Levels of Organization

Cells

Specialized cells to carry out specific functions. Organisms can also be unicellular, meaning there is no cell specialization. Example - epithelial cells, muscle cells, nerve cells, fat cells.

Tissues

Group of cells that are similar in shape and function. Example- the skin that covers the outside surfaces of your body is epithelial tissue.

Organs

Tissues that are organized into larger structures that have one function. Example- heart pumps blood through your body.

Organ Systems

Group of organs that have related functions. Example- Circulatory system includes the heart, arteries, capillaries, veins.

Organisms

An individual animal, plant, or single-celled form. Organisms can be unicellular or multicellular.