Raven Glossary- A

abiotic
nonliving
abyssal benthic zone
the ocean’s benthic environment that extends from a depth of 4000 to 6000 meters.
acid deposition
a type of air pollution that includes acid that falls from the atmostphere as precipitation or as dry acidic particles
acid mine drainage
pollution caused when sulfuric acid and dangerous dissolved materials such as lead, arsenic, and cadmium wash from coal and metal mines into nearby lakes and streams.
acid precipitation
precipitation that is acidic as a result of both sulfur and nitrogen oxides forming acids when they react with water in the atmosphere- partially due to the combustion of coal
active solar heating
a system in which a series of collection devices mounted on a roof or in a field are used to absorb solar energy. Pumps or fans distribute the collected heat.
acute toxicity
adverse effects that occur within a short period or after exposure to a toxicant
adaptation
an evolutionary modification that improves the chances of survival and reproductive success of a population in a given environment
adaptive radiation
the evolution of a large number of related species from an unspecialized ancestral organism
additivity
a phenomenon in which two or more pollutants interact in such a way that their combined effects are what one would expect given the individual effects of each component of the mixture
aerobic respiration
the process by which cells use oxygen to break down organic molecules into waste products (CO2 and H2O) with the release of energy that can be used for biological work
aerosol
tiny particles of natural and human-produced air pollution that are so small they remain sustpended in the atmosphere for days or even weeks
aerosol effect
atmospheric cooling that occurs as a result of aerosol pollution
age structure
the number and proportion of people at each age in a population
agroforestry
forestry and agricultural techniques that are used to improve degraded areas; in this practice, tree and crops are often planted together
A-horizon
the topsoil;; located just beneath the O-horizon of the soil. Rich in various kinds of decomposing matter
air pollution
various chemicals present in high enough levels in the atmosphere to harm humans, other naimals, plants, or materials.
albedo
the proportional reflectance of Earth’s surface; glaciers and ice sheets have high numbers of this
alcohol fuel
a liquid fuel such as methanol or ethanol which may be used in internal combustion engines; mixing gasoline with 10 % ethanol produces a cleaner-burning mixture known as gasohol
algae
unicellular or simple multicellular photosynthetic organisms; important producers in aquatic ecosystems
alpine tundra
a distinctive ecosystem located in the higher elevations of mountains, above the tree line, characteristic vegetation includes grasses, sedges, and small tufted plants
altitude
the height of a thing above sea level
amino acids
organic compounds that are linked together to form proteins
ammonifiation
the conversion of nitrogen-containing organic compounds to ammonia and ammonium ions by certain bacteria in the soil. Part of the nitrogen cycle
annual
a plant that grows, reproduces, and dies in one growing season
antagonism
a phenomenon in which two or more pollutants interact in such a way that their combined effects are less severe than the sum of their individual effects
anthracite
the highest grade of coal; has the highest known heat content and burns the cleanest of any crade of coal. Also known as hard coal
anticline
an upward folding of rock layers or strata
antioxidant
food additive that prevents oxidation of food molecules
aquaculture
the rearing of aquatic organisms, either freshwater or marine, for human consumption.
aquatic
pretaining to the water
aqueduct
a large pipe or conduit constructed to carry water from a distant source
aquifer
the underground caverns and porous layers of underground rock in which groundwater is stored
aquifer depletion
the removal by humans of more groundwater than can be recharged by precipitation or melting snow
arid land
a fragile ecosystem in which lack of precipitation limits plant growth. Arid lands are found in both temperate and tropical regions
artificial eutrophication
overnourishment of an aquatic ecosystem by nutrients such at nitrates and phosphates. accelerated due to human activities such as agriculture and discharge from sewage treatment plants
artificial insemination
a technique in which sperm collected from a suitable male of a rare species is used to artificially impregnate a female
assimilation
the incorporation of a substance into the cells of an organism
atmosphere
the gaseous envelope surrounding Earth
atom
the smallest quantity of an element that retains the chemical properties of that element; composed of protons, neutrons, and electrons.
atomic mass
a number that represents the sum of the number of protons and neutrons in the nucleus of an atom. Represents the relative mass of an atom.
atomic number
a number that represents the number of protons in the nucleus of an atom. Each element has its own.
acid
a substance that releases hydrogen ions (protons) in water. It has a sour taste and turn blue litmus paper red.