How are organs defined in biological terms?

In biological terms, organs are defined as structures made up of two or more different types of tissues that work together to perform specific functions. This definition emphasizes the complexity of organs, where each tissue type contributes unique properties and functions that allow the organ to operate effectively as a whole.

For example, in the stomach, you have epithelial tissue that lines the cavity and enables secretion and absorption, muscle tissue that allows for contractions to churn food, and connective tissue that supports and binds all these components together. This collaborative functioning is essential for the organ to fulfill its role within the larger system, such as the digestive system.

Other options, while describing components related to biological organization, do not capture the specific interaction between different tissue types that is foundational to the definition of an organ. A combination of atoms or molecules focuses on the chemical and physical basis of life, while a collection of cells, although vital, does not take into account the specialized arrangement and function of those cells within tissues. Thus, the essence of what distinguishes an organ in biology lies in the collaboration of multiple tissue types working synergistically.