(ecology) A graphical model showing the interconnecting food chains in an ecological community
A food web is a graphical model depicting the many food chains linked together to show the feeding relationships of organisms in an ecosystem. It differs from a food chain in a way that the latter is a linear system showing a succession of organisms whereby each species is eaten in turn by another species. Food web is a more complex network of what-eats-what in a particular ecosystem. The position that an organism occupies in a food chain or food web is called the trophic level. The two main categories of trophic levels are the autotrophs and the heterotrophs. The autotrophs are those organisms that are capable of producing organic matter from inorganic materials, e.g. carbon dioxide, and utilizing energy, e.g. light energy from the sun. Photosynthetic organisms such as plants are an example of an autotroph. In a food chain, they are also referred to as the producers. The heterotrophs are those organisms that rely on other organisms to obtain organic matter because they lack the ability as that in autotrophs. The heterotrophs feed on organisms for nourishment. They include the herbivores, carnivores or predators, and omnivores. Nevertheless, there are autotrophs that feed on other organisms to partially obtain organic matter directly from other organisms, such as carnivorous plants. They are called mixotrophs. Other feeding relations in a food web include scavenging and parasitism.