So far we have seen that cells work together to form tissues. Tissues in turn work together forming organs, which themselves work together on important jobs, forming organ systems. What do you think comes next?

Organisms

An organism is a completely self-sufficient lifeform. You are an organism. All of your cells, tissues, organs and organ systems come together to keep you alive. An organism cannot live without its organ systems. Remove the circulatory system from a frog, and what do you think will happen? Without the ability to move blood throughout its body, the frog will die.

Likewise, an organ system cannot live without its fellow organs nor can an organ survive without its tissues and cells. From the smallest cells to the complete organism, everything has a job to do and a role to play.