preservation		movement of individuals into a population
endangered species		solid wastes that can be broken down by natural processes
nonrenewable resource		species with numbers of individuals so low that it is in danger of extinction
acid precipitation		planned management of wildlife habitats and other natural areas to prevent exploitation or destruction
fossil fuel		the movement of individuals out of a population
carrying capacity		maximum, stable population size an environment can support over time
threatened species		study of populations that includes birth rates and death rates, fertility rates, age structure, and geographic distribution
greenhouse effect		occurs when the last members of a species die
ozone layer		protective layer at the top of the stratosphere; it absorbs most of the sun's harmful radiation
age structure		factors that limit population density
conservation		most often weather-related occurrences that affect populations regardless of their density
immigration		renewable or nonrenewable parts of the natural environment that are used by humans
biodegradable		solid particles of soot contained in smoke released by burning fossil fuels
demography		resources replaced or recycled by natural processes
pollution		proportions of any given population that are either in their pre-reproductive, reproductive, or post-reproductive years
renewable resources		resources available in limited amounts that cannot be replaced and cannot be recycled quickly by natural means
exponential growth		keeping an organism or an area from harm or destruction by the establishment of parks, wildlife habitats, and other refuges
groundwater		rain or snow more acidic than unpolluted rainwater
nonbiodegradable		coal, oil, and natural gas formed from the buried remains of organisms
extinction		species that have rapidly decreasing numbers of individuals
natural resource		type of urban air pollution resulting from a combination of chemical pollutants, particulate matter, and sulfur dioxide
density-dependent factor		fresh water from rain and surface streams that accumulates in underground reservoirs
particulate		a natural phenomenon by which carbon dioxide and other atmospheric gases prevent heat from escaping into space
emigration		contamination of air, water, or land by wastes produced in such excess that they cannot be recycled by natural processes
smog		explosive population growth in which the number of reproducing individuls increases by an ever-increasing rate
density-independent factor		types of wastes that are not easily broken down and can exist in the enrionment for many years