What term describes a collection of tissues working together to perform a specific function?

The correct term that describes a collection of tissues working together to perform a specific function is "organ." An organ is made up of two or more types of tissues that coordinate their activities to fulfill particular roles in the body. For instance, the heart is an organ composed of muscle tissue, connective tissue, and nerve tissue, all of which work in concert to pump blood throughout the circulatory system.

In contrast, "tissue" refers to a group of similar cells that perform a specific function, but it does not encompass the collective functioning of multiple tissue types. "Cell" is the basic unit of life and represents the smallest structural and functional unit of an organism, but it is not a group of tissues. "System" refers to a group of organs that work together for a broader function in the body, like the digestive system or respiratory system, but it implies a hierarchy above the organ, rather than focusing on the level of organization that the term "organ" encompasses.