Introduction to Cells
📘 What is a Cell?
- A cell is the smallest structural and functional unit of life.
- All living organisms — from the tiniest bacteria 🦠 to the largest whale 🐋 — are made up of cells.
- The study of cells is called Cytology.
🧪 Discovery of Cells
- The word “cell” was first used by Robert Hooke in 1665.
- He observed thin slices of cork under a self-made microscope and saw small box-like structures, which he called cells.
- These were actually dead cells (just the cell walls).
🗨️ Fun Fact: The cork cells Hooke observed looked like the rooms (called “cells”) of a monastery!
👨🔬 Cell Theory
Introduced by Schleiden and Schwann and later expanded by Rudolf Virchow.
- All living organisms are made of cells.
- The cell is the basic unit of structure and function in living organisms.
- All cells arise from pre-existing cells (Omnis cellula e cellula – Virchow).
🧬 Organisms Based on Number of Cells
| Type of Organism | Description | Examples |
|---|---|---|
| Unicellular | Organism made of a single cell | Amoeba, Bacteria, Paramecium |
| Multicellular | Organism made of many cells | Humans, Trees, Fish, Birds |
🔍 In multicellular organisms, cells perform specialized functions (like muscle cells, nerve cells, blood cells, etc.)
📝 Quick Recap
- Cell = Basic unit of life
- Robert Hooke discovered cells in 1665
- Unicellular = 1 cell | Multicellular = Many cells
- Cell theory explains cell as the fundamental unit of life
🧠 Think & Explore
- 👉 If all organisms are made up of cells, why are they so different in size and shape?
- 👉 Can a single cell perform all functions in a living being?