How can an ecosystem support a variety of organisms in a rainforest

I'm not sure what kind of answer you're looking for, but due to the great amount of sunlight, there's lots of energy in rainforests. That energy is stored in plant vegetation, which gets eaten by animals. The canopy of the rainforest also provides many places for animals to live and plants to grow. It also provides interactions between species. For example, there are some plants in the canopy called bromeliads. Frogs and some other animals use these for hunting & laying their eggs.