What is the term for a group of cells that work together to perform a specific function?

The term for a group of cells that work together to perform a specific function is tissue. In biological terms, tissues are formed when similar cells cluster together to achieve a common goal, such as contracting to facilitate movement in muscle tissue or forming protective layers in epithelial tissue. Tissues are classified into different types based on their structure and function, including connective tissue, muscle tissue, nervous tissue, and epithelial tissue.

The other options represent different levels of biological organization. A single cell is the basic unit of life, but it does not constitute a group. An organ is made up of multiple types of tissues working together to carry out specific functions, such as the heart or lungs. A system consists of various organs that collaborate to perform broader functions essential for the organism's survival, such as the digestive or circulatory system. Therefore, the most precise term for a group of cells performing a specific function is tissue.