Biology Basics – Study Notes
(For the Tamil Nadu Patwari / Lekhpal General Awareness & Current Affairs Exam)
1. Simple Explanation
Biology is the science of life. It studies living organisms—from single‑cell microbes to complex mammals—focusing on their structure, function, growth, origin, evolution, and distribution.
Key themes:
- Cell theory – all life is made of cells.
- Genetics – the study of heredity and variation.
- Ecology – interactions between organisms and their environment.
- Human biology – anatomy, physiology, and the body’s systems.
2. Key Points
| Topic | Core Concept | Important Terms | Typical Exam Question Type |
|---|---|---|---|
| Cell Biology | Cell as the basic unit of life | Cell membrane, cytoplasm, nucleus, mitochondria, ribosomes, chloroplasts | “Define cell membrane and name its main function.” |
| Genetics | DNA, genes, chromosomes, inheritance patterns | DNA, RNA, gene, allele, dominant/recessive, Punnett square | “What is a Punnett square used for?” |
| Evolution | Natural selection, adaptation | Natural selection, adaptation, speciation, phylogeny | “Explain how natural selection leads to speciation.” |
| Ecology | Ecosystem, food chain, energy flow | Ecosystem, biotic/abiotic, trophic level, biogeochemical cycle | “Draw a simple food chain.” |
| Human Physiology | Organ systems & functions | Circulatory, respiratory, digestive, excretory, endocrine, nervous | “Describe the role of the pancreas.” |
| Biotechnology | Applying biology for technology | PCR, cloning, GMOs, CRISPR | “What is CRISPR‑Cas9 used for?” |
| Health & Disease | Pathogens, immunity, public health | Bacteria, viruses, immunity, vaccination | “What is a vaccine?” |
| Environmental Issues | Conservation, pollution, climate change | Biodiversity, deforestation, CO₂, global warming | “What is biodiversity and why is it important?” |
3. Worked Example
Question: Using a Punnett square, determine the probability of a child inheriting the allele for blue eyes (recessive) if both parents are heterozygous (Aa).
Step‑by‑Step
| Step | Explanation | Result |
|---|---|---|
| 1. Identify alleles | Parent 1: A (dominant) / a (recessive) Parent 2: A / a |
|
| 2. Draw grid | 2 × 2 grid – rows = parent 1 alleles, columns = parent 2 alleles | |
| 3. Fill grid | ||
| Row 1 (A from Parent 1) | A | |
| Row 2 (a from Parent 1) | A | |
| 4. Read outcomes | AB combinations: AA, Aa, aA, aa | |
| 5. Count phenotypes | Dominant (brown) = 3/4, Recessive (blue) = 1/4 | |
| Result | Probability of blue‑eyed child = 25 % |
Answer: 25 % chance that the child will have blue eyes.
4. Quick Revision Summary
- Cell: Membrane (selective permeability), nucleus (DNA), mitochondria (energy), ribosomes (protein synthesis).
- DNA: Double helix, genes encode proteins, RNA transcribes DNA.
- Inheritance: Dominant vs recessive alleles; Punnett square predicts genotype ratios.
- Evolution: Natural selection → adaptation → speciation.
- Ecosystem: Producers → consumers → decomposers; energy flows through trophic levels.
- Human body: 7 major systems; each with key organs and functions.
- Biotech: PCR amplifies DNA, cloning produces identical organisms, CRISPR edits genes.
- Health: Vaccines stimulate immunity; microbes cause disease.
- Environment: Biodiversity protects ecosystem services; pollution and climate change threaten it.
Quick Flashcard Style
| Concept | Question | Answer |
|---|---|---|
| Cell membrane | What enables selective transport? | Phospholipid bilayer + proteins |
| Dominant allele | What happens when a dominant allele is present? | Phenotype shows dominant trait |
| Ecosystem | What are abiotic factors? | Non‑living parts like temperature, light |
| CRISPR | What is it used for? | Precise gene editing |
| Vaccination | How does it protect? | Stimulates immune memory |
Use this table to test yourself before the exam. Good luck!