Biology Basics – Study Notes
For the Delhi Patwari / Lekhpal General Awareness & Current Affairs Exam
Tip: Keep these notes handy for quick revision. Cover one section per day and test yourself with the example problems.
1. Simple Explanation
Biology is the science that studies life and living organisms. It covers everything from the smallest cell to entire ecosystems, looking at structure, function, growth, evolution, and distribution.
Why it matters: Patwaris and Lekhpal often encounter agricultural, environmental, and health issues. A basic grasp of biology helps explain crop diseases, animal health, and ecological changes that affect land records.
2. Key Points
| Topic | Core Concepts | Quick Facts |
|---|---|---|
| Cell Theory | 1️⃣ All living things are made of cells. 2️⃣ Cells are the smallest unit of life. 3️⃣ All cells arise from pre‑existing cells. |
Prokaryotes (bacteria, archaea) vs Eukaryotes (plants, animals, fungi). |
| Cell Structure | Prokaryotic: Plasma membrane, cytoplasm, ribosomes, DNA (circular). Eukaryotic: Organelles – nucleus, mitochondria, chloroplasts, ER, Golgi, vacuoles. |
Mitochondria = “powerhouse”; Chloroplasts = “green factory”. |
| Cell Function | Metabolism: Anabolism & catabolism. Transport: Passive (diffusion, osmosis) vs Active (ATP‑driven). Signal transduction: Hormones, neurotransmitters. |
Cells communicate via hormones (e.g., insulin). |
| Genetics | DNA structure (double‑helix, bases A‑T, G‑C). Genes, alleles, genotype vs phenotype. Inheritance patterns – Mendelian laws. |
Punnett square predicts offspring ratios. |
| Taxonomy (Classification) | Kingdom → Phylum → Class → Order → Family → Genus → Species. Binomial nomenclature (genus + species). |
Homo sapiens – Homo (genus) + sapiens (species). |
| Plant Biology | Photosynthesis (light & dark reactions). Plant parts – roots, stems, leaves, flowers, fruits. Reproduction – sexual (flower → seed) & asexual (cuttings, runners). |
Chlorophyll a & b absorb light; CO₂ → glucose. |
| Animal Biology | Body plans – invertebrates vs vertebrates. Major organ systems: circulatory, respiratory, digestive, excretory, nervous, reproductive. |
RBCs lack nucleus; WBCs defend body. |
| Human Body Systems | <ul><li>Circulatory: heart, blood, vessels</li><li>Respiratory: lungs, trachea</li><li>Digestive: mouth, stomach, intestines</li><li>Excretory: kidneys, bladder</li><li>Nervous: brain, spinal cord, nerves</li><li>Reproductive: ovaries/testes, uterus, prostate</li></ul> | Hemoglobin carries O₂; Insulin regulates glucose. |
| Evolution & Ecology | Natural selection, adaptation, speciation. Biomes, ecosystems, food chains & webs. |
Darwin’s finches on Galápagos—adaptive radiation. |
| Health & Hygiene | Basic disease transmission (vector, contact, airborne). Sanitation, vaccination, nutrition. |
Handwashing with soap reduces diarrheal diseases. |
3. Worked Example – Genetics (Punnett Square)
Problem:
A pea plant with a heterozygous gene for tallness (Tt) is crossed with a homozygous short plant (tt). What are the expected phenotypic ratios of the offspring?
| Step | Explanation |
|---|---|
| 1️⃣ Write the genotypes | Parent 1: Tt (Tall) Parent 2: tt (Short) |
| 2️⃣ List gametes | Parent 1 → T or t Parent 2 → t |
| 3️⃣ Build Punnett square | 2 × 2 grid |
| 4️⃣ Fill in | |
| 5️⃣ Count | Tt (Tall) = 2/4 = 50% tt (Short) = 2/4 = 50% |
| 6️⃣ Answer | 1:1 ratio (Tall : Short) |
Quick Check
- Genotype ratio: 1 Tt : 1 tt
- Phenotype ratio: 1 Tall : 1 Short
4. Quick Revision Summary
- Cell – unit of life; eukaryote vs prokaryote.
- DNA – genetic material; bases A/T, G/C; double helix.
- Genes – DNA segments; alleles determine traits.
- Punnett Square – predicts offspring ratios.
- Taxonomy – 7‑level hierarchy; binomial names.
- Photosynthesis – light → glucose; CO₂ + H₂O → C₆H₁₂O₆ + O₂.
- Human Systems – circulatory, respiratory, digestive, excretory, nervous, reproductive.
- Evolution – natural selection → adaptation.
- Health – hygiene, vaccination, vector control.
Revision tip: Test yourself by explaining each concept in 2‑3 sentences and drawing a single diagram (e.g., cell, Punnett square, or organ system).
Happy studying!