Biology Basics – J&K PSC (General Awareness & Current Affairs)
Purpose:
To provide a concise, exam‑friendly overview of the fundamentals of biology that will help you quickly grasp key concepts and remember them during the PSC exam.
1. Simple Explanation
Biology is the science of life – it studies living organisms, their structure, function, growth, origin, evolution, and distribution. It combines observations, experiments, and theory to explain how life works, from single cells to entire ecosystems.
Key Takeaway:
Biology seeks to answer what life is, how it functions, why it changes, and how it interacts with its environment.
2. Key Points
| # | Concept | Main Idea | Why It Matters |
|---|---|---|---|
| 1 | Definition of Life | - Metabolism - Growth & Development - Reproduction - Response to stimuli - Homeostasis |
Sets the criteria for distinguishing living from non‑living. |
| 2 | Levels of Biological Organization | 1. Atom → 2. Molecule → 3. Cell → 4. Tissue → 5. Organ → 6. Organ system → 7. Organism → 8. Population → 9. Community → 10. Ecosystem → 11. Biosphere | Provides a framework for studying biology from micro to macro scales. |
| 3 | Cell Theory | 1. All living organisms are composed of cells. 2. Cells are the basic units of life. 3. All cells arise from pre‑existing cells. |
Foundation for cellular biology, genetics, and medicine. |
| 4 | Cell Types | - Prokaryotic: Bacteria & Archaea (no nucleus, simple). - Eukaryotic: Plants, animals, fungi, protists (nucleus, organelles). |
Distinguishes major life forms and their cellular machinery. |
| 5 | Key Cell Organelles | Nucleus, mitochondria, chloroplasts, ribosomes, endoplasmic reticulum, Golgi, lysosomes, vacuoles, cytoskeleton. | Explain specific functions: energy, protein synthesis, transport, waste disposal. |
| 6 | DNA & RNA | DNA holds genetic info; RNA transcribes & translates it. | Basis for heredity, protein synthesis, and genetic disorders. |
| 7 | Gene & Inheritance | Genes (DNA segments) control traits. Inheritance follows Mendelian laws (dominant/recessive, segregation, independent assortment). | Explains familial traits, disease patterns, breeding. |
| 8 | Evolution & Natural Selection | Organisms change over generations; natural selection favours advantageous traits. | Explains biodiversity, adaptation, speciation. |
| 9 | Taxonomy & Classification | 1. Domain → 2. Kingdom → 3. Phylum → 4. Class → 5. Order → 6. Family → 7. Genus → 8. Species. | Organizes life into a hierarchical system; useful for identification. |
| 10 | Ecology Basics | - Biotic & Abiotic factors. - Energy flow (food chains, webs). - Nutrient cycles (carbon, nitrogen, water, phosphorus). |
Highlights interdependence of organisms and environment. |
| 11 | Human Impact | Pollution, deforestation, climate change, invasive species. | Emphasises conservation and sustainable practices. |
3. Worked Example
Problem:
A farmer notices that a particular variety of wheat is producing taller grains but smaller kernels compared to a conventional variety. Explain the possible genetic and environmental factors involved and predict the outcome if this variety is cross‑bred with the conventional variety.
Step‑by‑Step Solution
| Step | Explanation |
|---|---|
| 1. Identify the traits | Height (tall) and kernel size (small). |
| 2. Determine if traits are heritable | Both traits are quantitative (polygenic) and influenced by environmental conditions (soil, water). |
| 3. Apply Mendelian genetics | Although polygenic, we can treat each trait as a separate locus. Assume T = tall allele, t = standard; K = small kernel allele, k = standard. |
| 4. Predict cross‑breeding outcome | Cross TtKk (tall, small) with ttkk (standard). The progeny will show: • Height: 50 % tall (Tt) & 50 % standard (tt). • Kernel size: 50 % small (Kk) & 50 % standard (kk). |
| 5. Environmental influence | If the farmer cultivates under similar conditions, the proportion of tall & small kernels will follow the genetic ratios. Under poorer soil, the expression of height may be suppressed, leading to more standard heights. |
| 6. Practical implication | Breeding programs should select for T and K together, or use marker‑assisted selection to combine tallness with desirable kernel size. |
Key Takeaway:
Genetic traits are inherited according to Mendelian principles, but environmental factors can modulate phenotypic expression.
4. Quick Revision Summary
| Topic | Quick Points |
|---|---|
| Life Criteria | Metabolism, growth, reproduction, response, homeostasis |
| Organization | 11 levels from atoms to biosphere |
| Cell Theory | Cells = life units; all cells from pre‑existing cells |
| Cell Types | Prokaryotic vs. Eukaryotic |
| Organelles | Nucleus, mitochondria, chloroplasts, ribosomes, ER, Golgi, lysosomes, vacuoles, cytoskeleton |
| DNA/RNA | Genetic code, transcription, translation |
| Inheritance | Genes, dominant/recessive, Mendelian laws |
| Evolution | Natural selection, adaptation, speciation |
| Taxonomy | Domain → Kingdom → Phylum → Class → Order → Family → Genus → Species |
| Ecology | Biotic/abiotic, food webs, nutrient cycles |
| **Conservation |