What are tissues composed of?

Tissues are defined as groups of cells that share a similar structure and function, working together to perform specific activities within an organism. This definition highlights the importance of cellular organization in biological systems, where similar types of cells come together to form a functional unit. For example, muscle tissue is composed of muscle cells that contract to facilitate movement, while epithelial tissue consists of tightly packed cells that form protective barriers.

The key to understanding the composition of tissues lies in the idea of specialization; cells within a tissue type typically have similar characteristics and perform complementary roles. This allows for efficiency and specialization within multicellular organisms, where various tissues work collaboratively to support the organism as a whole.

The other options do not reflect the precise definition of what constitutes a tissue, as they either imply a lack of organization or include a mixture of unrelated cell types, which is not representative of how tissues are structured in biological systems.