Textbook: Chapter 17 - Community Structure Flashcards
Aphotic zone
A deepwater area of marine ecosystems below the depth of effective light penetration
Benthic zone
The area of the sea bottom
Basal species
Species that feed on no other species but are fed upon by others
Canopy
Uppermost layer of vegetation formed by trees; also the uppermost layer of vegetation in shrub communities or in any terrestrial plant community where the upper layer forms a distinct habitat
Continuum concept
THe view, first proposed by H.A. Gleason,t hat vegetation is a continuous variable in a continuously changing environment; therefore, no two vegetational communities are identical, and associations of species arise only from similarities in requirements.
Community
A group of interacting plants and animals inhabiting a given area
Diversity index
The mathematical expression of species richness of a given community or area
Dominant
Population possessing ecological dominance in a given community and thereby governing type and abundance of other species in the community
Functional type (group)
A collection of species that exploit the same array of resources or perform similar functions within the community
Forest floor
Term describing the ground layer of leaves and detritus; site of decomposition
Food web
Interlocking pattern formed by a series of interconnecting food chains
Food chain
Movement of energy and nutrients from one feeding group of organisms to another in a series that begins with plants and ends with carnivores, detrital feeders and decomposers
Guild
A group of populations that utilize a gradient of resources in a similar way.
Herb layer
Lichens, moss, ferns, herbceous plants and small woody seedlings growing on the forest floor
Individualistic concept
The view, first proposed by HA gleason, that vegetation is a continuous variable in a continuously changing environment; therfore, not two vegetational communities are identical and associations of species arise only from silarities in requirements
Intermediate species
Species that feed on other species and they themselves are prey of other species
Keystone species
A species whose activites have a significant role in determining community structure
Link
In a foodweb, the arrows leading from a consumer to a species being consumed
Organismic concept of community
Idea that species, especially plant species, are integrated into an internally interdependent unit; upon maturity and death of the community, another identical plant community replaces it
Photic zone
Lighted water column of a lake or ocean, inhabited by plankton
Percent base saturation
The extent to which the exchange sites of soil particles are occupied by exhcnagable base cations or by cations other tha hydrogen and aluminum, expressed as percentage of total cation exchange capacity; compare cation exchange capacity
Rank-abundance diagram
Plots of relative abundance of each species against rank, defined as the order of species from the most to the least abundant
Relative abundance
Proportional representaiton of a species in a community or sample of a community
Simpson’s index
A measure of the probability that two individuals randomly selected from a sample will belong to the same species
Shannon index
An index of diversity that considers both species richness and evenness
Species richness
Number of species in a given area
Species evenness
A component of species diversity index; a measure of the distribution of individuals among total species occupying a given area
Sorensen’s coefficicent of community
Index of similarity between two stands of communities. The index ranges from 0 to indicate communities with no species in common to 100 to indicate communities with identical sepcies composition
Trophic level
Functional classification of organisms in an ecosystem according to feeding relationships, ranging from first-level autrophs through succeeding levels of herbivores and carnivores
Top predator
Species not subjected to predators; they prey on intermediate and basal species
Understory
Growth of medium-height and small trees beneath the canopy of a forest; sometimes includes a shrub layer as well
Zonation
Changes in the physical and biological structures of communities as one moves across the landscape; spatial changes in community structure
