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Food
Web
In most ecosystems, many complex levels exist between producers and consumers. A food
web is a network of exchanges that occur in a food chain.
A food chain is the process through which nutrients pass from producers
(green plants) to primary consumer (herbivore) to secondary consumer (predator
on herbivore) to tertiary consumer (predator on predator).
>> For
an animated example of a food chain, click here.
(Requires Quicktime
player, available here)
Plants are primary producers in a food chain because they supply food
to many other organisms. It takes an enormous number of individual plants
to support the other parts of a food chain.
At the next level of a food chain are primary consumers, which are plant-eating
animals or herbivores. Examples of primary consumers are rabbits, mice,
deer, and certain other mammals, some insects and fish, dabbling ducks and geese.
Primary consumers are eaten by secondary consumers, or carnivores (meat-eaters). This
group includes predators such as birds of prey, snakes, foxes, wild cats, and
people.
Secondary consumers are eaten by tertiary consumers, which may be predators
or scavengers such as turkey vultures, opossums, and sometimes people.
Any of the food web components mentioned above can be broken down by decomposers,
organisms such as bacteria and fungi that reduce dead plant or animal matter
into smaller particles. A decaying plant, for example, will be broken down
into nutrients that enrich the soil. This process supports the growth of
more plants.
Food webs and food chains are simplified ways for understanding the relationships
between organisms. Note that these categories are very broad and general. Many
animals fit into more than one group. Also, energy and matter do not usually
follow such a simple pathway. |
