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Population and Community Ecology


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The concept that in certain (K-selected) populations, life history is centered around producing relatively few offspring that have a good chance of survival.
Integrated hypothesis
The concept, put forth by F.E Clements, that a community is an assemblage of closely linked species, locked into associated by mandatory biotic interactions that cause the community to function as an integrated unit, a sort of super organism.
Zero population growth
A period of stability in population size, when the per capita birth rate and death rate are equal.
The larger participant in a symbiotic relationship, serving as home and feeding ground to the symbiont
An interaction in which an herbivore eats parts of a plant or alga
Logisitic population growth
A model describing population growth that levels off as population size approaches carrying capacity.
A parasite that feeds on the external surface of a host
Keystone species
A species that is not necessarily abundant in a community yet exerts strong control on community structure by the nature of its ecological role or niche.
A life history in which adults have but e a single reproductive opportunity to produce large numbers of offspring, such as the life history of the Pacific salmon; also known as semelparity.
Dominant species
Those species in a community that have the highest abundance or highest biomass. These species exert a powerful control over the occurrence and distribution of other species.
Population dynamics
The study of how complex interactions between biotic and abiotic factors influence variations in population size.
An interaction between species in which one species, the predator, eats the other, the prey.
Intermediate disturbance hypothesis
The concept that moderate levels of disturbance can foster greater species diversity than low or high levels of disturbance.
Dynamic stability hypothesis
The idea that long food chains are less stable than short chains.
Reproductive table
An age-specific summary of the reproductive rates in a population.
Ecological footprint
A method of using multiple constraints to estimate the human carrying capacity of Earth by calculating the aggregate land and water area in various ecosystem categories appropriated by a nation to produce all the resources it consumes and to absorb all the waste it generates.
Ecological niche
The sum total of a species' use of the biotic and abiotic resources in its environment.
The evaporation of water from soil plus the transpiration of water from plants.
Age structure
the relative number of individuals of each age in a population
Life expectancy at birth
The predicted average length of life at birth.
The movement of individuals out of a population.
A type of parasitism in which an insect lays eggs on or in a living host; the larvae then feed on the body of the host, eventually killing it
Life tables
table of data summarizing mortality in a population.
Species-area curve
The biodiversity pattern, first noted by Alexander von Humboldt, that illustrates that the larger the geographic area of a community, the greater the number of species.
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 species
A symbiotic relationship in which one organism benefits but the other is neither helped nor harmed.
A subdivided population of a single species.
Species diversity
The number and relative abundance of species in a biological community.
Mark-recapture method
A sampling technique used to estimate wildlife populations.
Mullerian mimicry
mutual mimicry by two unpalatable species
Invasive species
A species that takes hold outside of its native range; usually introduced b y humans.
Carrying capacity
The maximum population size that can be supported by the available resources, symbolized as K.
Interspecific competition
Competition for resources between plants, between animals, or between decomposers when resources are in short supply
An organism that benefits by living in or on another organism at the expense of the host
Density independent
Referring to any characteristic that is not affected by population density.
The mutual evolutionary influence between two different species interacting with each other and reciprocally influencing each other's adaptations.
Top-down model
A model of community organization in which predation controls community organization because predators control herbivores, which in turn control plants, which in turn control nutrient levels; also called the trophic cascade model.
Trophic structure
The different feeding relationships in an ecosystem, which determine the route of energy flow and the pattern of chemical cycling.
Exponential population growth
The geometric increase of a population as it grows in an ideal, unlimited environment.
The dry weight of organic matter comprising a group of organisms in a particular habitat.
A species that has a positive effect of the survival and reproduction of other species in a community and that contributes to community structure.
Nonequilibrium model
The model of communities that emphasizes that they are not stable in time but constantly changing after being buffeted by disturbances.
All the organisms that inhabit a particular area; an assemblage of populations of different species living close enough together for potential interaction.
Redundancy model
The concept, put forth by H.A Gleason and Brian Walker, that most of the species in a community are not tightly coupled with one another (that is, the wbe of life is very loose). According to this model, an increase or decrease in one species in a community has little effect on species in a community has little effect on other species, which operate independently.
The study of statistics relating to births and deaths in populations
Bottom-up model
A model of community organization in which mineral nutrients control community organization because nutrients control plant numbers, which in turn control herbivore numbers, which in turn control predator numbers.
The study of statistics relating to births and deaths in populations
Primary succession
A type of ecological succession that occurs in a virtually lifeless area, where there were originally no organisms and where soil has not yet formed.
Batesian mimicry
A type of mimicry in which a harmless species looks like a species that is poisonous or otherwise harmful to predators
A disease-causing agent.
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 abiotic requirements.
Aposematic coloration
The bright coloration of animals with effective physical or chemical defenses that acts as a warning to predators
Character displacement
The tendency for characteristics to be more divergent in sympatric populations of two species than in allopatric populations of the same two species.
Energetic hypothesis
The concept that the length of a food chain is limited by the inefficiency of energy transfer along the chain.
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.
Secondary succession
A type of succession that occurs where an existing community has been cleared by some disturbance that leaves the soil intact.
A group of individuals of the same age, from birth until all are dead.
The concept that in certain (r-selected) populations, ahigh reproductive rate is the chief determinant of life history.
Ecological capacity
The actual resource base of a country
Competitive exclusion
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
Species richness
The number of species in a biological community
Infant mortality
The number of infant deaths per thousand life births.
Demographic transition
A shift from zero population growth in which birth rates and death rates are high to zero population growth characterized instead by low birth and death rates.
A life history in which adults produce large numbers of offspring over many years; also known as repeated reproduction.
Rivet model
The concept, put forth by Paul and Anne Ehrlich, that man or most of the species in a community are associated tightly with other species in a web of life. According to this model, an increase or decrease in one species in a community affects many other species.
A symbiotic relationship in which both participants benefit.
Relative abundance
Differences in the abundance of different species within a community.
Density dependent
Referring to any characteristic that varies according to an increase in population density
The number of individuals per unit area or volume.
Population ecology
The study of populations in relation to the environment, including environmental influences on population density and distribution, age structure, and variations in population size.
a parasite that lives within a host
A technique for restoring eutrophic lakes that reduces populations of algae by manipulating the higher-level consumers in the community rather than by changing nutrient levels of adding chemical treatments.
The study of statistics relating to births and deaths in populations
A localized group of individuals that belong to the same biological species (that are capable of interbreeding and producing fertile offspring).
Surviviorship curve
A plot of the number of members of a cohort that are still alive at each age; one way to represent age-specific mortality.
The pattern of spacing among individuals on both extremes of a phenotypic range over intermediate phenotypes.
Food webs
The elaborate, interconnected feeding relationships in an ecosystem.

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