| Observation
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| Things or phenomena that are perceived through one or more of the basic five senses in their normal state. In addition, to be accepted as factual, the observations must be verifiable by other.
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| Ocean islands
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| Islands in the ocean; formed by breaking away from a continental landmass, volcanic action, coral formation, or a combination of sources; support distinctive communities.
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| Ocean shorelines
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| Rocky coats and sandy beaches alone the oceans; support rich, stratified communities.
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| Ocean thermal electric conversion (OTEC)
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| Energy derived form temperature differentials between warm ocean surface waters and cold deep waters. This differential can be used to drive turbines attached to electric generators.
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| Off-road vehicle (ORV)
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| Any vehicle used cross-country, especially in a recreational capacity (four-wheel-drive vehicles, dune buggies, all-terrain vehicles, snowmobiles, and trail bikes).
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| Offset allowances
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| A controversial component of air quality regulations that allows a polluter to avoid installation of control equipment on one source with an ¡§offsetting¡¨ pollution reduction at another source.
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| Oil
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| see petroleum
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| Oil field
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| The area in which exploitable oil is found
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| Oil sand
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| Sedimentary material containing bitumen, a tar-like hydrocarbon, subject to exploitation under favorable economic conditions.
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| Oil shale
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| A fine-grained sedimentary rock rich in solid organic material called kerogen. When heated, the kerogen liquefies to produce a fluid petroleum fuel.
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| Old growth forest
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| Ancient forests with trees often 150 to 1000 or more years old.
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| Oligotrophic
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| Condition of rivers and lakes that have clear water and low biological productivity (oligo = little; trophic = nutrition); are usually clear, cold, infertile headwater lakes and streams.
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| Omnivore
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| An organism that eats both plants and animals.
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| Open access system
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| A commonly held resource for which there are no management rules.
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| Open canopy
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| A forest where tree crowns cover less than 20 percent of the ground; also called woodland.
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| Open range
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| Unfenced, natural grazing Lands; includes woodland as well as grassland.
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| Open system
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| A system that exchanges energy and matter with its environment.
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| Opportunity costs
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| Costs of lost money-making opportunities (and potentially higher income) incurred when we make a decision to invest our money in a particular way.
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| Optimal range
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| With respect to any particular factor or combination of factors, the maximum variation that still supports optimal or near-optimal growth of the species in question.
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| Optimum
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| The most favorable condition in regard to an environmental factor.
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| Orbital
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| The space or path in which an electron orbits the nucleus of an atom.
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| Ore
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| Rock bearing important minerals, for example, uranium ore.
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| Ore deposit
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| A valuable mineral located in high concentration in a given region.
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| Organic compounds/ molecules
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| Classical definition: all living things and products that are uniquely produced by living things such as wood, leather, and sugar. Chemical definition: All chemical compounds or molecules, natural or synthetic, that contain carbon atoms as an integral part of their molecular structure. Their structure is based on bonded carbon atoms with hydrogen atoms attached. They can be either biodegradable to nonbiodegradable. (Contrast inorganic compounds.)
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| Organic farming
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| Agricultural system in which natural fertilizers (manure and crop residues), crop rotation, contour planting, biological insect control measures, and other techniques are used to ensure soil fertility, erosion control, and pest control.
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| Organic fertilizer
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| Material such as plant and animal wastes added to cropland and pastures to improve soil. Provides valuable soil nutrients and increases the organic content of soil (thus increasing moisture content).
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| Organic gardening/farming/food
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| Gardening or farming without the use of inorganic fertilizers, synthetic pesticides, or other humanmade materials; food raised with organic farming techniques.
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| Organic phosphate
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| Phosphate (PO4-3) bonded to an organic molecule.
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| Organically grown
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| Generally refers to produce grown without the use of hard chemical pesticides or inorganic fertilizer. However, as of yet there are no official standards defining the use of the term.
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| Organism
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| Any living thing ¡V plant, animal, or microbe.
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| Organismic phase
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| The part of the nutrient cycle in which nutrients are located in organisms: plants, animals, bacteria, fungi, or others.
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| Orphan site
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| The location of a hazardous waste site abandoned by former workers.
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| OSHA (Occupational Safety and Health Administration)
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| Promulgates regulations concerning measures that must be taken to protect workers.
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| Osmosis
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| The phenomenon whereby water diffuses through a semipermeable membrane toward an area where there is more material in solution (where there is a relatively lower concentration of water). Has particular application regarding salinization of soils where plants are unable to grow because of osmotic water loss.
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| Otimum
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| The condition or amount of any factor or combination of factors that will product the best result. For example, the amount of hear, light, moisture, nutrients, and so on that will product the best growth. Either more or less than the optimum is not as good.
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| Outbreak
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| A population explosion of a particular pest. Often caused by an application of pesticides that destroys the pest¡¦s natural enemies.
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| Out-migration
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| Movement of people out of a state or region within a country to set up residence elsewhere in that country.
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| Output approach
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| A method of solving an environmental problem by controlling the outputs. For example, composting or burning trash reduces the land requirements for solid waste disposal. Control devices reduce air and water pollution.
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| Overburden
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| Overlying Layers of noncommercial sediments that must be removed to reach a mineral or coal deposit.
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| Overcultivation
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| The practice of repeated cultivation and crop growing more rapidly than the soil can regenerate, leading to a decline in soil quality and productivity.
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| Overgrazing
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| The phenomenon of animals¡¦ grazing in greater numbers than the land can support in the long term. There may be a temporary economic gain in the short term, but the grassland (or other ecosystem) is destroyed, and its ability to support life in the long term is vastly diminished.
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| Overnutrition
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| Receiving too many calories.
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| Overpopulation
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| A condition resulting when the number of organisms in an ecosystem exceeds its ability to assimilate wastes and provide resources. Creates physical and mental stress on a species as a result of competition for limited resources and deterioration of the environment.
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| Overshoot
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| The extent to which a population exceeds the carrying capacity of its environment.
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| Oxidants
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| Oxidizing chemicals (for example, ozone) found in the atmosphere.
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| Oxidation
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| Chemical reaction process that generally involves breakdown through combining with oxygen. Both burning and cellular respiration are examples of oxidation. In both cases, organic matter is combined with oxygen and broken down to carbon dioxide and water.
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| Oxygen cycle
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| The circulation and reutilization of oxygen in the biosphere.
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| Oxygen sag
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| Oxygen decline downstream from a pollution source that introduces materials with high biological oxygen demands.
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| Oxygen-demanding wastes
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| Organic wastes that are broken down in water by aerobic bacteria. Aerobic breakdown causes the oxygen levels to drop.
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| Ozone
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| A highly reactive molecule containing three oxygen atoms; a dangerous pollutant in ambient air. In the stratosphere, however, ozone forms an ultraviolet absorbing shield that protects us from mutagenic radiation.
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| Ozone hole
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| First discovered over the Antarctic, this is region of stratospheric air that is severely depleted of its normal levels of ozone during the Antarctic spring because of CFCs from anthropogenic (human-made) sources.
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| Ozone layer
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| Thin layer of ozone molecules in the stratosphere. Absorbs ultraviolet light and converts it to infrared radiation. Effectively screens out 99% of the ultraviolet light.
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| Ozone shield
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| The layer of ozone gas (O3) in the upper atmosphere that screens out harmful ultraviolet radiation form the Sum.
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