Glossary

Anaerobic - Referring to any process that can occur without oxygen, or to the metabolism of an organism that can live without oxygen; strict anaerobes cannot survive in the presence of oxygen.

Coniferous Trees - A cone-bearing tree.

Ecosystem - The complex of a community and its enviroment functioning as an ecological unit in nature.

Fertile Crescent - The domestication of plants and animals began about 11,000 years ago in the area known as the fertile crescent.

Jet Stream - A long narrow meandering current of high-speed winds near the tropopause blowing from a generally weterly direction and often exceeding a speed of 250 mile per hour.

Lahar - A flowing mass of mingled volcanic debris and water.

Latitude - Distance north or south of the equator, measured in degrees. A degree of latitude is about 69 miles.

Nitrate - A form of nitrogen commonly used by plants. Nitrate is composed of one nitrogen atom and three oxygen atoms.

Nitrite - An oxidized form of nitrogen toxic to plants composed of one nitrogen atom and two oxygen atoms.

Nucleic acid - An organic acid consisting of joined nucleotide complexes; the two types are deoxyribonucleic acd (DNA) and ribonucleic acd (RNA).

Permafrost - A layer of ground which stays frozen year round.

Producers - Plants and unicellular photosynthetic organisms which convert the suns energy into food for other organisims. Producers form the foundation of the earths ecosystems.

Pyroclastic flows - Formed by or involving fragmentation as a result of volcanic or igneous action.

Saprophytic - An organism is consider saprophytic if it obtains its food from nonliving organic matter, these organisms are called saprophytes.

Stalactites - A deposit of calcium carbonate resembling an icicle hanging from the roof or sides of a cavern.

Stalagmites - A deposit of calcium carbonate like an inverted stalactite formed on the floor of a cave by the drip of calcareous water.

Tephra - Solid material ejected during the eruption of a volcano and transported through the air.