What does an organism refer to in biological terms?

In biological terms, an organism refers to a single living entity, which can be a plant, animal, fungus, or microorganism. Organisms are characterized by their ability to grow, reproduce, respond to stimuli, and maintain homeostasis. They are the fundamental units of life, made up of cells that perform various functions necessary for survival.

This definition emphasizes the individuality of an organism, whether it exists as a unicellular entity, like bacteria, or as a multicellular one, like humans. Each organism operates as a coherent whole, distinct from other living beings and from non-living systems.

The other options do not accurately capture the essence of what an organism is. A non-living system does not possess the characteristics that define life, including metabolism and reproduction. A group of organisms refers to populations or communities, which are collections of individuals rather than a single entity. A hypothetical construct typically pertains to theoretical frameworks or models that are not tangible entities. Thus, the true essence of an organism is encapsulated in its definition as a single living entity.