​Recall that a system is a collection of structures that work together to perform a function. Consider the wheelbarrow shown below. Each structure has a shape that helps it to perform its function.



Is this wheelbarrow a system? How?

​Cells as Systems

​An organism is a type of living system. Even the smallest cell consists of smaller parts. Those smaller structures work together to keep the cell alive.

Bacteria and archaea are unicellular. The single cell is a system because it contains many parts that work together to help the cell grow, obtain energy, and reproduce.

Examine this illustration of a bacterium. Note that even this life form, which scientists describe as simple, contains many different structures.


Unicellular organisms are systems because they contain structures that work together to help the cell function.

​How would you feel if you walked into a room that looked like this?

​Organization of Cells in Eukaryotes

​Recall that eukaryotes can be multicellular. Multicellular organisms have many cells. Humans have trillions of cells that work together to help your body function. The cells of multicellular eukaryotes work together in groups called:

• tissues

• organs

• organ systems

​Types of Tissues

​What organs do tissues make up in our bodies?

​From Cell to System

​Examine a Plant System

​Nearly all multicellular eukaryotes are organized into tissues, organs, and organ systems. One major organ system of plants is called the vascular system. The vascular system consists of tubes that carry water, sugar, and nutrients around the plant.

​Cotton Stem Slide

​TED-Ed: How to 3D Print Human Tissue

If you needed an organ transplant, would you accept an organ produced using bioprinting? Why or why not?