Biology
🔒 Log in to trackCell and genetics, human body systems, vitamins and minerals, diseases with pathogens, vectors and vaccines, plant physiology and classification, and branches of biology with ecology. Biology is the most-asked science area in CGL GA — mostly direct one-line facts.
One page per subtopic: detailed notes, every question type, formulas, tricks and practice sets.
Every formula on one printable page, grouped by subtopic.
4 exam-level questions worked step by step.
120 questions — untimed practice or a timed test with analysis.
Track record in the exam
Questions per shift in recent SSC CGL papers.
Test difficulty mix (120 questions)
Question patterns exams keep repeating
Taken from previous-year papers. If a pattern is marked "very common", expect to see it in your exam.
Vitamin/mineral → deficiency disease
very common'Scurvy / rickets / goitre / anaemia is caused by deficiency of…', 'which vitamin is fat-soluble', kwashiorkor vs marasmus, wrong-pair questions on the vitamin table.
How to solve: Sing the ladder: A–night blindness, B₁–beriberi, B₃–pellagra, B₁₂–pernicious anaemia, C–scurvy, D–rickets, E–sterility, K–clotting. Fat-soluble = A, D, E, K. Minerals: iron–anaemia, iodine–goitre, calcium–bones. Kwashiorkor = protein lack (swollen), marasmus = protein + calories (shrunken).
Example: Deficiency of vitamin C causes:
Scurvy — bleeding gums and slow healing. Sailors avoided it with citrus; amla is the richest Indian source.
Disease → pathogen type / vector
very common'Dengue / malaria / TB is caused by or spread by…', 'which of these is a viral disease', 'elephantiasis is transmitted by', odd-one-out among pathogens.
How to solve: Classify first: bacteria (TB, cholera, typhoid, tetanus, leprosy, plague), virus (dengue, rabies, polio, measles, AIDS), protozoa (malaria, kala-azar, amoebiasis), fungus (ringworm). Vectors: Anopheles–malaria, Aedes–dengue/chikungunya, Culex–elephantiasis, sandfly–kala-azar, tsetse–sleeping sickness, rat flea–plague. Dengue (viral) and malaria (protozoan) both ride mosquitoes but are different microbes — the favourite odd-one-out.
Example: Which mosquito transmits dengue?
Aedes aegypti — it bites by day and also carries chikungunya and zika. Malaria rides the female Anopheles instead.
Human body records and functions
very common'Largest gland / largest organ / longest bone / smallest bone', 'universal blood donor', 'bile is produced in', 'pace-maker of the heart', 'how many bones in an adult'.
How to solve: Records: skin largest organ, liver largest gland, thyroid largest endocrine gland, femur longest bone, stapes smallest bone, 206 adult bones. Blood: O− universal donor, AB+ universal recipient, platelets clot, SA node pace-maker. Secretions: liver makes bile (gall bladder stores it, no enzymes), stomach HCl + pepsin, pancreas insulin + trypsin. Pituitary is the master gland; thyroxine needs iodine.
Example: The smallest bone in the human body is:
Stapes, in the middle ear. The largest gland is the liver and the longest bone the femur — keep the three records separate.
Scientist → discovery (cell, vaccine, antibiotic)
very common'Who discovered penicillin / the cell / the vaccine', 'insulin was discovered by', 'who proved mosquitoes carry malaria', match-the-column of biologists.
How to solve: Timeline table: Hooke–cell (1665), Leeuwenhoek–living cells, Brown–nucleus, Schleiden + Schwann–cell theory, Virchow–omnis cellula; Jenner–first vaccine (smallpox, 1796), Pasteur–rabies vaccine and pasteurisation, Koch–TB bacterium, Fleming–penicillin (1928), Banting & Best–insulin (1921), Ross–mosquito-malaria link, Mendel–genetics, Watson & Crick–DNA double helix.
Example: Who discovered penicillin?
Alexander Fleming, in 1928, from the mould Penicillium notatum. Koch identified the TB bacterium; Pasteur gave the rabies vaccine.
Cell organelles and genetics
very common'Powerhouse of the cell / suicide bags', 'which organelle makes protein', 'human body cell has how many chromosomes', 'sex of the child is determined by', 'Mendel worked on'.
How to solve: Nickname pairs: mitochondria–powerhouse, ribosome–protein factory, lysosome–suicide bag, Golgi–post office; mitochondria and chloroplasts have their own DNA. Genetics: 46 chromosomes (23 pairs), meiosis halves to 23 in gametes, XX female / XY male so the father decides sex; Mendel = father of genetics (pea plant), Watson & Crick = DNA double helix.
Example: The sex of a child is determined by:
The father's sperm — it carries either X (girl, XX) or Y (boy, XY); the mother's egg always gives X.
Branch of study / culture word
very common'Ornithology / entomology / sericulture / apiculture is the study or rearing of', 'study of cancer', 'ichthyology', match-the-column of -ology words.
How to solve: Branches: ornithology–birds, entomology–insects (not etymology!), ichthyology–fish, herpetology–reptiles and amphibians, mycology–fungi, cytology–cells, oncology–cancer, cardiology–heart. Cultures: apiculture–bees, sericulture–silkworms, pisciculture–fish, vermiculture–earthworms, horticulture–gardens. Decode the Latin root when unsure (api-, seri-, pisci-).
Example: Sericulture is associated with:
Rearing silkworms for silk. Apiculture keeps bees, pisciculture farms fish — root + culture decodes each word.
Plant hormones, edible parts and classification
very common'Which hormone ripens fruit / bends shoots to light', 'potato / carrot / onion is a modified…', 'five-kingdom classification', 'monocot vs dicot', 'xylem carries…'.
How to solve: Hormones: auxin–elongation and phototropism, gibberellin–stem growth, cytokinin–cell division, ethylene–fruit ripening, abscisic acid–stress. Edible parts: carrot–root, potato/ginger/onion–stem, cabbage–leaf, cauliflower–flower, tomato–fruit, groundnut–seed. Classification: Linnaeus–binomial, Whittaker–5 kingdoms, bacteria in Monera; monocot one cotyledon + parallel veins, dicot two + reticulate; xylem water up, phloem food.
Example: Which plant hormone is a gas that ripens fruit?
Ethylene — a ripe banana releases it and ripens neighbouring fruit. Auxin bends shoots toward light; ABA closes stomata under stress.
Scientific names
common'The scientific name of mango / neem / rice / tiger', 'in binomial nomenclature the first word is', italics and capitalisation rules.
How to solve: Binomial = Genus (capital) + species (small), both italics. Mango Mangifera indica, neem Azadirachta indica, banyan Ficus benghalensis, tamarind Tamarindus indica, potato Solanum tuberosum, rice Oryza sativa, tiger Panthera tigris, frog Rana tigrina. Watch the two -indica pairings: mango and neem share the species name, not the genus.
Example: In Mangifera indica, the word Mangifera denotes the:
Genus — the first, capitalised word; indica is the species. The binomial system is Linnaeus's.