Final answer:
A single-species group of individuals in an area is a population, while a community is comprised of multiple populations of different species interacting together. These biotic elements, along with abiotic environmental factors, constitute an ecosystem.
Step-by-step explanation:
All individuals of all species living within an area of interest represent a community. However, when referring only to individuals of a single species within a specific area, this is known as a population. A population includes all the individual organisms of the same species that live and interact in the same area, such as a population of angelfish in a specific part of the ocean. When multiple populations of different species coexist and interact in the same area, like pine trees, flowering plants, insects, and microbial populations in a forest, they form a community. Furthermore, an ecosystem encompasses all the living things, or biotic factors, in an area along with the abiotic, nonliving parts of that environment, such as nitrogen in the soil or rainwater.