NEET 2027 Biology Notes: Chapter-wise Summary and Key Points

These NEET 2027 Biology notes give a short summary and the high-yield points of every Botany and Zoology chapter in the latest NMC syllabus, with a free notes PDF for each chapter. The chapters follow the NEET UG 2026 syllabus released on 22 December 2025, which stays the reference until NMC releases the 2027 syllabus.

NEET 2027 Biology Notes

Chapter-wise key points and notes PDFs for NEET UG 2027 Biology, arranged by the units of the NMC syllabus.

How are these NEET 2027 Biology notes arranged?

The notes follow the 10 Biology units of the NEET UG 2026 syllabus that the National Medical Commission (NMC) released on 22 December 2025. The 2027 syllabus is expected around December 2026, and these notes will be matched to it. The full topic list is on the NEET UG 2027 syllabus page.

NMC lists Biology as one subject, but the NEET question paper splits it into Botany and Zoology. The split below follows how recent NEET papers have grouped the chapters; NTA does not publish an official chapter list for each section. Each chapter has a download table row and a short set of key points for quick revision.

NEET Botany Notes PDF: Chapter-wise Download

These 17 Botany chapters come from NCERT Class 11 and Class 12 Biology. Each PDF has key notes and important questions with answers for the chapter.

NEET Botany Key Points: Chapter-wise Summary

The Living World (Unit 1, Class 11)

This chapter explains what makes an organism living and how organisms are named and ranked.

• Growth and reproduction are not defining features of life; metabolism, cellular organisation and consciousness (response to the surroundings) are.
• Binomial nomenclature was given by Carolus Linnaeus: the genus name starts with a capital letter, the species epithet with a small letter, and both are printed in italics.
• Taxonomic hierarchy, from lowest to highest: species, genus, family, order, class, phylum (division in plants), kingdom.
• Examples to remember: Mangifera indica (mango) and Homo sapiens (human, order Primata, family Hominidae).

Biological Classification (Unit 1, Class 11)

This chapter covers the five-kingdom system and the features of Monera, Protista and Fungi, plus viruses, viroids and lichens.

• R.H. Whittaker (1969) proposed five kingdoms: Monera, Protista, Fungi, Plantae and Animalia, based on cell structure, body organisation, nutrition, reproduction and phylogeny.
• Monera are prokaryotes: archaebacteria (methanogens, halophiles, thermoacidophiles) and eubacteria, including cyanobacteria such as Nostoc and Anabaena that fix nitrogen in heterocysts. Mycoplasma have no cell wall.
• Protista: chrysophytes (diatoms), dinoflagellates (Gonyaulax causes red tides), euglenoids (pellicle instead of a cell wall), slime moulds and protozoans such as Plasmodium and Trypanosoma.
• Fungi have chitin cell walls. Learn one example per class: Phycomycetes (Rhizopus, Albugo), Ascomycetes (Penicillium, Neurospora, yeast), Basidiomycetes (Agaricus, Puccinia), Deuteromycetes (Alternaria, Trichoderma).
• Viruses are nucleoproteins that multiply only inside living cells; viroids (T.O. Diener, 1971) are free RNA without a protein coat; lichens are an alga and a fungus living together and indicate clean air.

Plant Kingdom (Unit 1, Class 11)

This chapter classifies plants into algae, bryophytes, pteridophytes and gymnosperms with their key features and examples.

• Algae by pigment and stored food: green algae (chlorophyll a and b, starch; Chlamydomonas, Spirogyra), brown algae (fucoxanthin, laminarin or mannitol; Laminaria, Sargassum), red algae (r-phycoerythrin, floridean starch; Polysiphonia, Gracilaria).
• Bryophytes are the amphibians of the plant kingdom: the gametophyte is dominant and the sporophyte depends on it. Examples: Marchantia (liverwort), Funaria and Sphagnum (mosses).
• Pteridophytes are the first land plants with xylem and phloem; the sporophyte is dominant and the gametophyte is a small prothallus. Selaginella and Salvinia are heterosporous, a step towards the seed habit.
• Gymnosperms have naked ovules. Cycas has coralloid roots with nitrogen-fixing cyanobacteria, and Pinus has needle-like leaves.

Morphology of Flowering Plants (Unit 2, Class 11)

This chapter describes the external form of roots, stems, leaves, inflorescences, flowers, fruits and seeds and their modifications.

• Dicots have a tap root and monocots a fibrous root. Root modifications: prop roots (banyan), stilt roots (maize, sugarcane) and pneumatophores (Rhizophora).
• Stem modifications: tendrils (cucumber, grapevine), thorns (Citrus, Bougainvillea), underground storage stems (potato, ginger, turmeric) and flattened phylloclades (Opuntia).
• In a racemose inflorescence the main axis keeps growing and flowers open from base to tip; in a cymose inflorescence the axis ends in a flower.
• Aestivation: valvate (Calotropis), twisted (China rose), imbricate (Cassia, gulmohur), vexillary (pea, bean). Placentation: marginal (pea), axile (China rose, tomato), parietal (mustard), free central (Dianthus), basal (sunflower, marigold).
• The NMC syllabus also names five plant families (Malvaceae, Cruciferae, Leguminosae, Compositae and Gramineae), so learn their floral features with the practical syllabus.

Anatomy of Flowering Plants (Unit 2, Class 11)

This chapter covers plant tissues and the internal structure of roots, stems and leaves in dicots and monocots.

• Meristems are apical, intercalary (grasses) or lateral. Simple permanent tissues are parenchyma, collenchyma and sclerenchyma; complex tissues are xylem and phloem.
• Xylem has tracheids, vessels, fibres and parenchyma; gymnosperms lack vessels. Gymnosperm phloem has sieve cells and albuminous cells instead of sieve tubes and companion cells.
• Roots have radial vascular bundles: 2 to 4 xylem bundles in dicots and more than six (polyarch) in monocots. Stems have conjoint bundles, open in dicots and closed and scattered in monocots.
• Dicot leaves are dorsiventral with palisade and spongy mesophyll; monocot leaves are isobilateral, and grasses have bulliform cells that help the leaf roll.

Cell: The Unit of Life (Unit 3, Class 11)

This chapter covers cell theory and the structure and function of prokaryotic and eukaryotic cells and their organelles.

• Schleiden and Schwann gave cell theory; Rudolf Virchow added that new cells arise from pre-existing cells (omnis cellula e cellula).
• Prokaryotes have no membrane-bound organelles and have 70S ribosomes; eukaryotic cytoplasm has 80S ribosomes, while mitochondria and chloroplasts carry their own DNA and 70S ribosomes.
• The fluid mosaic model of the cell membrane was proposed by Singer and Nicolson (1972).
• The endomembrane system is the ER, Golgi bodies, lysosomes and vacuoles; mitochondria, chloroplasts and peroxisomes are not part of it. Smooth ER makes lipids, and the Golgi body forms glycoproteins and glycolipids.
• Centrioles have nine triplet microtubules in a cartwheel pattern; cilia and flagella have a 9+2 axoneme. Chromosomes are metacentric, sub-metacentric, acrocentric or telocentric by centromere position.

Cell Cycle and Cell Division (Unit 3, Class 11)

This chapter explains the phases of the cell cycle, mitosis and meiosis, and why each division matters.

• Interphase has G1, S and G2. DNA doubles in S phase (2C to 4C) but the chromosome number does not change. Cells that stop dividing enter G0.
• Mitosis: prophase, metaphase (chromosomes line up on the metaphase plate, best stage to study their shape), anaphase (centromeres split, chromatids move to the poles) and telophase.
• Cytokinesis happens by a cleavage furrow in animal cells and by a cell plate in plant cells.
• Prophase I of meiosis: leptotene, zygotene (synapsis, synaptonemal complex), pachytene (crossing over), diplotene (chiasmata visible) and diakinesis (terminalisation of chiasmata).
• Meiosis halves the chromosome number, keeps it constant across generations and creates variation.

Photosynthesis in Higher Plants (Unit 4, Class 11)

This chapter covers the light reactions in the thylakoids, the Calvin cycle in the stroma, C4 plants and photorespiration.

• The reaction centre of PS I is P700 and of PS II is P680. Water is split on the PS II side, which releases oxygen.
• Non-cyclic photophosphorylation makes ATP and NADPH; cyclic photophosphorylation uses only PS I in the stroma lamellae and makes only ATP.
• ATP is made by chemiosmosis: protons build up in the thylakoid lumen and flow out through ATP synthase.
• In the Calvin cycle RuBisCO fixes CO2 to RuBP. Making one glucose needs six turns, 18 ATP and 12 NADPH.
• C4 plants such as maize and sugarcane have Kranz anatomy; PEP carboxylase forms oxaloacetic acid first, and they avoid photorespiration, which wastes energy in C3 plants.

Respiration in Plants (Unit 4, Class 11)

This chapter traces how glucose is broken down to release energy through glycolysis, fermentation, the Krebs cycle and the electron transport system.

• Glycolysis (EMP pathway) happens in the cytoplasm and turns one glucose into two pyruvic acid, with a net gain of 2 ATP and 2 NADH.
• Without oxygen, yeast ferments pyruvate to ethanol and CO2, while muscle makes lactic acid.
• In mitochondria, pyruvate becomes acetyl CoA, which joins oxaloacetic acid to form citric acid at the start of the Krebs (TCA) cycle.
• The electron transport system lies in the inner mitochondrial membrane, and oxygen is the final hydrogen acceptor. One glucose gives a net 38 ATP in theory.
• Respiration is an amphibolic pathway. Respiratory quotient (CO2 released / O2 used) is 1 for carbohydrates, about 0.7 for fats and about 0.9 for proteins.

Plant Growth and Development (Unit 4, Class 11)

This chapter covers growth phases and rates, differentiation and the five main plant growth regulators.

• Growth is an irreversible increase in size. The phases are meristematic, elongation and maturation.
• Arithmetic growth follows Lt = L0 + rt; geometric growth follows W1 = W0 e^rt and gives a sigmoid curve over time.
• Cells can differentiate, dedifferentiate (for example, parenchyma forming interfascicular or cork cambium) and redifferentiate.
• Auxins (IAA, 2,4-D as a weedicide) cause apical dominance and rooting; gibberellins cause stem elongation and bolting; cytokinins promote cell division and delay leaf senescence.
• Ethylene is a gas that ripens fruits (ethephon is its source in farming); abscisic acid closes stomata and keeps seeds and buds dormant, so it is called the stress hormone.

Sexual Reproduction in Flowering Plants (Unit 6, Class 12)

This chapter covers the male and female gametophytes, pollination, double fertilisation, and seed and fruit formation.

• The anther wall has the epidermis, endothecium, middle layers and tapetum, which nourishes developing pollen. The pollen exine is made of sporopollenin, absent at the germ pores.
• The typical embryo sac is 7-celled and 8-nucleate: an egg apparatus (egg and two synergids with filiform apparatus), three antipodals and a central cell with two polar nuclei.
• Pollination types are autogamy, geitonogamy and xenogamy. Cleistogamous flowers (Viola, Oxalis, Commelina) self-pollinate; Vallisneria and Hydrilla are water-pollinated.
• Double fertilisation is syngamy plus triple fusion, which forms the triploid primary endosperm nucleus. Coconut water is free-nuclear endosperm.
• Special modes: apomixis (seeds without fertilisation), parthenocarpy (seedless fruit, banana) and polyembryony (citrus, mango). Apple and strawberry are false fruits.

Principles of Inheritance and Variation (Unit 7, Class 12)

This chapter covers Mendel’s laws, deviations from them, sex determination, linkage and genetic disorders.

• A monohybrid F2 gives a 3:1 phenotypic and 1:2:1 genotypic ratio; a dihybrid F2 gives 9:3:3:1. A test cross with the recessive parent reveals the unknown genotype.
• Incomplete dominance: flower colour in snapdragon (1:2:1 in F2). ABO blood groups show both multiple alleles and co-dominance (IA and IB). Phenylketonuria shows pleiotropy, and human skin colour is polygenic.
• Sutton and Boveri gave the chromosome theory of inheritance; Morgan’s work on Drosophila showed linkage and recombination.
• Sex determination is XX-XY in humans (male heterogametic), ZW in birds (female heterogametic) and haplodiploid in honey bees, where males develop from unfertilised eggs.
• Haemophilia and colour blindness are sex-linked recessive; thalassemia is autosomal recessive. Down’s syndrome is trisomy 21, Klinefelter’s is 47, XXY and Turner’s is 45, X0.

Molecular Basis of Inheritance (Unit 7, Class 12)

This chapter covers the proof that DNA is the genetic material, DNA structure and replication, transcription, the genetic code, translation, the lac operon and the Human Genome Project.

• Griffith’s transformation experiment, the work of Avery, MacLeod and McCarty, and the Hershey-Chase experiment showed that DNA is the genetic material.
• B-DNA is a right-handed double helix with about 10 base pairs per turn, a pitch of 3.4 nm and 0.34 nm between base pairs; Chargaff’s rule is A = T and G = C.
• Meselson and Stahl used 15N in E. coli to prove that replication is semi-conservative. DNA polymerase works only in the 5′ to 3′ direction, so the lagging strand is made as Okazaki fragments joined by ligase.
• The genetic code is a triplet code with 64 codons: 61 code for amino acids, AUG is the start codon, and UAA, UAG and UGA are stop codons.
• In the lac operon (Jacob and Monod), lactose is the inducer that removes the repressor. The human genome has about 3,164.7 million base pairs, and DNA fingerprinting uses VNTRs.

Microbes in Human Welfare (Unit 8, Class 12)

This chapter covers microbes used in household food, industry, sewage treatment, biogas, biocontrol and biofertilisers.

• Lactobacillus turns milk into curd and raises its vitamin B12; the large holes in Swiss cheese come from CO2 made by Propionibacterium sharmanii.
• Industrial products: citric acid (Aspergillus niger), acetic acid (Acetobacter aceti), streptokinase (Streptococcus), cyclosporin A (Trichoderma polysporum) and statins (Monascus purpureus). Penicillin was discovered by Alexander Fleming.
• In sewage treatment, the secondary (biological) stage uses flocs of bacteria in aeration tanks to lower BOD; the sludge is then digested anaerobically to give biogas.
• Biogas is mostly methane made by methanogens such as Methanobacterium, which also live in cattle dung.
• Biocontrol agents include Bacillus thuringiensis, Trichoderma and baculoviruses (Nucleopolyhedrovirus); biofertilisers include Rhizobium, Azotobacter, cyanobacteria and mycorrhiza (Glomus).

Organisms and Populations (Unit 10, Class 12)

The NEET syllabus takes population attributes, population growth and population interactions from this chapter.

• Population attributes include birth rate, death rate, sex ratio and age distribution; age pyramids can be expanding, stable or declining.
• Population size changes with natality and immigration (increase) and mortality and emigration (decrease).
• Exponential growth (dN/dt = rN) gives a J-shaped curve; logistic growth (dN/dt = rN(K – N)/K) gives an S-shaped curve that levels off at the carrying capacity K.
• Interactions: mutualism (+/+, lichens, fig and wasp), competition (-/-), predation and parasitism (+/-), commensalism (+/0, orchid on a mango branch) and amensalism (-/0).
• Gause’s competitive exclusion principle says two closely related species competing for the same resource cannot coexist indefinitely.

Ecosystem (Unit 10, Class 12)

This chapter covers ecosystem structure, productivity, decomposition, energy flow and ecological pyramids.

• Net primary productivity is gross primary productivity minus the energy used in respiration.
• Decomposition steps are fragmentation, leaching, catabolism, humification and mineralisation; it is fast in warm, moist conditions and slow when detritus is rich in lignin and chitin.
• Photosynthetically active radiation (PAR) is about half of incoming sunlight, and plants capture only 2 to 10 percent of it.
• Energy flow is one-way and about 10 percent passes to the next trophic level (Lindeman’s 10 percent law).
• The pyramid of energy is always upright; the pyramid of biomass is inverted in the sea, and the pyramid of numbers is inverted for a single tree.

Biodiversity and Conservation (Unit 10, Class 12)

This chapter covers the levels and patterns of biodiversity, why it is lost and how it is conserved.

• India has about 2.4 percent of the world’s land area but about 8.1 percent of its species diversity, and is one of 12 megadiversity countries.
• Diversity falls from the equator towards the poles. Humboldt’s species-area relation is log S = log C + Z log A, with Z usually 0.1 to 0.2.
• The four main causes of loss (the ‘Evil Quartet’) are habitat loss and fragmentation, over-exploitation, alien species invasions (Nile perch in Lake Victoria) and co-extinctions.
• In situ conservation includes biodiversity hotspots, biosphere reserves, national parks, sanctuaries and sacred groves (for example the Khasi and Jaintia Hills). India has 3 of the 34 global hotspots: Western Ghats and Sri Lanka, Indo-Burma and the Himalaya.
• Ex situ conservation includes zoos, botanical gardens and seed banks. The IUCN Red Data Book lists threatened species.

NEET Zoology Notes PDF: Chapter-wise Download

These 15 Zoology chapters cover animal diversity, human physiology, human reproduction, evolution, human health and biotechnology.

NEET Zoology Key Points: Chapter-wise Summary

Animal Kingdom (Unit 1, Class 11)

This chapter classifies animals by their basic features: non-chordates up to phylum and chordates up to class.

• Basis of classification: level of organisation, symmetry, germ layers (diploblastic or triploblastic), coelom (acoelomate, pseudocoelomate, coelomate), segmentation and notochord.
• Key phylum features: Porifera (canal system, choanocytes), Cnidaria (cnidoblasts, polyp and medusa, metagenesis in Obelia), Ctenophora (comb plates), Platyhelminthes (flame cells), Aschelminthes (pseudocoelom), Annelida (nephridia, metameric segmentation).
• Arthropoda is the largest phylum (jointed legs, chitin exoskeleton, Malpighian tubules); Mollusca has a radula and mantle; Echinodermata has a water vascular system; Hemichordata includes Balanoglossus.
• Chordates have a notochord, a dorsal hollow nerve cord and pharyngeal gill slits. Cartilaginous fishes lack an air bladder (Torpedo has an electric organ); crocodiles have a four-chambered heart; Ornithorhynchus is an egg-laying mammal.

Structural Organisation in Animals (Unit 2, Class 11)

This chapter covers the four animal tissues and the body systems of the frog.

• Simple squamous epithelium lines blood vessels and lung air sacs; cuboidal lines gland ducts and kidney tubules; columnar lines the stomach and intestine; compound epithelium covers the skin and buccal cavity.
• Tendons join muscle to bone and ligaments join bone to bone. Cartilage, bone and blood are specialised connective tissues.
• Skeletal muscle is striated and voluntary, smooth muscle is unstriated and involuntary, and cardiac muscle is striated, involuntary and has intercalated discs.
• Neuroglia make up more than half the volume of neural tissue.
• The frog is cold-blooded, has a three-chambered heart, breathes through its skin in water, is ureotelic and has 10 pairs of cranial nerves. Males have vocal sacs and a copulatory pad.

Biomolecules (Unit 3, Class 11)

This chapter covers the structure and role of proteins, carbohydrates, lipids and nucleic acids, and how enzymes work.

• Proteins, nucleic acids and polysaccharides are macromolecules; lipids also appear in the acid-insoluble fraction because they form membranes, even though they are small (under 800 Da).
• RuBisCO is the most abundant protein in the biosphere and collagen the most abundant in animals. Haemoglobin has four subunits (two alpha, two beta) and shows quaternary structure.
• Starch gives a blue-black colour with iodine, but cellulose does not. Inulin is a polymer of fructose, and chitin forms the arthropod exoskeleton.
• A nucleotide has a nitrogen base, a pentose sugar and a phosphate. Adenine and guanine are purines; cytosine, thymine and uracil are pyrimidines.
• Enzymes lower activation energy. The six classes are oxidoreductases, transferases, hydrolases, lyases, isomerases and ligases. Malonate is a competitive inhibitor of succinic dehydrogenase.

Breathing and Exchange of Gases (Unit 5, Class 11)

This chapter covers the human respiratory system, the mechanism of breathing, gas exchange and transport, and respiratory disorders.

• Inspiration happens when the diaphragm and external intercostal muscles contract, the chest volume rises and lung pressure falls below air pressure.
• Average values: tidal volume about 500 mL, inspiratory reserve volume 2500 to 3000 mL, expiratory reserve volume 1000 to 1100 mL and residual volume 1100 to 1200 mL. Vital capacity is ERV + TV + IRV.
• Alveolar air has pO2 104 and pCO2 40 mm Hg. CO2 is 20 to 25 times more soluble than O2.
• About 97 percent of O2 travels as oxyhaemoglobin. About 70 percent of CO2 travels as bicarbonate, 20 to 25 percent as carbamino-haemoglobin and about 7 percent dissolved in plasma.
• The respiratory rhythm centre is in the medulla and the pneumotaxic centre in the pons. Disorders: asthma, emphysema (often from smoking) and occupational disorders such as silicosis.

Body Fluids and Circulation (Unit 5, Class 11)

This chapter covers blood, lymph, the human heart, the cardiac cycle, ECG and disorders of circulation.

• Plasma is about 55 percent of blood. RBCs number 5 to 5.5 million per cubic mm and live about 120 days; neutrophils are the most common WBCs and basophils the least.
• Blood group AB is the universal recipient and O the universal donor. Rh incompatibility can cause erythroblastosis foetalis in a second Rh-positive baby of an Rh-negative mother.
• During clotting, thrombokinase helps turn prothrombin into thrombin, which turns fibrinogen into fibrin; calcium ions are needed.
• The SA node is the pacemaker. One cardiac cycle takes about 0.8 seconds, stroke volume is about 70 mL and cardiac output about 5 litres per minute.
• In an ECG, the P wave is atrial depolarisation, QRS is ventricular depolarisation and T is ventricular repolarisation. Hypertension is a pressure of 140/90 mm Hg or more.

Excretory Products and their Elimination (Unit 5, Class 11)

This chapter covers modes of excretion, the nephron, urine formation, the counter-current mechanism and how kidney function is regulated.

• Ammonotelic animals include bony fishes; ureotelic animals include mammals and marine fishes; uricotelic animals include reptiles, birds and insects.
• Each kidney has about one million nephrons. The glomerular filtration rate is about 125 mL per minute (180 litres a day), and nearly 99 percent of the filtrate is reabsorbed.
• The loop of Henle and vasa recta form a counter-current system that builds a medullary gradient from about 300 to 1200 mOsmol per litre, helping to make concentrated urine.
• ADH increases water reabsorption, and its shortage causes diabetes insipidus. The renin-angiotensin system raises blood pressure and GFR, and atrial natriuretic factor opposes it.
• Disorders: uraemia (treated by haemodialysis), renal failure, renal calculi and glomerulonephritis. Lungs, liver and skin also help in excretion.

Locomotion and Movement (Unit 5, Class 11)

This chapter covers types of movement, muscle contraction, the human skeleton, joints and their disorders.

• Movement can be amoeboid (macrophages), ciliary (trachea, fallopian tubes) or muscular.
• The sarcomere, between two Z lines, is the functional unit of a muscle fibre. In contraction the I band and H zone shorten while the A band stays the same.
• In the sliding filament theory, calcium binds troponin to expose binding sites on actin, and the myosin head uses ATP to pull actin filaments.
• The adult skeleton has 206 bones: 80 axial and 126 appendicular. There are 12 pairs of ribs (7 true, 3 false, 2 floating) and 22 skull bones.
• Synovial joints: ball and socket (shoulder), hinge (knee), pivot (atlas and axis), gliding (carpals), saddle (thumb). Disorders: myasthenia gravis, tetany, muscular dystrophy, arthritis, osteoporosis and gout.

Neural Control and Coordination (Unit 5, Class 11)

The NEET syllabus takes neurons, the human nervous system and nerve impulse generation and conduction from this chapter.

• A neuron has a cell body, dendrites and an axon. Myelinated fibres have Schwann cells and nodes of Ranvier.
• At rest the axon membrane is polarised (inside negative). The sodium-potassium pump moves 3 Na+ out for every 2 K+ in.
• A stimulus opens Na+ channels, the membrane depolarises and an action potential (nerve impulse) travels along the axon, faster in myelinated fibres.
• At a chemical synapse, neurotransmitters cross the synaptic cleft to pass the impulse on.
• The central nervous system is the brain and spinal cord. The peripheral nervous system has somatic and autonomic parts; the visceral nervous system carries impulses between the CNS and the internal organs.

Chemical Coordination and Integration (Unit 5, Class 11)

This chapter covers the human endocrine glands, their hormones, how hormones act and the disorders caused by too much or too little of them.

• The hypothalamus controls the anterior pituitary through releasing and inhibiting hormones. Oxytocin and vasopressin are made in the hypothalamus and released from the posterior pituitary.
• Too much growth hormone causes gigantism in children and acromegaly in adults; too little causes pituitary dwarfism.
• Iodine shortage causes goitre; low thyroid hormone during pregnancy can cause cretinism; Graves’ disease (exophthalmic goitre) is hyperthyroidism. Thyrocalcitonin lowers blood calcium and parathyroid hormone raises it.
• The adrenal medulla makes adrenaline and noradrenaline, the emergency hormones; the adrenal cortex makes cortisol and aldosterone, and its underactivity causes Addison’s disease.
• Insulin from beta cells lowers blood glucose and glucagon from alpha cells raises it. Peptide hormones act through second messengers such as cAMP; steroid hormones enter the cell and bind intracellular receptors.

Human Reproduction (Unit 6, Class 12)

This chapter covers the male and female reproductive systems, gametogenesis, the menstrual cycle, fertilisation, implantation, pregnancy and birth.

• The scrotum keeps the testes 2 to 2.5 degrees C below body temperature. Leydig cells make androgens, and Sertoli cells nourish developing sperm.
• Spermatogenesis starts at puberty. Oogenesis starts before birth: primary oocytes stay in prophase I, and the secondary oocyte finishes meiosis II only after a sperm enters it.
• The menstrual cycle lasts about 28 days. An LH surge causes ovulation around day 14, and the corpus luteum then secretes progesterone.
• Fertilisation happens in the ampullary region of the fallopian tube. The zygote forms a morula and then a blastocyst, whose trophoblast attaches to the endometrium.
• The placenta makes hCG, hPL, estrogens and progestogens. Birth is set off by the foetal ejection reflex and oxytocin, and colostrum gives the baby IgA antibodies.

Reproductive Health (Unit 6, Class 12)

This chapter covers birth control, medical termination of pregnancy, sexually transmitted infections, infertility and assisted reproductive technologies.

• Contraceptive methods: natural (periodic abstinence, lactational amenorrhoea), barriers (condoms, diaphragms), IUDs (Lippes loop, CuT, LNG-20), oral pills, injectables, implants and surgical sterilisation (vasectomy, tubectomy).
• Saheli, a once-a-week non-steroidal pill, was developed at CDRI Lucknow. Emergency contraception works within 72 hours of intercourse.
• India legalised medical termination of pregnancy (MTP) in 1971; it is relatively safe in the first trimester.
• Common STIs include gonorrhoea, syphilis, genital herpes, chlamydiasis, hepatitis B and HIV. Hepatitis B, genital herpes and HIV are not completely curable.
• In ZIFT a zygote or early embryo (up to 8 blastomeres) goes into the fallopian tube; in IUT a later embryo goes into the uterus; in GIFT an ovum is placed in the fallopian tube. Amniocentesis tests foetal genetic disorders, and its misuse for sex testing is banned.

Evolution (Unit 7, Class 12)

This chapter covers the origin of life, evidence for evolution, Darwin’s theory, the mechanisms of evolution, Hardy-Weinberg principle and human evolution.

• In Miller’s experiment (1953), electric discharge in a closed flask of CH4, H2, NH3 and water vapour formed amino acids.
• Homologous organs (forelimbs of whale, bat and human) show divergent evolution; analogous organs (wings of butterfly and bird) show convergent evolution.
• Darwin’s finches and Australian marsupials are examples of adaptive radiation. Hugo de Vries proposed mutation theory from work on evening primrose.
• Hardy-Weinberg principle: p squared + 2pq + q squared = 1. Allele frequencies change through gene flow, genetic drift, mutation, recombination and natural selection (stabilising, directional or disruptive).
• Human evolution: Dryopithecus and Ramapithecus (about 15 million years ago), Australopithecines, Homo habilis (650 to 800 cc brain), Homo erectus (about 900 cc), Neanderthals (about 1400 cc) and Homo sapiens, which arose in Africa.

Human Health and Disease (Unit 8, Class 12)

This chapter covers common human diseases and their causes, immunity, vaccines, cancer, HIV and AIDS, and drug, alcohol and tobacco abuse.

• Pathogens: typhoid (Salmonella typhi, Widal test), pneumonia (Streptococcus pneumoniae), common cold (rhinoviruses), amoebiasis (Entamoeba histolytica), ascariasis (Ascaris), filariasis (Wuchereria) and ringworm (Microsporum, Trichophyton). Dengue and chikungunya spread through Aedes mosquitoes.
• Malaria is caused by Plasmodium and spread by female Anopheles; P. falciparum causes the most serious form. Haemozoin causes the chill and high fever, and sporozoites are the infective stage.
• Innate immunity uses barriers present from birth; acquired immunity has memory. An antibody has two heavy and two light chains (H2L2), and B cells give humoral immunity while T cells give cell-mediated immunity.
• HIV is a retrovirus that infects macrophages and helper T cells; ELISA is used for diagnosis. Cancer cells lose contact inhibition and can spread by metastasis.
• Heroin (smack) is made from morphine of the poppy and is a depressant; cocaine comes from Erythroxylum coca and interferes with dopamine transport. Nicotine makes the adrenal gland release adrenaline and noradrenaline.

Biotechnology: Principles and Processes (Unit 9, Class 12)

This chapter covers the tools and steps of recombinant DNA technology.

• Stanley Cohen and Herbert Boyer made the first recombinant DNA in 1972 using a plasmid of Salmonella typhimurium.
• Restriction enzymes are molecular scissors that cut at palindromic sites; EcoRI (from E. coli RY13) cuts GAATTC and leaves sticky ends. DNA ligase joins the pieces.
• In gel electrophoresis, negatively charged DNA moves towards the anode through agarose gel and is seen as orange bands after ethidium bromide staining under UV light.
• A cloning vector needs an origin of replication, a selectable marker (such as ampicillin or tetracycline resistance in pBR322) and cloning sites. Insertional inactivation of beta-galactosidase gives blue-white screening.
• Host cells are made competent with calcium ions and a heat shock at 42 degrees C. PCR (denaturation, annealing, extension) uses heat-stable Taq polymerase.

Biotechnology and its Applications (Unit 9, Class 12)

This chapter covers uses of biotechnology in agriculture and medicine, transgenic animals and the ethical issues they raise.

• Bt cotton carries cry genes from Bacillus thuringiensis (cryIAc and cryIIAb against cotton bollworms). The toxin is inactive until the alkaline gut of the insect activates it.
• RNA interference protects tobacco from the nematode Meloidogyne incognitia by silencing a key mRNA of the pest.
• In 1983 Eli Lilly made human insulin by producing chains A and B separately in E. coli and joining them by disulphide bridges.
• The first gene therapy (1990) treated ADA deficiency in a four-year-old girl. More than 95 percent of transgenic animals are mice; Rosie the cow (1997) gave milk with human alpha-lactalbumin.
• In India, the Genetic Engineering Appraisal Committee (GEAC) decides on GM research and release. Biopiracy is the use of bio-resources without paying the people they belong to.

Which old Biology chapters are not in the NEET syllabus?

Six chapters that were in older NEET syllabi are not in the latest NMC syllabus, so they have no notes on this page:

• Transport in Plants (Class 11)
• Mineral Nutrition (Class 11)
• Digestion and Absorption (Class 11)
• Reproduction in Organisms (Class 12)
• Strategies for Enhancement in Food Production (Class 12)
• Environmental Issues (Class 12)

Some topics inside the remaining chapters are also not listed in the syllabus, for example reflex action and sense organs in Neural Control, photoperiodism and vernalisation in Plant Growth, and ecological succession and nutrient cycles in Ecosystem. The notes PDFs were written for the older NCERT books, so skip any topic that is not in the syllabus.

How should you revise NEET Biology for 2027?

Read the NCERT chapter first, then use these notes to revise and test yourself. NEET UG 2027 is expected in May 2027; dates are on the NEET UG 2027 page.

1. Read each chapter line by line in the NCERT Class 11 or Class 12 Biology textbook.
2. Revise the key points above and open the notes PDF for the chapter’s important questions.
3. Watch a chapter lecture on the NEET preparation videos page if a topic is unclear.
4. Solve the Biology questions on that chapter from NEET previous year question papers.
5. Take timed tests on the NEET mock test and note every wrong answer.
6. Practise full 180-question papers with the NEET 2027 sample papers.

NEET 2027 Biology Notes FAQs