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| The theoretical temperature at which a substance possesses no thermal energy. |
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| The part of the ocean floor that is mostly flat and deep. |
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| The rate at which velocity changes with time; the change in velocity may be in magnitude, or in direction, or in both. It is usually measured in m/s2. |
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| Acid A substance that donates hydrogen ions. |
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| A solution in which the hydronium ion concentration is higher than the hydroxide ion concentration. |
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| A system of highly specific body defenses in which particular features of pathogens are recognized. |
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| A change in voltage across the neuron’s cell membrane that represents the way neurons send signals. |
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| Movement of molecules across the cell membrane by a carrier protein that requires energy input. |
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| An evolutionary trait that makes organisms more suited to living and reproducing in their environments. |
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| The evolution of multiple species, each adapted to a distinct way of life, from a single ancestor. |
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| A large body of air with characteristic temperature and humidity. |
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| The force of friction acting on an object due to its motion through air. |
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| An organic molecule that contains a hydroxyl group bonded to a saturated carbon. |
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| An organic molecule containing a carbonyl group in which the carbon is bonded either to one carbon atom and one hydrogen atom or to two hydrogen atoms. |
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| An alternate version of a gene. |
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| Speciation that occurs after a geographic barrier divides a group of organisms into two isolated populations. |
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| The nucleus of a helium atom, which consists of two neutrons and two protons, ejected by certain radioactive elements. |
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Definition
| Electric current that repeatedly reverses its direction; the electric charges vibrate about relatively fixed positions. In the United States, the vibrational rate is 60 Hz. |
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| Alternation of generations |
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Definition
| The plant life cycle, which alternates between a haploid gametophyte stage and a diploid sporophyte stage. |
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| Tiny sacs of air in the lungs where gas exchange occurs. |
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| An organic molecule containing a carbonyl group in which the carbon is bonded to a nitrogen atom. |
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| An organic molecule containing a nitrogen atom bonded to one or more saturated carbon atoms. |
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| The fluid-filled membrane that immediately surrounds and protects a developing embryo. |
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| A description of a substance that can behave as either an acid or a base. |
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| The distance from the midpoint to the crest (or to the trough) of a wave. |
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| A group of multicellular heterotrophic eukaryotes that take food into their bodies for digestion. |
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| A large protein that binds to an antigen with a lock-and-key fit and that helps to disable a pathogen. |
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| A sequence of three nucleotides on a tRNA molecule that pairs with the complementary codon on an mRNA molecule. |
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Definition
| An area of high pressure around which winds flow. |
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| A part of a molecule from a pathogen or other foreign body that is recognized by cells of the acquired immune system. |
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Definition
| The brightness of a star as it appears to our eyes. |
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| Research dedicated to the development of useful products and processes. |
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| A zone of water-bearing rock through which groundwater can flow. |
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| One of the three domains of life, consisting of prokaryotic organisms, many of which are adapted to extreme environments. |
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| Any organic molecule containing a benzene ring. |
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| A blood vessel that carries blood away from the heart. |
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| The selective breeding of organisms with desirable traits in order to produce offspring with the same traits. |
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| A small, rocky, planetlike fragment that orbits the Sun. Tens of thousands of these objects make up an asteroid belt between the orbits of Mars and Jupiter. |
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| The most plastic layer of the mantle, which flows slowly over time. |
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| A thin envelope of atmospheric gas molecules that surrounds a planet. |
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| Pressure that the atmosphere exerts on a surface due to the weight of molecules above that surface. |
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| The smallest particle of an element that has all of the element’s chemical properties. |
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| The mass of an element’s atoms listed in the periodic table as an average value based on the relative abundance of the element’s isotopes. |
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| The standard unit of atomic mass, which is equal to one-twelfth the mass of the common atom of carbon, arbitrarily given the value of exactly 12. |
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| The core of an atom, consisting of two basic subatomic particles: protons and neutrons. |
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| The number that designates the identity of an element, which is the number of protons in the nucleus of an atom; in a neutral atom, the atomic number is also the number of electrons in the atom. |
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| A region of space in which an electron in an atom has a 90 percent chance of being located. |
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| The pattern of frequencies of electromagnetic radiation emitted by the atoms of an element, considered to be the element’s “fingerprint.” |
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| During this kind of change, atoms in a substance are rearranged to give a new substance having a new chemical identity. |
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| A representation of a chemical reaction. |
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| A notation used to indicate the composition of a compound, consisting of the atomic symbols for the different elements of the compound and numerical subscripts indicating the ratio in which the atoms combine. |
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| A property that relates to how a substance changes its chemical identity. |
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| A rearrangement of atoms so that one or more new compounds are formed from preexisting compounds or elements. |
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| The study of matter and the transformations it can undergo. |
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| Autotrophs that use energy from inorganic chemicals to make their food and organic materials. |
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| A form of sensing in which chemicals bind to receptors on chemosensory cells, causing ion channels to open and action potentials to happen. |
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| The organelle in plant cells where photosynthesis occurs. |
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| Linear structures found in the nucleus of eukaryotic cells that contain the cell’s DNA. |
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| A group of species that includes an ancestor and all its descendants. |
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| A diagram that shows the history of speciation events among a group of species. |
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| The general pattern of weather that occurs in a region over a period of years. |
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| A visible aggregate of minute water droplets or tiny ice crystals. |
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| A situation in which the combination of two alleles in a heterozygote results in both traits being expressed. |
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| A sequence of three nucleotides in an mRNA molecule that codes for a single amino acid. |
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| A number used in a chemical equation to indicate either the number of atoms/molecules or the number of moles of a reactant or product. |
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| A front along which a cold air mass moves under and displaces a warm air mass. |
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| An exothermic oxidation–reduction reaction between a nonmetallic material and molecular oxygen. |
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| A body composed of ice and dust that orbits the Sun, usually in a very eccentric orbit, and that casts a luminous tail when it is close to the Sun. |
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| All the organisms that live within a given area. |
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| A material in which atoms of different elements are bonded to one another. |
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| A quantitative measure of the amount of solute in a solution. |
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| A representation of a system that helps in making predictions about how the system behaves. |
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| A transformation from a gas to a liquid. |
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Definition
| The transfer of thermal energy by molecular and electronic collisions within a substance (especially within a solid). |
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| Any material having free charged particles that easily flow through it when an electric force acts on them. |
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| One of the possible spatial orientations of a molecule. |
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| In the absence of external work input or output, the energy of a system remains unchanged. Energy cannot be created or destroyed. |
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| In the absence of an external force, the momentum of a system remains unchanged. Hence, the momentum before an event involving only internal forces is equal to the momentum after the event: mv (before event) = mv (after event) |
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| An organism that obtains food by eating other organisms. |
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| The hypothesis that continents are in motion and that they travel over the face of the Earth rather than remaining fixed in one location. |
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| A transition zone between dry land and the ocean bottom. |
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| A test that excludes the variable being investigated in a scientific experiment. |
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| An abbreviation for an element or atom. |
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| Adenosine triphosphate, the basic unit of energy used in cellular processes. |
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| Living organisms that make their own food and organic materials. |
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Definition
| The part of a neuron that transmits information to other cells, either effector cells or other neurons. |
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Definition
| A cell of the acquired immune system that targets pathogens in bodily fluids. |
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Definition
| One of the three domains of life, consisting of a wide range of generally single-celled prokaryotic organisms. |
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| A substance that accepts hydrogen ions. |
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Definition
| Research dedicated to the discovery of the fundamental workings of nature. |
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Definition
| A solution in which the hydroxide ion concentration is higher than the hydronium ion concentration. |
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| An electron (or positron) emitted during the radioactive decay of certain nuclei. |
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| The primordial explosion of space at the beginning of time. |
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Definition
| A pair of stars that orbit about a common center. |
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Definition
| The movement of substances such as water, carbon, and nitrogen between the tissues of living organisms and the abiotic world. |
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| The amount of organic matter present in an ecosystem. |
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| Major types of terrestrial ecosystems, as classified by their plant life, including tropical forest, temperate forest, coniferous forest, tundra, savanna, temperate grassland, chaparral, and desert. |
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| Pertaining to living organisms. |
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| The remains of a giant star that has collapsed upon itself, so dense, and with a gravitational field so intense, that light itself cannot escape from it. |
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| Evaporation in which bubbles form beneath the liquid surface. |
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Definition
| The amount of heat needed to change the temperature of 1 gram of water by 1 degree Celsius. |
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Definition
| A small blood vessel from which materials are exchanged with body tissues. |
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Definition
| Sugars, starches, and other organic molecules composed of carbon, hydrogen, and oxygen atoms. |
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Definition
| An organic molecule containing a carbonyl group in which the carbon is bonded to a hydroxyl group. |
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Definition
| Proteins that help molecules normally unable to cross the cell membrane to do so, either with or without energy input. |
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| A maximum number of individuals or maximum population density that a habitat can support. |
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| A substance that increases the rate of a chemical reaction by lowering its activation energy. |
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| An imaginary sphere surrounding Earth to which the stars are attached. |
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Definition
| The series of steps cells go through when they divide. |
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| The membrane that separates the inside of the cell from the outside. |
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| The units that make up all living organisms (except viruses). |
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| Following glycolysis, the aerobic breakdown of glucose that results in production of ATP. |
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| The time of “recent life,” from 65 million years ago to the present. |
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| The brain and spinal cord. |
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| Any force that is directed at right angles to the path of a moving object and that tends to produce circular motion. |
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Definition
| A self-sustaining reaction in which the products of one reaction event stimulate further reaction events. |
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Definition
| The attraction between two atoms that holds them together in a compound. |
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Definition
| The transfer of thermal energy in a gas or liquid by means of currents in the heated fluid. The fluid flows, carrying energy with it. |
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| Air that rises upward carrying thermal energy. |
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| Convergent plate boundary |
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| A place where neighboring plates move toward each other; old lithosphere is destroyed here. |
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Definition
| The central, metallic, spherical layer of Earth, consisting of a solid inner part and liquid outer part. |
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Definition
| The tendency for moving bodies not attached to Earth (such as air molecules) to turn in their path relative to Earth’s surface. |
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Definition
| The deterioration of a metal, typically caused by atmospheric oxygen. |
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Definition
| The study of the origin and structure of the physical universe. |
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Definition
| The SI unit of electrical charge. One coulomb (symbol C) is equal in magnitude to the total charge of electrons. |
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Definition
| The relationship among force, charge, and distance: F = k q1q2/d2. If the charges are alike in sign, the force is repelling; if the charges are unlike, the force is attractive. |
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Definition
| A chemical bond in which atoms are held together by their mutual attraction for two electrons they share. |
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| The minimum mass of fissionable material in a reactor or nuclear bomb that will sustain a chain reaction. |
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Definition
| A relative dating principle stating that where an igneous intrusion or fault cuts through other rocks, the intrusion or fault is younger than the rock it cuts. |
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| The thin, rocky surface layer of the Earth. |
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Definition
| A group of atoms arranged in an orderly, repeating geometric structure. |
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Definition
| The process of forming a crystalline structure during solidification. |
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Definition
| Value given by voltage/resistance. |
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Definition
| An area of low pressure around which winds flow. |
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Definition
| The portion of the cell outside the nucleus. |
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| An accumulation of sediment where a stream enters a lake or ocean. |
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Definition
| The parts of a neuron that receive information from other cells, either sensory cells or other neurons. |
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Definition
| A measure of mass per volume for a substance. |
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Definition
| The process of eroded particles coming to rest at a particular location. |
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Definition
| The temperature at which saturation is reached and condensation occurs. |
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Definition
| The process by which gravity separates materials of different densities. |
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Definition
| Any bending of light by means other than reflection and refraction. |
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Definition
| The random movement of molecules resulting in the transport of molecules from an area of high concentration to an area of low concentration. |
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Definition
| The process through which food is broken down into organic molecules that can be absorbed and used by the body. |
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Definition
| Cells containing two of each kind of chromosome. |
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Definition
| A separation of charge that occurs in a chemical bond because of differences in the electronegativities of the bonded atoms. |
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Definition
| An electric current flowing in one direction only. |
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Definition
| The separation of light into colors arranged by frequency. |
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Definition
| The process of mixing a solute in a solvent. |
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Definition
| A place where neighboring plates move away from each other; new lithosphere is created here. |
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Definition
| Line that traces the highest ground between streams. |
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Definition
| Deoxyribonucleic acid, the cell’s genetic material, a double-stranded molecule consisting of sugar-phosphate backbones attached by pairs of matched nitrogenous bases; in the form of a double helix. |
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Definition
| The allele that is expressed in a heterozygote. |
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Definition
| The change in frequency of a wave due to the motion of the source (or due to the motion of the receiver). |
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Definition
| The shaking or trembling of the ground that results when rock under Earth’s surface moves or breaks. |
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Definition
| The plane of Earth’s orbit. |
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| Changes in the species composition of an ecosystem following a disturbance. |
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Definition
| The study of how organisms interact with their environments. |
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| All the organisms that live within a given area and all the abiotic |
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