Chapter 15 Key Terms
o A term used to describe the diversity of important ecological entities that span
multiple spatial scales, from genes to species to communities.
o A group of interacting species that occur together at the same place and time.
x community structure
o The set of characteristics that shape a community, including the number,
composition, and abundance of species.
o A view of species interactions as variable in strength and direction under different
x direct interactions
o Interactions between two species, including traditional relationships such as
competition, predation, and positive interactions. Compare indirect interactions.
x dominant species
o A species that has large, community-wide effects by virtue of its size or
abundance, its strong competitive ability, or its provision of habitat or food for
other species, also called a foundation species.
x ecosystem engineer
o A dominant species that influences its community by creating, modifying, or
maintaining physical habitat for itself and other species.
x functional group
o A subset of the species in a community that function in similar ways, but do not
necessarily use the same resources. Compare guild.
o A subset of the species in a community that use the same resources, whether or
not they are taxonomically related. Compare functional group.
x horizontal interactions
o Non-trophic interactions, such as competition and some positive interactions, that
occur within a trophic level.
x indirect interactions
o Interactions in which the relationship between two species is mediated by a third
(or more) species. Compare direct interactions.
x interaction strength
x interaction web
o A concept that has been introduced to describe both the trophic (vertical) and non-
trophic (horizontal) interactions in a traditional food web.
x keystone species
o A strongly interacting species that has a large effect on energy flow and on
community structure and composition disproportionate to its abundance or