The phrase 'organ system' is best defined as:

• A. A living thing
• B. A single organ
• C. A group of organs working together to perform a function
• D. A collection of cells

Answer: (C)

An organ system is a set of different organs that work together to carry out a broad function for the organism. That coordination is what makes an organ system different from a single organ or just a bunch of cells. For example, the digestive system includes the stomach, intestines, liver, and pancreas, all collaborating to break down food and absorb nutrients. A living thing is the whole organism, not the system itself, and a single organ is only one part of a system. A collection of cells forms tissues and organs, but it’s the teamwork of multiple organs that defines an organ system.