What is a tissue?

A tissue is defined as a group of similar cells that work together to perform a specific function. This fundamental concept forms the basis of biological organization within multicellular organisms. Tissues are essential because they allow for specialization; different types of tissues can carry out distinct roles that contribute to the overall operation and maintenance of the organism.

For instance, muscle tissue consists of muscle cells that enable movement, while epithelial tissue forms protective layers and facilitates absorption and secretion. This classification into tissues is a key concept in understanding how biological systems are structured and function, which is essential knowledge for studying biology at the GCSE level.

While groups of organs working together form systems and can perform complex functions, that description pertains to a higher level of biological organization than what is defined as a tissue. Similarly, the mention of stem cells and organs, as seen in other choices, relates to different biological concepts that do not accurately capture the essence of what a tissue is.