What is an organ?

An organ is defined as a structure composed of specialized tissues that work together to perform specific functions vital to an organism's survival and health. This concept encompasses a variety of organs in the body, such as the heart, lungs, and liver, each made up of different types of tissues that contribute to its unique role.

In the context of the body’s organization, cells form tissues, which in turn combine to form organs. This hierarchy of biological organization—with cells, tissues, organs, and systems—demonstrates how complex functions are carried out.

Understanding this definition is crucial, as it highlights the intricate relationships between different biological components, explaining why options describing mere collections of cells or types of tissue do not fully capture the essence of what an organ is. An organ cannot simply be a collection of similar cells or be classified solely as a basic tissue or molecule; it embodies a more complex structure with specific roles essential for survival.