different organisms interact to make up a community by working together to survive. mutualism is when both benefit, commensalism is where one benefits one isn't harmed , a parasitism is where one is benefiting and one is harmed. these 3 things are all used in making up a community and helping the organisms that live there survive.
a community is a group of organisms living in the same place or having a particular characteristic in common
an ecosystem is a biological community of interacting organisms and their physical environment.
organisms depend on abiotic factors found in the ecosystem for energy, sometimes food. They depend on biotic factors for food also.