| A | B |
|---|
| community | ana assemblage of species living close enough together for potential interaction |
| species richness | the number of species a community contains |
| relative abundance | differences in the abundance of species within a community |
| individualistic hypothesis | the concept, put forth by H.A. Gleason, that a plant community is a chance assemblage of species found in the same area simply because they happen to have similar biotic requirements |
| interactive hypothesis | the concept, put forth by F.E. Clements, that a community is an assemblage of closely linked species, locked into association bu mandatory biotic interactions that cause the community to function as an integrated unit, a sort of superior organism |
| rivet model | the concept, put forth by Paul and Anne Ehrlich, that many or most of the species in a community are associate tightly with other species in a web of life. An increase or decrease in one species in a community affects many other species |
| redundancy model | The concept, put forth by Henry Gleason, that most of the species in a community are not tightly coupled with one another, meaning that the web of life is very loose. An increase or decrease in one species in a comunity has little effect on other species, which operate independently. |
| interspecific interactions | relationships between the species of a community |
| interspecific competition | competition for other resources between plants, between animals, or between decomposers when resources are in short supply |
| competitive exclusion principle | The concept that when populations of two similar species compete for the same limited resources, one population will use the resources more efficiently and have a reproductive advantage that will eventually lead to the elimination of the other population |
| ecological niche | the sum total of species' use of the biotic and abiotic resources in the environment |
| resource partitioning | The division of environmental resources by coexisting species such that the niche of each species differs by one or more significant factors from the niches of all coexisting speicies |
| character displacement | the tendency for characteristics to be more divergent in sympatric populations of two species than in alopatric populations of the same two species |
| predation | an interaction between species in which one species, the predator, eats the other, the prey. |
| herbivory | The consumption of plant material by an herbivore |
| parasitism | a symbiotic relationship in which the symbiont benefits at the expense of the the host by living either within the host or outside the host. |
| cryptic coloration | camoflauge, making potential prey difficult to spot against its background |
| aposematic coloration | The bright coloration of animals with effective physical or chemical defenses that acts as a warning to predators. |
| batesian mimicry | A type of mimcry in which a harmless species looks like a species that is poisonous or otherwise harmful to predators. |
| mullerian mimicry | a mutual mimicry by by two unpalatable species |
| parasite | an organism that absorbs nutrients from the body fluids of living hosts |
| host | The larger participant in a symbiotic relationship, serving as a home and feeding ground to the symbiont |
| endoparasites | parasites that live within a host |
| ectoparasites | parasites that feed on the external surface of a host |
| parasitoidism | insects lay eggs in living hosts |
| commensalism | A symbiotic relationship in which the symbiont benefits but the host is neither helped nor harmed |
| coevolution | The mutual influence on the evolution of two different species interacting with eachother and reciprocally influencing each other's adaptations |
| trophic structure | the different feeding realtionships in an ecosystem, which determine the route of energy flow and the pattern of chemical cycling |
| food chain | the pathway along which food in transferred from trophic level to trophic level, beginning with producers. |
| trophic levels | Any of ther several levels of a food chain, whose species are based on their main nutritional source. the trophic level that ultimately supports all others consists of autotrophs, or primary producers |
| food webs | The elaborate, interconnected feeding relationships in an ecosystem |
| energetic hypothesis | The concept that the length of a food chain is limited by the inefficiency of energy transfer along the chain |
| dynamic stability hypothesis | long food chains are less stable than short chains |
| dominant species | those species in a community that have the highest abundance or highest biomass. These species exert a powerful control over the occurence and distribution of other species |
| biomass | The dry weight of organic matter comprising a group of organisms in a particular habitat |
| keystone species | species that are not usually abundant in a community yet exert strong control on community structure byt the nature of their ecological roles or niches |
| bottum-up model | a model of community organisms in which mineral nutrients control community organization because nutrients control plant numbers, which in turn control hherbivore numbers, which in turn control predator numbers. |
| top-down model | a model of a community organization in which predation controls community organization because predators control herbivores, which in return control plants, which in return control nutrient levels; also called the trophic cascade model |
| nonequilibrium model | the model of communities that emphasizres that they are not stable in time but constantly changing after being buffeted by disturbances |
| stability | the tendency of a biological community to to resist change and return to its original species composition after being disturbed |
| ecological succession | transition in the species composition of a biological community, often following ecological disturbance of the community; the establishment of a biological community in an area virtually barren of life. |
| primary succession | A type of ecological succession that occurs in a virtually lieless are, where there were originally no organisms and where soil has not yet formed |
| secondary succession | a type of succession that occurs where an existing community has been cleared by some disturbance that leaves the soil intact |
| biodiversity | the number and relative abundance of species in a biological community |
| heterogeneity | a measurement of biological diversity considering richness and relative abundance |
| species richness | the number of species in a biological community |
| relative abundance | differences in the abundance of species within a community |
| species-area curve | the biodiversity pattern, first noted by Alexander Von Hunboldt, noting that the larger the geographic area of a community we sample, the greater the number of species. |
| mutualism | an interspecific interaction hat benefits both species |
| disturbances | are events such as storms, fire, floods, droughts, overgrazing, or human activites, that damage communitiesm remove organisms from them, and alter resource ability |
