What term describes a collection of similar cells grouped together for a specific function?

The term that describes a collection of similar cells grouped together for a specific function is "tissue." Tissues are fundamental to the structure and function of organisms, as they consist of cells that share common characteristics and work together to perform specific tasks. For instance, muscle tissue comprises muscle cells that are organized to facilitate contraction and movement.

In contrast, other terms in the context of an organism's biological organization serve different purposes. An organ is made up of various types of tissues that work together to perform more complex functions, such as the heart or liver. A system refers to a group of organs that work together in more complex biological functions, for example, the cardiovascular system. Structure generally refers to the physical arrangement of different biological components, but it does not denote the functional relationship established by a collection of similar cells, which is the defining characteristic of tissue.

This understanding is pivotal in biology and medicine, as it links cellular makeup with the physiological functions that sustain life.