Explain why all organisms in the food web are directly or indirectly dependent on the sun for energy?

The primary producers of the food web are plants. Algae, ferns, etc ... All require energy from the sun. Now up the next level is plant eaters and omnivores. Next up the ladder are the carnivores and omnivores. The energy transfer. Works from the sun, to the plants, to the animals to the other animals, to finally decomposes.