General Knowledge
Intermediate Level
Biology
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Jul 11, 2026
About This Cheat Sheet
Hey there! Welcome to your complete guide to Biology for competitive exams. I've put together everything you need to know in one place — from Cell Biology and Genetics to Human Body Systems, Diseases, Nutrition, Plant Biology, Ecology, and more. Whether you're preparing for SSC, Banking, Railways, UPSC, or State PSC exams, this cheat sheet covers important systems, vitamins, hormones, diseases, and shortcut techniques to help you score better.
🔬 Cell Biology
- Cell - Basic unit of life
- Cell Wall - Plant cells only
- Cell Membrane - Semi-permeable
- Nucleus - Control center (DNA)
- Mitochondria - Powerhouse of cell
- Ribosomes - Protein synthesis
- Prokaryotic - No nucleus (Bacteria)
- Eukaryotic - Has nucleus (Plants, Animals)
🧬 Genetics
- DNA - Genetic material
- RNA - Protein synthesis
- Genes - Units of heredity
- Chromosomes - DNA + Proteins
- Mendel's Laws - Inheritance
- Monohybrid Cross - One trait
- Dihybrid Cross - Two traits
- Mutation - Change in DNA
🧠 Human Body Systems
- Digestive - Breaks down food
- Respiratory - Gas exchange
- Circulatory - Blood circulation
- Nervous - Body control
- Excretory - Removes waste
- Endocrine - Hormones
- Reproductive - Reproduction
- Skeletal - Support & movement
🦠 Diseases
- Bacterial - TB, Typhoid, Cholera
- Viral - COVID-19, Polio, Dengue
- Fungal - Ringworm, Athlete's Foot
- Parasitic - Malaria, Filariasis
- Deficiency - Scurvy, Rickets, Goitre
- Lifestyle - Diabetes, Hypertension
- Cancer - Uncontrolled cell growth
- Heart Disease - Cardiovascular issues
🥗 Nutrition
- Carbohydrates - Energy source
- Proteins - Growth & repair
- Fats - Energy storage
- Vitamins - 13 essential
- Minerals - Ca, Fe, I, Zn, Na
- Balanced Diet - All nutrients
- Malnutrition - Under/Over nutrition
- Obesity - Excess body fat
🌿 Plant Biology
- Photosynthesis - Food production
- Respiration - Energy release
- Transpiration - Water loss
- Reproduction - Asexual/Sexual
- Pollination - Pollen transfer
- Seed Dispersal - Seed spreading
- Plant Hormones - Auxin, Gibberellin
- Plant Tissues - Meristematic, Permanent
🔬 Cell
Basic Unit of Life
Prokaryotic/Eukaryotic🧬 DNA
Genetic Material
Double Helix❤️ Heart
Pumps Blood
4 Chambers🌿 Photosynthesis
Food Production
Plants🧠 Human Body Systems
🫃 Digestive System
- Function: Breaks down food
- Key Organs: Stomach, Intestine, Liver, Pancreas
- Enzymes: Amylase, Pepsin, Lipase
- Key: Digestion and absorption
🫁 Respiratory System
- Function: Breathing & gas exchange
- Key Organs: Lungs, Trachea, Diaphragm
- Gas Exchange: O₂ in, CO₂ out
- Key: Alveoli (gas exchange site)
❤️ Circulatory System
- Function: Blood circulation
- Key Organs: Heart, Arteries, Veins
- Blood: Plasma, RBC, WBC, Platelets
- Key: Transportation of substances
🧠 Nervous System
- Function: Body control
- Key Organs: Brain, Spinal Cord, Nerves
- Neuron: Basic unit
- Key: Coordination and response
🧠 More Human Body Systems
💧 Excretory System
- Function: Removes waste
- Key Organs: Kidneys, Ureter, Bladder
- Nephron: Functional unit
- Waste: Urea, Urine
⚖️ Endocrine System
- Function: Hormone secretion
- Key Organs: Pituitary, Thyroid, Adrenal
- Hormones: Chemical messengers
- Key: Regulates body functions
🦴 Skeletal System
- Function: Support & movement
- Bones: 206 in adults
- Joints: Hinge, Ball & Socket
- Key: Protection of organs
💪 Muscular System
- Function: Movement
- Types: Skeletal, Smooth, Cardiac
- Muscles: Biceps, Triceps
- Key: Voluntary & involuntary
💊 Important Vitamins
Vitamin A: Retinol — Night Blindness (Carrots, Eggs)
Vitamin B1: Thiamine — Beriberi (Whole grains, Meat)
Vitamin B2: Riboflavin — Cheilosis (Milk, Eggs)
Vitamin B3: Niacin — Pellagra (Meat, Fish, Nuts)
Vitamin B12: Cyanocobalamin — Pernicious Anaemia (Meat, Eggs, Milk)
Vitamin C: Ascorbic Acid — Scurvy (Citrus fruits, Tomatoes)
Vitamin D: Calciferol — Rickets (Sunlight, Fish, Eggs)
Vitamin E: Tocopherol — Infertility (Nuts, Seeds, Oils)
Vitamin K: Phylloquinone — Bleeding disorder (Green vegetables, Meat)
🦴 Important Minerals
Calcium (Ca): Bone health, Teeth (Milk, Dairy, Green leafy)
Iron (Fe): Haemoglobin formation, Anaemia (Red meat, Spinach, Pulses)
Iodine (I): Thyroid hormone, Goitre (Iodized salt, Seafood)
Zinc (Zn): Immune function, Wound healing (Meat, Seeds, Nuts)
Sodium (Na): Fluid balance, Nerve function (Table salt, processed food)
Potassium (K): Nerve function, Heart health (Banana, Potatoes, Beans)
Magnesium (Mg): Muscle function, Energy production (Nuts, Seeds, Whole grains)
⚖️ Important Hormones
🧪 Insulin
- Secreted By: Pancreas
- Function: Regulates blood sugar
- Deficiency: Diabetes
- Key: Lowers blood glucose
🧪 Thyroxine
- Secreted By: Thyroid
- Function: Regulates metabolism
- Deficiency: Goitre
- Key: Metabolic rate
🧪 Adrenaline
- Secreted By: Adrenal
- Function: Fight or flight
- Key: Emergency response
- Effect: Increases heart rate
⚖️ More Important Hormones
🧪 Growth Hormone
- Secreted By: Pituitary
- Function: Growth & development
- Deficiency: Dwarfism
- Excess: Gigantism
🧪 Oestrogen
- Secreted By: Ovaries
- Function: Female characteristics
- Role: Menstrual cycle
- Key: Female reproductive
🧪 Testosterone
- Secreted By: Testes
- Function: Male characteristics
- Role: Sperm production
- Key: Male reproductive
🦠 Important Diseases & Their Causes
🦠 Bacterial Diseases
- Tuberculosis: Mycobacterium tuberculosis
- Typhoid: Salmonella typhi
- Cholera: Vibrio cholerae
- Tetanus: Clostridium tetani
🦠 Viral Diseases
- COVID-19: SARS-CoV-2
- Polio: Poliovirus
- Dengue: Dengue virus
- HIV/AIDS: HIV virus
🦠 Parasitic Diseases
- Malaria: Plasmodium
- Filariasis: Wuchereria bancrofti
- Kala Azar: Leishmania
- Amoebiasis: Entamoeba histolytica
🦠 Deficiency Diseases
- Scurvy: Vitamin C deficiency
- Rickets: Vitamin D deficiency
- Goitre: Iodine deficiency
- Night Blindness: Vitamin A deficiency
🌿 Plant Biology
☀️ Photosynthesis
- Definition: Process of making food
- Equation: CO₂ + H₂O → C₆H₁₂O₆ + O₂
- Chlorophyll: Green pigment
- Key: Converts solar energy to chemical
🌱 Plant Reproduction
- Asexual: Vegetative propagation
- Sexual: Pollination, Fertilization
- Pollination: Transfer of pollen
- Seed Dispersal: Wind, Water, Animals
🧪 Plant Hormones
- Auxin: Growth & tropism
- Gibberellin: Stem elongation
- Cytokinin: Cell division
- Abscisic Acid: Stress response
🌍 Ecology
🌿 Ecosystem
- Producers: Plants (make food)
- Consumers: Animals (eat food)
- Decomposers: Microorganisms (break down)
- Food Chain: Energy flow
- Food Web: Multiple food chains
🌍 Biogeochemical Cycles
- Carbon Cycle: CO₂ - Atmosphere - Plants - Animals
- Nitrogen Cycle: N₂ - Ammonia - Nitrates - Denitrification
- Water Cycle: Evaporation - Condensation - Precipitation
- Oxygen Cycle: Photosynthesis - Respiration
🦁 Biodiversity Conservation
- National Parks: Jim Corbett, Kanha, Kaziranga
- Wildlife Sanctuaries: Protected areas
- Biosphere Reserves: Nilgiri, Sundarbans
- Biodiversity Hotspots: Western Ghats, Eastern Himalayas
🔬 Important Scientists & Their Contributions
🧬 Gregor Mendel
- Contribution: Laws of Inheritance
- Key: Father of Genetics
- Experiment: Pea plants
🧬 Watson & Crick
- Contribution: DNA Double Helix (1953)
- Key: Structure of DNA
- Nobel: 1962
🧬 Charles Darwin
- Contribution: Theory of Evolution
- Key: Natural Selection
- Book: Origin of Species
🧬 Louis Pasteur
- Contribution: Germ Theory, Pasteurization
- Key: Vaccines, Fermentation
- Impact: Modern medicine
🔬 More Scientists & Their Contributions
🧪 Alexander Fleming
- Contribution: Discovery of Penicillin
- Year: 1928
- Nobel: 1945
🧬 Gregor Mendel
- Contribution: Laws of Inheritance
- Key: Father of Genetics
- Experiment: Pea plants
🧬 Rosalind Franklin
- Contribution: DNA structure (X-ray)
- Key: Photo 51
- Impact: DNA discovery
🧬 Edward Jenner
- Contribution: Smallpox vaccine
- Key: Father of Immunology
- Impact: First vaccine
🔬 Important Cell Organelles
⚡ Mitochondria
- Function: Powerhouse of the cell
- Key: ATP production
- Has: Its own DNA
- Found: All eukaryotic cells
🧬 Nucleus
- Function: Control center
- Contains: DNA
- Key: Cell division
- Found: Eukaryotic cells
🧫 Ribosomes
- Function: Protein synthesis
- Found: All cells
- Made of: RNA & proteins
- Key: Translation
🔬 More Cell Organelles
🧫 Endoplasmic Reticulum
- Function: Protein & lipid synthesis
- Types: Rough (RER), Smooth (SER)
- RER: Ribosomes attached
- SER: Lipid synthesis
🧫 Golgi Apparatus
- Function: Packaging & shipping
- Key: Protein modification
- Found: Eukaryotic cells
- Structure: Stack of membranes
🧫 Lysosomes
- Function: Digestion & recycling
- Key: Cellular waste disposal
- Found: Animal cells
- Key: Suicidal bags
🎯 Biology Quick Revision
The Golden Rule: Focus on vitamins and their deficiency diseases, hormones and their functions, and human body systems. Most competitive exam questions test your ability to match diseases with their causes and vitamins with their deficiencies.
Quick Memory Tricks:
- 📌 Vitamins & Deficiency: "A=Night Blindness, C=Scurvy, D=Rickets, B1=Beriberi, K=Bleeding"
- 📌 Hormones: "Insulin=Diabetes, Thyroxine=Metabolism, Adrenaline=Fight/Flight, Growth=Dwarfism/Gigantism"
- 📌 Body Systems: "Digestive=Food, Respiratory=Air, Circulatory=Blood, Nervous=Brain, Excretory=Waste"
- 📌 Cell Organelles: "Mitochondria=Powerhouse, Nucleus=Control, Ribosomes=Proteins"
Exam Strategy:
- Step 1: Read the question — identify the topic (vitamins, diseases, systems)
- Step 2: For vitamins, match with deficiency disease
- Step 3: For diseases, match with their cause
- Step 4: For systems, know the organs involved
- Step 5: Use elimination to remove wrong options
💡 Pro Tips for Biology
✅ Learn Vitamins & Deficiencies
A=Night Blindness, B1=Beriberi, C=Scurvy, D=Rickets, K=Bleeding disorder.
✅ Remember Hormones & Functions
Insulin (Blood sugar), Thyroxine (Metabolism), Adrenaline (Fight/Flight).
✅ Body Systems & Organs
Digestive (Stomach, Liver), Respiratory (Lungs), Circulatory (Heart), Nervous (Brain).
✅ Disease Causes
Tuberculosis = Bacteria, Malaria = Parasite, COVID-19 = Virus, Scurvy = Deficiency.
✅ Cell Organelles
Mitochondria = ATP, Nucleus = DNA, Ribosomes = Proteins, Lysosomes = Digestion.
✅ Important Scientists
Mendel (Genetics), Darwin (Evolution), Fleming (Penicillin), Watson & Crick (DNA).
💊 Quick Reference: Vitamins & Deficiency Summary
💊 Vitamin
- Vitamin A
- Vitamin B1
- Vitamin B2
- Vitamin B3
- Vitamin B12
- Vitamin C
- Vitamin D
- Vitamin E
- Vitamin K
📚 Chemical Name
- Retinol
- Thiamine
- Riboflavin
- Niacin
- Cyanocobalamin
- Ascorbic Acid
- Calciferol
- Tocopherol
- Phylloquinone
🦠 Deficiency Disease
- Night Blindness
- Beriberi
- Cheilosis
- Pellagra
- Pernicious Anaemia
- Scurvy
- Rickets
- Infertility
- Bleeding disorder
🥗 Sources
- Carrots, Eggs
- Whole grains, Meat
- Milk, Eggs
- Meat, Fish, Nuts
- Meat, Eggs, Milk
- Citrus fruits
- Sunlight, Fish
- Nuts, Seeds, Oils
- Green vegetables
🦠 Quick Reference: Disease Summary
🦠 Disease
- COVID-19
- Malaria
- Tuberculosis
- Dengue
- Ringworm
- Scurvy
- Diabetes
- Goitre
- Polio
- HIV/AIDS
🧫 Cause
- SARS-CoV-2 virus
- Plasmodium
- Mycobacterium
- Dengue virus
- Fungus
- Vitamin C deficiency
- Insulin deficiency
- Iodine deficiency
- Poliovirus
- HIV virus
📚 Type
- Viral
- Parasitic
- Bacterial
- Viral
- Fungal
- Deficiency
- Lifestyle/Hormonal
- Deficiency
- Viral
- Viral
🛡️ Prevention
- Vaccination
- Mosquito control
- BCG Vaccine
- Mosquito control
- Hygiene
- Vitamin C rich food
- Lifestyle changes
- Iodized salt
- Polio vaccine
- Safe practices
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