All living things are interconnected through nutrient and energy cycles. The sun provides energy that moves through ecosystems in trophic levels from plants to herbivores to carnivores. Energy enters ecosystems from outside sources like the sun and flows through in a noncyclic manner, requiring constant replenishment. All life forms depend on the same planet for basic needs like air, heat, water, and habitat, demonstrating how interconnected all organisms are through the natural cycles that sustain life.