An organism describes an individual. You are an organism. I am an organism. The mosquito that flies by your window is an organism. An organism is a single, living thing and can be an animal, a plant, or a fungus. Organisms grow and respond to their environment.
A population is the term we use to describe multiple individuals or organisms of a single species that live within a particular geographic area. For example, there may be one population of painted turtles in one state and another population of painted turtles 250 miles away in another state.
