abiotic: the nonliving components of the environment such as rock types, slope, geographic setting and climate that affect ecological functions.
acid rain: rain that has become acidic (with a pH of less than 7) from mixing with sulfuric, nitric and other acids that are released into the atmosphere by the burning of fossil fuels.
adaptive radiation: the evolution of an ancestral species into several new species within a relatively short period of time and in a certain geographic area.
adversaries: opponents, enemies or any other mischievous persons that desire to compromise the security of others.
aerial images: images taken from the sky.
Africanized honeybees: a strain of bees that first originated in the 1950s in Brazil as a cross between an aggressive African bee and a honeybee. Also known as Africanized bee, Africanized honey bee, killer bee, Apis mellifera scutellata, Apis mellifera adansoni.
airborne pollutant: any substance introduced into the atmospheric environment that adversely affects the usefulness of a resource.
algae: a diverse group of, mainly aquatic, organisms. These are capable of photosynthesis, and range in size from single celled organisms to “seaweed”. Can grow very fast, especially if excess nutrients are added to the water.
alien species: species that do not naturally occur within an area and that have usually arrived in the area as a result of human intervention (whether deliberate or accidental). Alien species often have adverse effects on native species as a result of competition.
alkalinity: a measure of the capacity of water to neutralize acid. Alkali substances in water include hydroxides or bases.
allergic disease: a disease caused by a peculiar or excessive susceptibility especially to a specific factor.
alpha female: the highest ranked or most dominant individual in a pack.
alternative fuel: a fuel used in vehicles that comes from a source other than petroleum, such as ethanol made from corn and biodiesel made from vegetable oil.
altitude: elevation especially above sea level or above Earth's surface.
amok: wildly; without self-control; in a murderous frenzy.
aquaculture: the production and husbandry of aquatic animals and plants in a controlled environment.
aquifer: underground layer of soil, gravel or permeable rock that bears or transports water.
archipelago: a group of many islands in a large body of water.
arsenal: all the weapons and equipment of an entity.
Asian tiger mosquitoes: a striped mosquito (Aedes albopictus), native to Asia and now present in parts of tropical and subtropical America, that can transmit dengue, yellow fever and West Nile virus.
Aspergillus sydowi: a type of fungal pathogen found in African dust.
asthmatic: relating to breathing with a whistling sound; relating to having asthma.
Atrazine: an herbicide widely used on a variety of crops, notably maize, sorghum and sugarcane, for the pre- and post-emergent control of broad-leaved weeds.