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study of interations between prganisms and their environment

hierarchy of interations

biosphere -> ecosystem ->community -> population -> organism


the global system (earth)


all biotic and abiotic factors in a region


all organisms in the same region


all organisms of the same species in the same region


single living thing

population ecology

concentrates on factors that affect population density and growth


individuals in a specific area are counted

mark-recapture method

individuals are captured, marked, set free then they capture some of the marked organisms and unmarked individuals

pattersn of dispersion

way individuals are spaced in a habitat

clumped pattern

individuals are aggregated into patches. cause by unequal distribution of resources

uniform pattern

individuals spread out evenly. causes from interactions from individuals

random dispersion

individuals spaced in a patternless unpredictable way

populations dynamics

factors that change a population over time

birth rate

number of births over time

death rate

number of deaths over time

life expectancy

average lifespan of individuals in a population

age structure

proportion of individuals in different age groups

growth of a population

number of births - (minus) number of deaths

growth rate

change in population size over time

expotential growth

population size multiplies by a constant factor each generation; depends on size of population; occurs in ideal regulated conditions

logistic growth model

population growth is slowed by limiting factors

carry capacity

number of indiviudals in a population that the environment can support

density dependent factors

effects intensify as population size increases

intraspecific competition

competition between individuals for resources

density independent factors

intensity is unrelated to population size

environmental factors

these factors effect the availability of resources

crash and boom

populations experience periods of rapid growth alternating with periods of decline (ex: predator-prey interactions, life cycle of individuals in the population, and variations in food supply)

exponential growth

the growth pattern in human populations (causes: inventions of tools to control or eliminate predators, advances in medical techonology, totalitarian agriculture [able to feed everyone])

non-native species

species that are not indigenous to the area


if you remove this from a habitat, this reduced the primary productivity and may lead to increased CO2 levels


if you remove this from a habitat, prey populations expands and exeeds carrying capacity


if you remove this from a habitat, nutrients are not restored in soils and directly affect the producers

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