Class 9 Biology – The Fundamental Unit of Life (Easy Notes + Important Points + Q&A)

Class 9 Biology – The Fundamental Unit of Life
1. Cell – The Basic Unit of Life
A cell is the basic structural and functional unit of life.

All living organisms are made up of one or more cells. Cells perform all the essential functions
required for life.

Examples:

 Amoeba consists of a single cell.
 Human beings consist of billions of cells.




2. Discovery of Cell
 In 1665, Robert Hooke observed cork under a microscope and discovered cells.
 In 1674, Antonie van Leeuwenhoek observed living cells for the first time.




3. Cell Theory
Cell theory was proposed by Matthias Schleiden and Theodor Schwann.

Main Points:

 All living organisms are made up of cells.
 The cell is the basic unit of life.
 New cells arise from pre-existing cells.




4. Types of Organisms
(a) Unicellular Organisms

Organisms made up of only one cell.

Examples:

,  Amoeba
 Paramecium
 Bacteria

(b) Multicellular Organisms

Organisms made up of many cells.

Examples:

 Human beings
 Plants
 Animals




5. Shape and Size of Cells
Cells vary in shape and size according to their functions.

Examples:

 Nerve cell – long and branched
 Red blood cell – disc-shaped
 Muscle cell – elongated




6. Cell Structure
The main parts of a cell are:

(a) Cell Membrane

The cell membrane is the outer covering of the cell.

Functions:

 Protects the cell
 Controls the movement of substances in and out of the cell



(b) Cell Wall