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Boys & Girls; Do you know what is a "Food Chain" ?
A food chain is a linear
sequence of links in a food web starting from a trophic species that eats no other species in the
web and ends at a trophic species that is eaten by no other species in the web.
A food chain differs from a food web, because the complex polyphagous network of feeding relations are
aggregated into trophic species and the chain only follows linear monophagous pathways. A common metric used to
quantify food web trophic structure is food chain length. In its simplest form,
the length of a chain is the number of links between a trophic consumer and the
base of the web and the mean chain length of an entire web is the arithmetic
average of the lengths of all chains in a food web.
The food chain length is a continuous variable
that provides a measure of the passage of energy and an index of ecological structure
that increases in value counting progressively through the linkages in a linear
fashion from the lowest to the highest trophic (feeding) levels. Food chains are often
used in ecological modeling (such as a three species food chain). They are
simplified abstractions of real food webs, but complex in their dynamics and
mathematical implications. Ecologists have formulated
and tested hypotheses regarding the nature of ecological patterns associated
with food chain length, such as increasing length increasing with ecosystem
size, reduction of energy at each successive level, or the proposition that
long food chain lengths are unstable. Food chain studies have had an important
role in ecotoxicology studies
tracing the pathways and biomagnification of environmental
contaminants. Food chain vary in length from three to six or more
levels. A food chain consisting of a flower, a frog, a snake and an owl
consists of four levels; whereas a food chain consisting of grass, a
grasshopper, a rat, a snake and finally a hawk consists of five levels. Producers, such as plants, are organisms that
utilize solar energy or heat energy to synthesise starch. All food chains must
start with a producer. Consumers
are organisms that eat other organisms. All organisms in a food chain, except
the first organism, are consumers.
* Please click on the link below (for National Geographic Kids) for Flash Movie and Quiz about "Food Chain" http://magma.nationalgeographic.com/ngexplorer/0309/quickflicks/
Another short movie on "Food Chain"
