The Levels of Organization
The cell is the basic unit of structure and function of a living thing. Cells are specialized by size and shape for the job they do. Examples are single celled organisms, uni cells, and cells of multi cellular organisms.
Tissue are made of a group of similar cells that work together to do a specific job in the body. Examples are 4 different types of animal tissues are epithelial, muscle, nervous, and connective.
Organs are made up of two or more tissues that work together to do a specific job.
An organ system is a group of organs working together to perform particular jobs.
Sum of all cells, tissues, organs, and organ system makes an organism. An organism is made when a group of organ systems work together.