Module 3 · Agniveer Science

Biology Basics

Cell, human body systems, vitamins, diseases, plant biology.

Cell · Human Body · Vitamins · Diseases · Plants

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Learning Objectives

Understand the fundamental concepts of Biology Basics
Apply key formulas and techniques to solve problems
Practice with exam-level questions to build speed and accuracy

Key Concepts

What is Biology?

Biology is the study of life and living organisms. In Agniveer and defence exams, biology questions cover cell biology, human body systems, plant biology, nutrition, diseases, and genetics. Questions are at the high school level and emphasize understanding of basic life processes and their applications to daily life and health.

Key Topics in Biology

1. Cell — The Unit of Life: Cell is the basic structural and functional unit of all living organisms. Cell theory (Schleiden and Schwann). Prokaryotic (no nucleus — bacteria) vs Eukaryotic (with nucleus — plants, animals). Cell organelles: Nucleus (control centre, contains DNA), Mitochondria (powerhouse — energy production), Ribosomes (protein synthesis), ER (transport), Golgi apparatus (packaging), Lysosomes (digestion), Chloroplasts (photosynthesis in plants), Cell membrane (semi-permeable).

2. Human Body Systems: Digestive system (mouth → oesophagus → stomach → small intestine → large intestine → anus; organs: liver, pancreas, gall bladder). Respiratory system (nose → pharynx → larynx → trachea → bronchi → lungs; diaphragm; processes: inhalation, exhalation, gaseous exchange). Circulatory system (heart — 4 chambers: RA, RV, LA, LV; blood vessels — arteries, veins, capillaries; blood components: RBCs, WBCs, platelets, plasma). Excretory system (kidneys, ureters, urinary bladder, urethra; nephron = functional unit). Nervous system (brain — cerebrum, cerebellum, medulla; spinal cord, nerves). Reproductive system (male: testes, female: ovaries).

3. Plant Biology: Photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (requires sunlight, chlorophyll). Transpiration — loss of water vapour from leaves. Plant hormones: Auxin (growth), Gibberellin (stem elongation), Cytokinin (cell division), Abscisic acid (stress response).

4. Nutrition and Health: Carbohydrates, proteins, fats, vitamins (A, B complex, C, D, E, K), minerals (iron, calcium, iodine, phosphorus). Deficiency diseases: Scurvy (vitamin C), Rickets (vitamin D), Beriberi (vitamin B1), Night blindness (vitamin A), Goitre (iodine), Anaemia (iron). Balanced diet, malnutrition, obesity.

5. Diseases and Immunity: Communicable diseases (caused by pathogens): Bacteria (TB, typhoid, cholera), Virus (COVID-19, flu, HIV), Protozoa (malaria, amoebic dysentery), Fungi (ringworm). Non-communicable: Diabetes, hypertension, cancer. Immune system: Vaccines, antibiotics (effective against bacteria, not viruses), white blood cells.

6. Genetics and Evolution: DNA (double helix), genes (segment of DNA), chromosomes (23 pairs in humans). Mendel's laws: Law of segregation, Law of independent assortment. Dominant/recessive traits. Evolution — Darwin's theory of natural selection, survival of the fittest.

Solved Examples

Example 1 (Cell Biology)

Which organelle is known as the 'powerhouse of the cell'?

a) Nucleus b) Ribosome c) Mitochondria d) Golgi apparatus

Solution: c) Mitochondria produces ATP (energy) through cellular respiration, hence called the powerhouse of the cell.

Example 2 (Human Body)

Which vitamin is produced when the skin is exposed to sunlight?

a) Vitamin A b) Vitamin B c) Vitamin C d) Vitamin D

Solution: d) Vitamin D is synthesized in the skin when exposed to sunlight (UV rays). It is essential for calcium absorption and bone health.

Example 3 (Diseases)

Malaria is caused by which type of pathogen?

a) Bacteria b) Virus c) Protozoa d) Fungus

Solution: c) Malaria is caused by the protozoan parasite Plasmodium, transmitted through the bite of infected female Anopheles mosquitoes.

Shortcut Techniques

Remember vitamin deficiency diseases using mnemonics: 'See B1, B2, B3 — Beriberi, Pellagra, Niacin' or 'C for Scurvy, D for Rickets, A for Night blindness'.
For human body systems, trace the path: Food → Digestive tract; Air → Respiratory tract; Blood → Heart → Lungs → Heart → Body; Urine → Kidney → Bladder.
Group diseases by causative agent — bacterial (TB, typhoid, cholera, tetanus), viral (cold, flu, HIV, COVID-19), protozoan (malaria, amoebiasis).
For cell biology, associate functions with organelle names: 'Power = Mitochondria', 'Control = Nucleus', 'Protein = Ribosome', 'Package = Golgi'.

Pro Tip

In Agniveer exams, biology questions often focus on human physiology and common diseases. Pay special attention to nutrition, vitamins and their deficiency diseases, and the functions of major body organs. NCERT Class 9-10 science textbooks are sufficient for preparation.

Application-Based Learning

Connect concepts to real-world applications: Why sky is blue (Rayleigh scattering), how pressure cookers work, why apples turn brown (oxidation).

Problem-Solving Methodology

1) Identify given data. 2) Recall formulas. 3) Check unit consistency. 4) Solve step-by-step. 5) Verify through estimation.

Pro Tip

Check if your answer is reasonable through order-of-magnitude estimation to catch gross errors.

Application-Based Learning

Connect concepts to real-world applications: Why sky is blue (Rayleigh scattering), how pressure cookers work, why apples turn brown (oxidation).

Problem-Solving Methodology

1) Identify given data. 2) Recall formulas. 3) Check unit consistency. 4) Solve step-by-step. 5) Verify through estimation.

Pro Tip

Check if your answer is reasonable through order-of-magnitude estimation to catch gross errors.

Application-Based Learning

Connect concepts to real-world applications: Why sky is blue (Rayleigh scattering), how pressure cookers work, why apples turn brown (oxidation).

Problem-Solving Methodology

1) Identify given data. 2) Recall formulas. 3) Check unit consistency. 4) Solve step-by-step. 5) Verify through estimation.

Pro Tip

Check if your answer is reasonable through order-of-magnitude estimation to catch gross errors.

Application-Based Learning

Connect concepts to real-world applications: Why sky is blue (Rayleigh scattering), how pressure cookers work, why apples turn brown (oxidation).

Problem-Solving Methodology

1) Identify given data. 2) Recall formulas. 3) Check unit consistency. 4) Solve step-by-step. 5) Verify through estimation.

Pro Tip

Check if your answer is reasonable through order-of-magnitude estimation to catch gross errors.

Practice Questions

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