How can patterns of interactions between organisms be similar in different
ecosystems?

Although the species involved in relationships (e.g., competition, predation, mutualism, commensalism, parasitism) vary across ecosystems, the patterns of interactions of organisms with their environments, both living and nonliving, are shared.

Individual organisms live together in an ecosystem and depend on one another. ... Some organisms can make their own food, and other organisms have to get their food by eating other organisms. An organism that must obtain their nutrients by eating (consuming) other organisms is called a consumer, or a heterotroph.

Hope it helps  

Have a great Day : P