General Biology for competitive exams like Bihar Police Constable is not about memorising a textbook — it is about knowing exactly which facts get asked, year after year, across Bihar and UP police papers.
Look at the pattern: questions cluster around three zones.
Zone 1 — Plant biology facts. Things like what makes cork waterproof, what gives wood its strength, what pigments do in leaves. These are one-liner facts. One chemical, one function, one answer.
Zone 2 — Human body anatomy. Bone counts, organ locations, divisions of organ systems. The digestive system is a perennial favourite. Questions on the small intestine, its three divisions, and which organ it belongs to come up across multiple years.
Zone 3 — Diseases. Especially waterborne diseases, disease-organ connections, and the Hindi names of common diseases. Bihar papers have a history of asking disease names in Hindi (मियादी बुखार, आंत्र-ज्वर) and expecting you to match them with English equivalents. This is not difficult — but only if you have seen these terms before.
The analogy that helps here: think of the human body as a factory. The digestive tract is the raw-material processing unit — food enters, nutrients are extracted, waste exits. The small intestine is the most active section of that line. Diseases are failures in the factory's security system (immunity) or contamination of incoming raw material (food and water). Cork is like a factory's outer wall — it keeps water out precisely because of a special coating (suberin).
Master these three zones and you will cover nearly all biology questions in the Bihar Police Constable paper. This topic does not reward deep learning — it rewards correct, precise recall of anchor facts.
Cork is produced by the cork cambium (phellogen) in plants. The key fact: cork cells are dead at maturity. Their walls are impregnated with suberin, a complex polyester polymer that is both hydrophobic (water-repelling) and gas-impermeable.
Do not confuse the four common cell-wall substances:
| Substance | Location | Function | |---|---|---| | Suberin | Cork cells | Waterproofing, gas barrier | | Lignin | Xylem, sclerenchyma | Mechanical strength, rigidity | | Pectin | Middle lamella | Cell adhesion, holds cells together | | Hemicellulose | Primary cell wall | Structural support alongside cellulose |
The trick question in the PYQ is to confuse suberin with lignin. Lignin makes wood hard — it does not make cork waterproof. Suberin does. Remember: Suberin → Submerged = water-resistant. Suberin is why wine bottles sealed with cork do not leak, and why bark resists rain.
The human hand has 27 bones in total. These are divided into:
The phalanges per finger:
So: 2 + (3 × 4) = 2 + 12 = 14 phalanges total.
The thumb has only 2 bones because it lacks the middle phalanx. This is the direct answer to the PYQ. The thumb's two-bone structure gives it the wide range of movement (opposition) that distinguishes human grip.
The digestive tract (पाचन तंत्र / पाचक नाल) runs from the mouth to the anus. Key organs in sequence:
Mouth → Oesophagus → Stomach → Small Intestine → Large Intestine → Rectum → Anus
The small intestine (छोटी आँत) is divided into three parts:
Total length of small intestine in an adult: approximately 6–7 metres. Despite the name "छोटी" (small), it is longer than the large intestine — "small" refers to its narrower diameter.
The large intestine is wider but shorter (~1.5 metres) and primarily absorbs water.
Typhoid fever is caused by the bacterium Salmonella typhi. It is transmitted via the fecal-oral route — contaminated water and food are the primary vectors.
Hindi names you must know:
Organ affected: the intestines (आँत), specifically the Peyer's patches in the ileum. This is why the disease is called आंत्र-ज्वर — आंत्र means intestine.
Compare common diseases by transmission to avoid confusion:
| Disease | Cause | Transmission | |---|---|---| | Typhoid (आंत्र-ज्वर) | Salmonella typhi (bacteria) | Contaminated water/food | | Tuberculosis (यक्ष्मा / TB) | Mycobacterium tuberculosis | Airborne (droplets) | | Plague (प्लेग) | Yersinia pestis | Flea bites (rat fleas) | | Malaria (मलेरिया) | Plasmodium (protozoa) | Anopheles mosquito bite | | Cancer (कैंसर) | Genetic/environmental | Not communicable |
The PYQ directly tests whether you know that typhoid — not plague, not TB, not cancer — is the waterborne disease. The question gives you four options and relies on the fact that many aspirants confuse TB (respiratory) or plague (vector-borne) with waterborne infection.
When you see cork waterproofing, the word starts with SUB. Think: SUBerin keeps water SUBmerged away from cork. The other options — Lignin, Pectin, Hemicellulose — have no "sub" in them and no waterproofing role. Standard recall with no technique: 20 seconds of hesitation. With this pattern: 4 seconds. You eliminate 3 options in one mental move.
The word TWO has 3 letters but the thumb has 2 bones — not helpful. Better: the thumb is the ODD one out among fingers. Other fingers = 3 bones. Thumb = 3 minus 1 = 2. Reason: thumb has no middle phalanx. Remembering "thumb lacks the middle" is a 5-word sentence that gives you the answer instantly. Standard method (recalling bone anatomy from scratch): 30+ seconds. This method: under 5 seconds.
The three parts of the small intestine in order: Duodenum → Jejunum → Ileum. Mnemonic: DJI — like the drone brand. The drone flies your food from stomach to large intestine. D comes first (closest to stomach), I comes last (closest to large intestine). Any question asking for the number of divisions = 3. Any question asking for names = DJI. Standard memorisation: 3 separate recalls. DJI mnemonic: 1 recall with sequence built in.
Typhoid is आंत्र-ज्वर: आंत्र (intestine) + ज्वर (fever). The word itself tells you the organ (intestine). The disease name मियादी बुखार tells you the pattern (prolonged/periodic fever). When a question asks "which disease is caused by contaminated water," eliminate: TB (airborne), Plague (flea/rats), Cancer (non-infectious), Malaria (mosquito). Whatever remains = Typhoid. Elimination from 4 options takes 8 seconds using this method vs 20+ seconds trying to recall from memory alone.
Common confusion: छोटी आँत is actually longer (6-7 m) than बड़ी आँत (1.5 m). "Small" = narrow diameter. "Large" = wide diameter. Remember by analogy: a small lane (गली) is narrow, not short. If a question asks what छोटी आँत is part of, the answer is always पाचन तंत्र (digestive system) — never किडनी, फेफड़े, or नाक. Eliminate those three in 2 seconds.
When you see a Biology question in the Bihar Police exam, run this mental checklist in order:
Step 1 — Is this a "which chemical" question? Look for words like "deposition," "waterproof," "impermeable," "strength." Match: waterproof/cork → Suberin; rigid/wood → Lignin; adhesion → Pectin.
Step 2 — Is this a body-part count question? For bones: thumb = 2, other fingers = 3, total hand phalanges = 14. For intestine divisions: small = 3 (DJI), large = 3 (cecum, colon, rectum).
Step 3 — Is this a disease question? First identify transmission type from options. Waterborne → Typhoid. Airborne → TB. Mosquito → Malaria. Flea → Plague. Then match Hindi name if asked: आंत्र-ज्वर / मियादी बुखार = Typhoid.
Step 4 — Is this an organ-system classification question? छोटी आँत / बड़ी आँत → पाचन तंत्र. If options include किडनी (excretory), फेफड़े (respiratory), हृदय (circulatory) — eliminate all three immediately.
Total decision time per question using this framework: under 15 seconds.
Why this question: Cork waterproofing is a direct factual recall question. The trap is Lignin — it sounds structural and "wall-like," but it hardens wood, not cork.
Solving path: Read "impervious to water" + "cork" → immediately think SUBerin. Confirm by eliminating: Lignin = wood hardening, Pectin = cell adhesion, Hemicellulose = structural support. Suberin is the only waterproofing agent here. Time: 8 seconds.
Why this question: Human bone count questions are standard anatomy recall. The thumb is the single most commonly asked finger because it differs from all others.
Solving path: Recall — thumb lacks middle phalanx, so it has only proximal + distal = 2 bones. Options 4, 1, 3, 2 — eliminate 4 (too many), 1 (impossible, thumb is a multi-bone digit), 3 (that's for other fingers). Answer: 2. Time: 6 seconds.
Why this question: Disease-organ connection in Hindi. This question appears across Bihar Police papers in different forms. The word आंत्र-ज्वर itself contains the answer.
Solving path: Decode the word: आंत्र = intestine (आँत), ज्वर = fever. So आंत्र-ज्वर affects आँत. Options: फेफड़े (lungs) → for TB; हृदय (heart) → not an infection target here; किडनी → for urinary infections. आँत is the direct answer from the word itself. Time: 5 seconds.
Why this question: System-classification of the small intestine. This tests whether you know पाचन तंत्र as the correct system — the wrong options are from other body systems entirely.
Solving path: Eliminate by system: नाक = respiratory/smell, किडनी = excretory/urinary, फेफड़े = respiratory. The small intestine digests food, so it belongs to पाचक नाल (digestive tract). Time: 4 seconds (pure elimination).
Why this question: Division count of small intestine — a specific factual recall. Three is the answer; the distractor options (4, 10, 8) are designed to confuse students who have not pinned down this number.
Solving path: Recall DJI — Duodenum, Jejunum, Ileum = 3 parts. Option: तीन (three). Options four, ten, eight are clearly wrong once you know DJI. Time: 3 seconds.
Why this question: Waterborne disease identification is one of the highest-frequency disease questions. The trap options (TB, Plague, Cancer) have clearly different transmission routes.
Solving path: "दूषित जल पीने से" = from drinking contaminated water = waterborne. Eliminate: यक्ष्मा (TB) = airborne; प्लेग (Plague) = flea-borne; कैंसर (Cancer) = non-communicable. Only आंत्र-ज्वर (Typhoid) is waterborne. Time: 7 seconds.
Why this question: Hindi colloquial name for Typhoid. "मियादी बुखार" is a term specific to the regional medical vocabulary used in Bihar-UP, and it maps directly to Typhoid.
Solving path: Recall the term: मियादी = prolonged/periodic; बुखार = fever. Typhoid is characterised by sustained, periodic fever over weeks. Plague = sudden epidemic fever; Malaria = cyclical fever but not called मियादी; TB = not primarily a fever-name disease. Answer: Typhoid. Time: 6 seconds.
Suberin vs Lignin confusion. The single most common error in plant biology questions. Lignin = wood hardness and rigidity (xylem cells). Suberin = cork waterproofing. These are different substances, different locations, different functions. Never swap them.
Thumb has 3 bones (wrong). Many aspirants assume all fingers have 3 phalanges. The thumb has only 2. If the question says "thumb of hand," the answer is 2, always.
Small intestine = smaller/shorter than large intestine. The name छोटी refers to diameter, not length. The small intestine is actually longer. If a question asks about length, small intestine wins. If about diameter/width, large intestine wins.
Confusing मियादी बुखार with Malaria. Malaria also involves periodic fever, which is why this confusion happens. But Malaria is called मलेरिया in Hindi, not मियादी बुखार. मियादी बुखार is exclusively Typhoid.
Organ affected by Typhoid = Liver or Stomach. Typhoid primarily affects the intestines (आँत), not the liver or stomach. The word आंत्र-ज्वर literally contains this answer. Do not let general fever associations mislead you into writing liver or stomach.
Waterborne disease = Cholera instead of Typhoid. In these PYQs, when the options include आंत्र-ज्वर and a question mentions contaminated water, the answer is Typhoid (आंत्र-ज्वर). Cholera is also waterborne but if it is not among the options, do not write it. Work strictly with the options given.