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Definition
| an assemblage of populations of various species living close enough for potential interaction |
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Term
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Definition
| Integrated Hypotheses (Clements) and Individualistic Hypotheses (Gleason) |
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Term
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Definition
A community is an assemblage of closely linked species, locked into association by mandatory biotic interactions
-Predicts that the presence or absence of particular
species depends on the presence or absence of
other species
-One should see sharp ecotones between distinct
communities with little overlap in the species present in alternative communities |
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Term
| Individualistic Hypotheses |
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Definition
Proposes that communities are loosely organized associations of independently distributed species with the same abiotic requirements
-Predicts that each species is distributed according to its tolerance ranges for abiotic factors |
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| Populations in a community are potentially linked by |
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Definition
interspecific interactions
-A community’s interactions include competition, predation, herbivory, symbiosis, and disease |
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Term
| Interspecific competition |
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Definition
| occurs when species compete for a particular resource |
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| Strong competition can lead to |
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Definition
competitive exclusion
-the local elimination of one of the two competing species |
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| Gause studied competition in laboratory experiments using |
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Definition
Paramecium species
-Each species, when alone, shows logistic growth to a carrying capacity
-When both species are present, one is driven to extinction by the other
-Conclusion: two species cannot coexist if their niches are too similar |
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| The Competitive Exclusion Principle |
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Definition
| States that two species competing for the same limiting resources cannot coexist in the same place |
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Definition
The ecological niche is the multidimensional space that an organism occupies. The dimensions of the niche include abiotic factors as well as biotic resources and interactions
-Two Types: Fundamental and Realized |
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Definition
| is the space occupiable in the absence of biotic interactions |
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Definition
| is the space the organism actually occupies |
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| As a result of competition |
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Definition
| a species' fundamental niche may be different from its realized niche |
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| The Niche concept allows restatement of the |
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Definition
competitive exclusion principle
-two species cannot coexist in a community if their niches are identical |
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Term
| Ecologically similar species can coexist in a community only if |
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Definition
| there is one or more significant difference in their niches |
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Term
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Definition
| the differentiation of niches that enables similar species to coexist in a community |
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Definition
-The tendency for characteristics to be more divergent in sympatric populations than in allopatric populations of the same two species
-Evidence of divergence due to competition |
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Term
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Definition
predator and prey populations can strongly interact (eg. lynx and hare)
-Predation shapes many attributes of both predators and prey:
-Claws, teeth, fangs, stingers, and poison of predators
-crypsis, mimicry, shells, speed, sensory capabilities of prey |
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Term
| Cryptic coloration, or camouflage makes prey |
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Definition
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Term
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Definition
| warns predators to stay away from prey |
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Term
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Definition
a palatable or harmless species mimics an unpalatable or harmful model
-ex. hawkmoth larva, green parrot snake |
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Definition
| two or more unpalatable species resemble each other |
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Term
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Definition
the process in which an herbivore eats parts of a plant
-Has led to the evolution of plant mechanical and chemical defenses and consequent adaptations by herbivores |
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Term
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Definition
one organism, the parasite, derives its nourishment from another organism, its host, which is harmed in the process
-ex Cymothoa exigua and the rose snapper; parasite replaces rose snappers tongue to share food |
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Term
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Definition
an interspecific interaction that benefits both species
-Mutualisms are systems of mutual exploitation and can break down into interactions that benefit one player at the expense of the other |
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Term
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Definition
-tree provides food, nest sites for ants
-ant provides tree protection from competitors, herbivores |
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Definition
| one species benefits and the other is not affected |
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Term
| Two components of Species Diversity |
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Definition
-number of species
-relative abundance of each species (evenness) |
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Term
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Definition
the feeding relationship between organisms in a community
-is a key factor in community dynamics
-food chains, food webs, or trophic pyramids |
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Definition
link the trophic levels from producers to top carnivores
-usually only a few links long
-in many studies, there is a correlation between productivity and food chain length |
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Definition
| a branching food chain with complex trophic interactions |
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| Certain species have an especially large impact on the structure of entire communities either because |
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Definition
they are highly abundant or because they play a pivotal role in community dynamics
-dominant and keystone species |
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Term
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Definition
-Are those species in a community that are most abundant or have the highest biomass
-Exert powerful control over the occurrence and distribution of other species |
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Term
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Definition
-Are not necessarily abundant in a community
-Exert strong control on a community by their ecological roles, or niches |
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Term
| Ecosystem 'Engineers' (Foundation Species) |
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Definition
| Some organisms exert their influence by causing physical changes in the environment that affect community structure |
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Term
| Some foundation species act as |
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Definition
facilitators
-have positive effects on the survival and reproduction of some of the other species in the community |
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Term
| 2 Models of control that communities can be subjected to |
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Definition
| bottom-up and top-down controls, or both |
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Term
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Definition
-Proposes a unidirectional influence from lower to higher trophic levels
-in this case, the presence or absence of abiotic nutrients
determines community structure, including the abundance of primary producers |
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Term
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Definition
-Proposes that control comes from the trophic level
above
-The effects of top down control vary with the length of the food chain |
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Term
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Definition
-Is an event that changes a community
-Removes organisms from a community
-Alters resource availability
-Fire: Is a significant disturbance in most terrestrial ecosystems and is often a necessity in some communities (helps eradicate dead grass) |
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Term
| The large-scale fire in Yellowstone National Park in 1988 |
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Definition
| Demonstrated that communities can often respond very rapidly to a massive disturbance |
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Term
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Definition
orderly build-up of a community following disturbance and may proceed by any or a combination of tolerance, facilitation, and inhibition
-Diversity might be highest at intermediate rates of disturbance |
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Term
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Definition
Occurs where no soil exists when succession
begins
-retreating glaciers provide a valuable field-research opportunity on this type of succession |
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Term
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Definition
| Begins in an area where soil remains after a disturbance |
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Term
| three models of succession |
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Definition
Facilitation, Inhibition, Tolerance
-Facilitation: Early arriving species may facilitate the appearance of later species by making the environment more favorable
-Inhibition: Early arriving species may inhibit establishment of later species
-Tolerance: Early arriving species have no impact on later arriving species |
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Term
| Intermediate disturbance hypothesis |
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Definition
-Suggests that moderate levels of disturbance can
foster higher species diversity than low or high
levels of disturbance
-Frequently-disturbed habitats harbor primarily early
successional species
-Rarely-disturbed habitats harbor primarily climax
species
-Intermediate disturbance levels lead to highest levels of diversity |
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Term
| Two Key factors correlated with a community's species diversity |
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Definition
-geographic location (for instance latitude)
-size |
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| Species richness generally declines along an |
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Definition
along an equatorial-polar (latitudinal) gradient
-Diversity is usually highest near the equator (tropics) and declines toward the poles
-Many factors may contribute to this pattern including: Greater age of tropical environments (more time for the evolution of species) and Greater Productivity in the tropics due to greater sunlight and water availability |
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Term
| two main climatic factors correlated with biodiversity |
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Definition
temperature, solar energy input and water availability which are combined in measures of evapotranspiration
-*correlation need not imply causation* |
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| Latitudinal gradients in species richness may have both |
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Definition
| historical and ecological determinants |
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Term
| Species-area curve quantifies the idea that |
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Definition
| All other factors being equal, the larger the geographic area sampled, the greater the number of species |
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Term
| Equilibrium Model of Island Biogeography |
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Definition
Species richness on islands represents a balance between the rates of immigration and extinction
-explains variation in the species diversity of islands through the effects of island size and distance from source populations.
-Size of island affects both immigration and extinction rates
• Larger islands have higher rates of immigration and lower rates of extinction
-Distance from the source (mainland) affects immigration rates
• Immigration more frequent if island nearer mainland
-ex. Species richness increases with island size in the Galapagos and many other archipelagos |
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