A food web is made up of interconnected food chains. The arrows point from a member of the food web to another member of the food web that the first one eats. Humans are at the top of the food web, as they consume other organisms, but are not comsumed themselves, except by detritus. All organisms eventually revert to detritus , so the food chain does not only work in one direction, top to bottom. It has a circular quality, as well.
Plants have special adaptations for producing food.
One of these adaptations is a chemical called chlorophyll. Chlorophyll gives plants a green color. Marine and aquatic plants have other chemicals which also help them produce food. They have these other chemicals because they live underwater and do not receive as much sunlight as land plants. Animals have special adaptations which help them to hunt their food.