FUNDAMENTAL UNIT OF LIFE

📘 Chapter 2: Cell – Structure and Functions
(Detailed Notes)

🔬 1. What is a Cell?
 A cell is the smallest unit of life that can perform all vital functions.
 It is called the structural and functional unit of living organisms.
 Just like bricks build a house, cells build the body of living organisms.




🌍 2. Types of Organisms Based on Cells
🦠 Unicellular Organisms

 Made up of only one cell
 That single cell performs all life functions
 Examples:
o Amoeba
o Paramecium
o Bacteria




🧍 Multicellular Organisms

 Made up of many cells
 Cells are specialized for different functions
 Examples:
o Humans
o Animals
o Plants




🧪 3. Discovery of Cell
 The cell was discovered by Robert Hooke in 1665.
o He observed a thin slice of cork using a microscope.
o He saw small empty box-like structures.
o He named them “cells” (meaning small rooms).

,  Later, Antonie van Leeuwenhoek:
o Improved the microscope.
o First observed living cells in pond water.
o Saw bacteria and protozoa.




🧬 4. Cell Theory
Proposed by:

 Matthias Schleiden (plants)
 Theodor Schwann (animals)

📌 Main Points:

1. All living organisms are made up of cells.
2. Cell is the basic unit of life.



➕ Later Addition:

 Rudolf Virchow
o Proposed that:
👉 “All cells arise from pre-existing cells”




🔍 5. Number, Shape and Size of Cells


🔢 (A) Number of Cells

 Unicellular → 1 cell
 Multicellular → billions of cells

Example:

 Human body has trillions of cells