Glossary - Environmental Science - page 318

Appendix A: Glossary
acid deposition Commonly used when referring to acid rain; primary pollutants, sulfates, and nitrates combine
with water in the atmosphere to form sulfuric acid (H 2 SO 4 ) and nitric acid vapor (HNO 3 ).
active volcano A volcano that is presently erupting, or a volcano that has a large amount of seismic and
thermal activity.
acute exposure Intense exposure to pollutants, toxins or radioactive materials occurring over a brief period of
time.
adaptations The developed traits that make an organism especially suited to its environment; also called ad-
aptive traits.
aerosols Solid particles and droplets suspended in the atmosphere.
age structure The number of organisms in each age range within a population.
age structure diagrams Used to show the distribution of ages throughout a population and can help to forecast
what might happen to a population over time. Also called age pyramids.
Agricultural Revolution Began about 10,000 years ago when humans first started to grow crops and raise
livestock.
agriculture The growth of crops and the raising of livestock.
air pollution Any chemical or particulate matter found in the atmosphere at high enough concentrations to
harm humans, other animal life, vegetation, rocks, soils, and other building materials.
allergens Substances that overactivate the immune system, stimulating an unwanted or unnecessary response.
allopatric speciation The process of a new species being created over time due to a physical separation of a
population and resultant divergent evolution.
altitude The distance above the Earth's sea level.
amensalism A species interaction in which one organism harms another while remaining unaffected itself.
ammonification A step in the nitrogen cycle in which nitrogen is combined with hydrogen to form ammonia
(NH 3 ) during the process of nitrogen being fixed for use by plants.
anthropogenic Describes events that result from human activities.
aphelion The point, in July, at which the Earth is farthest from the sun.
artificial selection The process of humans selecting for desired traits during the breeding of organisms.
asbestos A naturally occurring, fibrous mineral previously used as insulation for pipes, soundproofing, roof
tiles, and fire retardant. It is considered a carcinogen.
asthenosphere Found below the lithosphere but above the lower mantle, a plastic-like layer within the Earth
that tends to flow.