One cell does it all. Breath, Eat, Excrete, Grow and Reproduce. One cell. Smaller than anything we can see unaided.
I assume you meant single "celled" organism. It is an organism (life form) that consists of only a sigle cell as opposed to most all other lifeforms on earth which are comprised of many (billions) of cells.
Any single celled organism carries out the functions of life, but, if considered living, a virus is much smaller than a cell. However, viruses are only DNA and can do little except control a cell with their DNA. They do not eat, or control their own movement, nor can they reproduce without a host.
The statement which best compares a multicellular organism to a single-celled organism is their functions. While multicellular organisms use organ systems to perform life functions, single-celled organisms do not use organs for the life functions.
Organelle
The life span of a Multicellular organism is not limited to the life of a single cell.
what is a single celled organism that can carry on all its life
The meaning of it is when you do not have a equal sign
A cell. Cells are the basic unit of life. Unicellular organisms can perform life tasks on its own, and they are one cell. Multicellular organisims have more than one cell (you and I), and can also perform life tasks.
A unicellular organism is made of only one cell, exists alone and performs all cell functions alone. Some examples include an Amoeba, Euglena, Paramecium
Unicellular are the organisms which are made of single cell. The single perform all the necessary vital functions of life. Mostly unicellular organisms are prokaryotes such as bacteria, but some are eukaryotes like fungi, and protozoans.
Many one-celled organisms perform all their life functions by themselves. Cells in a many-celled organism, however, do not work alone. Each cell carries on it's own life functions while depending in some way on other cells in the organism.
A unicellular organism is a life form consisting of a single cell.