Railway RRB – General Science
Biology Basics – Study Notes
Aim: Quick, clear, exam‑ready notes on core biology concepts that appear in the RRB General Science paper.
1. Simple Explanation
| Term | Simple Definition |
|---|---|
| Biology | The science of life – it studies living organisms, their structure, function, growth, origin, evolution, and distribution. |
| Cell | The smallest unit of life; the basic building block of all organisms. |
| Prokaryote | A cell that has no membrane‑bound nucleus (e.g., bacteria). |
| Eukaryote | A cell with a true nucleus and membrane‑bound organelles (e.g., plants, animals, fungi). |
| DNA | Deoxyribonucleic acid – the hereditary material that stores genetic instructions. |
| Gene | A segment of DNA that codes for a specific protein or RNA product. |
2. Key Points
2.1 Cell Theory (3 Pillars)
| Pillar | What it says |
|---|---|
| 1️⃣ | All living things are composed of cells. |
| 2️⃣ | The cell is the basic unit of structure and function. |
| 3️⃣ | All cells arise from pre‑existing cells (mitosis, meiosis). |
2.2 Prokaryotic vs. Eukaryotic Cells
| Feature | Prokaryote | Eukaryote |
|---|---|---|
| Nucleus | None (DNA in nucleoid) | True nucleus (membrane‑bound) |
| Size | 0.1–5 µm | 10–100 µm |
| Organelles | Few (ribosomes, plasmids) | Many (mitochondria, chloroplasts, ER, Golgi) |
| Cell Wall | Peptidoglycan (bacteria) | Cellulose (plants), chitin (fungi) |
| Reproduction | Binary fission | Mitosis & meiosis |
| Examples | E. coli, Bacillus | Human, plant, fungal cells |
2.3 Cell Organelles (Eukaryotic)
| Organelle | Function |
|---|---|
| Nucleus | Stores DNA, controls cell activities |
| Mitochondria | Powerhouse – ATP production |
| Chloroplast | Photosynthesis (plants, algae) |
| Endoplasmic Reticulum (ER) | Rough ER – protein synthesis; Smooth ER – lipid synthesis |
| Golgi Apparatus | Modifies, sorts, and packages proteins |
| Ribosomes | Protein synthesis |
| Lysosomes | Digestive enzymes |
| Cytoskeleton | Cell shape, movement, organelle transport |
| Peroxisomes | Detoxification, fatty‑acid β‑oxidation |
2.4 Biological Macromolecules
| Macromolecule | Building Blocks | Main Function |
|---|---|---|
| Carbohydrates | Sugars | Energy source, structure (cellulose) |
| Proteins | Amino acids | Enzymes, structure, transport, signalling |
| Lipids | Fatty acids, glycerol | Energy storage, membrane structure, signalling |
| Nucleic Acids | Nucleotides | Store & transmit genetic info (DNA, RNA) |
2.5 Genetics Basics
| Concept | Key Idea |
|---|---|
| DNA Structure | Double‑helix, base pairs (A‑T, C‑G) |
| Gene Expression | Transcription → mRNA → Translation → Protein |
| Inheritance | Mendelian laws – dominant/recessive, segregation, independent assortment |
| Mutation | Change in DNA sequence; causes variation |
2.6 Evolution & Natural Selection
| Idea | Explanation |
|---|---|
| Natural Selection | Organisms better adapted to environment survive and reproduce. |
| Speciation | New species arise when populations diverge. |
| Evidence | Fossil record, comparative anatomy, molecular data. |
2.7 Classification (Taxonomy)
| Rank | Representative Groups |
|---|---|
| Domain | Bacteria, Archaea, Eukarya |
| Kingdom | Animalia, Plantae, Fungi, Protista, Monera |
| Phylum/Division | Chordata, Arthropoda, Angiosperms, etc. |
3. Worked Example
Question (Typical RRB MCQ)
Which of the following cell types is not a eukaryotic cell?
A. Human red blood cell
B. Plant cell
C. Bacterial cell
D. Yeast cell
Solution
| Option | Cell type | Is it eukaryotic? | Why? |
|---|---|---|---|
| A | Human red blood cell | No | Mature RBCs lack a nucleus and most organelles. |
| B | Plant cell | Yes | Contains nucleus, chloroplasts, etc. |
| C | Bacterial cell | No | Prokaryotic – no nucleus. |
| D | Yeast cell | Yes | Fungal eukaryote. |
Answer: C