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the study of the interactions of living organisms with one another and with their physical environment (soil, water, climate...)


the place where a particular population of a species lives


the many different species that live together in a habitat


it consists of a community and all the physical aspects of its habitat, such as the soil, water, weather

abiotic factors

the physical aspects of a habitat

biotic factors

the living organisms in a habitat


the number of species living within an ecosystem

pioneer species

the first organisms to live in a new habitat - small, fast-growing plants


a somewhat regular progression of species replacement

primary succession

succession that occurs where plants have not grown before

secondary succession

succession that occurs in areas where there has been previous growth, such as in abandoned fields or forest clearings

primary productivity

the rate at which organic material is produced by photosynthetic organisms in an ecosystem


organisms that first capture energy - include plants, some kinds of bacteria, and algae


those organims that consume plants or other organisms to obtain the energy necessary to build their molecules

trophic level

the specific level to which an organism in an ecosystem is assigned - used by ecologists to study how energy moves theough an ecosystem

food chain

the path of energy through the trophic levels of an ecosystem


animals that eat plants or other primary producers - 2nd trophic level


secondary consumers, animals that eat herbivores - third trophic level


animals that are both herbivores and carnivores


organisms that obtain their energy from the organic wastes and dead bordies that are produced at all trophic levels


bacteria and fungi that cause decay and release nutrients back into the environment

food web

a complicated, interconnected group of food chains

energy pyramid

a diagram in which each trophic level is represented by a block, and the blocks are stacked on top of one another, with the lowest trophic level on the bottom


the dry weight of tissue and other organic matter found in a specific ecosystem.

biogeochemical cycle

the path of water, carbon, nitrogen, and phosphorus from the nonliving environment to living organisms, and then back to the nonliving environment

ground water

water retained beneath the surface of the Earth


a sun-driven process in which water moves into the atmposhere by evaporationgg from leaves


all organisms engage in this process, in which oxygen is used to oxidize organic molecules during cellular respiration - CO2 is made


the process of burning in which CO2 is released into the atmosphere


as limestone is broken down, it releases CO2 that is made availible to other organisms


the absorption and incorporation of nitrogen into plant and animal compounds


the production of ammonia by bacteria during the decay of nitrogen-containing urea


the production of nitrate from ammonia


the conversion of nitrate to nitrogen gas

nitrogen fixation

the process of combinign ntirogen with hydrogen to form ammonia


it consists of all the indiciduals of a species that live together in one place at one time

population size

the number of individuals in a population - this can affect the population's ability to survive

population density

the number of individuals that live in a given area


the way individuals of the population are arranged in space

population model

a hypothetical population that attempts to exhibit the hey characteristics of a real population

exponential growth curve

a curve in which the rate of ppulation growth stays the same, as a result the population size increases steadily J-curve

carrying capacity (K)

the population size that an environment can sustain

density-dependent factors

the limited resources - the rate at which they become depleted depends upon the population density of the population that uses them

logistic model

a population model in which exponential growth is limited by a density-dependent factor S-curve

density-independent factors

environmental conditions - those that don't depend on the number of organisms in a habitat


species found in rapidly changing environments that grow exponentially when environmental conditions allow them to reproduce


populations that grow slowly and that have small population sizes. They are limited by the carrying capacity and have long lifespans.

nonrandom mating

a situation in which individuals prefer to mate with others that live nearby or are of their own phenotype

stabilizing selection

selection eliminates extremes at both ends of a range of phenotypes, the frequencies of the middle phenotypes increase. fewer individuals in population with extreme phenotypes

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