The Fundamental Unit of Life

01 What Is The Living Being Made Up Of?

All organisms are made of tiny building blocks which are known as cells.
In fact, the cell is the basic structural and functional unit of living organisms.
However, cells are invisible to the naked eye.
Organisms that contain only one cell are thus, invisible to humans.
They are known as unicellular organisms.
But some organisms are made up of many cells and are known as multicellular organisms that can be easily spotted like birds, trees and human beings.
Also, it is the lowest level of organization that is alive.
The term cell was derived by Robert Hooke from a Latin word which means ‘little room’.
The size and shape of cells are related to the specific function they perform.
So some cell like Amoeba change their shape quite frequently while in most of the other cases, the cell shape is more or less fixed.

Discovery of Cell:

Robert Hooke, an English natural philosopher discovered cells in 1665.
It is derived Latin word which means small room.
He saw that the cork resembled the structure of honeycomb consisting of many little compartments.
All living forms on earth are composed of one or many cells that perform individual functions.

Types of Organisms:

A wide variety of living beings inhabit the earth.
Among these, the unicellular organisms require microscope to be identified.
However, many organisms are yet to be discovered and a lot more are going extinct.
The tiny organisms composed of only a single cell and hence are aptly named unicellular organisms.
On the other hand, organisms are made of more than one cell are called multicellular.
They represent only a tiny fraction of life on Earth.
For example, most plants, animals, and fungi that is visible to us.
The various cells in a multicellular organism are integrated and independent to various degrees.
Cellular specialization and division of labor are responsible for development of multicellular organisms.
These cells become efficient in one process and are dependent upon other cells for the necessities of life.
In that way, multiple cells work together in coordination and keep an organism alive and in as perfect condition as possible for their survival.

Differences between unicellular and multicellular organisms:

Unicellular organisms	Multicellular organisms
Organisms that consist of a single cell are called single celled organisms or unicellular organisms.	Organisms that consist of large number of cells are called multicellular organisms.
A single cell performs all the activities in a unicellular organism.	Different cells perform different activities in a multicellular organism.
As a single cell performs all life activities, there is no division of labour.	As cells are specialized to perform different functions of the body, there is a division of labour within cells.
Reproduction consumes a single cell.	Only some cells of the body called germ cells take part in reproduction whereas other cells (somatic cells) remain intact.
The life span of a unicellular individual is short.	The life span of a multicellular individual is long.