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380 Cards in this Set

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C3 plants
C3 plants a plant that fixes carbon exclusively through the Calvin cycle; named for the three-carbon compound that is initially formed
C4 pathway
C4 pathway a carbon-fixing process in which carbon dioxide is bound to a compound to form a four-carbon Cintermediate
calcareous ooze
calcareous ooze a type of ooze that is mostly calcium carbonate
calcitonin a hormone that stimulates removal of calcium from the blood
caldera a large, circular depression that forms when the magma chamber below a volcano partially empties and causes the ground above to sink
calendar a system used to measure and record the passage of time
the amount of energy needed to raise the temperature of 1 g of water 1°C; the Calorie used to indicate the energy content of food is a kilocalorie
calorimeter a device used to measure the heat absorbed or released in a chemical or physical change
calorimetry the measurement of heat-related constants, such as specific heat or latent heat
Calvin cycle
Calvin cycle a biochemical pathway of photosynthesis in which carbon dioxide is converted into glucose using ATP
CAM crassulacean acid metabolism, a biochemical pathway in certain plants in which carbon dioxide is incorporated into organic acids at night and released for fixation in the Calvin cycle during the day
Canadian shield
Canadian shield a plateau that extends over about a plant that fixes carbon exclusively through the Calvin cycle; named for the three-carbon compound that is initially formed 2 million square miles of Canada and the northeast of the United States
canCER a tumor in which the cells begin dividing at an uncontrolled rate and become invasive
canine a sharp tooth located on either s a plant that fixes carbon exclusively through the Calvin cycle; named for the three-carbon compound that is initially formed ide of the jaw
canopy the layers of treetops that shade the forest floor
capacitance the ability of a conductor to store energy in the form of electrically separated charges
capillarity the attraction between molecules that results in the rise of a liquid in small tubes
capillary a tiny blood vessel that allows an exchange between blood and cells in tissue
capillary action
capillary action the attraction of the surface of a liquid to the surface of a solid, which causes the liquid to rise or fall
capillary fringe
capillary fringethe region of soil just above the water table that contains water under low atmospheric pressure
cap rock
cap rock the top layer of impermeable a plant that fixes carbon exclusively through the Calvin cycle; named for the three-carbon compound that is initially formed rock in an artesian formation
capsid the region of soil just above the water table that contains water under low atmospheric pressure
capsule in mosses, the part that contains spores; in bacteria, a protective layer of polysaccharides around the cell wall
carageenan a substance that is found in the cell walls of red algae and that is used commercially as a smoothing agent in foods
carapace a shieldlike plate that covers the cephalothorax of some crustaceans
carbohydrate any organic compound that is made of carbon, hydrogen, and oxygen and that provides nutrients to the cells of living things
carbonation the conversion of a compound into a carbonate
carbon cycle
carbon cycle the movement of carbon from the nonliving environment into living things and back
carbon fixation
carbon fixation the synthesis of organic compounds from carbon dioxide, such as in photosynthesis
carbonization the process in which a substance that contains carbon, such as plant materials, is reduced into a carbon film
carboxylic acid
carboxylic acid an organic acid that contains the carboxyl functional group
carcinogen a cancer-causing substance
carcinoma a malignant tumor that can grow anywhere in the body and can spread through the bloodstream
cardiac muscle
cardiac muscle the type of involuntary muscle found in the heart
cardiac sphincter
cardiac sphinctera circular muscle located between the esophagus and the stomach
cardiac stomach
cardiac stomach the enlarged foregut of some crustaceans, echinoderms, and other animals
cardiovascular system
cardiovascular system a collection of organs that transport blood throughout the body; the organs in this system include the heart, the arteries, and the veins
carnivore an organism that eats animals
carotenoid a class of pigments that are present mostly in plants and that aid in photosynthesis
carpel the structure where the ovule is in flowering plants
carrier in biology, an individual who has one copy of a recessive autosomal allele that causes disease in the homozygous condition
carrier in physics, a wave that can be modulated to send a signal
carrier protein
carrier protein a protein that transports substances across a cell membrane
carrying capacity
carrying capacity the largest population that an environment can support at any given time
cartilage a flexible and strong connective tissue
cartography the science of mapmaking
cast a type of fossil that forms when sediments fill in the cavity left by a decomposed organism
caste a group of insects in a colony that have a specific function
catalysis the acceleration of a chemical reaction by a catalyst
catalyst a substance that changes the rate of a chemical reaction without being consumed or changed significantly
catastrophism a principle that states that geologic change occurs suddenly
catenation the binding of an element to itself to form chains or rings
cathode the electrode on whose surface reduction takes place
cathode-ray tube
cathode-ray tube a tube that uses an electron beam to create a display on a phosphorescent screen
cation an ion that has a positive charge
caudal fin
caudal fin in fish, a fin that extends from the tail
cause-and-effect relationship
cause-and-effect relationship a relationship between two variables in which a change in one variable leads to a change in the other
cavern a natural cavity that forms in rock as a result of the dissolution of minerals; also a large cave that commonly contains many smaller, connecting chambers
cecum a sac usually found at the beginning of the large intestine
celestial equator
celestial equator the great circle formed on the celestial sphere by extending the plane of the Earth's equator
cell in biology, the smallest unit that can perform all life processes; cells are covered by a membrane and contain DNA and cytoplasm
cell in electricity, a device that produces an electric current by converting chemical or radiant energy into electrical energy
cell cycle
cell cycle the life cycle of a cell; in eukaryotes, it consists of a cell-growth period in which DNA is synthesized and a cell-division period in which mitosis takes place
cell differentiation
cell differentiation the process by which a cell becomes specialized for a specific structure or function
cell division
cell division the formation of two cells from one existing cell
cell junction
cell junction the connection between cells that holds them together as a unit
cell-mediated immune response
cell-mediated immune response an immune response that involves the presence and reaction of T cells
cell membrane
cell membrane a phospholipid layer that covers a cell’s surface and acts as a barrier between the inside of a cell and the cell’s environment
cell plate
cell platethe precursor of a new plant cell wall that forms during cell division and divides a cell into two
cell theory
cell theory the theory that states that all living things are made up of cells, that cells are the basic units of organisms, that each cell in a multicellular organism has a specific job, and that cells come only from existing cells
cellular respiration
cellular respiration the process by which cells produce energy from carbohydrates; atmospheric oxygen combines with glucose to form water and carbon dioxide
cell wall
cell wall a rigid structure that surrounds the cell membrane and provides support to the cell
cementation the process in which minerals precipitate into pore spaces between sediment grains and bind sediments together to form rock
Cenozoic era
Cenozoic era the current geologic era, which began 65.5 million years ago; also called the Age of Mammals
center of mass
center of mass the point in a body that moves as if the entire mass were concentrated there and as if all of the forces were applied there
central nervous system
central nervous system the brain and the spinal cord; its main function is to control the flow of information in the body
central vacuole
central vacuole a large cavity or sac that is found in plant cells or protozoans and that contains air or partially digested food
centric diatom
centric diatom a radially symmetrical member of the phylum Bacillariophyta
centriole an organelle that is active during mitosis
centripetal acceleration
centripetal acceleration the acceleration directed toward the center of a circular path
centromere the region of the chromosome that holds the two sister chromatids together during mitosis
centrosome an organelle that contains the centrioles and is the center of dynamic activity in mitosis
cephalization the concentration of nerve tissue and sensory organs at the anterior end of an organism
cephalopod a marine mollusk that has tentacles extending from the head; an octopus, squid, cuttle-fish, or nautilus
cytotoxic T cell
cephalothorax in arachnids and some crustaceans, the body part made up of the head and the thorax
cereal any grass that produces grains that can be used for food, such as rice, wheat, corn, oats, or barley
cerebellum a posterior portion of the brain that coordinates muscle movement and controls subconscious activities and some balance functions
cerebral cortex
cerebral cortex the gray, outer portion of the cerebrum that controls the higher mental functions, general movement, organ function, perception, and behavioral reactions
cerebral ganglion
cerebral ganglion one of a pair of nerve-cell clusters that serve as a primitive brain at the anterior end of some invertebrates, such as annelids
cerebral hemisphere
cerebral hemisphere either of the two lobes of the cerebrum
cerebrospinal fluid
cerebrospinal fluid a fluid that provides a cushion that protects the brain and spinal cord
cerebrum the upper part of the brain that receives sensation and controls movement
cervix the inferior portion of the uterus
Chagas' disease
Chagas' disease a disease that is caused by trypanosomes and is characterized by a swollen face on only one side, fever, and swollen spleen and liver
chain reaction
chain reaction a reaction in which a change in a single molecule makes many molecules change until a stable compound forms
change of state
change of state the change of a substance from one physical state to another
channel the path that a stream follows
chaparral a type of vegetation that includes broad-leafed evergreen shrubs and that is located in areas with hot, dry summers and mild, wet winters
character displacement
character displacement the difference in character in populations of two species located in different geographical areas relative to populations of the same two species living in the same geographical area, as a result of competition for food and other re
Charles's law
Charles's law the law that states that for a fixed amount of gas at a constant pressure, the volume of the gas increases as the temperature of the gas increases and the volume of the gas decreases as the temperature of the gas decreases
chelicera in arachnids, either of a pair of appendages used to attack prey
cheliped in arthropods, one of the pair of appendages that have claws
chemical any substance that has a defined composition
chemical bond
chemical bond the attractive force that holds atoms or ions together
chemical bonding
chemical bonding the combining of atoms to form molecules or ionic compounds
chemical change
chemical change a change that occurs when one or more substances change into entirely new substances with different properties
chemical energy
chemical energy the energy released when a chemical compound reacts to produce new compounds
chemical equation
chemical equation a representation of a chemical reaction that uses symbols to show the relationship between the reactants and the products
chemical equilibrium
chemical equilibrium a state of balance in which the rate of a forward reaction equals the rate of the reverse reaction and the concentrations of products and reactants remain unchanged
chemical equilibrium expression
chemical equilibrium expression the equation for the equilibrium constant, Keq
chemical formula
chemical formula a combination of chemical symbols and numbers to represent a substance
chemical kinetics
chemical kinetics the area of chemistry that is the study of reaction rates and reaction mechanisms
chemical property
chemical property a property of matter that describes a substance's ability to participate in chemical reactions
chemical reaction
chemical reaction the process by which one or more substances change to produce one or more different substances
chemical sedimentary rock
chemical sedimentary rock sedimentary rock that forms when minerals precipitate from a solution or settle from a suspension
chemical structure
chemical structure the arrangement of the atoms in a molecule
chemical weathering
chemical weathering the process by which rocks break down as a result of chemical reactions
chemiosmosis In chloroplasts and mitochondria, a process in which the movement of protons down their concentration gradient across a membrane is coupled to the synthesis of ATP
chemistry the scientific study of the composition, structure, and properties of matter and the changes that
chemoautotroph an organism that synthesizes organic compounds by using inorganic compounds instead of light
chemosynthesis the production of carbohydrates through the use of energy from inorganic molecules instead of light
chemotropism the tendency of an organism or a part of an organism to grow toward or away from a chemical stimulus
chinook a wind that flows down the eastern slope of the Rocky Mountains
chitin a carbohydrate that forms part of the exoskeleton of arthropods and other organisms, such as insects,
chlorofluorocarbons hydrocarbons in which some or all of the hydrogen atoms are replaced by chlorine and fluorine; used in coolants for refrigerators and air conditioners and in cleaning solvents; their use is restricted because they destroy ozone molecul
chlorophyll a green pigment that is present in most plant cells, that gives plants their characteristic green color, and that reacts with sunlight, carbon dioxide, and water to form carbohydrates
chloroplast an organelle found in plant and algae cells where photosynthesis occurs
choanocyte any of the flagellate cells that line the cavities of a sponge
chordate an animal that at some stage in its life cycle has a dorsal nerve, a notochord, and pharyngeal pouches; examples include mammals, birds, reptiles, amphibians, fish, and some marine lower forms
chorion the outer membrane that surrounds an embryo
chorionic villi
chorionic villi fingerlike projections of the chorion that extend into the uterine lining (singular, chorionic villus)
chorionic villi sampling
chorionic villi sampling a procedure in which the chorionic villi to are analyzed to diagnose fetal genotypes
chromatic aberration
chromatic aberration a defect in a lens that makes the lens focus different colors of light at various points, producing a spectrum
chromatid one of the two strands of a chromosome that become visible during meiosis or mitosis
chromatina portion of the cell nucleus made up of DNA and proteins; it is the carrier of the genes in inheritance
chromatophore in photosynthetic bacteria, an organelle that contains chlorophyll and other pigments
chromosome in a eukaryotic cell, one of the structures in the nucleus that are made up of DNA and protein; in a prokaryotic cell, the main ring of DNA
chromosome map
chromosome map a diagram of gene positions on a chromosome
chromosphere the thin layer of the sun that is just above the photosphere and that glows a reddish color during eclipses
chronic bronchitis
chronic bronchitis a continued inflammation of the bronchi
chrysalis the hard-shelled pupa of certain insects, such as butterflies
chyme the mixture formed in the stomach from digested food particles and gastric fluid
cilium a hairlike structure arranged in tightly packed rows that projects from the surface of some cells
cinder cone
cinder cone a steep-sloped deposit of solid fragments ejected from a volcano
circadian rhythm
circadian rhythm a biological daily cycle
circuit a complete path of an electric current
circuit board
circuit board a sheet of insulating material that carries circuit elements and that is inserted in an electronic device
circuit breaker
circuit breaker a switch that opens a circuit automatically when the current exceeds a certain value
circulatory system
circulatory system the heart and vessels that move blood through the body
circumpolar describes any star that is always visible from a certain latitude
cirque a deep and steep bowl-like depression produced by glacier erosion
cirrhosis a disease in which normal liver tissues are replaced by fibrous tissue
cirri In insects, hairlike tufts located on an appendage (singular, cirrus)
cirrus cloud
cirrus cloud a feathery cloud that is composed of ice crystals and that has the highest altitude of any cloud in the sky
citric acid
citric acid a six-carbon compound formed in the Krebs cycle
cladistics a phylogenetic classification system that uses shared derived characters and ancestry as the sole criterion for grouping taxa
cladogram a diagram that is based on patterns of shared, derived traits and that shows the evolutionary relationships between groups of organisms
clasper in male fish, a structure that transfers sperm into the female's body
class a taxonomic category containing orders with common characteristics
classification the division of organisms into groups, or classes, based on specific characteristics
clastic sedimentary rock
clastic sedimentary rock sedimentary rock that forms when fragments of preexisting rocks are compacted or cemented together
clear cutting
clear cutting a method of harvesting timber in which all of the trees are removed from a land area, providing full sunlight to allow new seeds to develop
cleavage in biological development, a series of cell divisions that occur immediately after an egg is fertilized
cleavage in geology, the tendency of a mineral to split along specific planes of weakness to form smooth, flat surface
cleavage furrow
cleavage furrow the area of the zygote that pinches in and eventually separates the dividing cell
climate the average weather conditions in an area over a long period of time
climatologista scientist who gathers data to study and compare past and present climates and to predict future climate change
climax community
climax community a final, stable community in equilibrium with the environment
clitellum in many leeches and earthworms, a thick depression of the body wall that protects the eggs
cloaca in all vertebrates except mammals and reptiles, a chamber in the intestine that receives materials from the digestive, reproductive, and excretory systems
clone an organism that is produced by asexual reproduction and that is genetically identical to its parent; to make a genetic duplicate
cloning vector
cloning vector an agent, usually a plasmid, that is used to receive and transfer foreign DNA in gene cloning and in recombinant-DNA experiments
closed circulatory system
closed circulatory system a circulatory system in which the heart circulates blood through a network of vessels that form a closed loop; the blood does not leave the blood vessels, and materials diffuse across the walls of the vessels
closed system
closed system a system that cannot exchange matter or energy with its surroundings
cloud a collection of small water droplets or ice crystals suspended in the air, which forms when the air is cooled and condensation occurs
cloud seeding
cloud seeding the process of introducing freezing nuclei or condensation nuclei into a cloud in order to cause rain to fall
cluster a group of stars or galaxies bound by gravity
cnidocyte a stinging cell of a cnidarian
coacervate a mass of colloidal substances held together by electrostatic attraction
coal a combustible sedimentary rock formed by the compaction of partially decomposed plant material
coalescence the formation of a larger droplet by the combination of smaller droplets
coccus a sphere-shaped bacterium
cochlea a coiled tube that is found in the inner ear and that is essential to hearing
Coconino Sandstone
Coconino Sandstone the rock layer of the Grand Canyon that was deposited during the Permian period
cocoon a protective case produced by some insects at their pupal stage
code a set of rules used to interpret data that convey information
codominance a condition in which both alleles for a gene are fully expressed
codon in DNA, a three-nucleotide sequence that encodes an amino acid or signifies a start signal or a stop signal
coefficient a small whole number that appears as a factor in front of a formula in a chemical equation
coefficient of friction
coefficient of friction the ratio of the force of friction between two objects immediately before sliding to the normal force
coelom a body cavity that contains the internal organs
coelomate an animal that has a body cavity in which the internal organs are located
coenocytic describes filaments that do not have cell walls
coevolution the evolution of two or more species that is due to mutual influence, often in a way that makes the relationship more mutually beneficial
coherence The correlation between the phases of two or more waves
cohesion the force that holds molecules of a single material together
cold front
cold front the front edge of a moving mass of cold air that pushes beneath a warmer air mass like a wedge
collar cell
collar cell any of the flagellate cells that line the cavities of a sponge; also called a choanocyte
collenchyma a group of elongated, thick-walled plant cells that support the growth of leaves and stems
colligative property
colligative property a property that is determined by the number of particles present in a system but that is independent of the properties of the particles themselves
collision theory
collision theory the theory that states that the number of new compounds formed in a chemical reaction is equal to the number of molecules that collide, multiplied by a factor that corrects for low-energy collisions
colloblast a cell that is found on the tentacles of a ctenophore and that secretes a sticky substance
colloid a mixture consisting of tiny particles that are intermediate in size between those in solutions and those in suspensions and that are suspended in a liquid, solid, or gas
colon a section of the large intestine
colonial organism
colonial organism a collection of genetically identical cells that are permanently associated but in which little or no integration of cell activitiesOCCURS
color blindness
color blindness the inability to distinguish one color from another
columella the axis of the cochlea
coma a bright shell of gas and dust that surrounds the nucleus of a comet
combined gas law
combined gas law the relationship between the pressure, volume, and temperature of a fixed amount of gas
Combustion the burning of a substance
combustion reaction
combustion reaction the oxidation reaction of an organic compound, in which heat is released
comet a small body of ice, rock, and cosmic dust that follows an elliptical orbit around the sun and that gives off gas and dust in the form of a tail as it passes close to the sun
commensalism a relationship between two organisms in which one organism benefits and the other is unaffected
common-ion effect
common-ion effect the phenomenon in which the addition of an ion common to two solutes brings about precipitation or reduces ionization
communication a transfer of a signal or message from one animal to another that results in some type of response
community a group of various species that live in the same habitat and interact with each other
compact bone
compact bone the layer of bone that is just beneath the periosteum and that gives that bone its strength and rigidity
compaction the process in which the volume and porosity of a sediment is decreased by the weight of overlying sediments as a result of burial beneath other sediments
companion cell
companion cell a cell that gives rise to sieve tubes in angiosperms
competitionthe relationship between two species (or individuals) in which both species (or individuals) attempt to use the same limited resource such that both are negatively affected by the relationship
competitive exclusion
competitive exclusion the exclusion of one species by another due to competition
complementarya characteristic of nucleic acids in which the sequence of bases on one strand is paired to the sequence of bases on the other
complementary base pair
complementary base pair the nucleotide bases in one strand of DNA or RNA that are paired with those of another strand; adenine pairs with thymine or uracil, and guanine pairs with cytosine
complement system
complement system a system of proteins that circulate in the bloodstream and that combine with antibodies to protect against antigens
complete dominance
complete dominancea relationship in which one allele is completely dominant over another
complete metamorphosis
complete metamorphosis the transformation from larva to adult in insects
components of a vector
components of a vector the projections of a vector along the axes of a coordinate system
composite volcano
composite volcano a volcano made of alternating layers of lava and pyroclastic material; also called stratovolcano
composition the chemical makeup of a rock; describes either the minerals or other materials in the rock
compost a mixture of decomposing organic matter, such as manure and rotting plants, that is used as fertilizer and soil conditioner
compound a substance made up of atoms of two or more different elements joined by chemical bonds
compound eye
compound eye an eye composed of many light detectors separated by pigment cells
compound leaf
compound leaf a type of leaf in which the blade is divided into leaflets
compound light microscope
compound light microscope an instrument that magnifies small objects so that they can be seen easily by using two or more lenses, one lens to magnify the object and the other lens to magnify the first lens's image
compound machine
compound machine a machine made of more than one simple machine
compression in physics, a point of highest density in a longitudinal wave; corresponds to maximum amplitude
compression in geology, a reduction in the volume of a substance due to pressure changes
Compton shift
Compton shift an increase in the wavelength of a photon emitted relative to the photon absorbed when scattered by individual electrons or nucleons
computer an electronic device that can accept data and instructions, follow the instructions, and output the results
concave lens
concave lens a lens that is thinner in the middle than at the edges
concave mirror
concave mirror a mirror that is curved inward like the inside of a spoon
concave spherical mirror
concave spherical mirror a mirror whose reflecting surface is an inward-curved segment of a sphere
concentration the amount of a particular substance in a given quantity of a mixture, solution, or ore
concentration gradient
concentration gradient a difference in the concentration of a substance across a distance
conceptual model
conceptual model a verbal or graphical explanation for how a system works or is organized
concretion a piece of mineral matter that forms in the pores of a rock and that hasa different composition from that of the main rock body
condensation the change of state from a gas to a liquid
condensation nucleus
condensation nucleus a solid particle in the atmosphere that provides the surface on which water vapor condenses
condensation polymer
condensation polymer a polymer formed by condensation reactions
condensation reaction
condensation reaction a chemical reaction in which two or more molecules combine to produce water or another simple molecule
conditioning the process of learning by association
cone in plants, a seed-bearing structure
cone in animals, a photoreceptor within the retina that can distinguish colors and is very sensitive to bright light
cone of depression
cone of depression a lowered area of a water table produced when water withdraws from a well
conformer an organism whose physiological reactions follow environmental changes
conglomerate a sedimentary rock composed of rounded gravel or pebbles cemented together by minerals
conic projection
conic projection a map projection that is made by transferring the surface features of the globe onto a cone
conidiophore a type of hypha that bears asexual spores called conidia
conidium an asexual spore produced in certain fungi
conjugate acid
conjugate acid an acid that forms when a base gains a proton
conjugate base
conjugate base a base that forms when an acid loses a proton
conjugation in prokaryotes, algae, and fungi, a type of sexual reproduction in which two cells join temporarily to recombine nuclear material
conjugation bridge
conjugation bridge in certain algae and fungi, a passageway for the transfer of genetic information from one organism to another
connective tissue
connective tissue a tissue that has a lot of intracellular substance and that connects and supports other tissues
conservation the preservation and wise use of natural resources
conservation biology
conservation biology a branch of biology that is the study of the management of natural resources and the preservation of biodiversity
constellation one of 88 regions into which the sky has been divided in order to describe the locations of celestial objects; a group of stars organized in a recognizable pattern
constrictor a snake that kills its prey by crushing and suffocating it
constructive interference
constructive interference a superposition of two or more waves that produces a greater intensity than the sum of the intensities of the individual waves
consumer an organism that eats other organisms or organic matter instead of producing its own nutrients or obtaining nutrients from inorganic sources
consumption crisis
consumption crisis a situation in which natural resources are being used up, wasted, or polluted faster than they can be renewed, replaced, or cleaned up
contact metamorphism
contact metamorphism a change in the texture, structure, or chemical composition of a rock due to contact with magma
continental glacier
continental glaciera massive sheet of ice that may cover millions of square kilometers, that may be thousands of meters thick, and that is not confined by surrounding topography
continental crust
continental crust the rocks underlying the continents
continental drift
continental drift the hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations
continental margin
continental margin the shallow sea floor that is located between the shoreline and the deep-ocean bottom
continental polar
continental polar a cold air mass that forms over land and that has low humidity
continental rise
continental rise the gently sloping section of the continental margin located between the continental slope and the abyssal plain
continental shelf
continental shelf the gently sloping section of the continental margin located between the shoreline and the continental slope
continental slope
continental slope the steeply inclined section of the continental margin located between the continental rise and the continental shelf
continental tropical
continental tropicaa warm air mass that forms over land and that has low humidity
continuous spectrum
continuous spectrum the uninterrupted broad band of all colors (wavelengths) emitted by incandescent solids
contour feather
contour feather one of the most external feathers that cover a bird and that help determine its shape
contour interval
contour intervalthe difference in elevation between one contour line and the next
contour line
contour line a line that connects points of equal elevation on a map
contractile vacuole
contractile vacuole in protozoans, an organelle that accumulates water and then releases it periodically to maintain osmotic pressure
control group
control group in an experiment, a group that serves as a standard of comparison with another group to which the control group is identical except for one factor
controlled experiment
controlled experiment an experiment that tests only one factor at a time by using a comparison of a control group with an experimental group
control rod
control rod a neutron-absorbing rod that helps control a nuclear reaction by limiting the number of free neutrons
conus arteriosus
conus arteriosus in fish, the frontmost chamber of the heart
convection the movement of matter due to differences in density that are caused by temperature variations; can result in the transfer of energy as heat
convection cell
convection cell a pattern of circulation in which warmer materials rise in one location while cooler materials sink in another location
convection current
convection current the vertical movement of air currents due to temperature variations
convective cooling
convective coolingthe process in which the temperature of a mass of air decreases as the air rises and expands
convective zone
convective zone the region of the sun’s interior that is between the radiative zone and the photosphere and in which energy is carried upward by convection
convergent boundary
convergent boundary the boundary between tectonic plates that are colliding
convergent evolution
convergent evolution the process by which unrelated species become more similar as they adapt to the same kind of environment
conversion factor
conversion factor a ratio that is derived from the equality of two different units and that can be used to convert from one unit to the other
convex lens
convex lens a lens that is thicker in the middle than at the edges
convex mirror
convex spherical mirror a mirror whose reflecting surface is an outward-curved segment of a sphere
convex spherical mirror
copolymer a polymer made from two different monomers
coprolite ancient feces, or dung, that have become fossilized
coral reef a limestone ridge found in tropical climates and composed of coral fragments that are deposited around organic remains
coral reef
core The central part of the Earth below the mantle; also the center of the sun
core sample a cylindrical piece of sediment, rock, soil, snow, or ice that is collected by drilling
core sample
Coriolis effect the curving of the path of a moving object from an otherwise straight path due to the Earth's rotation
Coriolis effect
cork the outer layer of bark of any woody plant
cork cambium a layer of tissue under the cork layer where cork cells are produced
cork cambium
cornea a transparent membrane that forms the front portion of the eyeball
coronathe outermost layer of the sun's atmosphere
coronal mass ejectiona part of coronal gas that is thrown into space from the sun
coronal mass ejection
coronary artery one of the two arteries that supply blood directly to the heart
coronary artery
coronary circulation the flow of blood in the arteries that supply the heart
coronary circulation
corpus callosum
corpus callosum
the broad band of white matter that connects the cerebral hemispheres of the brain
corpus luteum
corpus luteum the structure that forms from the ruptured follicle in the ovary after ovulation; it releases hormones
correlation the linear dependence between two variables
corrosionthe gradual destruction of a metal or alloy as a result of chemical processes such as oxidation or the action of a chemical agent
cortex in plants, the primary tissue located in the epidermis; in animals, the outermost portion of an organ
cortisol a hormone that regulates certain phases of carbohydrate, protein, and water metabolism, affects muscle tone, increases gastric secretion, and alters tissue response to injury
cosmic background radiation
cosmic background radiation radiation uniformly detected from every direction in space; considered a remnant of the big bang
cosmology the study of the origin, properties, processes, and evolution of the universe
cotyledon the embryonic leaf of a seed
countercurrent flow
countercurrent flow in fish gills, an arrangement whereby water flows away from the head and blood flows toward the head
covalent bond
covalent bond a bond formed when atoms share one or more pairs of electrons
covalent compound
covalent compound a chemical compound that is formed by the sharing of electrons
coxal gland
coxal gland in some arthropods, a gland that has ducts that open at the base of the leg
cranial cavity
cranial cavity the area in which the brain rests
cranial nerve
cranial nerve one of the nerves that enter or emerge from the brain
cranium the skeleton of the head, especially the portion of the skull where thebrain is enclosed
crater a bowl-shaped depression that forms on the surface of an object when a falling body strikes the object’s surface or when an explosion occurs; a similar depression around the central vent of a volcano or geyser
craton a large area of the continental crust that has not experienced active deformation for a long time
creep the slow downhill movement of weathered rock material
crest the highest point of a wave
cretinism a form of mental retardation caused by hypothyroidism
crevasse in a glacier, a large crack or fissure that results from ice movement
crista one of the many foldings of the inner membrane of mitochondria
critical angle
critical angle the angle of incidence at which acoustic waves are totally reflected
critical mass
critical mass the minimum mass of a fissionable isotope that provides the number of neutrons needed to sustain a chain reaction
critical point
critical point the temperature and pressure at which the gas and liquid states of a substance become identical and form one phase
critical pressure
critical pressure the lowest pressure at which a substance can exist as a liquid at the critical temperature
critical temperature
critical temperature the temperature above which a substance cannot exist in the liquid state
critical thinking
critical thinking the ability and willingness to assess claims critically and to make judgments on the basis of objective and supported reasons
crop a sac or pouch used by birds and some insects to store food
crop milk
crop milk a nutritious milklike fluid secreted by the crop of pigeons and doves to feed their young
crossing-over the exchange of genetic material between homologous chromosomes during meiosis; can result in genetic recombination
cross-pollination a reproductive process in which pollen from one plant is transferred to the stigma of another plant
crude oil
crude oil unrefined petroleum
crustacean an arthropod that has mandibles, antennae, and other appendages; examples include lobsters, shrimp, barnacles, crabs, and water fleas
crustose a type of lichen that has a crustlike body
crystal a solid whose atoms, ions, or molecules are arranged in a regular, repeating pattern
crystal lattice
crystal lattice the regular pattern in which a crystal is arranged
crystalline solid
crystalline solid a solid that consists of crystals
crystal structure
crystal structure the arrangement of atoms, ions, or molecules in a regular way to form a crystal
cud partly digested food that is regurgitated, rechewed, and reswallowed for further digestion by mammals that have a rumen
cultivar a cultivated species or organism that does not have a known wild ancestor; a variety produced by selective breeding, also called cultigen
cumulus cloud
cumulus cloud a low-level, billowy cloud that commonly has a top that resembles cotton balls and a dark bottom
current in geology, a horizontal movement of water in a well-defined pattern, such as a river or stream; the movement of air in a certain direction
cuticle a waxy or fatty and watertight layer on the external wall of epidermal cells
cuttings a root, stem, or leaf that is cut from a living plant and that can produce a new plant
cyanobacterium a bacterium that can carry out photosynthesis, such as a blue-green alga
cyclic process
cyclic process a thermodynamic process in which one form of energy is partly converted into another and the remainder is released as heat
cycloalkane a saturated carbon chain that forms a loop or a ring
cyclone an area in the atmosphere that has lower pressure than the surrounding areas and has winds that spiral toward the center
cylindrical projection
cylindrical projectiona map projection that is made by moving the surface features of the globe onto a cylinder
cyst a cavity or cell that contains embryos or bacteria in a resting stage
cystic fibrosis
cystic fibrosis a fatal genetic disorder in which excessive amounts of mucus are secreted, blocking intestinal and bronchial ducts and causing difficulty in breathing
cytokinesis the division of the cytoplasma of a cell; cytokinesis follows the division of the cell's nucleus by mitosis or meiosis
cytokinin a plant hormone that affects cell division, plant metabolism, and the synthesis of RNA and proteins
cytolysis the bursting of a cell
cytoplasm the region of the cell within the membrane that includes the fluid, the cytoskeleton, and all of the organelles except the nucleus
cytoplasmic streaming
cytoplasmic streaming the flow of cytoplasm in larger cells to facilitate the dispersion of cellular components
cytosine one of the four bases found in DNA and RNA; cytosine pairs with guanine
cytoskeleton the cytoplasmic network of protein filaments that plays an essential role in cell movement, shape, and division
cytosol the soluble portion of the cytoplasm, which includes molecules and small particles, such as ribosomes, but not the organelles covered with membranes
cytotoxic T cell a type of T cell that recognizes and destroys cells infected by virus