structure and water holding
Vermiwash
Plant growth promoter; mild pest repellent
Earthworms
Protein-rich feed for fish and poultry
Benefits of vermiculture: recycles farm and kitchen waste, reduces chemical fertiliser use, low cost, gives rural employment.
५ महत्त्वाचे प्रश्न
Q1. What is brood lac?
Brood lac is a piece of twig carrying mature female lac insects that are about to release crawlers. It is tied to a new host tree so that the crawlers settle on fresh shoots; this is called inoculation.
Q2. Name two earthworm species used in vermiculture.
Eisenia fetida (red wiggler) and Eudrilus eugeniae (African nightcrawler). Perionyx excavatus is an Indian species also used.
Q3. Describe the life cycle of the lac insect.
Female and male structure.
Eggs, crawlers, swarming, settling.
Lac secretion, moulting, maturity, mating.
Two generations per year; draw the life cycle.
Q4. Explain the methods of lac cultivation and its economic importance.
Host plants and strains; crops.
Pruning, inoculation, crop care, harvesting.
Processing to shellac.
Uses; enemies and their control; lac industry in India.
Q5. Describe the method of vermicomposting and its advantages.
Selection of species and site.
Preparation of bed; layers; conditions.
Maintenance and harvesting.
Advantages to soil, farmers and environment.
परीक्षेसाठी टीप
Learn the four crop names with their strains (Kusmi: Aghani, Jethwi; Rangeeni: Katki, Baisakhi); they are favourite objective questions in applied zoology.
Aquaculture is the farming of aquatic organisms – fish, prawns, crabs, mussels and seaweeds – in controlled conditions in fresh, brackish or sea water. India is one of the world's leading producers of farmed fish. This topic covers types of aquaculture, composite fish culture of Indian major carps, induced breeding, pond management, prawn and pearl culture, and the Blue Revolution.
महत्त्वाचे मुद्दे
Aquaculture includes fish culture (pisciculture), prawn culture, pearl culture, crab culture and seaweed culture. Fish farming is मत्स्यपालन / मत्स्यशेती in Marathi.
Types by water: freshwater (ponds, tanks, reservoirs), brackish water (estuaries, coastal ponds) and mariculture (sea).
Types by intensity: extensive (low input, natural food), semi-intensive (some feeding and fertilising), intensive (high stocking, full feeding, aeration).
Composite fish culture: six compatible species (3 Indian + 3 exotic carps) are reared together in one pond so they use food at all levels without competing; it gives much higher yield.
Induced breeding (hypophysation): carps do not breed in stagnant ponds, so they are injected with pituitary gland extract from mature fish (or synthetic hormone preparations such as Ovaprim) to make them spawn. India's pioneers in this method include Dr. Hiralal Chaudhuri (1957), called the father of induced breeding in India.
Pond types in a fish farm: breeding pond (hapa), hatching pond, nursery pond, rearing pond and stocking pond.
Stages of fish seed: spawn (just hatched) → fry → fingerling.
Blue Revolution – rapid increase in fish production through aquaculture. The Government of India launched the "Blue Revolution" scheme (2015–16) and the PM Matsya Sampada Yojana (2020).
महत्त्वाच्या संज्ञा
Hapa – rectangular cloth net enclosure fixed in a pond for breeding fish.
Liming – adding lime to correct soil pH and kill pests.
Manuring – adding cow dung or fertilisers to grow plankton (natural fish food).
Eradication of predators – removing predatory and weed fish (e.g. with mahua oil cake) before stocking.
Stocking density – number of fish seed released per unit area.
Brackish water – mix of fresh and salt water, found in estuaries.
Pearl culture: pearl oyster Pinctada fucata (marine); freshwater mussel Lamellidens used for freshwater pearls. A small nucleus is surgically placed with mantle tissue; nacre layers form the pearl. The CMFRI (Central Marine Fisheries Research Institute) developed pearl culture technology in India (Tuticorin).
Fish diseases: epizootic ulcerative syndrome (EUS), fin rot, gill rot, white spot (Ichthyophthirius), argulosis (fish louse Argulus).
Composite fish culture is rearing several compatible fish species with different feeding habits (usually 3 Indian and 3 exotic carps) together in one pond. All food niches are used and fish do not compete, so yield increases.
Q2. Name the Indian major carps and their feeding zones.
Catla (Catla catla) feeds at the surface, rohu (Labeo rohita) in the column, and mrigal (Cirrhinus mrigala) at the bottom.
Q3. Describe the method of induced breeding in carps.
Select healthy, mature male and female brood fish.
Collect pituitary glands from mature donor fish; prepare extract (or use synthetic hormone).
Inject female (two doses) and male (one dose) intramuscularly near the dorsal fin or tail base.
Release in breeding hapa; spawning occurs in a few hours.
Collect fertilised eggs; transfer to hatching hapas/ hatchery; spawn hatch in about 15–18 hours (temperature-dependent).
Q4. Explain the management of a fish pond.
Pre-stocking: draining/drying, removing weeds and predatory fish, liming, manuring.
Stocking: right species and density of fingerlings.