In the context of biology, what is a 'tissue'?

A 'tissue' in biology is defined as a group of similar cells that work together to perform a specific function. This definition highlights the importance of both the similarity of the cells and their cooperative role in achieving a particular task within an organism. Different types of tissues are specialized for various functions, such as muscle tissue, which contracts to facilitate movement, or nervous tissue, which transmits signals throughout the body. This organization allows for greater efficiency and specialization within multicellular organisms. In contrast, the other choices describe concepts that do not align with the definition of a tissue: unrelated cells do not function in a coordinated way; a collection of organs refers to an even higher level of organization known as an organ system; and a type of microorganism does not pertain to tissues at all.