Class 11 · Biology · English medium
Class 11 Biology companion
An interactive companion to Class 11 Biology: original explanations, labelled diagrams, process steppers and practice for diversity, structure, cells, plant physiology and human physiology.
An original companion to Biology, NCERT Class 11 Biology (2026–27 edition). Official textbook ↗ ncert.nic.in
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Chapters
- ENHinglish
Chapter 1: The Living World
Opening Unit 1 (Diversity in the Living World), the chapter shows how biologists handle about 1.7–1.8 million described species, a variety called biodiversity. - ENHinglish
Chapter 2: Biological Classification
The chapter traces classification from use-based sorting, Aristotle and Linnaeus's two kingdoms to Whittaker's five kingdoms (1969), built o - ENHinglish
Chapter 3: Plant Kingdom
Kingdom Plantae now contains algae, bryophytes, pteridophytes, gymnosperms and angiosperms; fungi, walled monerans and protists, and cyanobacteria are excluded. - ENHinglish
Chapter 4: Animal Kingdom
Animals are classified by fundamental body-plan features: level of organisation (cellular, tissue, organ, organ system), symmetry (none, rad - ENHinglish
Chapter 5: Morphology of Flowering Plants (Plant Morphology)
Opening Unit 2, the chapter builds the standard vocabulary for describing flowering plants. - ENHinglish
Chapter 6: Anatomy of Flowering Plants (Plant Anatomy)
The chapter describes the internal structure of flowering plants. - ENHinglish
Chapter 7: Structural Organisation in Animals (Animal Tissues and Organs)
The chapter explains levels of organisation (cell, tissue, organ, organ system, organism) and division of labour, names the four basic tissu - ENHinglish
Chapter 8: Cell: The Unit of Life (The Cell)
Every organism is made of cells, the smallest units that can live on their own. - ENHinglish
Chapter 9: Biomolecules
Living tissue has the same elements as rock but far more carbon and hydrogen. - ENHinglish
Chapter 10: Cell Cycle and Cell Division
NCERT Class 11 Biology Chapter 10. - ENHinglish
Chapter 11: Photosynthesis in Higher Plants
Photosynthesis uses light to build sugar from CO2 and water and releases O2 that comes from water. - ENHinglish
Chapter 12: Respiration in Plants
Plants exchange respiratory gases by diffusion through stomata, lenticels and air spaces. - ENHinglish
Chapter 13: Plant Growth and Development
Growth is an irreversible increase in size driven by metabolism; in plants it is open because meristems keep dividing. - ENHinglish
Chapter 14: Breathing and Exchange of Gases
Unit 5 (Human Physiology) opens with breathing. - ENHinglish
Chapter 15: Body Fluids and Circulation
Class 11 Biology chapter 15. - ENHinglish
Chapter 16: Excretory Products and their Elimination (Excretion)
Class 11 Biology chapter 16. - ENHinglish
Chapter 17: Locomotion and Movement
Class 11 Biology chapter on how the body moves. - ENHinglish
Chapter 18: Neural Control and Coordination
The neural and endocrine systems coordinate the organs; the neural route is fast and point to point. - ENHinglish
Chapter 19: Chemical Coordination and Integration (Hormones)
Hormones are non-nutrient chemical messengers made in trace amounts.
Also in Hinglish
- Chapter 1: The Living World (Hinglish)
- Chapter 2: Biological Classification (Hinglish)
- Chapter 3: Plant Kingdom (Hinglish)
- Chapter 4: Animal Kingdom (Hinglish)
- Chapter 5: Flowering Plants ki Morphology (Hinglish)
- Chapter 6: Flowering Plants ki Anatomy (Hinglish)
- Chapter 7: Animals mein Structural Organisation (Hinglish)
- Chapter 8: Cell: Jeevan ki Unit (Hinglish)
- Chapter 9: Biomolecules (Hinglish)
- Chapter 10: Cell Cycle aur Cell Division (Hinglish)
- Chapter 11: Higher Plants mein Photosynthesis (Hinglish)
- Chapter 12: Plants mein Respiration (Hinglish)
- Chapter 13: Plant Growth aur Development (Hinglish)
- Chapter 14: Breathing aur Gases ka Exchange (Hinglish)
- Chapter 15: Body Fluids aur Circulation (Hinglish)
- Chapter 16: Excretory Products aur unka Elimination (Hinglish)
- Chapter 17: Locomotion aur Movement (Hinglish)
- Chapter 18: Neural Control aur Coordination (Hinglish)
- Chapter 19: Chemical Coordination aur Integration (Hinglish)
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absorption spectrumअवशोषण स्पेक्ट्रमA graph of how strongly a pigment absorbs light of each wavelength.Ch 11 · Photosynthesis in Higher Plantsaccessory pigmentsChlorophyll b, xanthophylls and carotenes: they absorb light that chlorophyll a misses, pass the energy to it and protect it from photo-oxidation.Ch 11 · Photosynthesis in Higher Plantsacid-soluble poolThe filtrate obtained when tissue ground in trichloroacetic acid is strained; it holds the small molecules (about 18–800 Da).Ch 9 · Biomoleculesactinएक्टिनThe protein of the thin filaments, made of two twisted F-actin strands, each a chain of G-actin units.Ch 17 · Locomotion and Movementactinomorphicत्रिज्यसममितRadially symmetrical: a flower divisible into equal halves along any plane through its centre (symbol ⊕).Ch 5 · Morphology of Flowering Plantsaction potentialThe reversed potential difference at a stimulated site of a neuron's membrane, caused by Na+ rushing in; the nerve impulse.Ch 18 · Neural Control and Coordinationaction spectrumक्रिया स्पेक्ट्रमA graph of the rate of photosynthesis under light of each wavelength.Ch 11 · Photosynthesis in Higher Plantsactivation energyसक्रियण ऊर्जाThe energy a substrate must gain to reach the transition state; enzymes lower it.Ch 9 · Biomoleculesactive siteThe pocket or cleft in an enzyme where the substrate fits and the reaction is catalysed.Ch 9 · Biomoleculesactive transportसक्रिय परिवहनMovement of a substance across a membrane against its concentration gradient, using energy from ATP.Ch 8 · Cell: The Unit of Lifeadventitious rootअपस्थानिक जड़A root that arises from any part of a plant other than the radicle, such as a stem node.Ch 5 · Morphology of Flowering Plantsaerobic respirationवायवीय श्वसनComplete oxidation of food to CO₂ and water using O₂.Ch 12 · Respiration in Plantsaestivationपुष्पदल विन्यासThe arrangement of sepals or petals in a bud relative to other members of the same whorl.Ch 5 · Morphology of Flowering Plantsaestivationग्रीष्म निद्राSummer sleep: a period of inactivity in a burrow to escape extreme heat.Ch 7 · Structural Organisation in Animalsafferent fibreअभिवाही तंतुA nerve fibre that carries impulses from tissues and organs to the CNS.Ch 18 · Neural Control and Coordinationalternation of generationsपीढ़ी एकांतरणThe alternation of a diploid sporophyte and a haploid gametophyte in a plant's life cycle.Ch 2 · Biological ClassificationalveolusकूपिकाA tiny, very thin-walled, irregular air sac at the end of a terminal bronchiole, wrapped in capillaries; the site of gas exchange.Ch 14 · Breathing and Exchange of Gasesamino acidऐमीनो अम्लAn organic compound whose α-carbon carries H, an amino group, a carboxyl group and a variable R group; proteins use 20 kinds.Ch 9 · BiomoleculesammonotelismExcreting nitrogenous waste mainly as ammonia, which needs plenty of water; typical of aquatic animals such as many bony fishes.Ch 16 · Excretory Products and their Eliminationamphibolic pathwayA pathway used both to break down and to build up molecules.Ch 12 · Respiration in PlantsanaerobeAn organism that can live without O₂: facultative anaerobes can switch, obligate anaerobes must avoid O₂.Ch 12 · Respiration in PlantsanatomyThe study of the internal structure of organisms; in plants, usually by examining thin sections under a microscope.Ch 6 · Anatomy of Flowering PlantsanatomyशारीरIn animals, the study of the form and arrangement of the internal organs.Ch 7 · Structural Organisation in AnimalsantheridiumपुंधानीThe male sex organ of bryophytes and pteridophytes, which releases antherozoids.Ch 3 · Plant Kingdomantidiuretic hormoneA hormone released from the neurohypophysis that makes the DCT and collecting duct reabsorb more water, preventing diuresis.Ch 16 · Excretory Products and their Eliminationantigenप्रतिजनA chemical, such as the A, B or Rh molecule on red cells, that can trigger an immune response and is bound by a matching antibody.Ch 15 · Body Fluids and Circulationapical dominanceSuppression of the growth of lateral (axillary) buds by the growing apical bud above them.Ch 13 · Plant Growth and Developmentappendicular skeletonउपांगीय कंकालThe 126 bones of the limbs and of the pectoral and pelvic girdles.Ch 17 · Locomotion and Movementarchegoniumस्त्रीधानीThe flask-shaped female sex organ, holding a single egg, of bryophytes, pteridophytes and gymnosperms.Ch 3 · Plant KingdomATPAdenosine triphosphate, the cell's energy currency; it is split wherever energy is needed.Ch 12 · Respiration in PlantsATP synthaseComplex V: protons flowing through its F₀ channel drive ATP synthesis at its F₁ head.Ch 12 · Respiration in Plantsautonomic neural systemस्वायत्त तंत्रिका तंत्रThe part of the PNS that carries impulses from the CNS to involuntary organs and smooth muscles; it has sympathetic and parasympathetic divisions.Ch 18 · Neural Control and Coordinationautotrophस्वपोषीAn organism that makes its own food from inorganic substances, using light or chemical energy.Ch 2 · Biological Classificationaxial skeletonअक्षीय कंकालThe 80 bones along the main axis of the body: skull, hyoid, ear ossicles, vertebral column, sternum and ribs.Ch 17 · Locomotion and MovementB
binomial nomenclatureद्विनाम पद्धतिNaming a species with two words, the generic name and the specific epithet, as applied by Linnaeus.Ch 1 · The Living Worldbiodiversityजैव विविधताThe number and variety of kinds of organisms on Earth or in a given area.Ch 1 · The Living Worldbiomoleculeजैव अणुAny carbon compound obtained from living tissue, from small amino acids and sugars to giant proteins and nucleic acids.Ch 9 · BiomoleculesbivalentA synapsed pair of homologous chromosomes, with four chromatids.Ch 10 · Cell Cycle and Cell DivisionboltingRapid lengthening of the internodes of a rosette plant just before it flowers.Ch 13 · Plant Growth and Developmentbreathingश्वसनExchange of oxygen from the atmosphere for carbon dioxide produced by cells; commonly also called respiration.Ch 14 · Breathing and Exchange of Gasesbulliform cellA large, empty, colourless cell of the upper epidermis of grass leaves; when these lose water the leaf rolls.Ch 6 · Anatomy of Flowering PlantsC
Calvin cycleThe cycle of carbon reactions in the stroma: carboxylation of RuBP, reduction to triose phosphate and regeneration of RuBP.Ch 11 · Photosynthesis in Higher PlantscapsidThe protein coat of a virus, built of capsomeres.Ch 2 · Biological Classificationcarbamino-haemoglobinकार्बामिनोहीमोग्लोबिनHaemoglobin carrying carbon dioxide; it carries 20–25 % of the CO2 in blood.Ch 14 · Breathing and Exchange of Gasescarbonic anhydraseकार्बोनिक एनहाइड्रेज़An enzyme, abundant in RBCs, that speeds up the reaction of CO2 with water to form carbonic acid, and its reverse.Ch 14 · Breathing and Exchange of Gasescardiac cycleहृद् चक्रOne complete round of systole and diastole of the atria and the ventricles; about 0.8 s at 72 beats a minute.Ch 15 · Body Fluids and Circulationcardiac outputहृद् निकासThe volume of blood each ventricle pumps per minute: stroke volume × heart rate, about 5 L per minute at rest.Ch 15 · Body Fluids and CirculationCasparian stripA band of suberin, a waterproof material, in the walls of root endodermal cells.Ch 6 · Anatomy of Flowering PlantscatecholamineAdrenaline or noradrenaline, the emergency hormones of the adrenal medulla.Ch 19 · Chemical Coordination and IntegrationcellकोशिकाThe smallest unit of structure and function that can live on its own.Ch 8 · Cell: The Unit of Lifecell cycleकोशिका चक्रThe sequence of growth, DNA replication and division by which one cell becomes two.Ch 10 · Cell Cycle and Cell Divisioncell plateकोशिका पट्टिकाThe partition growing outwards from the centre of a dividing plant cell; it becomes the middle lamella.Ch 10 · Cell Cycle and Cell Divisioncell theoryकोशिका सिद्धांतAll organisms are made of cells and cell products, and every cell arises from a pre-existing cell.Ch 8 · Cell: The Unit of Lifecellular respirationकोशिकीय श्वसनOxidation of food inside cells, step by step, with part of the energy stored as ATP.Ch 12 · Respiration in Plantscentral neural systemकेंद्रीय तंत्रिका तंत्रThe brain and the spinal cord, where information is processed and control is exercised.Ch 18 · Neural Control and Coordinationcentromereगुणसूत्रबिंदुThe primary constriction of a chromosome, which holds its two chromatids together.Ch 8 · Cell: The Unit of LifechemiosmosisरसोपरासरणATP synthesis driven by protons flowing back through ATP synthase down a gradient built across a membrane.Ch 11 · Photosynthesis in Higher PlantschiasmaAn X-shaped point where homologues stay joined in diplotene, at a crossover site.Ch 10 · Cell Cycle and Cell DivisionchoanocyteA flagellated collar cell lining a sponge's canals and spongocoel; it drives water and traps food.Ch 4 · Animal Kingdomclassificationवर्गीकरणGrouping organisms into convenient categories on the basis of easily observable characters.Ch 1 · The Living Worldcloacaअवस्करA small median chamber into which the rectum, ureters and genital ducts open; faeces, urine and gametes leave through it.Ch 7 · Structural Organisation in AnimalscnidoblastA stinging cell of cnidarians holding a nematocyst, used for anchorage, defence and catching prey.Ch 4 · Animal Kingdomcoagulationरुधिर स्कंदनThe clotting of blood: a cascade of reactions that turns soluble fibrinogen into a mesh of fibrin threads at a wound.Ch 15 · Body Fluids and CirculationcoelomA body cavity between gut and body wall that is lined all round by mesoderm.Ch 4 · Animal KingdomcofactorA non-protein part an enzyme needs for activity: a prosthetic group, a co-enzyme or a metal ion.Ch 9 · Biomoleculescompetitive inhibitorA substrate look-alike that competes for the active site and slows the reaction; extra substrate overcomes it.Ch 9 · Biomoleculescompound leafसंयुक्त पत्तीA leaf whose lamina is divided up to the midrib into leaflets; only its petiole has a bud in its axil.Ch 5 · Morphology of Flowering Plantscoordinationसमन्वयOrgans adjusting their activity together so that each supports the work of the rest.Ch 18 · Neural Control and Coordinationcorpus callosumThe broad tract of nerve fibres that connects the left and right cerebral hemispheres.Ch 18 · Neural Control and CoordinationcorticoidA steroid hormone of the adrenal cortex: a glucocorticoid such as cortisol or a mineralocorticoid such as aldosterone.Ch 19 · Chemical Coordination and Integrationcountercurrent mechanismExchange of NaCl and urea between the oppositely flowing limbs of Henle's loop and of the vasa recta, which keeps the medulla increasingly concentrated.Ch 16 · Excretory Products and their EliminationcristaeInfoldings of the inner mitochondrial membrane that increase its surface area.Ch 8 · Cell: The Unit of Lifecross bridgeThe temporary link formed when a myosin head binds to an active site on an actin filament.Ch 17 · Locomotion and Movementcrossing overExchange of segments between non-sister chromatids of homologues in pachytene.Ch 10 · Cell Cycle and Cell Divisioncutaneous respirationत्वचीय श्वसनGas exchange by diffusion through the moist skin.Ch 7 · Structural Organisation in AnimalscuticleA waxy layer over the epidermis of aerial parts that reduces water loss; roots lack it.Ch 6 · Anatomy of Flowering Plantscytokinesisकोशिकाद्रव्य विभाजनDivision of the cytoplasm after nuclear division.Ch 10 · Cell Cycle and Cell DivisionD
dedifferentiationनिर्विभेदनThe return of a living, differentiated cell to a dividing state, as when parenchyma forms cork cambium.Ch 13 · Plant Growth and Developmentdevelopmentपरिवर्धनAll the changes an organism goes through from germination to senescence; the sum of growth and differentiation.Ch 13 · Plant Growth and Developmentdiabetes mellitusमधुमेहA disorder of long-lasting hyperglycemia caused by too little insulin or a poor response to it.Ch 19 · Chemical Coordination and IntegrationdifferentiationविभेदनThe changes in wall and protoplasm by which a cell from a meristem matures to perform one function.Ch 13 · Plant Growth and Developmentdikaryonद्विकेंद्रकीA fungal cell with two unfused haploid nuclei (n + n).Ch 2 · Biological ClassificationdiploblasticBuilt from two embryonic germ layers, ectoderm and endoderm, with jelly-like mesoglea between them.Ch 4 · Animal Kingdomdouble circulationदोहरा परिसंचरणCirculation in which blood passes through the heart twice per round trip, through separate pulmonary and systemic circuits.Ch 15 · Body Fluids and CirculationE
efferent fibreअपवाही तंतुA nerve fibre that carries commands from the CNS out to tissues and organs.Ch 18 · Neural Control and Coordinationelectrocardiogram (ECG)विद्युत हृद्लेखA graph of the heart's electrical activity through each cardiac cycle, with P, QRS and T waves.Ch 15 · Body Fluids and Circulationelectron transport systemThe chain of carriers in the inner mitochondrial membrane that passes electrons from NADH and FADH₂ to O₂.Ch 12 · Respiration in Plantsemphysemaवातस्फीतिA long-lasting lung disease in which the walls between alveoli break down, cutting the area for gas exchange; smoking is a major cause.Ch 14 · Breathing and Exchange of Gasesendocrine glandअंतःस्रावी ग्रंथिA ductless gland whose secretions, the hormones, pass straight into the blood or tissue fluid.Ch 19 · Chemical Coordination and Integrationendodermisअंतस्त्वचाThe innermost layer of the cortex, one ring of tightly fitted cells; in roots it bears Casparian strips.Ch 6 · Anatomy of Flowering Plantsendomembrane systemThe ER, Golgi complex, lysosomes and vacuoles, whose functions are coordinated.Ch 8 · Cell: The Unit of Lifeendospermभ्रूणपोषA food-storing tissue of the seed formed after double fertilisation; present in ripe castor and maize seeds.Ch 5 · Morphology of Flowering PlantsenzymeएंजाइमA biological catalyst, almost always a protein, that speeds up a particular reaction without being used up.Ch 9 · Biomoleculesepidermisबाह्यत्वचाThe outermost cell layer of the primary plant body, usually one cell thick.Ch 6 · Anatomy of Flowering PlantsepiglottisA thin, elastic flap of cartilage that covers the glottis during swallowing so food does not enter the larynx.Ch 14 · Breathing and Exchange of Gasesepipetalousदललग्नDescribes stamens attached to the petals, as in brinjal.Ch 5 · Morphology of Flowering Plantserythroblastosis foetalisगर्भ रक्ताणु कोरकताDestruction of an Rh+ foetus's red cells by anti-Rh antibodies from its sensitised Rh− mother, causing anaemia and jaundice.Ch 15 · Body Fluids and Circulationerythrocyteलाल रुधिर कणिकाA red blood cell: a biconcave, haemoglobin-filled cell with no nucleus in most mammals that carries respiratory gases.Ch 15 · Body Fluids and Circulationeukaryoteससीमकेंद्रकीAn organism whose cells have a nucleus enclosed by a membrane, and other membrane-bound organelles.Ch 2 · Biological Classificationeukaryotic cellससीमकेंद्रकी कोशिकाA cell whose DNA lies in a nucleus bounded by a nuclear envelope, with membrane-bound organelles.Ch 8 · Cell: The Unit of Lifeexocrine glandबहिःस्रावी ग्रंथिA gland that delivers its secretion through a duct to a surface or cavity, such as a salivary or sweat gland.Ch 19 · Chemical Coordination and Integrationexpirationउच्छ्वसनReleasing alveolar air from the lungs, when intra-pulmonary pressure rises above atmospheric pressure.Ch 14 · Breathing and Exchange of GasesF
familyकुलA group of related genera, such as Felidae.Ch 1 · The Living Worldfermentationकिण्वनIncomplete breakdown of glucose without O₂ to ethanol and CO₂ or to lactic acid.Ch 12 · Respiration in Plantsfloral formulaपुष्पसूत्रA line of symbols summarising a flower's symmetry, sex, number of parts, fusion, adhesion and ovary position.Ch 5 · Morphology of Flowering Plantsfluid mosaic modelSinger and Nicolson's model of the membrane: proteins move sideways within a quasi-fluid lipid bilayer.Ch 8 · Cell: The Unit of Lifeformed elementsसंगठित पदार्थThe cells and cell fragments of blood: erythrocytes, leucocytes and platelets, about 45 % of its volume.Ch 15 · Body Fluids and CirculationG
gametophyteयुग्मकोद्भिदThe haploid generation of a plant, which produces gametes.Ch 3 · Plant KingdomgemmaA green, multicellular asexual bud formed in the gemma cups of liverworts.Ch 3 · Plant KingdomgenusवंशA group of closely related species, such as Panthera.Ch 1 · The Living Worldglomerular filtration rateThe volume of filtrate formed by the kidneys per minute; about 125 mL/min, or 180 L a day, in a healthy adult.Ch 16 · Excretory Products and their EliminationglomerulusA small knot of capillaries, branching from the afferent arteriole, that sits inside Bowman's capsule and filters the blood.Ch 16 · Excretory Products and their EliminationglycocalyxThe outermost layer of a bacterial envelope: a loose slime layer or a thick, tough capsule.Ch 8 · Cell: The Unit of LifeglycolysisThe breakdown of glucose to two pyruvic acid in the cytoplasm, with a net gain of 2 ATP and 2 NADH.Ch 12 · Respiration in PlantsgoitreघेंघाAn enlarged thyroid gland, most often caused by too little iodine in the diet.Ch 19 · Chemical Coordination and IntegrationgonadotrophinA pituitary hormone that acts on the gonads: LH or FSH.Ch 19 · Chemical Coordination and Integrationground tissueAll tissues except the epidermis and vascular bundles: cortex, pericycle, pith, medullary rays and leaf mesophyll.Ch 6 · Anatomy of Flowering Plantsgrowthवृद्धिAn irreversible, permanent increase in the size of a cell, organ or organism, powered by metabolism.Ch 13 · Plant Growth and DevelopmentH
haemodialysisClearing urea from the blood of a uremic patient by passing it through a cellophane tube bathed in dialysing fluid.Ch 16 · Excretory Products and their EliminationheterocystA thick-walled cell of some cyanobacteria, such as Nostoc, that fixes atmospheric nitrogen.Ch 2 · Biological Classificationheterophyllyविषमपर्णताThe presence of leaves of different shapes on the same plant.Ch 13 · Plant Growth and DevelopmentheterosporyProduction of two kinds of spores, microspores and megaspores, as in Selaginella, Salvinia and seed plants.Ch 3 · Plant KingdomheterotrophपरपोषीAn organism that obtains ready-made food from other organisms, living or dead.Ch 2 · Biological Classificationhibernationशीत निद्राWinter sleep: a period of inactivity in a burrow to escape extreme cold.Ch 7 · Structural Organisation in Animalsholozoic nutritionप्राणिसम पोषणNutrition by taking food into the body and digesting it internally, as animals do.Ch 2 · Biological ClassificationhomoiothermसमतापीAn animal that keeps a steady body temperature, such as birds and mammals.Ch 4 · Animal Kingdomhormoneहॉर्मोनA non-nutrient chemical, made in trace amounts, that carries a message from one cell to another.Ch 19 · Chemical Coordination and Integrationhormone receptorग्राहीA specific protein on or in a target cell that binds one particular hormone.Ch 19 · Chemical Coordination and Integrationhypercalcemic hormoneA hormone that raises the blood Ca²+ level; PTH is the example in this chapter.Ch 19 · Chemical Coordination and IntegrationhyperglycemiaA blood glucose level above normal. A level below normal is hypoglycemia.Ch 19 · Chemical Coordination and IntegrationhyphaकवकतंतुOne of the long, thin threads that make up the body of a fungus; plural hyphae.Ch 2 · Biological ClassificationhypogynousजायांगधरDescribes a flower whose ovary sits highest on the thalamus, with the other whorls below it; the ovary is superior.Ch 5 · Morphology of Flowering PlantsI
identificationपहचानDescribing an organism correctly and deciding which known kind it belongs to.Ch 1 · The Living Worldinflorescenceपुष्पक्रमThe arrangement of flowers on a floral axis: racemose if the axis keeps growing, cymose if it ends in a flower.Ch 5 · Morphology of Flowering Plantsinspirationअंतःश्वसनDrawing atmospheric air into the lungs, when intra-pulmonary pressure falls below atmospheric pressure.Ch 14 · Breathing and Exchange of Gasesinterphaseअंतरावस्थाThe part of the cycle between two M phases: G1, S and G2.Ch 10 · Cell Cycle and Cell Divisionislets of LangerhansClusters of endocrine cells in the pancreas; α -cells secrete glucagon and β -cells secrete insulin.Ch 19 · Chemical Coordination and IntegrationisogamySexual fusion of two gametes of the same size, with or without flagella, as in Ulothrix and Spirogyra.Ch 3 · Plant KingdomJ
juxtaglomerular apparatusA sensitive region formed where the DCT meets the afferent arteriole; its cells release renin when GFR falls.Ch 16 · Excretory Products and their EliminationK
karyokinesisकेंद्रक विभाजनDivision of the nucleus into two daughter nuclei.Ch 10 · Cell Cycle and Cell DivisionkinetochoreA disc-shaped structure on the centromere where spindle fibres attach.Ch 10 · Cell Cycle and Cell DivisionKranz anatomyThe leaf anatomy of C₄ plants: a wreath of large, chloroplast-rich, thick-walled bundle sheath cells around each vein.Ch 11 · Photosynthesis in Higher PlantsKrebs' cycleThe cycle in the mitochondrial matrix that oxidises acetyl CoA to CO₂, making NADH, FADH₂ and ATP.Ch 12 · Respiration in PlantsL
lenticelवातरंध्रA pore of loosely packed cells in bark that lets air reach the living tissue inside.Ch 12 · Respiration in Plantsleucocyteश्वेत रुधिर कणिकाA white blood cell: nucleated, colourless and short-lived; the five kinds defend the body.Ch 15 · Body Fluids and CirculationlichenलाइकेनA symbiotic association of an alga (phycobiont) and a fungus (mycobiont).Ch 2 · Biological Classificationlight reactionsThe steps on the thylakoid membranes that light drives directly: absorbing light, splitting water, giving off oxygen and making ATP and NADPH.Ch 11 · Photosynthesis in Higher Plantslimiting factorसीमाकारी कारकThe factor in shortest supply relative to need, which alone sets the rate of a process at that moment.Ch 11 · Photosynthesis in Higher PlantslipidA water-insoluble biomolecule such as a fatty acid, a fat or oil, a phospholipid or cholesterol.Ch 9 · BiomoleculeslocomotionगमनA voluntary movement that carries the whole organism from one place to another, such as walking or swimming.Ch 17 · Locomotion and MovementlymphलसीकाTissue fluid that has entered the lymphatic vessels: colourless, low in protein, rich in lymphocytes; it drains into large veins.Ch 15 · Body Fluids and CirculationM
macromoleculeA very large biomolecule, usually 10 000 Da or more, built as a polymer: proteins, nucleic acids and polysaccharides.Ch 9 · Biomoleculesmedullary rayA strip of parenchyma running radially between neighbouring bundles of a dicot stem.Ch 6 · Anatomy of Flowering Plantsmeiosisअर्धसूत्री विभाजनReduction division: one replication and two divisions giving four haploid cells.Ch 10 · Cell Cycle and Cell Divisionmeningesमस्तिष्कावरणThe three membranes covering the brain: dura mater, arachnoid and pia mater.Ch 18 · Neural Control and Coordinationmeristemविभज्योतकA group of cells that keeps the ability to divide and renews itself while it produces new cells.Ch 13 · Plant Growth and DevelopmentmesophyllThe chloroplast-rich parenchyma between the upper and lower epidermis of a leaf.Ch 6 · Anatomy of Flowering PlantsmesosomeAn infolding of the prokaryotic plasma membrane as vesicles, tubules or lamellae.Ch 8 · Cell: The Unit of LifemetagenesisAlternation of an asexual polyp generation with a sexual medusa generation, as in Obelia.Ch 4 · Animal KingdommetamerismDivision of the body, outside and inside, into a series of segments with some organs repeated in each.Ch 4 · Animal KingdommetamorphosisकायांतरणThe change of a larva into an adult of very different form, such as a tadpole into a frog.Ch 7 · Structural Organisation in Animalsmetaphase plateThe equatorial plane on which chromosomes align at metaphase.Ch 10 · Cell Cycle and Cell DivisionmicturitionThe release of urine from the urinary bladder, brought about by the micturition reflex.Ch 16 · Excretory Products and their EliminationmorphologyआकारिकीThe study of form; in animals, the external appearance of the body and its parts.Ch 7 · Structural Organisation in Animalsmotor unitA motor neuron together with all the muscle fibres it supplies; they contract together.Ch 17 · Locomotion and MovementmyceliumकवकजालThe network of hyphae that forms the body of a fungus.Ch 2 · Biological Classificationmyelin sheathAn insulating wrapping around an axon, formed by layers of Schwann cell membrane.Ch 18 · Neural Control and Coordinationmyofibrilमायोफाइब्रिलOne of the many long, parallel, banded threads that fill a muscle fibre; each is a chain of sarcomeres.Ch 17 · Locomotion and Movementmyoglobinमायोग्लोबिनA red, oxygen-storing pigment in muscle; abundant in red fibres.Ch 17 · Locomotion and MovementmyosinमायोसिनThe protein of the thick filaments; each meromyosin unit has an ATPase head that can bind actin.Ch 17 · Locomotion and MovementN
nephronवृक्काणुThe structural and functional unit of the kidney: a glomerulus and a renal tubule (Bowman's capsule, PCT, Henle's loop and DCT).Ch 16 · Excretory Products and their Eliminationneuromuscular junctionतंत्रिका-पेशी संधिThe junction between a motor neuron's ending and the sarcolemma of a muscle fibre.Ch 17 · Locomotion and Movementneuronतंत्रिका कोशिकाA cell specialised to detect stimuli and to receive and transmit signals; the unit of the neural system.Ch 18 · Neural Control and CoordinationneurotransmitterA chemical released from synaptic vesicles that carries a signal across a chemical synapse.Ch 18 · Neural Control and Coordinationnictitating membraneनिमेषक पटलA thin, transparent eyelid drawn across a frog's eye to protect it in water.Ch 7 · Structural Organisation in AnimalsnodeThe point on a stem where a leaf is attached; the length of stem between two nodes is an internode.Ch 5 · Morphology of Flowering Plantsnode of RanvierA short bare gap between two adjacent myelin sheaths along an axon.Ch 18 · Neural Control and Coordinationnomenclatureनामपद्धतिGiving each kind of organism a standard scientific name under agreed rules (ICBN for plants, ICZN for animals).Ch 1 · The Living Worldnotochordपृष्ठरज्जुA flexible rod of mesodermal origin along the back of chordate embryos.Ch 4 · Animal KingdomnucleotideThe unit of a nucleic acid: a nitrogenous base and a pentose sugar (a nucleoside) with a phosphate group.Ch 9 · BiomoleculesO
oogamyFusion of a large, non-motile egg with a small, motile male gamete, as in Volvox and Fucus.Ch 3 · Plant Kingdomopen growthGrowth in which meristems keep adding new cells to the body throughout life; also called indeterminate growth.Ch 13 · Plant Growth and DevelopmentorderगणA group of related families that share a few characters, such as Carnivora.Ch 1 · The Living WorldorganअंगA body part built from tissues arranged in a definite proportion and pattern to perform particular functions.Ch 7 · Structural Organisation in Animalsorgan systemअंग तंत्रA group of organs working together, through physical and/or chemical interactions, on one shared function.Ch 7 · Structural Organisation in AnimalsorganelleकोशिकांगA distinct structure inside a cell with its own job, such as a mitochondrion or a ribosome.Ch 8 · Cell: The Unit of Lifeosmoregulationपरासरण नियमनKeeping the water content and ion concentration of body fluids steady by adjusting how much water and salt is kept or lost.Ch 16 · Excretory Products and their EliminationovuleबीजांडA nucellus (megasporangium) wrapped in integuments; it becomes the seed after fertilisation.Ch 3 · Plant Kingdomoxidative phosphorylationऑक्सीकारी फॉस्फोरिलीकरणATP synthesis driven by the energy released when the ETS oxidises NADH and FADH₂.Ch 12 · Respiration in Plantsoxygen dissociation curveऑक्सीजन वियोजन वक्रThe sigmoid graph of percentage saturation of haemoglobin with oxygen against p O2.Ch 14 · Breathing and Exchange of Gasesoxyhaemoglobinऑक्सीहीमोग्लोबिनHaemoglobin reversibly bound to oxygen; the form in which about 97 % of the oxygen in blood travels.Ch 14 · Breathing and Exchange of GasesP
partial pressureआंशिक दाबThe part of a gas mixture's total pressure contributed by one gas, written p O2 or p CO2.Ch 14 · Breathing and Exchange of Gasespeptide bondThe –CO–NH– link between the carboxyl group of one amino acid and the amino group of the next, formed with loss of water.Ch 9 · Biomoleculespericarpफलभित्तिThe wall of a fruit, formed from the ovary wall; if fleshy, it has an epicarp, mesocarp and endocarp.Ch 5 · Morphology of Flowering PlantspericycleपरिरंभThe layer just inside the endodermis; in roots, lateral roots arise from it.Ch 6 · Anatomy of Flowering Plantsperipheral neural systemपरिधीय तंत्रिका तंत्रAll the nerves that connect the brain and spinal cord with the rest of the body.Ch 18 · Neural Control and Coordinationphotophosphorylationप्रकाश-फॉस्फोरिलीकरणMaking ATP from ADP and inorganic phosphate using energy from light: cyclic (PS I only, ATP only) or non-cyclic (both photosystems, ATP and NADPH).Ch 11 · Photosynthesis in Higher Plantsphotorespirationप्रकाश-श्वसनRuBisCO adding O₂ instead of CO₂ to RuBP; it yields phosphoglycolate, makes no sugar or ATP and releases fixed CO₂.Ch 11 · Photosynthesis in Higher Plantsphotosynthesisप्रकाश-संश्लेषणThe light-driven process in which green plants build sugars from carbon dioxide and water, releasing oxygen.Ch 11 · Photosynthesis in Higher Plantsphotosystemप्रकाश-तंत्रA pigment–protein complex in the thylakoid membrane: an antenna of light-harvesting pigments around one reaction centre. Plants have PS I and PS II.Ch 11 · Photosynthesis in Higher Plantsphyllotaxyपर्णविन्यासThe arrangement of leaves on a stem or branch: alternate, opposite or whorled.Ch 5 · Morphology of Flowering PlantsphylumसंघA group of related classes, such as Chordata; in plants the equivalent rank is a division.Ch 1 · The Living Worldpituitary glandपीयूष ग्रंथिA pea-sized gland hanging below the hypothalamus, made of the adenohypophysis and the neurohypophysis.Ch 19 · Chemical Coordination and Integrationplacentationबीजांडन्यासThe way ovules are attached inside the ovary: marginal, axile, parietal, free central or basal.Ch 5 · Morphology of Flowering Plantsplant growth regulatorपादप वृद्धि नियामकA small, simple molecule that controls some aspect of plant growth or development; also called a plant hormone or phytohormone.Ch 13 · Plant Growth and Developmentplasmaप्लाज़्माThe straw-coloured liquid part of blood, about 55 % of its volume; mostly water with proteins, ions, nutrients and clotting factors.Ch 15 · Body Fluids and CirculationplasmidA small circular DNA molecule outside a bacterium's genomic DNA; it can carry genes such as antibiotic resistance.Ch 8 · Cell: The Unit of Lifeplasticityसुघट्यताThe ability of a plant to follow different developmental pathways, and so form different structures, in response to its environment or life phase.Ch 13 · Plant Growth and Developmentplateletपट्टिकाणुA cell fragment budded off a megakaryocyte in the bone marrow; it releases substances that start clotting.Ch 15 · Body Fluids and Circulationpleuraफुफ्फुसावरणThe double membrane around each lung, with pleural fluid between its layers that reduces friction.Ch 14 · Breathing and Exchange of Gasespneumotaxic centreA centre in the pons that moderates the respiratory rhythm centre by shortening inspiration, which changes the breathing rate.Ch 14 · Breathing and Exchange of GasespoikilothermअसमतापीAn animal whose body temperature changes with its surroundings, such as fishes, amphibians and reptiles.Ch 4 · Animal KingdompoikilothermअसमतापीAn animal whose body temperature changes with the temperature of its surroundings.Ch 7 · Structural Organisation in AnimalspolysaccharideA long chain of monosaccharide units, such as cellulose, starch, glycogen, inulin or chitin.Ch 9 · Biomoleculesportal circulationVessels that carry blood from one capillary bed straight to a second one; it links the hypothalamus to the anterior pituitary.Ch 19 · Chemical Coordination and Integrationportal systemनिवाहिका तंत्रA venous link that carries blood from one organ to another before it returns to the heart.Ch 7 · Structural Organisation in AnimalsprionAn infectious agent made of abnormally folded protein, without nucleic acid.Ch 2 · Biological Classificationprokaryoteअसीमकेंद्रकीAn organism whose cells lack a membrane-bound nucleus, such as a bacterium.Ch 2 · Biological Classificationprokaryotic cellअसीमकेंद्रकी कोशिकाA cell with no nuclear membrane and no membrane-bound organelles, such as a bacterium.Ch 8 · Cell: The Unit of LifeprothallusThe small, free-living, thalloid gametophyte of a pteridophyte.Ch 3 · Plant KingdomprotochordateA chordate of subphylum Urochordata or Cephalochordata: marine, with a notochord but no vertebral column.Ch 4 · Animal Kingdomprotonemaप्रथम तंतुThe first, thread-like stage of a moss gametophyte, growing directly from a spore.Ch 3 · Plant KingdompseudocoelomA body cavity not lined by mesoderm; the mesoderm lies only in scattered pouches. Found in roundworms.Ch 4 · Animal KingdompyrenoidA storage body in the chloroplast of many algae, containing protein and starch.Ch 3 · Plant KingdomQ
quiescent stageG0: a non-dividing but metabolically active stage entered from G1.Ch 10 · Cell Cycle and Cell DivisionR
radial symmetryअरीय सममितिBody arranged around a central axis, so that every plane through the axis gives identical halves.Ch 4 · Animal KingdomradulaA file-like ribbon of tiny teeth in the mouth of molluscs, used to rasp food.Ch 4 · Animal Kingdomreaction centreअभिक्रिया केंद्रThe single chlorophyll a molecule of a photosystem that gives away an excited electron: P700 in PS I, P680 in PS II.Ch 11 · Photosynthesis in Higher Plantsredifferentiationपुनर्विभेदनThe maturing, once more, of cells produced by a dedifferentiated tissue, so that they lose the power to divide.Ch 13 · Plant Growth and Developmentrelative growth rateGrowth per unit time per unit of existing size; the r of W1 = W0e rt, also called the efficiency index.Ch 13 · Plant Growth and Developmentrenal corpuscleThe glomerulus together with the Bowman's capsule that encloses it; also called the Malpighian body.Ch 16 · Excretory Products and their Eliminationrespiratory climactericThe sharp rise in the rate of respiration of a fruit during ripening.Ch 13 · Plant Growth and Developmentrespiratory quotientश्वसन गुणांकVolume of CO₂ evolved ÷ volume of O₂ consumed in respiration.Ch 12 · Respiration in Plantsrespiratory substrateAn organic compound a cell oxidises for energy, most often glucose.Ch 12 · Respiration in Plantsresting potentialविराम विभवThe potential difference across the membrane of a neuron that is not conducting an impulse; the inside is negative.Ch 18 · Neural Control and CoordinationRuBisCORibulose bisphosphate carboxylase-oxygenase, the enzyme that adds CO₂ (or O₂) to RuBP; the most abundant enzyme on Earth.Ch 11 · Photosynthesis in Higher PlantsS
saprophyteमृतोपजीवीAn organism that absorbs soluble organic food from dead and decaying matter.Ch 2 · Biological Classificationsarcolemmaसार्कोलेमाThe plasma membrane of a muscle fibre.Ch 17 · Locomotion and Movementsarcomereसार्कोमियरThe part of a myofibril between two successive Z lines; the functional unit of contraction.Ch 17 · Locomotion and Movementsarcoplasmic reticulumपेशीद्रव्य जालिकाThe endoplasmic reticulum of a muscle fibre, which stores calcium ions and releases them to trigger contraction.Ch 17 · Locomotion and Movementsecond messengerA molecule such as cAMP, IP3 or Ca²+ that relays a hormone's signal inside the cell.Ch 19 · Chemical Coordination and Integrationsecondary metaboliteA compound made by plants, fungi or microbes that is not part of every cell's basic chemistry, such as an alkaloid, pigment, toxin or gum.Ch 9 · BiomoleculesserumसीरमPlasma from which the clotting factors have been removed.Ch 15 · Body Fluids and Circulationsexual dimorphismलैंगिक द्विरूपताVisible differences between the males and females of one species.Ch 7 · Structural Organisation in Animalssigmoid curveThe S-shaped graph of size against time, with a lag phase, an exponential (log) phase and a stationary phase.Ch 13 · Plant Growth and Developmentsino-atrial node (SAN)शिरा-अलिंद पर्वA patch of nodal tissue in the upper right corner of the right atrium that fires 70–75 times a minute and sets the heartbeat: the pacemaker.Ch 15 · Body Fluids and CirculationspeciesजातिThe lowest category: individuals with fundamental similarities, distinct in form from related species.Ch 1 · The Living Worldspecific epithetThe second word of a scientific name, marking out one species within a genus, such as tigris in Panthera tigris.Ch 1 · The Living Worldsporophyllबीजाणुपर्णA leaf-like structure that bears or subtends sporangia.Ch 3 · Plant Kingdomsporophyteबीजाणुद्भिदThe diploid generation, which grows from the zygote and makes spores by meiosis.Ch 3 · Plant KingdomsteleThe central cylinder: all tissues inside the endodermis, including pericycle, vascular tissues and pith.Ch 6 · Anatomy of Flowering Plantsstomatal apparatusरंध्रA stomatal pore with its two guard cells and the subsidiary cells around them.Ch 6 · Anatomy of Flowering Plantssubstrate-level phosphorylationMaking ATP (or GTP) by moving a phosphate directly from a substrate, without the ETS.Ch 12 · Respiration in PlantsSvedberg unit (S)Unit of the sedimentation coefficient, an indirect measure of a particle's size and density.Ch 8 · Cell: The Unit of Lifesynapseअंतर्ग्रथनA junction between two neurons, formed by the pre-synaptic and post-synaptic membranes.Ch 18 · Neural Control and CoordinationsynapsisPairing of homologous chromosomes in zygotene.Ch 10 · Cell Cycle and Cell DivisionsyncytiumA multinucleate cytoplasm formed when karyokinesis is not followed by cytokinesis.Ch 10 · Cell Cycle and Cell Divisionsynovial jointसाइनोवियल संधिA freely movable joint in which a fluid-filled synovial cavity separates the ends of the bones.Ch 17 · Locomotion and MovementsystematicsThe study of the diversity of organisms and the relationships among them, including evolutionary relationships.Ch 1 · The Living WorldT
tap rootमूसला जड़A main root that grows down from the radicle and bears smaller lateral roots; typical of dicots such as gram and mustard.Ch 5 · Morphology of Flowering PlantstaxonAny group of organisms treated as a unit of classification, at any rank (plural taxa).Ch 1 · The Living Worldtaxonomic hierarchyThe ordered series of taxonomic categories from species up to kingdom.Ch 1 · The Living Worldtaxonomyवर्गिकीThe study that characterises, identifies, classifies and names organisms on the basis of their characters.Ch 1 · The Living WorldthallusA simple plant body not differentiated into true root, stem and leaves.Ch 3 · Plant KingdomthylakoidA flattened membrane sac in the chloroplast stroma; stacks of thylakoids form grana.Ch 8 · Cell: The Unit of Lifetidal volumeज्वारीय आयतनThe volume of air breathed in or out in one quiet breath, about 500 mL in a healthy adult.Ch 14 · Breathing and Exchange of GasestissueऊतकA group of similar cells, with the intercellular substance around them, that performs a particular function.Ch 7 · Structural Organisation in Animalstissue systemA group of tissues defined by position and shared work. Flowering plants have three: epidermal, ground and vascular.Ch 6 · Anatomy of Flowering PlantstrichomeA hair on the shoot epidermis, usually multicellular; it may be branched or secretory.Ch 6 · Anatomy of Flowering PlantstriglycerideOne glycerol molecule with three fatty acids attached by ester bonds; fats and oils are triglycerides.Ch 9 · BiomoleculestriploblasticBuilt from three germ layers: ectoderm, mesoderm and endoderm.Ch 4 · Animal Kingdomtroponinट्रोपोनिनA complex protein on tropomyosin that keeps actin's binding sites covered at rest and uncovers them when it binds calcium.Ch 17 · Locomotion and MovementU
ultrafiltrationFiltration through the glomerular membranes so fine that almost all plasma constituents except proteins pass into Bowman's capsule.Ch 16 · Excretory Products and their Eliminationureotelicयूरिया उत्सर्जीExcreting nitrogenous waste mainly as urea.Ch 7 · Structural Organisation in AnimalsureotelismExcreting nitrogenous waste mainly as urea, made from ammonia in the liver; seen in mammals, many terrestrial amphibians and marine fishes.Ch 16 · Excretory Products and their EliminationuricotelismExcreting nitrogenous waste mainly as uric acid, as a pellet or paste with very little water; seen in reptiles, birds, land snails and insects.Ch 16 · Excretory Products and their EliminationV
vasa rectaA thin U-shaped capillary running alongside Henle's loop; well developed in juxtamedullary nephrons, absent or highly reduced in cortical ones.Ch 16 · Excretory Products and their Eliminationvascular bundleसंवहन बंडलA strand of xylem and phloem: radial or conjoint by arrangement, open or closed by the presence of cambium.Ch 6 · Anatomy of Flowering Plantsvenationशिराविन्यासThe pattern of veins and veinlets in a lamina: reticulate (a network) or parallel.Ch 5 · Morphology of Flowering PlantsviroidAn infectious agent made of free, low-molecular-weight RNA with no protein coat.Ch 2 · Biological Classificationvital capacityजैव क्षमताThe most air that can be moved in a single breath, from a complete breath out to the deepest breath in: ERV + TV + IRV.Ch 14 · Breathing and Exchange of GasesW
water vascular systemThe water-filled canal system of echinoderms, used for movement, feeding and breathing.Ch 4 · Animal KingdomZ
Z schemeThe zigzag path of electrons from water through PS II, an electron transport chain and PS I to NADP⁺, drawn on a redox-potential scale.Ch 11 · Photosynthesis in Higher PlantszoosporeचलबीजाणुA flagellated, swimming asexual spore, the commonest spore of algae.Ch 3 · Plant KingdomzwitterionA molecule carrying one positive and one negative charge, with zero net charge; amino acids take this form near neutral pH.Ch 9 · Biomoleculesncert.ai is an independent learning companion aligned to the NCERT curriculum. It is not affiliated with or endorsed by NCERT.