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IB Biology HL Ecology Unit Review Terms


group of same species living in the same area at the same time


a form of plant sampling and calculating the density of plants in the area- divide into quadrats, count in certain quadrats, find average, multiply by all the quadrats


the pattern of spacing among individuals within the boundaries of a population ie clumped, random, or uniform


study of vital statistics of populations and how they change over time


a group of individuals from birth until all are dead

Type I

a species with few offspring but lots of parent involvement (k species) high population density

Type III

a species that produces many offspring with little parent involvement (r species) low population density

per capita birth rate

number of offspring produced per unit of time by an average member of the population

zero population growth

when births and emigration=deaths and immigration

carrying capacity

the maximum population an environment can sustain


"one shot" reproduction


repeated reproduction

intrinsic rate

maximum rate of growth

density independent

a birth/death rate that does not change with population density

density dependent

as density increases, the birth rate drops and the death rate increases

population dynamics

population fluctuations from year to year

ecological footprint

aggregate land and water area required to produce resources consumed and absorb waste generated


all the organisms that live together in a place and interact


ecological role

fundamental niche

full range of habitat, resource, etc

realized niche

the resources an organism ends up using in their fundamental niche due to competition with other organisms

interspecific competition

different species compete for resources

competitive exclusion

local elimination of inferior competitor

species diversity

variety of organisms in a community

species richness

number of species in a community

trophic structure

feeding between organisms


mass of all individuals in an ecosystem

dominant species

the species that is the most abundant with the greatest biomass in an ecosystem

keystone species

species that are not dominant but are important to ecosystem


remove/alter an organism due to fire, storm, etc.

ecological succession

disturbed area/species replaced by new species

primary succession

no soil for succession, starts with lichens and moss

secondary succession

ecological succession with soil to begin with


disease-causing organisms


sum of all organisms living in a given area and the abiotic factors with which they interact


primary producers



primary production

amount of light energy->chemical energy

gross primary production

total primary production (GPP)

net primary production

GPP subracted by energy used by producers for cellular respiratio

limiting nutrient

element that must be added for production to increase in an ecosystem


ecological impact of increase of cyanobacteria and algae in aquatic ecosystems due to an increase in the limiting nutrient (usually nitrogen or phosphorus)

secondary production

chemical energy in consumer food that is converted to their own new biomass

trophic efficiency

% of production transferred from one trophic level to the next (usually 5-20)


oxidation of ammonium in the soil to nitrite and nitrate

nitrogen fixation

reduction of atmospheric nitrogen to ammonia


process in which fixed nitrogen compounds are converted back into nitrogen gas and returned to the atmosphere

resource partitioning

the differentiation of niches that enables similar species to coexist in a community

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