Step-by-step explanation:
Plants and animals need to coexist in order to thrive. Plants need animals just as much as animals need plants. A simple example of this would be trees. Trees provide many things to many different organisms but I will use shelter as an example. Trees provide shelter to many animals such as birds, so in essence they protect birds. Birds eat plants and in turn spread the seeds which grow. Insects, like bees, collect pollen from the flowers, etc. It is all part of a complex system in which species all depend on one another for some specific reason. So, interdependence is when plants and animals depend on each other for survival.
In general, the interdependency of organisms extends ecologically to their environment. Organisms rely on each other to sustain the ecological environment, something that humans have been lacking in. So, in general, organisms are interdependent because they have no choice.