A food web represents feeding relationships among organisms. It combines several food chains and helps show that an ecosystem contains connected pathways. A change in one population can affect others, but the effect is not always simple or immediate. Producers use an energy source, commonly sunlight, to build organic matter. Consumers obtain energy by eating other organisms. Decomposers break down dead material and help return nutrients to the environment. In a common diagram convention, arrows point from the food source toward the organism receiving energy. Energy flows through an ecosystem and some is dispersed as heat during transfers. Nutrients cycle through living and non-living parts of the environment. Do not confuse these two patterns. Real organisms may change diet with age, season, or availability, which makes a web a simplified model. Practice: Draw a five-organism food web from a familiar habitat. Label the arrow convention and identify one relationship you would need to verify.