Living Environment Translated Arabic 2014 | Page 80

 A food web is a model that shows the complex network of
feeding relationships within an ecosystem.
 A energy pyramid is a diagram that compares energy used
by producers, primary consumers, secondary consumers,
and tertiary consumers.
o Tropic levels are the levels of nourishment in an
area.
o Producers are the largest energy level in an energy
pyramid.
o Primary consumers are herbivores because they are
the first consumer above the producer level.
o Secondary consumers are carnivores that eat
herbivores.
o Tertiary consumers are carnivores that eat other
secondary consumers.
 The amount of available energy decreases from the base to
the top of the energy pyramid.
 Generalists are consumers that have a varying diet.
 Specialists are consumers that eat only one specific
organism or feeds on a very small number of organisms.
 Symbiosis is any close relationship between species.
o Mutualism is a symbiotic relationship in which both
species benefit from each other.
o Commensalism is a symbiotic relationship in which
one organism benefits and the other organism is not
affected.
o Parasitism is a symbiotic relationship in which one
organism benefits but the other organism is harmed.
 An organism’s niche describes the ways in which the
organism obtains food, avoids danger, and finds shelter.