vocabulary

science biographies

cross timbers
intermediate

constructive & destructive

habitats biomes ecosystems

inherited & learned traits



AA: A slow moving type of lava that hardens to form rough chunks; cooler than pahoehoe. ABDOMEN: The region of an organism, such as an insect, that contains its reproductive organs and part of its digestive tract. ABIOTIC FACTOR: A nonliving part of an ecosystem. ACCELERATION: The rate at which velocity changes. ACID RAIN: Rain that is more acidic then normal, caused by the release of molecules of sulfur dioxide and nitrogen oxide into the air. ACTIVE TRANSPORT: The movement of materials through a cell membrane using energy. ACTIVE: Said of a volcano that is erupting or shows signs of eruption in the near future. ADAPTATION: A characterisitic that helps an organism survive in its environment or reproduce. AIR MASS: A huge body of air that has similar temperature, pressure and humidity throughout. AIR PRESSURE: A force that is the result of the weight of a column of air pushing down on an area. ALTITUDE: Elevation above sea level. AMORPHOUS SOLID: A solid made up of particles that are not arranged in a regular pattern. ANEMOMETER: An instrument used to measure wind speed. ANEROID BAROMETER: An instrument that measures changes in air pressure without using a liquid. Changes in the shape of an airtight metal box cause a needle on the barometer dial to move. ANTICLINE: An upward fold in rock formed by compression of Earth's crust. ANTICYCLONE: A high-pressure center of dry air. ANUS: The opening at the end of an organism's digestive system through which wastes are eliminated. AQUIFER: An underground layer of rock or soil that holds water. ARACHNID: An arthropod with two body sections. ARTESIAN WELL: A well in which water rises because of pressure within the aqcuifer. ARTHROPOD: An invertebrate that has an external skeleton, a segmented body, and jointed attachments called apendages. ASEXUAL REPRODUCTION: The reproductive process that involves only one parent and produces offspring that are identical to the parent. ASTEROID BELT: The region of the solar system between the orbits of Mars and Jupiter, where many asteroids are found. ASTEROIDS: Objects revolving around the sun that are too small and too numerous to be considered planets. ATMOSPHERE: The mixture of gases that surrounds Earth. The outermost of the four spheres into which scientists divide Earth. ATOM: The smallest particle of an element. ATRIUM: Each of the two upper chambers of the heart that recives blood coming into the heart. AURORA BOREALIS: A colorful, glowing display in the sky caused when particles from the sun strike oxygen and nitrogen atoms in the ionosphere; also called the Northern Lights. AUTOTROPH: An organism that makes its own food.

		BALANCED FORCES: Equal forces acting on an object in opposite directions. BAROMETER: An instrument used to measure changes in air pressure. BATHOLITH: A mass of rock formed when a large body of magma cooled inside the crust. BILATERAL SYMMETRY: Line symmetry; the quality of being divisible into two halves that are mirror images. BINARY FISSION: A form of asexual reproduction in which one cell divides to form two identical cells. BINOMIAL NOMENCLATURE: The naming system for organisms in which each organism is given a two-part name - a genus name and a species name. BIOMASS: The living or formerly living material in an ecosystem. BIOMASS FUEL: Fuel made from things that once were alive. BIOTIC FACTOR: A living part of an ecosystem: BIRD: An endothermic vertebrate that has feathers and a four-chambered heart, and lays eggs. BIRTH RATE: The number of births in a population in a certain amount of time. BOILING: Vaporization that occurs on and below the surface of a liquid. BOILING POINT: The temperature at which a substance changes from a liquid to a gas. BOYLE'S LAW: The relationship between the pressure and volume of a gas at a constant temperature; when volume increases, pressure decreases. BUDDING: A form of asexual reproduction in which a new organism grows out of the body of the parent.

	CALDERA: The large hole at the top of a volcano formed when the roof of a volcano's magma chamber collapses. CARNIVORE: An animal that eats only other animals. CARRYING CAPACITY: The largest population that an area can support. CARTILAGE: A connective tissue that is more flexible than bone and that gives support to some parts of the body. CELSIUS SCALE: The temperature scale at which zero and 100 are the temperatures at which water freezes and boils. CELL: The basic unit of structure and function in an organism. CELL CYCLE: The regular sequence of growth and division that cells undergo. CELL MEMBRANE: THe outside boundary of a cell; controls which substances can enter or leave the cell. CELL THEORY: A widely accepted explanation of the relationship between cells and living things. CELL WALL: A rigid layer of nonliving material that surrounds the cells of plants and some other organisms. CHARLE'S LAW: The relationship between the temperature and volume of a gas at a constant pressure; when temperature increases, volume increases. CHEMICAL BOND: The force that holds two atoms together. CHEMICAL CHANGE: A change in matter that produces new substances. CHEMICAL PROPERTY: A characteristic that is observed when a substance interacts with another substance. CHEMISTRY: The study of the properties of matter and how matter changes. CHLOROPHYLL: A substance that gives chloroplasts their green color and captures light energy during photosynthesis. CHLOROPLAST: A structure in the cells of plants and some other organisms that captures energy from sunlight and uses it to produce food. CHROMATID: One of the pair of the identical rods of a chromosome. CHROMATIN: Material in cells that contains DNA and carries genetic information. CHROMOSOME: A rod-shaped cellular structure made of condensed chromatin; contains DNA, which carries the genetic information that controls inherited characteristics suchas eye color and blood type. CHROMOSPHERE: The middle layer of the sun's atmosphere. CILIA: The hairlike projections on the outside of the cells that move in a wavelike manner. CINDER CONE: A steep, cone-shaped hill or mountain made of volcanic ash, cinders, and bombs piled up around a volcano's opening. CIRRUS: Wispy, feathery clouds made of mostly ice crystals that form at high levels, above about 6 kilometers. CLASSIFICATION: The process of grouping things based on their similarities. CLEAVAGE: A mineral's ability to split easily along flat surfaces. CNIDARIANS: Animals that use stinging cells to capture prey and defend themselves, and take food into a hollow central cavity. COMBUSTION: A rapid reaction between oxygen and fuel that produces thermal energy. COMET: A ball of ice and dust whose orbit is a long, narrow ellipse. COMMUNITY: All the different populations that live together in an area. COMPOSITE VOLCANO: A tall, cone-shaped mountain in which layers of lava alternate with layers of ash and other volcanic materials. COMPOSTING: The process by which the wastes and remains of living things decay in the soil. COMPOUND: A substance made of two or more elements chemically combines in a set ratio. COMPOUND MICROSCOPE: A light micrscope that has more than one lens. COMPRESSION: Stress that squeezes rock until it folds or breaks. CONDENSATION: The change from the gaseous to the liquid state of matter; also, the process by which a gass, such as water vapor, changes to a liquid, such as water. CONDUCTION: The trasfer of heat by movements of fluids. CONJUGATION: The process in which a unicellular organism transfers some of its genetic material to another unicellular organism. CONSERVATION: The process of using a resource wisely so it will not be used up. CONSUMER: An organism that obtains energy by feeding on other organisms. CONTINENTAL (AIR MASS): A dry air mass that forms over land. CONTOUR LINE: A line on a topographic map that connects points of equal elevation. CONTROL RODS: Cadmium rod used in a nuclear reactor to absorb neutrons from fission. CONTROLLED EXPERIMENT: An experiment in which all of the variables except for one remain the same. CONVECTION: The transfer of heat by movement of current within a fluid. CONVEX LENS: A lens that is thicker in the center than at the edges. CORE: The central part of the sun, where nuclear fusion occurs. CORIOLIS EFFECT: The way the Earth's rotation makes winds in the Northern Hemisphere curve to the right and winds in the Southern Hemisphere to curve to the left. CORONA: The outer layer of the sun's atmosphere. COTYLEDON: A seed leaf that stores food. CRATER: A bowl-shaped area that forms around a volcano's central opening. CROP: A bird's internal storage tank that allows it to store food inside its body after swallowing the food. CRUST: The layer of rock that forms Earth's outer layer. CRUSTACEAN: An arthropod that has two or three body sections, five or more pairs of legs, two pairs of antennae, and usually three pair of appendages for chewing. CRYSTAL: A solid in which the atoms are arranged in a pattern that repeats again and again. CRYSTALLINE SOLID: A substance that is made of crystals in which the particles are arranged in a regular, repeating pattern. CUMULUS: Clouds that form less than 2 kilometers above the ground and look like fluffy, rounded piles of cotton. CYCLONE: A swirling center of low air pressure. CYTOKINESIS: The final stage of the cell cycle, in which the cell's cytoplasm divides, distributing the organelles into each of the two new cells. CYTOPLASM: The region of a cell located inside the cell membrane (in prokaryotes) or between the cell membrane and nucleus (in eukaryotes); contains gel-like material and cell organelles.

	DATA: The facts, figures, and other evidence collected in an experiment. DEATH RATE: The number of deaths in a certain amount of time. DECAY: The destruction or decomposition of organic matter as a result of bacterial or fungal action; to rot. DECOMPOSER: An organism that breaks down large chemicals fromdead organisms into small chemicals and returns important materials to the soil and water. DEFORMATION: A change in the volume or shape of the Earth's crust. DELTA: A landform made of sediment that is deposited where a river flows into an ocean or lake. DENSITY: The measurement of how much mass of a substance is contained in a given volume. DEPOSITION: The process by which sediment settles out of the water or wind that is carrying it, and is deposited in a new location. DESALINATION: The process of obtaining fresh water from salt water by removing salt. DEW POINT: The temperature at which condensation begins. DIAPHRAGM: A large, dome-shaped muscle that has an important important function in breathing. DIFFUSION: The process by which molecules move from an area in which they are highly concentrated to an area in which they are less concentrated. DIKE: A slab of volcanic rock formed when magma forces itself across rock layers. DIRECTLY PROPORTIONAL: A term used to describe the relatinoship between two variables whose graph is a straight line passing through the point (0,0). DIVIDE: A ridge of land that separates one drainage basin or watershed from another. DNA (DeoxyriboNucleic Acid): The genetic material that carries information about an organism and is passed from parent to offspring. DORMANT: Said of a volcano that does not show signs of erupting in the near future. DROUGHT: A water shortage caused by long periods of low precipitation in a particular area.

	EARTHQUAKE: The shaking that results from the movement of rock beneath Earth's surface. ECHINODERM: A radially shaped symmetrical invertebrate that lives on the ocean floor and has a spiny internal skeleton. ECOLOGY: The study of how living things interact with each other and with their environment. ECOSYSTEM: All the living and nonliving things that interact in an area. ECTOTHERM: An animal whose body does not produce much internal heat. EFFICIENCY: The percentage of energy that is used by a device to perform work. EGG: A female sex cell. EL NINO: An abnormal climate event that occurs every 2 to 7 years in the Pacific Ocean, causing changes in winds, currents, and weather patterns that can lead to dramatic climate changes. ELECTRODE: A metal strip that gains or loses electrons during electrolysis. ELECTROLYSIS: A process by which an elecetric current breaks chemical bonds. ELECTROMAGNETIC WAVE: A form of energy that cna travel through space. ELEMENT: A substance that cannot be broken down into other substances by chemical and physical means. ELLIPSE: An elongated circle, or oval shape; the shape of the planets' orbits. EMBRYO: The young organism that develops from a zygote. EMIGRATION: Leaving a population. ENDOPLASMIC RETICULUM: A cell structure that forms a maze of passageways in which proteins and other materials are carried from one part of the cell to another. ENDOSKELETON: An internal skeleton. ENDOSPORE: A small, rounded, thick-walled, resting cell that forms inside a bacterial cell. ENDOTHERM: An animal whose body controls and regulates it remperature by controlling the internal heat it produces. ENERGY: The ability to do work or cause change. ENERGY CONSERVATION: The practice of reducing energy use. ENERGY TRANSFORMATION: Any change from one form of energy to another. EPICENTER: The point on Earth's surface directly above an earthquake's focus. EQUATOR: An imaginary line halfway between the North and South that circlec the Earth. EROSION: The process by which wwater, ice, wind, or gravity moves fragments of rock and soil. ESTIMATE: An approximation of a number, based on reasonable assumption. ETHANOL: An alternative fuel; aliquid alcohol fuel with vapors denser than air; produced from agricultural products such as corn, grain, and sugar cain. EUKARYOTE: An organism with cells that contain nuclei and other cell structures. EVACUATE: To move away temporarily. EVAPORATION: The process that occurs when vaporization takes place only on the surface of a liquid; also, the process by which molecules at the surface of a liquid, such as water, absorb enough energy to change to a gaseous state, such as water vapor. EXOSKELETON: An outer skeleton. EXOSPHERE: The outer layer of the thermosphere, extending outward into space. EXTERNAL STIMULUS: A change in an organism's surroundings that causes the organism to react. EXTINCT: Describes a type of organism that no longer exists anywhere on Earth; also, a volcano that is unlikely to erupt again. EXTRUSIVE ROCK: Igneous rock that forms from lava on Earth's surface.

	FAULT: A break or crack in Earth's lithosphere along which rocks move. FAULT-BLOCK MOUNTAIN: A mountain that forms where a normal fault uplifts a block of rock. FERMENTATION: The process by which cells break down molecules to release energy without using oxygen. FERTILIZATION: The joining of a sperm cell and an egg cell. FLAGELLUM: A long, whiplike structure that helps a unicellular organism move. FLASH FLOOD: A sudden, violent flood that occurs within a few hours, or even minutes, of a heavy rainstorm. FLOOD: The overflowing of a river's channel due to the increase of the volume of water in the river. FLOOD PLAIN: A broad, flat valley through which a river flows. FLOWER: The reproductive structure of an angiosperm. FOCUS: The point beneath Earth's surface where rock breaks under stress resulting in an earthquake. FOLD: A bend in rock that forms where part of Earth's crust is compressed. FOOD CHAIN: The series of events in which one organism eats another, resulting in a flow of energy among the organisms involved. FOOD WEB: The pattern of overlapping food chains in an ecosystem. FOOTWALL: The block of rock that forms the lower half of a fault. FORCE: A push or pull exerted on an object. FOSSIL FUEL: An energy-rich substance (such as coal, oil, or natural gas) formed from the remains of organims. FRACTURE: The way a mineral looks when it breaks apart in an inrregular way. FREEZING: The change in state from a liquid to a solid. FRONT: The area where air masses meet and do not mix. FRUIT: The ripened ovary and other structures that enclose one or more seeds of an angiosperm. FUEL: A material that releases energy when it burns. FUEL ROD: The uranium rod that undergoes fission in a nuclear reactor.

	GAMETE: A sperm or egg cell. GAS: A state of matter with no definite shape or volume. GAS GIANTS: The name given to the first four outer planets: Jupiter, Saturn, Uranus, and Neptune. GEMSTONE: A hard, colorful mineral that has a brilliant or galssy luster. GENE: A segment of DNA on a chromosome that codes for a specific trait. GENUS: A classification grouping that consists of a number of similar, closely related species. GEOCENTRIC SYSTEM: A description of the solar system in which all of the planets revolve around Earth. GEOLOGIST: A scientist who studies the forces that make and shape planet Earth. GEOLOGY: The study of the solid Earth. GEOSYNCHRONOUS ORBIT: The orbit of a satellite that revolves around Earth at the same rate that Earth rotates. GEOTHERMAL ENERGY: Heat energy in Earth's interior from water or steam that has been heated by magma. GESTATION PERIOD: The length of time between fertilization and the birth of a mammal. GEYSER: A typ of hot spring that builds up pressure underground and erupts at regular intervals as a fountain of water ans steam. GILL: An organism's breathing organ that removes oxygen from water. GIZZARD: The thick-walled, muscular part of a bird's stomach that squeezes and grinds partially digested food. GLOBAL WINDS: Winds that blow steadily from specific directions over long distances. GOLGI BODY: A structure in a cell that receives proteins and other newly formed materials from the endoplasmic reticulum, packages them, and distributes them to other parts of the cell. GRAIN: A particle of mineral or other rock that gives a rock its texture. GRAPH: A diagram that shows how two variables are related. GRAVITY: The force that pulls objects toward each other. GREENHOUSE EFFECT: The process by which heat is trapped in the atmosphere by water vapor, cabon dioxide, methane, and other gases that form a "blanket" around the Earth. GROUNDWATER: Water that fills the cracks and spaces in underground soil and rock layers.

	HABITAT: The place where an organism lives and that provides the things it needs to survive. HANGING WALL: The block of rock that forms the upper half of a fault. HEADWATERS: THe many small streams that come together at the source of a river. HEAT: The movement of thermal energy from one substance to another. HELIOCENTRIC SYSTEM: A description of the solar system in which all the planets revolve around the sun. HERBIVORE: An animal that eats only plants. HEREDITY: The passing of traits from parents to offspring. HETEROTROPH: An organism that cannot make its own food. HOMEOSTASIS: The process by which an organism's internal environment is kept stable in spite of changes in its external environment. HORMONE: The chemical product of an endocrine gland that speeds up or slows down the activities or an organ or tissue; also, a chemical that affects a plant's growth and development. HOST: An organism that provides a source of energy or a suitable environment for a virus or for another organism to live. HUMIDITY: A measure of the amount of water vapor in the air. HURRICANE: A tropical storm that has winds of 119 kilometers per hour or higher; typically about 600 kilometers across. HYDROCARBON: A compound that contains carbon and hydrogen atoms. HYDROELECTRIC POWER: Electricity produced by flowing water moving over a waterfall or dam. HYPOTHESIS: A possible explanation for a set of observations or answers to scientific questions; must be testable; based on observations and prior knowledge.

	IGNEOUS ROCK: A type of rock that forms from the colling of molten rock at or below the surface of the Earth. IMMIGRATION: Moving into a population. IMPERMEABLE: Characteristics of materials through which water does not easily pass, such as clay or granite. INERTIA: THe tendenct of a moving object to continue in a straight line or a stationary object to remain in place. INEXHAUSTIBLE RESOURECES: Any living or nonliving thing in the environment for which theere is a limitless supply. INFERENCE: An interpretation of an observation based on evidence and prior knowledge. INFRARED RADIATION: A form of energy with wavelengths that are longer than visible light. INNER CORE: A dense sphere of solid iron and nickel in the center of the Earth. INSECT: An arthropod with three body sections, six legs, one pair of antennae, and usually one or two pairs of wings. INSULATION: A building material that blocks heat transfer between the air inside and the air outside. INTERNAL STIMULUS: A change from within an organism, such as hunger and thirst, that causes the organism to respond. INTERNATIONAL SYSTEM OF UNITS: A system of measurement based on multiples of ten and on established measures of mass, length, and time. INTERPHASE: The stage of the cell cycle that takes place before cell division occurs; during this stage, the cell grows, copies its DNA, and prepares to divide. INTRUSIVE ROCK: Igneous rock that forms when magma hardens beneath Earth's surface. INVERTEBRATE: An animal without backbone. IONOSPHERE: The lower part of the thermosphere, where electrically charged particles called ions are found. IRRIGATION: The process of supplying water to areas of land to make them suitable for growing crops. ISOBARS: Lines on a map joining places that have the same air pressure. ISOTHERMS: Lines on a map joining places that have the same temperature.

	JET STREAMS: Bands of high-speed winds about 10 kilometers above Earth's surface.

	KELVIN SCALE: The temperature scale on which zero is the temperature at which no more energy can be removed from matter. KIDNEY: A major organ of the excretory system; eliminates urea, excess water, and other waste materials from the body.

	LAND BREEZE: THe flow of air from land to a body of water. LARVA: The immature form of an animal that looks very fidderent from the adult. LATITUDE: The distance north or south from the equator, measure in degrees. LAVA: Magma that reaches the surface; also the rock formed when liquid lava hardens. LAVA FLOW: The area covered by lava as it pours out of a volcano's vent. LEAF: The organ of a vascular plant where photosynthesis occurs. LEVEE: A long ridge formed by deposits of sediment alonside a river channel. LIGHTNING: A sudden spark, or energy discharge, cause when electrical charges jump between parts of a cloud or between a cloud and the ground. LIMITING FACTOR: An environmental factor that prevents a population from increasing. LINEAR: The term used to describe the relationship between variables whose graph is a straight line. LIQUID: A state of matter that has a definite volume but no definite shape. LITHOSPHERE: A rigid layer made up of the uppermost part of Earth's mantle and crust. One of four spheres into which scientists divide Earth. LOCAL WIND: Wind that blows over short distances. LUSTER: The way a mineral reflects light from its surface. LYSOSOME: A small rounded cell structure that contains chemicals that break down large food particles into smaller ones.

	MAGMA: The molten mixture of rock-forming substances, gases, and water that makes up part of Earth's mantle. MAGMA CHAMBER: The pocket beneath a volcano where magma collects. MAGNIFICATION: The ability to make things look larger than they are. MAGNITUDE: The measurement of an earthquake's strength based on seismic waves and movement along faults. MAMMARY GLAND: The organ that produces the milk with which mammals feed their young. MANIPULATED VARIABLE: The one factor that a scientist changes during an experiment; also called an independent variable. MANTLE: The layer of hot, solid material between Earth's crust and core. MARITIME (AIR MASS): A humid air mass that forms over oceans. MARSUPIAL: A mammal whos young are born alive at an early age of development, and then usually continue to develop in a puch on their mother's body. MASS: A measure of how much matter is in an object. MATTER: Anything that has mass and takes up space. MEANDER: A looping curve formed in a river as it winds through its flood plains. MELTDOWN: A dangerous condition caused by overheating inside a nuclear reactor. METLING: The change from the solid state to the liquid state of matter. MELTING POINT: THe temperature at which a substance changes from a solid to a liquid. MERCALLI SCALE: A scale that rates earthquakes according to their intensity and how much damage they cause. MERCURY BAROMETER: An instrument that measures changes in air pressure, consisting of a glass tube partly filled with mercury, with its open end resting in a dish of mercury. Air pressure pushig on the mercury in the dish forces the mercury in the tueb higher. MESOSPHERE: The middle layer of the Earth's atmosphere; the layer in which most meteroids burn up. METAMORPHIC ROCK: A type of rock that forms from an existing rock that is change by heat, pressure, or chemical reactions. METAMORPHOSIS: A process in which an animal's body undergoes dramatic changes during its life cycle. METEOR: A streak of light in the sky produced by the burning of a meteroid in Earth's atmosphere. METEORITE: A meteroid that has hit Earth's surface. METEOROID: A chunk of rock or dust in space. METEOROLOGIST: A scientist who studies the causes of weather and tries to predict it. METHANE: An odorless gas produced by the decomposition of organic matter. MICROSCOPE: An instrument that makes small objects look larger. MINERAL: A naturally occurring inorganic solid that has a crystal structure and a definite chemical composition. MITOCHONDRIA: Rod-shaped cell structures that produce most of the energy needed to carry oput the cell's function. MITOSIS: The stage of the cell cycle during which the cell's nucleus divides into two new nuclei and one copy of the DNA is distributed into each daughter cell. MIXTURE: Two or more substances that are mixed together but not chemically combined. MOLECULE: A particle made of two or more atoms bonded together. MOLLUSK: An invertebrate with a soft, unsegmented body; most are protected by hard outer shells. MOMENT MAGNITUDE SCALE: A scale that rates earthquakes by estimating the total energy released by an earthquake. MONOTREME: A mammal that lays eggs. MONSOON:

	NET FORCE: The overall force on an object when all the individual forces acting on an object are added together. NITROGEN FIXATION: The process of changing free nitrogen into form. NONLINEAR: The term used to describe a relationship between variables whose graph is not a straight line. NONERENEWABLE RESOURCE: A natural resource that is not replaced as it is used. NORMAL FAULT: A type of fault where the hanging wall slides downward; caused by tension in the crust. NUCLEAR FISSION: the splittting of an atom's nucleus into to smaller nuclei. NUCLEAR FUSION: The combonation of two atomic nuclie to produce a single larger nucleus as when two hydrogen atoms join together to form helium, releasing energy. NUCLEUS: The control center of the cell that directs the cells' activity and determines the cell's characteristics; also, the central core of an atom containing protons and usually neutrons. NYMPH: A stage of gradual metamorphosis that usually resembles the adult insect.

			OBSERVATION: The process of using one or more sense to gather information. OCCLUDED: Cut off, as the warm air mass oat an occluded front is cut off from the ground by cooler air beneath it. OMNIVOIRE: An animal that eats plants and animals. ORGAN: A structure in the body that is composed of different kinds of tissue. ORGAN SYSTEM: A group of organs that work together to preform a major function in the body. ORGANELLE: A tiny cell structure that carries out a sprcific function within the cell. ORGANIC: Something living or derived from living things. ORGANISM: A living thing. OSMOSIS: The difusion of water molocules through a selectivly permeable membrane. OUTER CORE: A layer of molten iron and nickel that surrounds the inner core of Earth. OVARY:An organ of the female reproductive system in which eggs and estrogen are produced: also, a protective structure in plants that encloses the developing eggs. OVULE: Aplant structure in seed plants that contains an egg cell. OXBOW LAKE: The cresnt-shaped, cut off body of water that remains after a river carves a new channel. OZONE: Aform of oxegen that has three oxegen atoms in each molocule instead of the usual two.

	P WAVE: A type of seismic wave that compresses and expands the ground. PAHOEHOE: A hot, fast-moving type of lava that hardens to form smooth, rope like coils. PANGAEA: The nameof the sinle land mass that broke apart 225 million years ago and gave rise to todays continents. PARASITE: An organism that lives on or in a host and causes harm to that host. PASSIVE TRANSPORT:The movement of materialsthrough a cell membrane with out using energy. PERMEABLE: Characteristics of materials such as sand and gravel which allow water to pass easily through them. PESTICIDE: A chemical intended to kill insects and other organisms that damage crops. PETROCHEMICAL: A compound made from oil. PETROLEUM: Liquid fossil fuel; oil. PHOTOCHEMICAL SMOG: A brownish haze that is a mixture of ozone and other chemicals, formed when nitrogen oxides, and hydrocarbons, and other polutants acts with one another in the presence of sunligt. PHOTOSPHERE: The inner layer of the suns atmosphere. PHOTOSYNTHESIS: The prcess by which plants and some other organisms capture light energy and use it to make food from carbon dioxide and water . PHYSICAL CHANGE: A change that alters the form or appearance of a substance but does not make the material into another substance. PHYSICAL PROPERTY: A characteristic of a substance that can be observed without changing the substance to something else. PIPE: A long tube through which magma moves from the magma chamber to the Earth's surface. PLACENTA: A membrane that becomes the link between the developing embryo or fetus and the mother. PLACENTAL MAMMAL: A mammal that develops inside its mother's body until its body system can function independently. PLATE BOUNDARY: A crack in the lithosphere where two of Earth's plates meet. PLATE: A section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of continental and oceanic crust. PLATEAU: A landform that has a more or less level surface and is elevated high above sea level. POLAR (AIR MASS): A cold air mass that forms north of 50 degrees north latitude and south of 50 degrees sout latitude and has high air pressure. POLLEN: Tiny particles produced by pants that contain the micrscopic cells that later become sperm cells. POLLUTANT: A harmful sunstance in the air, water, or soil. POPULATION: All the members of one species in a particular area. PORES: Tiny opening in and between particles of rock and soil which may contain air or water. PRECIPITATION: Forms of water such as rain , snow, sleet, or hail that fall from clouds and reach Earth's surface. PREDATOR: A carnivore that hunts and kills other animals for food and has adaptations that help it capture the animals it preys upon. PRESSURE: The force pushing on an area or surface; also, the force of a gas's outward push divided by the area of the walls of the container. PREY: An animal that a predator feeds upon. PRIME MERIDIAN: The line that makes a half-circle from thge North pole to the South pole, passing through Greenwich, England. PRODUCER: An organism that can make its own food. PROKARYOTE: An organism whose cells lack a nuclesu and some other cell structures. PROMINENCE: A loop of gas that protrudes from the sun's surface, linking parts of sunspot regions. PROTOZOAN: An animal-like protist. PSUEDOPOD: A "false foot" or temporary bulge og the cell membrane used for feeding and movement in some protozoans. PYSCHROMETER: An instrument used to measure relative humidity, consisting of a wet-bulb thermometer and a dry-bulb thermometer. PUPA: THe second stage of complete metamorphosis, in which an insect is enclosed in a protective covering and gradually changes from a larva to an adult. PYROCLASTIC FLOW: The explosion of ash, cinders, bombs, and gases during an explosive volcanic eruption.

	None at this time.

	RADIAL SYMMETRY: The quality of having many lines of symmetry that all pass through a central point. RADIATION: The direct transfer of energy by electromagnetic waves. RADULA: A flexible ribbon of tiny teeth in mollusks. RAIN GAUGE: An insturment used to measure the amount of precipitation, consisting of an open-ended container topped by a collecting funnel and having a collecting tube and measuring scale inside. REACTOR VESSEL: The part of a nuclear reactor where nuclear occurs. RECHARGE: New water that enters the aqufier from the surface. REFERENCE POINT: A place or object used for comparison to determin if an object is in motion. REFINERY: A factory where crude oil is seperated into fuels and other products. RELATIVE HUMIDITY: The percentage of water vapors in the air compared to the maximum amount the air can hold at that tempreture. RENEWABLE RESOURCE: A resource that is naturally replaced in a relativley short time. REPLICATION: The process of by which a cell makes a copy of the DNA in it's nucleus. REPRODUCE: The production of offspring that are similar to the parents. RESERVE: A known deposit of fuels. RESERVOIR: A natural or artificial lake that stores water for human use. RESOLUTION: The ability to clearly distinguish theindividual part of the object. RESPIRATION: The process by which cells break down simple food molucles to release the energy they contain. RESPONDING VARIABLE: The factor that changes as a result of changes of the manipulated in an experiment. RETROGADE ROTATION: The spinning motion of a planetfrom west to east, oppoosite to the direction of the direction of most planets and moons. RESPONSE: An action or change in the behavior that occurs as the result of stimulus. REVERSE FAULT: A type of fault where the hanging wall slides upward; caused by compression in the crust. REVOLUTION: The movment of an object around another object. RIBOSOME: A tiny structure of a cell where protiens are made. RICHTER SCALE: A scale that rates seismec waves as measured by a mechanical seismograph. RIVER: A large stream. ROCK: The material that forms Earth's hard surface. ROCK CYCLE: A series of processes on the surface and inside the Earth that slowly changes rocks from one kind to another. ROOT: The under ground part of any plant which anchors the plant in the ground and absorbs water and nutrients from the soil. ROTATION: The spinning motion of a planet about it's axis.

	S WAVES: A type of seismic wave that moves the ground up and down or side to side. SATELLITE: Any object that revolves around another object in space. SATURATED ZONE: A layer of permeable rock or soil in which the cracks and poores are completely filled with water. SCALE: Relates distance on a mpa to the corresponding distance on Earth's surface. SCATTERING: Reflection of light in all directions. SCIENCE: A way of learning about the natural world. SCIENTIFIC INQUIRY: The divers ways in which scientists study the natural world. SCIENTIFIC LAW: A statment that describes what scientists expect to happen every time under a particular set of conditions. SCIENTIFIC THEORY: A well-tested scientific concept that explains a wide range of observations. SEA BREEZE: The flow of air from an ocean or lake to the land. SEDIMENT: Small, solid particles of material from rocks or organisms which are moved by water or wind, resulting in erosion and deposition. SEDIMENTARY ROCK: A type of rock that forms when particles from other rocks or the remains of plants and animals are pressed and cemented together. SEED: The plant structure that contains a young plant inside a protective covering. SEISMIC WAVE: A vibration that travels through the Earth carrying the energy released during an earthquake. SEISMOGRAPH: A device thatrecords ground movements caused by seismic waves as they move through Earth. SELECTIVE BREEDING: The process of selecting a few organisms with desired traits to serve as parents of the next generation. SELECTIVELY PERMEABLE: A property of cell membranes that allows some substances to pass through, while others cannot. SEXUAL REPRODUCTION: The reproductive process that involves two parents who combine their genetic material to produce a new organism, which differs from both parents. SHEARING: Stress that pushes a mass of rock in opposite directions. SHIELD VOLCANO: A wide, gently sloping mountain made of layers of lava and formed by quiet eruptions. SILICA: A material that is formed from the elements oxygen and silicon; silicon is found in magma. SILL: A slab of volcanic rock formed when magma squeezes between layers of rock. SOLAR ENERGY: Energy from the sun. SOLAR FLARE: An explosion of hydrogen gas from the sun's surface that occurs when loops in sunspot regions suddenly connect. SOLAR SYSTEM: A large planetary system that consists of a combination of many smaller planetary systems and objects. SOLAR WIND: A stream of electrically charged particles produced by the sun's corona. SOLID: A state of matter that has a definite volume and definite shape. SPECIES: A group of similar organisms whose members can mate with one another and produce fertile offspring. SPEED: The distance an object travels i none unit of time. SPERM CELL: A male sex cell. SPONTANEOUS GENERATION: The mistaken idea that living things arise from nonliving sources. SPORE: A tiny cell that is able to grow into a new organism. SPRING: A place where groundwater bubbles or flows out of cracks in the rock. STAMEN: The male reproductive parts of a flower. STEM: The stalk-like organ that supports a plant and that connects the roots to the leaves. STIMULUS: A change in an organism's surroundings that causes the organism to respond. STOMATA: The small openings on the undersides of most leaves through which oxygen and carbon dioxide can move. STORM: A violent disturbance in the atmosphere. STORM SURGE: A "dome" of water that sweeps across the coast where the hurricane lands. STRATOSPHERE: The second lowest layer of Earth's atmosphere; the ozone layer is located in the upper stratosphere. STRATUS: Clouds that form in flat layers. STREAK: The color of a mineral's powder. STRESS: The reastion of a person's body and mind to threatening, challenging, or disturbing events. STRIKE-SLIP FAULT: A type of fault hwere rock on either side move past each other sideways with little up-or-down motion. SUBLIMATION: The change in state from a solid directly into a gas without passing through the liquid state. SUBSTANCE: A single kind of matter that has distinct physical and chemical properties. SUNSPOT: A dark, cooler region on the surface of the sun. SURFACE WAVES: A type of seismic wave that forms when P waves and S waves reach Earth's surface. SYNCLINE: A downward fols in rock formed by compression in Earth's crust.

	TAXONOMY: The scientific study of how living things are classified. TEMPERATURE: The average amount of energy of motion in the molecules of a substance. TEMPERATURE INVERSION: A layer of warm air between two cooler layers that oprevent the air close to Earth from escaping. TENSION: Stress that streatches rock so that it becomes thinner in the middle. TERRESTRIAL PLANETS: The name given to the four inner planets: Mercury, Venus, Earth and Mars. TEXTURE: The size, shape and pattern of a rock's grains. THEORY OF PLATE TECTONICS: The theory that pieces of Earth's lithosphere are in constant motion, driven by convection currents in the mantle. THERMAL ENERGY: The total energy of a substance's particles due to their movement or vibration; also, the energy of motion in the molecules of a substance. THERMOMETER: An instrument used to measure the temperature, consisting of a thin, glass tube with a bulb on one end that contains a liquid, usually mercury or alcohol. THERMOSPHERE: The outermost layer of Earth's atmosphere. THORAX: An insect's mid-section, to which its wings and legs are attached. TISSUE: A group of similar cells that perform a specific function in an organism. TORNADO: A rapidly whirling, funnel-shaped cloud that reaches down from a storm cloud to touch Earth's surface, usually leaving a destructive path. TRAIT: A characteristic that an organism can pass onto its offspring through its genes. TRANSPIRATION: The process by which water is lost through a plant's leaves. TRIBUTARY: A stream or small river that flows into a larger stream. TROPICAL (AIR MASS): A warm air mass that forms in the tropics and has low air pressure. TROPISM: The growth response of a plant toward or away from a stimulus. TROPOSPHERE: The lowest layer of the Earth's atmosphere; where most weather occurs.

	ULTRAVIOLET RADIATION: A form of energy with wavelengths that are shorter than visible light. UNBALANCED FORCES: A nonzero net force that changes an object's motion. UNSATURATED ZONE: A layer of rocks and soil above the water table in which the pores contain air as well as water.

	VACUOLE: A water-filled sac inside a cell that acts as a storage area. VAPORIZATION: The change from the liquid to the gaseous state of matter. VARY INVERSELY: A term used to describe the relationship between two variables whose graph forms a curve that slopes downward from left to right. VASCULAR TISSUE: The internal transporting tissue in some plants that is made up of tube-like structures. VEIN: A blood vessel that carries blood back to the heart. VELOCITY: Speed in a given direction. VENT: An opening thorugh which molten rock and gas leave a volcano. VENTRICLE: A lower chamber of the heart that pumps blood out to the lungs and body. VERTEBRAE: The bones that make up the backbone of an animal. VERTEBRATE: An animal with a backbone. VISCOSITY: The resistance of a liquid to flowing. VOLCANIC ROCK: A deposit of hardened magma in a volcano's pipe. VOLUME: The amount of space that matter occupies.

	WATER CYCLE: The continuous process by which water moved from Earth's surface to the atmosphere and back passing through the living and nonliving parts of the environment. WATER POLLUTION: The addition of any substance that has a negative effect on water or the living things that depend on the water. WATER TABLE: The top of the saturated zone, or depth to the groundwater in an aquifer. WATER VAPOR: The invisible, gaseous form of water. WATERSHED: THe land area that supplies water to a river system. WEATHER: The condition of the Earth's atmosphere at a particular time and place. WEIGHT: A measure fo the force of gravity on an object. WIND: THe horizontal movement of air from an area of high pressure to an area of lower pressure. WIND-CHILL FACTOR: Increased cooling caused by the wind.

	NONE at this time.

	NONE at this time.

	ZYGOTE: A fertilized egg, produced by the joining of a sperm cell and egg cell.

Hosted by www.Geocities.ws