Glossary - Environmental Science - page 328

lichen Organisms made up of the symbiotic relationship between a fungus and a photosynthetic organism (usu-
ally a green alga) or a cyanobacterium. Lichen are able to colonize nutrient-poor environments and are com-
monly seen on leaves, tree branches, bare rock, and exposed soil.
light pollution A result of the excessive use of artificial light, which can cause glare, over-illumination, sky
glow, and decreased night visibility, while also using excessive amounts of energy.
limiting factors The factors that control a population's growth. These include availability of food, shelter, wa-
ter, mates, or anything else an organism depends upon for survival.
lithosphere The rigid outer layer of the Earth. It is comprised of the crust and upper mantle.
lithospheric plates See tectonic plates .
logistic growth curve Represents a population that grows exponentially and then levels off as it reaches envir-
onmental carrying capacity (K).
longitude The east/west location on Earth in relationship to the Prime Meridian, which runs from the poles
through Greenwich, England, usually measured in degrees from 0° to 180°. The longitude lines, which are
farthest apart at the equator and meet at the poles, are often referred to as meridian lines.
long-lasting tomatoes Genetically modified tomatoes that remain fresh longer.
long-lining The practice of dragging a long fishing line behind a boat or attaching it to an anchor with baited
hooks along the length of the line.
malnutrition A condition afflicting people who do not receive enough daily nutrients.
manganese nodules Ball-like structures that form on the ocean floor and contain manganese, along with many
other minerals in smaller amounts, such as copper, zinc, and nickel.
mantle The layer of the Earth found below the crust; contains the upper mantle and lower mantle.
marginal benefit An economic term describing the change in additional benefit associated with a change in
output level.
marginal costs Costs associated with an increase or decrease in output.
market effect Results that are measurable in dollar amounts.
mass extinction event An extinction that occurs quickly and on a large scale, affecting many species.
mesopause The boundary between the mesosphere and the thermosphere. The lowest temperatures on Earth
exist in the mesopause.
mesosphere The third layer of the Earth's atmosphere.
metamorphic rock A rock type formed under extreme heat and pressure, usually deep underground.
mechanical energy Energy possessed by moving objects (kinetic) or energy stored in objects by tension or po-
sition (potential).
methane A naturally occurring gas with the chemical formula CH 4 ; one of the major fossil fuels. Methane in
the atmosphere is considered a greenhouse gas.