Which of the following best defines a system in biological terms?

A system in biological terms is best defined as a group of organs that work together to perform a specific function or set of functions within an organism. This concept is fundamental to understanding the organization of living organisms, which are structured in a hierarchical manner.

In biological systems, organs are composed of different types of tissues that collaborate to accomplish particular tasks. For instance, the digestive system includes organs such as the stomach, intestines, and liver, which all interact to break down food and absorb nutrients. This coordinated function exemplifies how multiple components come together to operate as a system, highlighting the intricacy and interconnectivity of biological processes.

The other options refer to more specific components of biological organization. A group of similar cells defines a tissue, while a single type of tissue is an even narrower concept. A molecular structure pertains to the molecular level of biology, dealing with the composition and arrangement of molecules within cells and tissues. However, these definitions do not capture the broader collaborative function of multiple organs that characterize a biological system.