Question

Difference between unicellular and multicellular.

Answer 1

Unicellular organisms are made up of only one cell Example: Bacteria, paramecium, yeast etc.Multicellular organisms are made up of numerous cells Example: Plants, Animals etc. Multicellular organisms have three types of cell: undifferentiated (stem cells), differentiated and dedifferentiated cells.

Complete answer:

Unicellular organism	Multicellular organism
The body is composed of only one single cell.	Body is composed of many cells.
A single cell carries out all the life activities.	Different cells are specialized for various life activities.
A cell body can’t attain a large size.	Many celled bodies can attain large size by increasing the number of cells.
Have a short lifespan.	Have a long life span.
They have remarkable power of regeneration.	Have lesser power of regeneration.
They have simple body organization.	They have complex body organization.
They include both prokaryotes and eukaryotes Example: Bacteria, paramecium, yeast etc.	They include only eukaryotes Example: human, animals, plants, birds etc.
Injury leads to the death of an organism.	Injury does not cause death.
They have an irregular body shape.	They have definite body shapes.
They reproduce asexually.	They reproduce by asexual method.
They are too small to be seen by naked eyes.	They can be seen by naked eye.
Mostly they are heterotrophic.	They are autotrophic and heterotrophic.
Their body is exposed to the environment from all sides.	Their body is not exposed to the environment.
They have no distinct cell organs, as only a single cell is responsible to carry all life processes.	They have distinct and specialized organs to carry out specific functions.

Note: Unicellular organisms have unique characteristics to survive in extreme environmental conditions. For example some archaebacteria can live in hot springs, thermal oceans, Polar Regions as they have specialized cell membranes. In multicellular organisms, the division of labor is perfectly carried out by specialized organs.