Glossary - Environmental Science - page 336

transpiration The loss of water vapor from plants, especially in the leaves, but also through stems, flowers,
and roots.
trophic level The position an organism occupies on the food chain, defined as the number of energy levels an
organism is from the original source of energy. For example, all producers belong to the first trophic level and
all herbivores belong to the second trophic level in a food chain or web.
tropopause The boundary between the troposphere and the stratosphere.
troposphere The first layer of the Earth's atmosphere. It contains 75 percent of the Earth's atmospheric mass
but is the shallowest atmospheric level.
tsunami A giant wave generated from undersea earthquakes or volcanic eruptions. Tsunami is Japanese for
"seismic seawave."
tundra A cold biome of restricted tree growth, further divided into arctic and alpine regions. The arctic tundra
is located between the ice caps of the North Pole and the boreal forest and is characterized by permafrost. The
alpine tundra is located in the higher elevations of the mountains around the world, above the tree line and be-
low the permanent snow line.
ultraviolet radiation (UV) Radiant energy with wavelengths shorter than the minimum that the human eye is
able to see.
undernourished A term used to describe people who do not receive enough calories on a daily basis.
uniform distribution Even spacing of organisms.
urbanization The movement of human populations from rural to urban lifestyles.
vernal equinox The date with night and day of equal length that signifies the start of spring in the Northern
Hemisphere and start of fall in the Southern Hemisphere, occurring on or about March 21.
volatile organic compounds (VOCs) Unstable substances that can be released as gases from a wide variety of
products, including carpeting, paints, aerosol sprays, cleaning products, building supplies, pesticides, printers,
glues, wood preservatives, moth balls, and air fresheners.
waste-to-energy A term used to describe waste incineration plants where heat that is generated during waste
combustion is captured and used to generate electricity.
wastewater Water that is flushed, goes down the drain, or runs into sewers from streets.
water pollution Any physical or chemical change to the water (surface or groundwater) that can be harmful to
living organisms or make it unfit for other uses.
water vapor Gaseous water.
waterlogged A term used to describe soil that has become saturated or oversaturated with water due to over-ir-
rigation and a rising water table, which can ultimately suffocate plant roots, compact soil, and lead to saliniza-
tion.
weather The short-term description of temperature, wind, and precipitation in a given geographical area.
weathering The process whereby parent material is broken down or eroded by water, wind, sunlight, temperat-
ure fluctuations, and living organisms.