| abiotic | Nonliving. |
| abiotic interactions | Interactions between organisms and nonliving components of the environment. |
| biotic | Having to do with life or living organisms. |
| biotic interactions | Interactions between organisms and living components of the environment. |
| population densities | Numbers of individuals in a population relative to the area in which they live. |
| population structure | Distribution of species in different age groups and different areas. |
| population dynamics | Patterns which affect growth or change within a population. |
| community | A group of organisms inhabiting the same region and interacting with each other. |
| competition | Type of interaction between organisms when resources (like food, mates, shelters, etc.) are scarce. |
| predation | When one species feeds on another species. |
| predator | Any animal that lives by killing and eating on other animals. |
| prey | An organism that is killed and eaten by another as food. |
| parasitism | Interaction between organisms from different species in which one member depends on the other for its life functions; the dependent member (the parasite) benefits from the relationship while the other (the host) is harmed by it. |
| parasite | An organism that takes nutrients from another living organism (the host), without giving that organism anything in return. |
| host | An organism that is infected with or fed upon by a parasitic or pathogenic organism. |
| amensalism | Type of interaction between organisms in which one organism is unaffected and the other suffers. |
| commensalism | Type of interaction where one organism benefits while the other is neither harmed nor benefited. |
| mutualism | Interdependent interaction between organisms in which all the organisms involved benefit. |
| disturbance | An event that affects the survival of some or all of the species in a community. |
| ecological succession | The gradual and orderly process of change in an ecosystem brought about by the progressive replacement of one community by another until a stable climax is established. |
| primary succession | The initial colonization of barren or sterile areas by organisms; examples include vegetation growth on lava newly formed lava flows. |
| secondary succession | The series of community changes which take place on a previously colonized, but disturbed or damaged habitat; examples include areas which have been cleared of existing vegetation by floods or fires. |
| pioneer species | The first organisms to colonize an area after a disturbance. |
| shade intolerant species | Plants that grow best in open sun. |
| shade tolerant species | Plants that grow well in the shade. |
| intermediate disturbance hypothesis | The theory that diversity is maximized through moderate amounts of disturbance. |
| density dependent factors | Factors which affect the population of a species due to the actual population size of the species; some examples are increased predation (higher frequency falling to prey) and shortage of food. |
| density independent factors | Factors which affect the population regardless of its population size; usually from abiotic causes such as forest fires. |
| environmental carrying capacity | The maximum population size that can be supported indefinitely by a given environment. |
| logistical growth | Population growth pattern that begins with rapid growth, and slows down as the environmental carrying capacity is reached; characterized by an S-shaped curve when graphed. |
| resources | Available supplies that can be drawn on when needed. |
| ecology | The study of the interactions among organisms and between organisms and their environment. |
| natural resource | A substance created by natural processes that humans obtain from the environment. |
| nonrenewable resource | A resource that cannot be replenished by natural processes in any reasonable time period. |
| renewable resources | Natural resources that can regenerate themselves if alive, and replenish themselves through chemical cycles if they're not alive. |
| perpetual resources | Renewable resources that can be rapidly replaced through short term natural processes and can therefore be considered inexhaustible. |
| potentially renewable resources | Resources that can renew themselves over a short period of time, but that can be damaged or overused to the extent that they're no longer capable of replenishing themselves. |
| fossil fuel | A hydrocarbon deposit, such as petroleum, coal, or natural gas, derived from living matter millions of years ago and used for energy. |
| rangeland | Land that has the primarily purpose of feeding grazing animals. |
| carrying capacity | The maximum number of organisms that can be supported by a given area of land. |
| overgraze | To permit animals to graze excessively, to the detriment of the vegetation. |
| erosion | The process by which soil and other materials are worn away from the Earth's surface. |
| biofuels | Fuels, such as ethanol or methanol, that are created from the fermentation of plants or plant products. |
| atmosphere | The layer of gas surrounding the Earth. |
| troposphere | The layer of the Earth's atmosphere that is closest to the earth's surface. |
| stratosphere | The middle layer of the Earth's atmosphere. |
| mesosphere | Outermost layer of the Earth's atmosphere. |
| surface water | The liquid water sitting on top of the land in the major water bodies. |
| groundwater | The water that penetrates the Earth's surface and seeps into deeper levels of the crust. |
| aquifers | Underground stores of water. |
| watershed | The area of land from which water and sediments are transported into a major stream or stream system. |
| pollution | The contamination of soil, water, and the atmosphere by the discharge of harmful substances. |
| pollutants | Substances that make the environment unfit for or harmful to living things. |
| degradable pollution | Pollution that can be quickly broken down by natural processes, such as by bacteria or other microorganisms. |
| persistent pollution | Pollution that cannot be broken down quickly, taking many years to disappear from the environment. |
| nondegradable pollution | Pollution that cannot be broken down through natural processes over any reasonable time period. |
| point source pollutants | Pollutants that come from a few clearly identifiable sources. |
| non-point source pollutants | Pollutants that come from many widely dispersed sources. |
| Environmental Protection Agency | EPA |
| National Ambient Air Quality Standards | NAAQS |
| wetlands | Land that is shallowly covered by surface or ground water often enough to support the growth of plants that live in water-saturated soil; examples include swamps, marshes, and bogs. |
| biomagnification | Process by which poisons become more concentrated in animal and plant tissue as they move higher in the food web. |
| deforestation | Loss or change of forest habitat. |
| desertification | The process by which productive lands are converted to deserts, often through poor agricultural practices. |
| greenhouse gases | Gases like methane and carbon dioxide which trap heat between the earth and the lower atmosphere. |
| greenhouse effect | The trapping of infrared light reflected off the earth's surface, by gaseous molecules in the Earth's atmosphere. |
| halons | Molecules that contain carbon and one of the halogen atoms. |
| halogen | A family of elements that includes fluorine, chlorine, bromine, iodine, and astatine. |