Final answer:
Omnivores obtain energy from primary producers, such as plants, that capture sunlight through photosynthesis and gain energy. Herbivores eat these plants and carnivores eat the herbivores, contributing to the nutrient pool through decomposition.
Step-by-step explanation:
Omnivores obtain energy from primary producers which can convert light energy by photosynthesis. These primary producers include plants that capture sunlight and gain energy. Herbivores then eat these plants to obtain energy, and carnivores eat the herbivores. Eventually, decomposition of plant and animal material contributes to the nutrient pool.