What is a food web? A
food web (or
food cycle) depicts feeding connections (what eats what) in an
ecological community and hence is also referred to as a
consumer-resource system. Ecologists can broadly lump all life forms into one of two categories called
trophic levels: 1) the
autotrophs, and 2) the
heterotrophs. To
maintain their bodies, grow, develop, and to
reproduce, autotrophs produce
organic matter from
inorganic substances, including both
minerals and
gases such as
carbon dioxide. These
chemical reactions require
energy, which mainly comes from the
sun and largely by
photosynthesis, although a very small amount comes from
hydrothermal vents and
hot springs.
A gradient exists between trophic levels running from complete
autotrophs that obtain their sole source of carbon from the atmosphere,
to
mixotrophs (such as
carnivorous plants) that are autotrophic organisms that partially obtain organic matter from sources other than the atmosphere, and complete
heterotrophs
that must feed to obtain organic matter. The linkages in a food web
illustrate the feeding pathways, such as where heterotrophs obtain
organic matter by feeding on autotrophs and other heterotrophs. The food
web is a simplified illustration of the various methods of feeding that
links an ecosystem into a unified system of exchange. There are
different kinds of feeding relations that can be roughly divided into
herbivor
