Final answer:
A collection of populations interacting with one another forms a community, which is the sum of all species living and interacting in a particular area. A community is integral to natural selection and evolution due to various relationships like symbiosis, predation, and competition.
Step-by-step explanation:
A collection of populations interacting with one another forms a community. In biological terms, a community includes all the populations of different species living and interacting in a given area. This interaction forms a complex web of relationships that are critical for natural selection and evolution.
Three crucial types of relationships found within a community are symbiosis, predation, and competition, shaping how species evolve over time. For example, in a forest, we may find a population of pine trees. Together with populations of flowering plants, insects, and microbes, they are part of the forest's community. However, an ecosystem consists not only of these biological communities but also the abiotic factors, such as soil and water, that interact with the living components.