Why is the sun so important for life on earth?
The laws of thermodynamics ensure that everything goes from order to disorder. 90% of the energy at any tropic level is used by the organisms at that tropic level. Without the sun providing new sources of energy life would quickly run out of energy and all living things would die.
The sun is the source of energy for almost all producers. ( examples such as organisms in deep sea volcanic vents are rare)
The producers are able to absorb the energy from sunlight and convert the energy into organic compounds. The organic compounds are then used by the plants producers for metabolism.
Consumers get their energy for metabolism from the organic compounds produced by plants. Without the sun the plants would not produce the organic compound the Consumers need for life.
Without the sun there would not be enough energy for life to exist.