Final answer:
In ecosystems where multiple organisms or species coexist, interactions like predation, competition, and symbiosis occur, influencing community dynamics and leading to outcomes such as the competitive exclusion of less adapted species.
Step-by-step explanation:
When many organisms or species live together in an ecosystem, a number of interactions may take place which are crucial in shaping the community's structure and dynamics. These interactions include predation, herbivory, competition for resources, and various forms of symbiosis such as commensalism, mutualism, and parasitism. For instance, if two species occupy the same ecological niche in an area and compete for the same resources, typically one species may become predominant and the other may become locally extinct—a concept known as competitive exclusion.
Community structure can also be influenced by the roles of specific species, categorized as foundation or keystone species, as well as by the process of succession which leads to a stable community over time. The variety of species in a given area, or biodiversity, affects how these interactions play out, with some ecosystems like tropical rainforests having incredibly high diversity, while others, like the glaciers of Antarctica, having less diversity but still a significant variety of life forms.