What is an organism?

An organism is defined as a living entity that can function independently and possesses characteristics of life. These characteristics typically include the ability to grow, reproduce, respond to stimuli, adapt to the environment, and maintain homeostasis. Organisms can range from single-celled bacteria to complex multicellular organisms such as plants and animals, all sharing these fundamental traits that allow them to survive and thrive in their respective environments.

The other options describe different concepts. The first option refers to non-living entities, which do not possess the attributes necessary for defining life. The third option speaks about a group of cells, but does not encompass the functional independence and life characteristics that qualify an organism. Finally, the fourth option describes ecological community structures, which involve multiple species and are not focused on the individual organism level. Thus, the specificity of the definition in the correct answer is what makes it the appropriate choice.