Class 12 · Biology · English medium
Class 12 Biology companion
An original companion to Biology, NCERT Class 12 Biology (2026–27 edition). Official textbook ↗ ncert.nic.in
Start: Chapter 1 Sexual Reproduction in Flowering Plants0 of 13 chapters done
Every chapter is ready
Every chapter is ready
Chapters
- ENHinglish
Chapter 1: Sexual Reproduction in Flowering Plants
Flowers are the site of sexual reproduction in angiosperms. - ENHinglish
Chapter 2: Human Reproduction
Human reproduction for Class 12: the male system (testes in the scrotum, seminiferous tubules with spermatogonia and Sertoli cells, Leydig c - ENHinglish
Chapter 3: Reproductive Health
Reproductive health is physical, emotional, behavioural and social well-being in all matters of reproduction. - ENHinglish
Chapter 4: Principles of Inheritance and Variation
Class 12 Biology chapter 4 explains inheritance and variation. - ENHinglish
Chapter 5: Molecular Basis of Inheritance
DNA is a double helix of two antiparallel chains paired A–T and G–C, packed on histones into nucleosomes and chromatin. - ENHinglish
Chapter 6: Evolution
The chapter traces life from the Big Bang (13.8 bya) and the Earth's formation (4.54 bya) through chemical evolution (Oparin–Haldane, Miller - ENHinglish
Chapter 7: Human Health and Disease
Class 12 Biology chapter 7 covers human health and disease. - ENHinglish
Chapter 8: Microbes in Human Welfare
Most microbes are harmless or useful. - ENHinglish
Chapter 9: Biotechnology: Principles and Processes
Modern biotechnology combines genetic engineering (moving chosen genes into hosts) with bioprocess engineering (sterile large-scale culture). - ENHinglish
Chapter 10: Biotechnology and its Applications
Applications of biotechnology. - ENHinglish
Chapter 11: Organisms and Populations
Ecology studies organisms' interactions with each other and with abiotic factors at the levels of organisms, populations, communities and biomes. - ENHinglish
Chapter 12: Ecosystem
An ecosystem is a functional unit of organisms interacting with each other and with abiotic factors. - ENHinglish
Chapter 13: Biodiversity and Conservation
Biodiversity is the variety of life at genetic, species and ecological levels.
Also in Hinglish
- Chapter 1: Sexual Reproduction in Flowering Plants (Hinglish)
- Chapter 2: Human Reproduction (Hinglish)
- Chapter 3: Reproductive Health (Hinglish)
- Chapter 4: Principles of Inheritance and Variation (Hinglish)
- Chapter 5: Molecular Basis of Inheritance (Hinglish)
- Chapter 6: Evolution (Hinglish)
- Chapter 7: Human Health and Disease (Hinglish)
- Chapter 8: Microbes in Human Welfare (Hinglish)
- Chapter 9: Biotechnology: Principles aur Processes (Hinglish)
- Chapter 10: Biotechnology aur uske Applications (Hinglish)
- Chapter 11: Organisms and Populations (Hinglish)
- Chapter 12: Ecosystem (Hinglish)
- Chapter 13: Biodiversity aur Conservation (Hinglish)
A
acquired immunityउपार्जित प्रतिरक्षाSpecific defence that develops after meeting a pathogen or vaccine and remembers it.Ch 7 · Human Health and Diseaseactivated sludgeसक्रियित आपंकThe flocs that settle after aeration; part is returned to the aeration tank as inoculum and the rest is digested anaerobically.Ch 8 · Microbes in Human Welfareadaptive radiationअनुकूली विकिरणEvolution of many species from one ancestor in a region, each adapted to a different way of life.Ch 6 · Evolutionaddictionव्यसनA compulsive psychological craving for a substance's effects that persists despite harm.Ch 7 · Human Health and Diseaseage pyramidA bar diagram of the share of a population in each age group; its shape shows growth, stability or decline.Ch 11 · Organisms and Populationsalien speciesविदेशी जातिA species living outside its native range because people moved it; invasive ones spread and harm native species.Ch 13 · Biodiversity and Conservationalleleयुग्मविकल्पीOne of the alternative forms of a gene, such as G (green pods) and g (yellow pods).Ch 4 · Principles of Inheritance and Variationallele frequencyयुग्मविकल्पी आवृत्तिThe proportion of a gene's copies in a population that are a given allele; p + q = 1 for two alleles.Ch 6 · EvolutionallergenA usually harmless substance, such as pollen or dust mites, that triggers an allergy in sensitive people.Ch 7 · Human Health and Diseaseamniocentesisउल्ववेधनA prenatal test in which a little amniotic fluid is drawn off and its foetal cells are checked for genetic disorders.Ch 3 · Reproductive Healthanalogous organsसमरूप अंगOrgans with similar functions but different structure and origin, produced by convergent evolution.Ch 6 · EvolutionaneuploidyअसुगुणिताGain or loss of one or a few chromosomes, as in trisomy 21.Ch 4 · Principles of Inheritance and Variationantibioticप्रतिजैविकA substance made by a microbe (or a modified form of one) that kills or stops the growth of other microbes, especially disease-causing bacteria.Ch 8 · Microbes in Human Welfareantibodyप्रतिरक्षीA Y-shaped protein (H2L2) made by B cells that binds a specific antigen.Ch 7 · Human Health and Diseaseantigenप्रतिजनA molecule, usually on a pathogen or its toxin, that the immune system recognises and responds to.Ch 7 · Human Health and DiseaseapomixisअसंगजननFormation of seeds without fertilisation; an asexual process whose embryos are genetic copies of the mother plant.Ch 1 · Sexual Reproduction in Flowering Plantsassisted reproductive technologiesMedical techniques, such as IVF, GIFT, ICSI and artificial insemination, that help infertile couples have children.Ch 3 · Reproductive Healthautoimmunityस्वप्रतिरक्षाAn immune attack on the body's own cells or tissues.Ch 7 · Human Health and DiseaseB
biochemical oxygen demand (BOD)जैव रासायनिक ऑक्सीजन माँगThe oxygen, in mg, that bacteria would use to oxidise all the organic matter in one litre of water; a high BOD means heavy organic pollution.Ch 8 · Microbes in Human Welfarebiocontrolजैव नियंत्रणThe use of living organisms, such as predators, bacteria, fungi or viruses, to control pests and plant diseases.Ch 8 · Microbes in Human Welfarebiodiversityजैव विविधताThe variety of life at every level of organisation, especially genetic, species and ecological diversity.Ch 13 · Biodiversity and Conservationbiodiversity hotspotA region with at least 1,500 endemic plant species that has lost at least 70 % of its original vegetation.Ch 13 · Biodiversity and Conservationbiofertiliserजैव उर्वरकLiving microbes added to soil or seeds to raise the soil's supply of plant nutrients such as nitrogen and phosphorus.Ch 8 · Microbes in Human Welfarebiogasजैव गैसA fuel gas, mostly methane with carbon dioxide, made when microbes break down organic matter without oxygen.Ch 8 · Microbes in Human WelfarebiopiracyUsing a country's biological resources or traditional knowledge without authorisation and without fair payment or benefit sharing.Ch 10 · Biotechnology and its ApplicationsbioprospectingSearching biodiversity for genes, molecules or species of economic value.Ch 13 · Biodiversity and ConservationbioreactorA large, sterile, controlled vessel in which cells convert raw materials into a product.Ch 9 · Biotechnology: Principles and Processesbiotechnologyजैव प्रौद्योगिकीPutting organisms, cells or their enzymes to work making products or running processes that people need.Ch 9 · Biotechnology: Principles and ProcessesblastocystकोरकपुटीA hollow ball of cells, an outer trophoblast and an inner cell mass, that implants in the uterus.Ch 2 · Human ReproductionC
C peptideThe connecting stretch of proinsulin that joins chain B to chain A and is cut out when insulin matures.Ch 10 · Biotechnology and its ApplicationscarcinogenA physical, chemical or biological agent that can turn normal cells into cancer cells.Ch 7 · Human Health and Diseasecarrying capacityThe largest population of a species that a habitat can support indefinitely.Ch 11 · Organisms and Populationschemical evolutionरासायनिक विकासThe non-living formation of organic molecules from simple inorganic substances, thought to have come before the first life.Ch 6 · Evolutioncloning vectorसंवाहकA plasmid or phage DNA that carries foreign DNA into a host and is copied there.Ch 9 · Biotechnology: Principles and Processesco-dominanceसहप्रभाविताInheritance in which both alleles are fully expressed in the heterozygote, as in group AB.Ch 4 · Principles of Inheritance and Variationco-extinctionThe extinction of a species that follows the loss of a partner it depends on completely, such as its host or pollinator.Ch 13 · Biodiversity and Conservationcodonप्रकूटA group of three mRNA bases that stands for one amino acid or a stop signal; a tRNA reads it with a matching anticodon.Ch 5 · Molecular Basis of InheritancecommensalismसहभोजिताA one-sided association: one partner gains and the other is unaffected (+, 0).Ch 11 · Organisms and Populationscompetitionप्रतिस्पर्धाAn interaction that lowers the fitness of one or both species using the same resource (−, −).Ch 11 · Organisms and Populationscomplementary strandsTwo strands whose bases pair A with T (or U) and G with C, so the sequence of one fixes the other.Ch 5 · Molecular Basis of Inheritancecontraceptiveगर्भनिरोधकA method, device or medicine used to prevent pregnancy.Ch 3 · Reproductive Healthconvergent evolutionअभिसारी विकासIndependent evolution of similar features in unrelated groups living in similar ways.Ch 6 · Evolutioncorpus luteumपीत पिंडThe yellowish body formed from a burst Graafian follicle; it secretes progesterone.Ch 2 · Human Reproductioncry geneA gene of Bacillus thuringiensis that codes for an insecticidal crystal (Cry) protein.Ch 10 · Biotechnology and its ApplicationsD
decompositionअपघटनDecomposers' conversion of dead organic remains into carbon dioxide, water and mineral nutrients.Ch 12 · EcosystemdetritivoreअपरदाहारीAn animal, such as an earthworm, that eats detritus and breaks it into smaller pieces.Ch 12 · EcosystemdetritusअपरदDead organic matter of any kind (shed plant parts, dead animals, droppings) that decomposers feed on.Ch 12 · EcosystemDNA fingerprintingडीएनए अंगुलिछापीComparing people by the band pattern of highly variable repeat DNA, such as VNTRs.Ch 5 · Molecular Basis of InheritanceDNA ligaseThe enzyme that seals DNA fragments together by joining their sugar–phosphate backbones.Ch 9 · Biotechnology: Principles and ProcessesDNA polymorphismबहुरूपताInherited variation at a DNA locus, counted as a polymorphism when a second allele has a frequency above 0.01 in a population.Ch 5 · Molecular Basis of Inheritancedominantप्रभावीDescribes an allele that shows its effect even when only one copy is present.Ch 4 · Principles of Inheritance and Variationdouble fertilisationThe two fusions in one embryo sac: a male gamete with the egg (syngamy) and the other male gamete with the two polar nuclei (triple fusion).Ch 1 · Sexual Reproduction in Flowering Plantsdownstream processingअनुप्रवाह संसाधनSeparating, purifying and formulating a product after cells have made it, with quality testing.Ch 9 · Biotechnology: Principles and ProcessesE
ecological diversityपारिस्थितिक विविधताThe variety of ecosystems, such as forests, grasslands, wetlands and reefs, in a region.Ch 13 · Biodiversity and Conservationecological pyramidपारिस्थितिक पिरामिडA diagram that stacks trophic levels as bars showing their numbers, biomass or energy.Ch 12 · Ecosystemecologyपारिस्थितिकीThe study of how organisms interact with one another and with their physical surroundings.Ch 11 · Organisms and Populationsecosystemपारितंत्रA community of organisms together with its physical surroundings, working as one system.Ch 12 · Ecosystemecosystem servicesपारितंत्र सेवाएँBenefits people get from working ecosystems, such as pollination, clean water, flood control and climate regulation.Ch 13 · Biodiversity and ConservationELISAA test that uses antigen–antibody binding plus an enzyme-made colour to detect antigens or antibodies.Ch 10 · Biotechnology and its ApplicationsemasculationविपुंसनRemoving the anthers of a bisexual flower bud before they shed pollen, as the first step of a controlled cross.Ch 1 · Sexual Reproduction in Flowering Plantsembryo sacभ्रूणकोषThe female gametophyte of a flowering plant, usually 7-celled and 8-nucleate, formed from one functional megaspore.Ch 1 · Sexual Reproduction in Flowering Plantsendemicस्थानिकFound naturally in one region and nowhere else.Ch 13 · Biodiversity and ConservationendometriumThe inner glandular lining of the uterus, which is rebuilt and shed in each menstrual cycle and receives the embryo.Ch 2 · Human Reproductionendospermभ्रूणपोषThe triploid food-storing tissue of a seed, formed from the primary endosperm cell.Ch 1 · Sexual Reproduction in Flowering Plantsex situ conservationबाह्यस्थाने संरक्षणConserving species away from their natural habitat, in zoos, botanical gardens, seed banks or cryobanks.Ch 13 · Biodiversity and ConservationexonA part of a split gene that remains in the mature RNA. The intervening parts that are cut out are introns.Ch 5 · Molecular Basis of Inheritanceexplantकर्तोतकA small piece of tissue, such as a leaf disc, stem segment, bud or root tip, cut from a plant to start a tissue culture.Ch 10 · Biotechnology and its ApplicationsF
fermentorकिण्वकA large closed vessel in which a chosen microbe is grown under controlled conditions to make a product on an industrial scale.Ch 8 · Microbes in Human Welfarefertile periodThe days around ovulation when conception is most likely; about days 10–17 of a regular 28-day cycle.Ch 3 · Reproductive HealthfertilisationनिषेचनThe fusion of a haploid sperm with a haploid ovum to form a diploid zygote.Ch 2 · Human Reproductionfitnessयोग्यताReproductive success: an individual's ability to survive and leave offspring in a given environment.Ch 6 · Evolutionflocऊर्णकA loose, mesh-like mass of bacteria and fungal threads that grows in the aeration tank and feeds on organic matter.Ch 8 · Microbes in Human Welfarefood webखाद्य जालThe network formed when the food chains of an ecosystem cross-link.Ch 12 · Ecosystemfossilजीवाश्मPreserved remains or traces of an organism from the distant past, usually in sedimentary rock.Ch 6 · Evolutionfounder effectसंस्थापक प्रभावDrift that occurs when a few individuals start a new population with an unrepresentative set of alleles.Ch 6 · EvolutionG
gametogenesisयुग्मकजननThe formation of gametes (sperms or ova) from germ cells by mitosis, meiosis and maturation.Ch 2 · Human ReproductionGEACIndia's Genetic Engineering Appraisal Committee, which appraises large trials and environmental release of GM organisms.Ch 10 · Biotechnology and its Applicationsgel electrophoresisSeparation of DNA fragments by size as an electric field drives them through an agarose gel towards the anode.Ch 9 · Biotechnology: Principles and Processesgene poolजीन पूलAll the genes and their alleles present in a population.Ch 6 · Evolutiongene therapyजीन चिकित्साTreating a disease by putting a working gene into a person's cells to replace or make up for a faulty one.Ch 10 · Biotechnology and its Applicationsgenetic diversityआनुवंशिक विविधताVariation in genes and alleles among the individuals and populations of one species.Ch 13 · Biodiversity and Conservationgenetic driftआनुवंशिक विचलनRandom change in allele frequencies by chance, strongest in small populations.Ch 6 · Evolutiongenetic engineeringAltering an organism's DNA or RNA and introducing it into a host to change the host's characters.Ch 9 · Biotechnology: Principles and Processesgenetically modified organismआनुवंशिकतः रूपांतरित जीवA plant, animal or microbe whose genetic material has been changed by genetic engineering.Ch 10 · Biotechnology and its Applicationsgenotypeजीनप्ररूपThe genetic make-up of an individual for a character, written as alleles, e.g. Gg.Ch 4 · Principles of Inheritance and VariationGraafian follicleग्राफी पुटकThe mature ovarian follicle, with a large antrum and a secondary oocyte, which bursts at ovulation.Ch 2 · Human Reproductiongross primary productivityसकल प्राथमिक उत्पादकताThe rate at which producers make organic matter by photosynthesis, before respiration.Ch 12 · EcosystemH
Hardy–Weinberg equilibriumहार्डी-वेनबर्ग साम्यावस्थाConstant allele and genotype frequencies across generations in a population free of disturbing factors.Ch 6 · Evolutionheterozygousविषमयुग्मजीHaving two different alleles of a gene, as in Gg.Ch 4 · Principles of Inheritance and Variationhomologous organsसमजात अंगOrgans with the same basic structure and origin that may do different jobs; evidence of common ancestry.Ch 6 · Evolutionhomozygousसमयुग्मजीHaving two identical alleles of a gene, as in GG or gg.Ch 4 · Principles of Inheritance and Variationhumusह्यूमसA dark, colloidal organic material in soil that resists microbes, decomposes very slowly and stores nutrients.Ch 12 · EcosystemI
immunityप्रतिरक्षाThe body's overall ability, through its immune system, to resist disease-causing organisms.Ch 7 · Human Health and Diseaseimplantationअंतर्रोपणThe embedding of the blastocyst in the endometrium, which starts a pregnancy.Ch 2 · Human Reproductionin situ conservationस्वस्थाने संरक्षणConserving species in their natural habitat by protecting the whole ecosystem.Ch 13 · Biodiversity and Conservationin vitro fertilisation–embryo transferFertilising ova with sperm in the laboratory and placing the zygote or embryo in the fallopian tube (ZIFT) or uterus (IUT).Ch 3 · Reproductive Healthincomplete dominanceअपूर्ण प्रभाविताInheritance in which the heterozygote is intermediate between the two homozygotes.Ch 4 · Principles of Inheritance and Variationinfant mortality rateशिशु मृत्यु दरDeaths of babies under one year of age per 1000 live births in a year.Ch 3 · Reproductive Healthinfertilityबंध्यताFailure to achieve a pregnancy despite regular unprotected intercourse, usually for 12 months or more.Ch 3 · Reproductive HealthinheritanceवंशागतिThe passing on of characters from parents to offspring; the basis of heredity.Ch 4 · Principles of Inheritance and Variationinnate immunityसहज प्रतिरक्षाNon-specific defence present from birth: physical, physiological, cellular and cytokine barriers.Ch 7 · Human Health and Diseaseinsertional inactivationLoss of a vector gene's function when foreign DNA is inserted into it; used to spot recombinants.Ch 9 · Biotechnology: Principles and Processesintegrated pest management (IPM)Keeping pests below damaging levels by combining biological, cultural and mechanical methods, using chemicals only when really needed.Ch 8 · Microbes in Human Welfareintra-uterine deviceA small device placed in the uterus that prevents pregnancy; it may be non-medicated, copper-releasing or hormone-releasing.Ch 3 · Reproductive Healthintrinsic rate of natural increaseThe per capita birth rate minus the per capita death rate, r = b - d.Ch 11 · Organisms and PopulationsL
lactational amenorrhoeaAbsence of periods during full breastfeeding after childbirth, when ovulation is suppressed; useful as contraception for up to about six months.Ch 3 · Reproductive Healthlactic acid bacteria (LAB)लैक्टिक अम्ल जीवाणुBacteria such as Lactobacillus that ferment sugars to lactic acid; they turn milk into curd.Ch 8 · Microbes in Human Welfarelinkageसहलग्नताThe tendency of genes on one chromosome to be inherited together.Ch 4 · Principles of Inheritance and Variationlogistic growthGrowth that slows as numbers approach the carrying capacity, dN/dt = rN(K - N)/K, giving an S-shaped curve.Ch 11 · Organisms and Populationslymphoid organलसीकाभ अंगAn organ where lymphocytes are made and mature (primary) or meet antigens and multiply (secondary).Ch 7 · Human Health and DiseaseM
maternal mortality ratioमातृ मृत्यु दरDeaths of women from pregnancy-related causes per 100 000 live births.Ch 3 · Reproductive Healthmedical termination of pregnancyDeliberately ending a pregnancy before full term; legal in India under the MTP Act.Ch 3 · Reproductive Healthmegadiverse countryOne of the few countries (17 on the most-used list) that together hold most of Earth's species; India is one.Ch 13 · Biodiversity and Conservationmenstrual cycleआर्तव चक्रThe roughly 28-day reproductive cycle of female primates, counted from one menstruation to the next.Ch 2 · Human ReproductionmetastasisThe spread of cancer cells through blood or lymph to form new tumours in distant organs.Ch 7 · Human Health and DiseasemethanogenA microbe, such as Methanobacterium, that makes methane in oxygen-free places such as sludge digesters and the rumen of cattle.Ch 8 · Microbes in Human Welfaremicrobeसूक्ष्मजीवAn organism or infectious agent too small to see singly without a microscope, such as a bacterium, protozoan, microscopic fungus or virus.Ch 8 · Microbes in Human Welfaremicropropagationसूक्ष्मप्रवर्धनProducing thousands of identical plants quickly from explants by tissue culture.Ch 10 · Biotechnology and its ApplicationsmicrosporangiumलघुबीजाणुधानीOne of the four pollen sacs of an anther, where pollen mother cells divide by meiosis to form microspores.Ch 1 · Sexual Reproduction in Flowering Plantsmortalityमृत्यु दरHow many members of a population die over a stated time.Ch 11 · Organisms and Populationsmutationउत्परिवर्तनA change in the DNA sequence, from a single base to a whole chromosome segment.Ch 4 · Principles of Inheritance and Variationmutationउत्परिवर्तनA sudden heritable change in genetic material; the ultimate source of new alleles.Ch 6 · EvolutionmutualismसहोपकारिताAn interaction in which both species benefit (+, +).Ch 11 · Organisms and PopulationsmycorrhizaकवकमूलA partnership between a fungus and plant roots: the fungus supplies phosphorus and water, the plant supplies sugars.Ch 8 · Microbes in Human WelfareN
natalityजन्म दरHow many new individuals are born into a population over a stated time.Ch 11 · Organisms and Populationsnatural selectionप्राकृतिक वरणIndividuals with inherited traits suited to their environment leave more offspring, so those traits spread.Ch 6 · Evolutionnet primary productivityनेट प्राथमिक उत्पादकताGPP minus the producers' respiration (R): the organic matter left for growth, herbivores and decomposers.Ch 12 · EcosystemnucleosomeAbout 200 bp of DNA wrapped around an octamer of histone proteins; the repeating unit of chromatin.Ch 5 · Molecular Basis of Inheritancenucleotideन्यूक्लियोटाइडA unit of a nucleic acid: a nitrogenous base and a pentose sugar (together a nucleoside) with a phosphate on the 5′ carbon.Ch 5 · Molecular Basis of InheritanceO
oogenesisअंडजननThe formation of the female gamete from oogonia; it begins before birth and is completed only at fertilisation.Ch 2 · Human ReproductionoperonA group of bacterial genes transcribed together from one promoter and controlled by one operator, such as the lac operon.Ch 5 · Molecular Basis of Inheritanceorigin of replicationThe sequence where DNA copying starts; it also controls the copy number of linked DNA.Ch 9 · Biotechnology: Principles and Processesovulationअंडोत्सर्गThe release of a secondary oocyte from a ruptured Graafian follicle, about the middle of a menstrual cycle.Ch 2 · Human ReproductionovuleबीजांडThe megasporangium inside the ovary: a funicle, integuments with a micropyle, and a nucellus holding the embryo sac. It becomes the seed.Ch 1 · Sexual Reproduction in Flowering PlantsP
parasitismपरजीविताAn interaction in which one species lives on or in a host and feeds from it, harming it (+, −).Ch 11 · Organisms and PopulationsparthenocarpyअनिषेकफलनDevelopment of a fruit without fertilisation; the fruit is seedless, as in banana.Ch 1 · Sexual Reproduction in Flowering Plantsparturitionप्रसवChildbirth: the expulsion of the full-term foetus by strong contractions of the uterus.Ch 2 · Human ReproductionpathogenरोगजनकAn organism, such as a bacterium, virus, fungus, protozoan or worm, that causes disease.Ch 7 · Human Health and Diseasepedigree analysisवंशावली विश्लेषणTracing a trait through a family chart over several generations.Ch 4 · Principles of Inheritance and VariationperispermRemains of the nucellus kept as stored food in a few mature seeds, for example black pepper and beet.Ch 1 · Sexual Reproduction in Flowering Plantsphenotypeलक्षणप्ररूपThe observable form of a character, e.g. green pods.Ch 4 · Principles of Inheritance and Variationphotosynthetically active radiationThe part of sunlight (roughly 400–700 nm) that plants can use for photosynthesis; it is under half of the incident sunlight.Ch 12 · EcosystemplacentaअपराThe organ formed by chorionic villi and uterine tissue through which mother and foetus exchange materials; it also secretes hormones.Ch 2 · Human Reproductionpleiotropyबहुप्रभाविताThe effect of a single gene on several different characters.Ch 4 · Principles of Inheritance and VariationpollinationपरागणThe transfer of pollen grains from an anther to a stigma.Ch 1 · Sexual Reproduction in Flowering Plantspolyembryonyबहुभ्रूणताTwo or more embryos in one seed, as in many citrus and mango varieties.Ch 1 · Sexual Reproduction in Flowering Plantspolygenic inheritanceबहुजीनी वंशागतिInheritance of a character controlled by several genes with additive effects, giving continuous variation.Ch 4 · Principles of Inheritance and Variationpolymerase chain reactionपॉलीमरेज शृंखला अभिक्रियाRepeated cycles of denaturation, annealing and extension that copy a chosen DNA segment in vitro.Ch 9 · Biotechnology: Principles and Processespolymerase chain reactionA method that copies a chosen DNA sequence over and over, roughly doubling it each cycle.Ch 10 · Biotechnology and its Applicationspopulationसमष्टिAll the individuals of one species in a defined area that share resources and can interbreed.Ch 11 · Organisms and Populationspopulation densityसमष्टि घनत्वPopulation size per unit area or volume, as numbers, per cent cover or biomass.Ch 11 · Organisms and Populationspredationपरभक्षणAn interaction in which one species kills and eats, or feeds on, another (+, −).Ch 11 · Organisms and PopulationspromoterThe DNA sequence at the upstream end of a transcription unit where RNA polymerase binds to start transcription.Ch 5 · Molecular Basis of Inheritanceprotoplastजीवद्रव्यकA plant cell whose wall has been removed by enzymes, leaving the plasma membrane as its boundary.Ch 10 · Biotechnology and its ApplicationsR
recessiveअप्रभावीDescribes an allele whose effect shows only when two copies are present.Ch 4 · Principles of Inheritance and Variationrecombinant DNAपुनर्योगज डीएनएDNA made by joining pieces from two different sources, such as a gene and a vector.Ch 9 · Biotechnology: Principles and Processesreproductive healthजनन स्वास्थ्यPhysical, emotional, behavioural and social well-being in everything connected with reproduction.Ch 3 · Reproductive Healthresource partitioningDividing a shared resource by time, place or feeding method, which lets competing species coexist.Ch 11 · Organisms and Populationsrestriction enzymeA bacterial enzyme that cuts both DNA strands at a specific, usually palindromic, recognition sequence.Ch 9 · Biotechnology: Principles and ProcessesretrovirusAn RNA virus that copies its genome into DNA with reverse transcriptase and inserts it into the host's DNA.Ch 7 · Human Health and DiseaseRNA interferenceSilencing of a gene by double-stranded RNA whose sequence matches that gene's mRNA, which is then destroyed or blocked.Ch 10 · Biotechnology and its ApplicationsS
sacred groveपवित्र उपवनA patch of forest protected by a community for religious reasons, where felling and hunting are forbidden.Ch 13 · Biodiversity and Conservationsecondary productivityद्वितीयक उत्पादकताThe rate at which consumers form new organic matter in their own bodies.Ch 12 · Ecosystemselectable markerA vector gene, often for antibiotic resistance, that lets only cells carrying the vector grow.Ch 9 · Biotechnology: Principles and Processesself-incompatibilityA genetic mechanism by which the pistil rejects pollen from the same plant, so self-pollination cannot lead to seed.Ch 1 · Sexual Reproduction in Flowering Plantssemiconservative replicationCopying in which each daughter DNA keeps one parental strand and gains one newly made strand.Ch 5 · Molecular Basis of Inheritanceseminiferous tubuleशुक्रजनक नलिकाOne of the tightly coiled tubules inside each testicular lobule, whose wall produces sperms.Ch 2 · Human Reproductionsewageवाहित मलWaste water from homes and towns, carrying human excreta, organic matter and large numbers of microbes.Ch 8 · Microbes in Human Welfaresex chromosomeलिंग गुणसूत्रA chromosome involved in deciding sex, such as X, Y, Z or W.Ch 4 · Principles of Inheritance and Variationsexually transmitted infectionयौन संचारित संक्रमणAn infection passed mainly through sexual contact, such as syphilis, gonorrhoea, hepatitis B or HIV.Ch 3 · Reproductive HealthsomacloneA plant raised by tissue culture that is genetically identical to the plant it came from.Ch 10 · Biotechnology and its Applicationsspecies diversityजातीय विविधताThe variety of species in an area: how many there are (richness) and how evenly individuals are shared among them.Ch 13 · Biodiversity and Conservationspecies–area relationshipThe rise of species richness with area, S = CA Z, which is the straight line log S = log C + Z log A on log axes.Ch 13 · Biodiversity and Conservationspermatogenesisशुक्राणुजननThe production of sperms from spermatogonia in the seminiferous tubules, from puberty onwards.Ch 2 · Human ReproductionsplicingRemoving the introns from a primary transcript and joining its exons in order.Ch 5 · Molecular Basis of Inheritancespontaneous generationस्वतः जननThe disproved idea that life arises directly from non-living matter today.Ch 6 · EvolutionsporopolleninThe extremely resistant polymer of the pollen exine; heat, strong acids and alkalis do not destroy it, and no enzyme is known to digest it.Ch 1 · Sexual Reproduction in Flowering Plantsstanding cropखड़ी फसलThe biomass, or number of organisms, in a trophic level per unit area at a given time.Ch 12 · Ecosystemstarter (inoculum)A small amount of a culture, such as a spoonful of old curd, added to fresh material to start a fermentation.Ch 8 · Microbes in Human WelfaresterilisationनसबंदीA permanent surgical method that blocks the vas deferens (vasectomy) or the fallopian tubes (tubectomy).Ch 3 · Reproductive Healthsticky endsचिपचिपे सिरेSingle-stranded overhangs left by a staggered cut; ends from the same enzyme pair by hydrogen bonds.Ch 9 · Biotechnology: Principles and Processesstratificationस्तरविन्यासThe vertical layering of species in an ecosystem, each layer at a different height.Ch 12 · EcosystemT
tapetumटेपीटमThe innermost wall layer of a microsporangium; its cells feed the developing pollen and supply material for the pollen wall.Ch 1 · Sexual Reproduction in Flowering Plantstemplate strandThe DNA strand (3′→5′) that RNA polymerase reads. Its partner, the coding strand, has the RNA's sequence with T for U.Ch 5 · Molecular Basis of Inheritancetest crossपरीक्षार्थ संकरणA cross of a dominant-phenotype individual with a homozygous recessive one, to reveal its genotype.Ch 4 · Principles of Inheritance and Variationtotal fertility rateThe average number of children a woman would have over her lifetime at current birth rates; about 2.1 replaces each generation.Ch 3 · Reproductive Healthtotipotencyपूर्णशक्तताThe ability of a single living plant cell to grow into a complete plant.Ch 10 · Biotechnology and its ApplicationstranscriptionअनुलेखनMaking RNA from one strand of a DNA segment, by base pairing, with U in place of T.Ch 5 · Molecular Basis of InheritancetransformationA heritable change in a bacterium caused by DNA taken up from outside, as in Griffith's R to S change.Ch 5 · Molecular Basis of InheritancetransformationरूपांतरणUptake of foreign DNA, such as a recombinant plasmid, by a host cell.Ch 9 · Biotechnology: Principles and Processestransgenic animalपारजीनी जंतुAn animal carrying a gene from another source, deliberately inserted into its DNA, which it expresses.Ch 10 · Biotechnology and its ApplicationstranslationBuilding a polypeptide on a ribosome in the order set by the codons of an mRNA.Ch 5 · Molecular Basis of Inheritancetriple fusionत्रिसंलयनFusion of a male gamete with the two polar nuclei, giving the triploid primary endosperm nucleus.Ch 1 · Sexual Reproduction in Flowering Plantstrophic levelपोषण स्तरAn organism's feeding position in a food chain, counted from the producers (first level) upwards.Ch 12 · EcosystemV
vaccineटीकाA harmless preparation of a pathogen's antigens that makes the body build immune memory against it.Ch 7 · Human Health and DiseasevariationविविधताThe degree to which offspring differ from their parents and from each other.Ch 4 · Principles of Inheritance and VariationvectorरोगवाहकAn organism, often an insect, that carries a pathogen from one host to another.Ch 7 · Human Health and DiseaseZ
zygoteयुग्मनजThe single diploid cell formed by fertilisation; it divides to form the embryo.Ch 2 · Human Reproductionncert.ai is an independent learning companion aligned to the NCERT curriculum. It is not affiliated with or endorsed by NCERT.