The Levels of Organization

There are five levels of life: cells, tissue, organs, organ systems and organisms


The cell is the basic unit of structure and function of a living thing.

Example 1: single celled organisms, bacteria

Example 2: white blood cells

Example 3: plant cells


Tissues are made of a group of similar cells that work together to do a specific job in the body.

Example 1: muscle tissue

Example 2: scar tissue

Example 3: Connective tissue


Organs are made up of two or more tissues that work together to do a specific job.

Example 1: the heart

Example 2: the liver

Example 3: the brain

Organ Systems:

An organ system is a group of organs working together to perform particular jobs.

Example 1: the respiratory system

Example 2: the digestive system

Example 3: the nervous system  


Sum of all cells, tissues, organs and organ systems makes an organism. An organisms is made when a group of organ systems work together.

Example 1: flowers

Example 2: people

Example 3: animals


    All of the systems work together to create life. The cells are what the organs are made of, without them there would be no organs and without organs there would be no organ systems. If any one of these systems were missing the entire organism would not work.