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a group of individuals of one species living in one area who can interbreed and interact with each other


all the organisms living in one area


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

abiotic factors

nonliving environmental factors (e.g. temperature, water, sunlight, wind, rocks, and soil)

biotic factors

all the organisms with which an organism might react


the global ecosystem


the total number of individuals in a population


births, deaths, immigration, and emigration affect the size of this


the number of individuals per unit area or volume


definied by its size, density, and dispersion


the pattern of spacing of individuals within the area the population inhabits


the most common pattern of dispersal

biotic potential

the maximum rate at which a population could increase under ideal conditions

carrying capacity

limit to then umber of individuals that can occupy one area at a particular time

exponential growth

a population with no predation, parasitism, or competition, no immigration or emigration, and in an environment with unlimited resources

exponential growth

characteristic of a popultion that has been recently introduced into an area


reproduce rapidly when the environment is uncrowded and resources are vast


maximize population size near the carrying capacity for an environment

limiting factors

factors that limit population growth; divided into: density-dependent and density independent factors

density-dependent factors

factors that increase directly as the population density increases (e.g. competition, predation, disease)

density-independent factors

factors whose occurence is unrelated to the population density (e.g. natural disasters)


symbiotic relationship where both organisms benefit


symbiotic relationship in which one organism benefits and one is not affected


symbiotic relationship where one organisms benefits while the other is harmed

food chain

the pathway along which food is transferred from one trophic level to another

food web

interwoven food chains


convert light energy into chemical energy and have the greatest biomass of any trophic level


only about ___% of the energy stored in any trophic level is converted to organic matter at the next trophic level

gross primary productivity

the amount of energy converted to chemical energy by photosynthesis per unit time in an ecosystem

net primary productivity

the gross primary productivity minus the energy used by the primary producers for respiration

biological magnification

organisms at higher trophic levels have greater concentrations of accumulated toxins stored in their bodies than those at lower trophic levels


nutrients would not be recycled back to the soil to nourish plants, and there would be no food chain and no life without these


bacteria and fungi

ecological succession

the rebuilding of an ecosystem after either natural or man-made destruction

primary ecological succession

the rebuilding of an ecosystem in a lifeless area where soil has been removed

soil building

the essential and dominant characteristic of primary ecological succession

pioneer organisms

the first organisms to inhabit a barren area after an ecosystem is destroyed

secondary ecological succession

when an existing community has been cleared by some disturbance that leaves the soil intact


large regions of Earth whose distribution depends on the amountof rainfall and the temperature in an area


each characterized by different vegetation and animal life


largest biome on Earth, covering 3/4 of the Earth's surface


most stable biome


biome that provides most of Earth's food and oxygen

tropical rainforest

biome that has the greatest diversity of animal species

tropical rainforest

biome that accounts for more than 20% of Earth's net carbon fixation (food production)


biome with the most extreme fluctuations in temperature of any biome


largest terrestrial biome


conifer forest

carbon cycle

the basis of this is photosynthesis and respiration


most nitrogen enters ecosystems by this

nitrogen-fixing bacteria

live in the nodules of the roots of legumes and convert free nitrogen into ammonium

nitrifying bacteria

convert ammonium into nitrites and then into nitrates

denitrifying bacteria

convert nitrates into free atmospheric nitrogen


depletion of oxygen in water because of increase of nutrients that cause eccessive growth of oxygen-depleting plants


organic material accumulates on the bottom of a lake body and reduces the depth of the lake


detritivores use up oxygen as they decompose the dead organic matter; the depletion of oxygen makes it impossible for other organisms to live

greenhouse effect

increased concentration of carbon dioxide in the air; carbon dioxide and water vapor in the air absorb much of the infared radiation reflect off the Earth

global warming

the increase in temperature due to the greenhouse effect


chemical used for refrigerators and aerosols that have caused the formation of a hole in the oxone layer, allowing more UV light to reach Earth

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