Section 1
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Cards (645)
Section 1
(50 cards)
anthropoids
humanlike primates
asteroid
rocky remnant of the early solar system found mostly between the orbits of Mars and Jupiter in the asteroid belt.
aorta
largest blood vessel in the body; transports oxygen-rich blood from the left ventricle of the heart to the arteries.
abiotic factors
nonliving parts of an organism's environment.
armature
The wire coil of an electric motor, made up of many loops mounted on an axle or shaft.
artesian well
Fountain of water that spurts above the land surface when a well taps a deep, confined aquifer containing water under pressure.
acceleration
The rate at which the velocity of an object changes.
artery
large, thick-walled muscular vessel that carries blood away from the heart.
aphelion
Point in a planet's orbit where it is farthest from the Sun.
active transport
energy-expending process by which cells transport materials across the cell membrane against a concentration gradient.
antibodies
proteins in the blood plasma produced in reaction to antigens that react with and disable antigens.
appendicular skeleton
one of two main parts of the human skeleton, includes the bones of the arms and legs and associated structures, such as the shoulders and hip bones.
asexual reproduction
type of reproduction where one parent produces one or more identical offspring without the fusion of gametes.
anaerobic
chemical reactions that do not require the presence of oxygen.
adaptive radiation
divergent evolution in which ancestral species evolve into an array of species to fit a number of diverse habitats.
aquifer
Permeable underground layer through which groundwater flows relatively easily.
analog forecast
Weather forecast that compares current weather patterns to patterns that occurred in the past.
amplitude
The height of a wave from the origin to a crest, or from the origin to a trough.
aerobic
chemical reactions that require the presence of oxygen.
acid
any substance that forms hydrogen ions in water and has a pH below 7.
albedo
Amount of sunlight that is reflected by the surface of a planet or a satellite, such as the Moon.
allotropes
Forms of an element with different structures and properties when they are in the same state—solid, liquid, or gas.
activation energy
The minimum amount of energy required by reacting particles in order to form the activated complex and lead to a reaction.
alkaline earth metals
Group 2A elements in the modern periodic table.
alloy
A mixture of elements that has metallic properties.
analogous structures
structures that do not have a common evolutionary origin but are similar in function.
alpha particle
A particle with two protons and two neutrons, emitted during radioactive decay.
amniotic egg
major adaptation in land animals; amniotic sac encloses an embryo and provides nutrition and protection from the outside environment.
air mass
Large body of air that takes on the characteristics of the area over which it forms; can be described by its stability, temperature, and humidity.
algae
photosynthetic, plantlike, autotrophic protists.
anterior
head end of bilateral animals where sensory organs are often located.
aqueous solution
A solution in which the solvent is water.
amorphous solid
A solid in which particles are not arranged in a regular, repeating pattern that often is formed when molten material cools too quickly to form crystals.
anion
An ion that has a negative charge.
anaphase
third phase of mitosis in which the centromeres split and the chromatid pairs of each chromosome are pulled apart by microtubules.
alkali metals
Group 1A elements, except for hydrogen, that are on the left side of the modern periodic table.
aphotic zone
deep water that never receives sunlight.
artificial selection
process of breeding organisms with specific traits in order to produce offspring with identical traits.
anode
In an electrochemical cell, the electrode where oxidation takes place.
alveoli
sacs in the lungs where oxygen diffuses into the blood and carbon dioxide diffuses into the air.
adrenal glands
pair of glands located on top of the kidneys that secrete hormones, such as adrenaline, that prepare the body for stressful situations.
adaptation
evolution of a structure, behavior, or internal process that enables an organism to respond to environmental factors and live to produce offspring.
actin
structural protein in muscle cells that makes up the thin filaments of myofibrils; functions in muscle contraction.
ADP (adenosine diphosphate)
molecule formed from the breaking off of a phosphate group for ATP; results in a release of energy that is used for biological reactions.
allele
alternative forms of a gene for each variation of a trait of an organism.
archaebacteria
chemosynthetic prokaryotes that live in harsh environments.
annual
anthophyte that lives for one year or less.
aggregate
Naturally accumulating mixture of sand, gravel, and crushed stone found in floodplains, alluvial fans, or glacial deposits.
antigens
foreign substances that stimulate an immune response in the body.
amino acid
An organic molecule that has both an amino group (—NH2) and a carboxyl group (—COOH).
Section 2
(50 cards)
biomass
the total mass or weight of all living matter in a given area.
autosomes
pairs of matching homologous chromosomes in somatic cells.
barrier island
Long ridge of sand or other sediment deposited or shaped by longshore currents that is separated from the mainland and can be up to tens of kilometers long.
breaker
Collapsing wave that forms when a wave reaches shallow water and is slowed by friction with the ocean bottom.
autonomic nervous system (ANS)
in humans, portion of the peripheral nervous system that carries impulses from the central nervous system to internal organs; produces involuntary responses.
biotic factors
all the living organisms that inhabit an environment.
birthrate
number of live births per 1000 population in a given year.
base
any substance that forms hydroxide ions in water and has a pH above 7.
biome
group of ecosystems with the same climax communities.
bedrock
Unweathered, solid parent rock that may consist of limestone, marble, granite, or other quarried rock.
blastula
hollow ball of cells in a layer surrounding a fluid-filled space; an animal embryo after cleavage but before the formation of the gastrula.
atomic number
Number of protons contained in an atom's nucleus.
axial skeleton
one of two main parts of the human skeleton, includes the skull and the bones that support it, such as the vertebral column, ribs, and sternum.
biennial
anthophyte that has a life span of two years.
ATP
Adenosine triphosphate—a nucleotide that functions as the universal energy-storage molecule in living cells.
black hole
Small, extremely dense remnant of a star whose gravity is so immense that not even light can escape its gravity field.
calorimeter
An insulated device that is used to measure the amount of heat released or absorbed during a physical or chemical process.
bedding
Horizontal layering in sedimentary rock that can range from a millimeter thick to several meters thick.
biogenesis
idea that living organisms come only from other living organisms.
calorie
The amount of heat required to raise the temperature of one gram of pure water by one degree Celsius.
australopithecine
early African hominid, genus Australopithecus, that had both apelike and humanlike characteristics.
binary star
Describes two stars that are bound together by gravity and orbit a common center of mass.
binary fission
asexual reproductive process in which one cell divides into two separate genetically identical cells.
bipedal
ability to walk on two legs.
asthenosphere
Partially molten, plasticlike, flowing layer located below the solid part of Earth's mantle.
bursa
fluid-filled sac located between the bones that absorb shock and keep bones from rubbing against each other.
autumnal equinox
Occurs when the Sun is directly overhead at the equator and results in day and night of equal length for both northern and southern hemispheres.
axon
a single cytoplasmic extension of a neuron; carries impulses away from a nerve cell.
base unit
A defined unit in a system of measurement that is based on an object or event in the physical world and is independent of other units.
atomic mass
The weighted average mass of the isotopes of that element.
Avogadro's number
The number 6.022 1367 x 1023, which is the number of representative particles in a mole.
buffer
A solution that resists changes in pH when limited amounts of acid or base are added.
boiling point
The temperature at which a liquid's vapor pressure is equal to the external or atmospheric pressure.
bilateral symmetry
animals with a body plan that can be divided down its length into two similar right and left halves that form mirror images of each other.
atomic orbital
A three-dimensional region around the nucleus of an atom that describes an electron's probable location.
atria
two upper chambers of the mammalian heart through which blood enters.
budding
type of asexual reproduction in unicellular yeasts and some other organisms in which a cell or group of cells pinch off from the parent to form a new individual.
autotrophs
organisms that use energy from the sun or energy stored in chemical compounds to manufacture their own nutrients.
beat
The oscillation of wave amplitude that results from the superposition of two sound waves with almost identical frequencies.
binomial nomenclature
two-word system developed by Carolus Linnaeus to name species.
atom
Smallest particle of an element, having all the characteristics of that element; the basic building block of matter, consisting of protons, neutrons, and electrons.
buffer capacity
The amount of acid or base a buffer solution can absorb without a significant change in pH.
base ionization constant
The value of the equilibrium constant expression for the ionization of a base.
buoyant force
The upward force exerted on an object immersed in a fluid.
beta particle
A high-speed electron that is emitted during radioactive decay.
bioremediation
Use of organisms to clean up toxic waste.
Brownian motion
The jerky, random, rapid movements of colloid particles that results from collisions of particles of the dispersion medium with the dispersed particles.
bile
chemical substance produced by the liver and stored in the gallbladder that helps break down fats during digestion.
biosphere
portion of Earth that supports life; extends from high in the atmosphere to the bottom of the oceans.
biodiversity
variety of life in an area.
Section 3
(50 cards)
chlorophyll
light-absorbing pigment in plants and some protists that is required for photosynthesis; absorbs most wavelengths of light except green.
catalyst
A substance that increases the rate of a chemical reaction by lowering activation energies but is not itself consumed in the reaction.
cellular respiration
chemical process where mitochondria break down food molecules to produce ATP.
chemical bond
Force that holds the atoms of elements together in a compound.
chain reaction
Continual process of repeated fission reactions caused by the release of neutrons from previous fission reactions.
cathode ray
A ray of radiation that originates from the cathode and travels to the anode of a cathode ray tube.
class
taxonomic grouping of similar orders.
cerebrum
largest part of the brain, composed of two hemispheres connected by bundles of nerves; controls conscious activities, intelligence, memory, language, skeletal muscle movements, and the senses.
chemical equilibrium
The state in which forward and reverse reactions balance each other because they occur at equal rates.
carrying capacity
Number of organisms that a specific environment can support.
camouflage
structural adaptation that enables species to blend with their surroundings; allows a species to avoid detection by predators.
cancer
uncontrolled cell division that may be caused by environmental factors and/or changes in enzyme production in the cell cycle.
clastic
Describes rock and mineral fragments produced by weathering and erosion and classified according to particle size and shape.
cell cycle
continuous sequence of growth (interphase) and division (mitosis) in a cell.
centripetal acceleration
The center-seeking acceleration of an object moving in a circle at a constant speed.
chemical property
The ability or inability of a substance to combine with or change into one or more new substances.
chitin
complex carbohydrate that makes up the cell walls of fungi.
cave
Underground opening connected to Earth's surface, usually formed when groundwater dissolves limestone.
cation
An ion that has a positive charge.
cinder-cone volcano
Steep-sided, generally small volcano that is built by the accumulation of tephra around the vent.
cell
basic unit of all organisms; all living things are composed of cells.
capacitance
The ratio of an object's stored charge to its electric potential difference.
chemical equation
A statement using chemical formulas to describe the identities and relative amounts of the reactants and products involved in the chemical reaction.
cervix
lower end of the uterus that tapers to a narrow opening into the vagina.
centrioles
in animal cells, a pair of small cylindrical structures composed of microtubules that duplicate during interphase and move to opposite ends of the cell during prophase.
cementation
Process of sedimentary rock formation that occurs when dissolved minerals precipitate out of groundwater and either a new mineral grows between the sediment grains or the same mineral grows between and over the grains.
cleavage
Ability of a mineral to break easily and evenly along one or more flat planes.
center of mass
The point on the object that moves in the same way that a point particle would move.
carrier
an individual heterozygous for a specific trait.
capillaries
microscopic blood vessels with walls only one cell thick that allow diffusion of gases and nutrients between the blood and surrounding tissues.
chemical reaction
The process by which the atoms of one or more substances are rearranged to form different substances.
centripetal force
The net force exerted toward the center of the circle that causes an object to have a centripetal acceleration.
chromosomes
cell structures that carry the genetic material that is copied and passed from generation to generation of cells.
cardiac muscle
type of involuntary muscle found only in the heart.
circadian rhythm
innate behavior based on the 24-hour cycle of the day; light- regulated; may determine when an animal sleeps and wakes.
chromosomal mutations
mutation that occurs at the chromosome level resulting in changes in the gene distribution to gametes during meiosis; caused when parts of chromosomes break off or rejoin incorrectly.
cilia
short, numerous, hairlike projections composed of pairs of microtubules; frequently aid in locomotion.
chromatin
long strands of DNA found in the eukaryotic cell nucleus; condense to form chromosomes.
cathode
In an electrochemical cell, the electrode where reduction takes place.
cerebellum
rear portion of the brain; controls balance, posture and coordination.
chloroplasts
chlorophyll-containing organelles found in the cells of green plants and some protists; capture light energy and convert it to chemical energy.
chromatography
A technique that is used to separate the components of a mixture based on the tendency of each component to travel or be drawn across the surface of another material.
centrifugal "force"
The apparent force that seems to pull on a moving object, but does not exert a physical outward push on it, and is observed only in rotating frames of reference.
carbohydrate
organic compound used by cells to store and release energy; composed of carbon, hydrogen, and oxygen.
central nervous system (CNS)
in humans, the central control center of the nervous system made up of the brain and spinal cord.
cast
Fossil formed when an earlier fossil of a plant or animal leaves a cavity that becomes filled with minerals or sediment.
centromere
cell structure that joins two sister chromatids of a chromosome.
classical conditioning
learning by association.
chemical change
A process involving one or more substances changing into new substances; also called a chemical reaction.
cartilage
tough flexible material making up the skeletons of agnathans, sharks, and their relatives, as well as portions of bony-animal skeletons.
Section 4
(50 cards)
concave lens
A diverging lens, thinner at its middle than at its edges, that spreads out light rays passing through it when surrounded by material with a lower index of refraction; produces a smaller, virtual, upright image.
consonance
A pleasant set of pitches.
concave mirror
A mirror that reflects light from its inwardly curving surface and can produce either an upright, virtual image or an inverted, real image.
constellation
Group of stars that forms a pattern in the sky that resembles an animal, mythological character, or everyday object.
continental slope
Sloping oceanic region found beyond the continental shelf that generally marks the edge of the continental crust and may be cut by submarine canyons.
components
Projections of the component vectors.
climate
Average weather of a particular area over a long period of time.
comet
Small, eccentrically orbiting body made of rock and ice that consists of a nucleus, a coma, and one or more tails that point away from the Sun.
cohesive forces
The electromagnetic forces of attraction that like particles exert on one another; responsible for surface tension and viscosity.
colligative property
A physical property of a solution that depends on the number, but not the identity, of the dissolved solute particles.
compound light microscope
instrument that uses light and a series of lenses to magnify objects in steps; can magnify an object up to 1500 times its original size.
complementary color
A color of light, which when combined with another color of light, produces white light.
conservation biology
field of biology that studies methods and implements plans to protect biodiversity.
continental shelf
Shallowest part of a continental margin, with an average depth of 130 m and an average width of 60 km, that extends into the ocean from the shore and provides a nutrient-rich home to large numbers of fish.
colony
group of unicellular or multicellular organisms that live together in a close association.
companion cells
nucleated cells that help transport sugars and other organic compounds through the sieve cells of the phloem.
conjugation
form of sexual reproduction in some bacteria where one bacterium transfers all or part of its genetic material to another through a bridgelike structure called a pilus.
continental rise
Gently sloping accumulation of sediments deposited by a turbidity current at the foot of a continental margin.
complex reaction
A chemical reaction that consists of two or more elementary steps.
condensation
The energy-releasing process by which a gas or vapor becomes a liquid.
condensation nuclei
Small particles in the atmosphere around which cloud droplets can form.
cones
in coniferophytes; scaly structures that support male and female reproductive structures; scaly structures produced by some seed plants that support male or female reproductive structures and are the sites of seed production. receptor cells in the retina adapted for sharp vision in bright light and color detection.
condensation polymerization
Occurs when monomers having at least two functional groups combine with the loss of a small by-product, usually water.
coefficient
In a chemical equation, the number written in front of a reactant or product; tells the smallest number of particles of the substance involved in the reaction.
concentration
A quantitative measure of the amount of solute in a given amount of solvent or solution.
collision theory
States that atoms, ions, and molecules must collide in order to react.
combustion reaction
A chemical reaction that occurs when a substance reacts with oxygen, releasing energy in the form of heat and light.
composite volcano
Large, sloping volcano built by violent eruptions of volcanic fragments and lava that accumulate in alternating layers.
compound
Substance composed of atoms of two or more different elements that are chemically combined.
continental margin
Submerged part of a continent and shallowest part of the ocean that consists of the continental shelf, the continental slope, and the continental rise.
conclusion
A judgment based on the information obtained.
cochlea
snail-shaped structure in the inner ear containing fluid and hairs; produces electrical impulses that the brain interprets as sound.
coelom
fluid-filled body cavity completely surrounded by mesoderm.
community
collection of several interacting populations that inhabit a common environment.
cold wave
Extended period of lower-than-normal temperatures caused by large, high-pressure systems of continental polar or arctic origin.
conditioning
response to a stimulus learned by association with a specific action.
colloids
Heterogeneous mixtures containing particles larger than solution particles but smaller than suspension particles that are categorized according to the phases of their dispersed particles and dispersing mediums.
conductor
A material, such as copper, through which a charge will move easily.
codominant alleles
pattern where phenotypes of both homozygote parents are produced in heterozygous offspring so that both alleles are equally expressed.
cogeneration
Production of two usable forms of energy at the same time from the same process, which can conserve resources and generate income.
commensalism
symbiotic relationship in which one species benefits and the other species is neither harmed nor benefited.
climax community
a stable, mature community that undergoes little or no change in species over time.
continental glacier
Glacier that forms over a broad, continent-sized area of land and usually spreads out from its center.
clones
genetically identical copies of an organism or gene.
communication
exchange of information that results in a change of behavior.
conduction
Energy transfer that occurs when molecules collide; takes place only when substances are in contact with each other.
coma
Extended volume of glowing gas that forms when a comet's nucleus is heated.
closed circulatory system
system in which blood moves through the body enclosed entirely in a series of blood vessels.
combined gas law
For a fixed amount of an ideal gas, the pressure times the volume, divided by the Kelvin temperature equals a constant.
continental drift
Wegener's hypothesis that Earth's continents were joined as a single landmass, called Pangaea, that broke apart about 200 million years ago and slowly moved to their present positions.
Section 5
(50 cards)
convergent boundary
Place where two of Earth's tectonic plates are moving toward each other; is associated with trenches, islands arcs, and folded mountains.
covalent bond
Attraction of two atoms for a shared pair of electrons that holds the atoms together.
cortex
layer of ground tissue in the root that is involved in the transport of water and ions into the vascular tissue of the root.
control
In an experiment, the standard that is used for comparison.
decibel
The unit of measurement for sound level; also can describe the power and intensity of sound waves.
conversion factor
A ratio of equivalent values used to express the same quantity in different units; is always equal to 1 and changes the units of a quantity without changing its value.
cracking
The process by which heavier fractions of petroleum are converted to gasoline by breaking their large molecules into smaller molecules.
coulomb
The SI standard unit of charge; one coulomb, C, is the magnitude of the charge of 6.241018 electrons or protons.
deep-sea trench
Long, relatively narrow depression in the seafloor that can extend for thousands of kilometers, is the deepest part of the ocean basin, and is found primarily in the Pacific Ocean.
contour interval
Difference in elevation between two side-by-side contour lines on a topographic map.
convex lens
A converging lens, thicker at its center than at its edges, that refracts parallel light rays so the rays meet at a point when surrounded by material with a lower index of refraction; can produce a smaller, inverted, real image, or a larger, upright, virtual image.
corona
Top layer of the Sun's atmosphere that extends from the top of the chromosphere and ranges in temperature from 1 million to 2 million K.
cross-bedding
Depositional feature of sedimentary rock that forms as inclined layers of sediment are carried forward across a horizontal surface.
contour line
A line on a topographic map that connects points of equal elevation.
cytokinesis
cell process following meiosis or mitosis in which the cell's cytoplasm divides and separates into new cells.
delta
Triangular deposit, usually made up of silt and clay particles, that forms where a stream enters a large body of water.
cosmic background radiation
Weak radiation that is left over from the early, hot stages of the Big Bang expansion of the universe.
deforestation
Removal of trees from a forested area without adequate replanting, often using clear-cutting, which may result in loss of topsoil and water pollution.
convex mirror
A mirror that reflects light from its outwardly curving surface and produces an upright, reduced, virtual image.
conventional current
A flow of positive charges that move from higher potential to lower potential.
critical mass
The minimum mass of a sample of fissionable material necessary to sustain a nuclear chain reaction.
death rate
number of deaths per 1000 population in a given year.
Coriolis effect
Deflects moving particles such as air to the right above the equator and to the left below the equator; caused by Earth's rotation and combines with the heat imbalance found on Earth to create the trade winds, polar easterlies, and prevailing westerlies.
crossing over
exchange of genetic material between nonsister chromatids from homologous chromosomes during prophase I of meiosis; results in new allele combinations.
dendrochronology
Science of comparing annual growth rings in trees to date events and environmental changes.
Coulomb's law
States that the force between two charges varies directly with the product of their charge and inversely with the square of the distance between them.
cyanobacteria
Microscopic, photosynthetic prokaryotes that formed stromatolites and changed early Earth's atmosphere by generating oxygen.
crystallization
A separation technique that produces pure solid particles of a substance from a solution that contains the dissolved substance.
decomposers
organisms, such as fungi and bacteria, that break down and absorb nutrients from dead organisms.
data
information obtained from experiments, sometimes called experimental results.
deciduous plants
plants that drop all of their leaves each fall or when water is scarce or unavailable; an adaptation for reducing water loss when water is unavailable.
convergent evolution
evolution in which distantly related organisms evolve similar traits; occurs when unrelated species occupy similar environments.
demography
study of population characteristics such as growth rate, age structure, and geographic distribution.
courtship behavior
an instinctive behavior that males and females of a species carry out before mating.
cytoplasm
clear, gelatinous fluid in cells that is the site of numerous chemical reactions; in eukaryotic cells, it suspends the cell's organelles.
critical angle
The certain angle of incidence in which the refracted light ray lies along the boundary between two media.
dendrite
branchlike extension of a neuron; transports impulses toward the cell body.
coordinate covalent bond
Forms when one atom donates a pair of electrons to be shared with an atom or ion that needs two electrons to become stable.
Cro-Magnon
modern form of Homo sapiens that spread throughout Europe between 35 000 to 40 000 years ago; were identical to modern humans in height, skull and tooth structure, and brain size.
coordinate system
A system used to describe motion that gives the zero point location of the variable being studied and the direction in which the values of the variable increase.
denaturation
The process in which a protein's natural, intricate three- dimensional structure is disrupted.
crystalline solid
A solid whose atoms, ions, or molecules are arranged in an orderly, geometric, three-dimensional structure; can be classified by shape and by composition.
correlation
Matching of rock outcrops of one geographic region to another.
decomposition reaction
A chemical reaction that occurs when a single compound breaks down into two or more elements or new compounds.
crest
Highest point of a wave.
cross-cutting relationships
Principle stating that a fault or intrusion is younger than the rock it cuts across.
creep
Slow, steady downhill movement of loose weathered Earth materials, especially soils, causing objects on a slope to tilt.
crater
Bowl-shaped depression, usually less than 1 km in diameter, that forms around the central vent at the summit of a volcano.
crystalline structure
Regular geometric pattern of particles in most solids, giving a solid a definite shape and volume.
convection
A type of thermal energy transfer that occurs from the motion of fluid in liquid or gas that is caused by differences in temperature.
Section 6
(50 cards)
deposition
Occurs when sediments are laid down on the ground or sink to the bottom of a body of water.
divide
Elevated land that divides one watershed, or drainage basin, from another.
ecosystem
interactions among populations in a community; the community's physical surroundings, or abiotic factors.
desertification
Process by which productive land becomes desert.
displacement
A change in position having both magnitude and direction; is equal to the final position minus the initial position.
drag force
The force exerted by a fluid on an object moving through the fluid; depends on the object's motion and properties and the fluid's properties.
dominant
observed trait of an organism that masks the recessive form of a trait.
diffraction
The bending of light around a barrier.
divergent evolution
evolution in which species that once were similar to an ancestral species diverge.
depletion layer
The region around a pn-junction diode where there are no charge carriers and electricity is poorly conducted.
dormancy
period of inactivity in a mature seed prior to germination.
DNA replication
process in which chromosomal DNA is copied before mitosis or meiosis.
dispersion
The separation of white light into a spectrum of colors by such means as a glass prism or water droplets in the atmosphere.
diffusion
net, random movement of particles from an area of higher concentration to an area of lower concentration, eventually resulting in even distribution.
dependent variable
Factor in an experiment that can change if the independent variable is changed.
density
A ratio that compares the mass of an object to its volume.
dune
Pile of wind-blown sand that develops over time, whose shape depends on sand availability, wind velocity and direction, and amount of vegetation present.
dinosaur
Terrestrial reptile that developed an upright posture and dominated the Mesozoic land.
dew point
Temperature to which air is cooled at a constant pressure to reach saturation, at which point condensation can occur.
double helix
shape of a DNA molecule formed when two twisted DNA strands are coiled into a springlike structure and held together by hydrogen bonds between the bases.
dimensional analysis
A method of treating units as algebraic quantities, which can be cancelled.
deoxyribonucleic acid (DNA)
a nucleic acid; the copy of an organism's information code that contains the instructions used to form all of an organism's enzymes and structural proteins.
dissonance
An unpleasant, jarring set of pitches.
depressant
type of drug that lowers or depresses the activity of the nervous system.
ectoderm
layer of cells on the outer surface of the gastrula; eventually develops into the skin and nervous tissue of an animal.
Doppler effect
The change in the frequency of sound caused by the movement of either the source, the detector, or both the detector and the source.
development
all of the changes that take place during the life of an organism; a characteristic of all living things.
doubling time
time needed for a population to double in size.
ectotherm
animal that has a variable body temperature and derives its heat from external sources.
division
taxonomic grouping of similar classes; term used instead of phyla by plant taxonomists.
desalination
Process that removes salt from ocean water in order to provide freshwater.
discharge
Measure of a volume of stream water that flows over a specific location in a particular amount of time.
digital forecast
Weather forecast that uses numerical data to determine how atmospheric variables change over time.
drought
Extended period of low rainfall, usually caused by shifts in global wind patterns, allowing high-pressure systems to remain for weeks or months over continental areas.
dorsal
upper surface of bilaterally symmetric animals.
downburst
Violent, damaging thunderstorm wind that is concentrated in a local area.
dynamic equilibrium
result of diffusion where there is continuous movement of particles but no overall change in concentration.
drawdown
Difference between the water level in a pumped well and the original water-table level.
dielectrics
Nonconducting materials—glass, air, and water—through which electromagnetic waves move at less than the speed of light in a vacuum.
drug
chemical substance that affects body functions.
desert
arid region with sparse to almost nonexistent plant life; the driest biome, usually receives less than 25 cm of precipitation annually.
diploid
cell with two of each kind of chromosome; is said to contain a diploid, or 2n, number of chromosomes.
diaphragm
in mammals, the sheet of muscles located beneath the lungs that separates the chest cavity from the abdominal cavity.
dry cell
An electrochemical cell that contains a moist electrolytic paste inside a zinc shell.
dermis
inner, thicker portion of the skin that contains structures such as blood vessels, nerves, nerve endings, hair follicles, sweat glands, and oil glands.
dominance hierarchy
innate behavior by which animals form a social ranking within a group in which some individuals are more subordinate than others; usually has one top-ranking individual.
diode
The simplest semiconductor device; conducts charges in one direction only.
distillation
A technique that can be used to physically separate most homogeneous mixtures based on the differences in the boiling points of the substances involved.
derived unit
A unit defined by a combination of base units.
distance
A scalar quantity that describes how far an object is from the origin.
Section 7
(50 cards)
electronegativity
Indicates the relative ability of an element's atoms to attract electrons in a chemical bond.
electron cloud
The region in which there is a high probability of finding an electron.
environment
biotic and abiotic surroundings to which an organism must constantly adjust; includes air, water, weather, temperature, other organisms, and many other factors.
electromagnet
A magnet created when current flows through a wire coil.
endotherm
animal that maintains a constant body temperature and is not dependent on the environmental temperature.
erosion
Movement of weathered materials from one location to another by agents such as water, wind, glaciers, and gravity.
embryo
earliest stage of growth and development of both plants and animals; differences and similarities among embryos can provide evidence of evolution.
endangered species
a species in which the number of individuals falls so low that extinction is possible.
enzymes
type of protein found in all living things that changes the rate of chemical reactions.
electric field
The field that exists around any charged object; produces forces that can do work, transferring energy from the field to another charged object.
equilibrium
The condition in which the net force on an object is zero.
electromagnetic radiation
A form of energy exhibiting wavelike behavior as it travels through space; can be described by wavelength, frequency, amplitude, and speed and includes visible light, microwaves, X rays, and radio waves.
electron
A negatively charged, fast-moving particle with an extremely small mass that is found in all forms of matter and moves through the empty space surrounding an atom's nucleus.
electron microscope
instrument that uses a beam of electrons instead of light to magnify structures up to 500 000 times actual size; allows scientists to view structures within a cell.
endocytosis
active transport process where a cell engulfs materials with a portion of the cell's plasma membrane and releases the contents inside of the cell.
endoderm
layer of cells on the inner surface of the gastrula; will eventually develop into the lining of the animal's digestive tract and organs associated with digestion.
electrolysis
The process that uses electrical energy to bring about a chemical reaction.
eddy current
A current generated in a piece of metal that is moving through a changing magnetic field, producing a magnetic field that opposes the motion that caused the current.
eon
Longest time unit in the geological time scale, measured in billions of years.
era
Second-longest time unit in the geological time scale, measured in hundreds of millions of years, and defined by differences in life-forms that are preserved in rocks.
energy level
Represents the area in an atom where electrons are most likely to occur.
egg
haploid female sex cell produced by meiosis.
endoskeleton
internal skeleton; provides support, protects internal organs, and acts as an internal brace for muscles to pull against.
elastic collision
Describes a collision in which kinetic energy may be transferred between the colliding particles but the total kinetic energy of the two particles remains the same.
endoplasmic reticulum
organelle in eukaryotic cells with a series of highly folded membranes surrounded in cytoplasm; site of cellular chemical reactions.
electrochemical cell
An apparatus that uses a redox reaction to produce electrical energy or uses electrical energy to cause a chemical reaction.
electric current
A flow of charged particles.
energy
The capacity to do work or produce heat; exists as potential energy, which is stored in an object due to its composition or position, and kinetic energy, which is the energy of motion.
endemic disease
disease that is constantly present in a population.
electromagnetic wave
Coupled, changing electric and magnetic field that travels through space.
electric circuit
A closed loop or pathway that allows electric charges to flow.
enthalpy
The heat content of a system at constant pressure.
entropy
A measure of the disorder or randomness of the particles of a system.
epidermis
in plants, the outermost layer of flattened cells that covers and protects all parts of the plant; in humans and some other animals, the outermost protective layer composed of an outer layer of dead cells and an inner layer of living cells.
electromagnetic spectrum
Arrangement of electromagnetic radiation, including gamma rays, X rays, and microwaves.
equipotential
The electric potential difference of zero between two or more positions in an electric field.
endothermic
A chemical reaction in which a greater amount of energy is required to break the existing bonds in the reactants than is released when the new bonds form in the product molecules.
emission spectrum
A plot of the intensity of light emitted from a hot body over a range of frequencies.
efficiency
The ratio of output work to input work.
element
A pure substance that cannot be broken down into simpler substances by physical or chemical means.
electromotive force
The potential difference, measured in volts, given to the charges by a battery; is abbreviated EMF.
empirical formula
A formula that shows the smallest whole-number mole ratio of the elements of a compound, and may or may not be the same as the actual molecular formula.
electrolyte
An ionic compound whose aqueous solution conducts an electric current.
epidemic
occurs when many people in a given area are afflicted with the same disease at about the same time.
emigration
movement of individuals from a population.
El Niño
Warm ocean current that develops off the western coast of South America and can cause short-term climatic changes felt worldwide.
epoch
Time unit in the geological time scale, smaller than a period, measured in millions of years to tens of millions of years.
epicenter
Point on Earth's surface directly above the focus of an earthquake.
effort force
The force a person exerts on a machine.
equator
Imaginary line that lies at zero latitude and circles Earth midway between the north and south poles, dividing Earth into the northern hemisphere and the southern hemisphere.
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fins
in fishes, fan-shaped membranes used for balance, swimming, and steering.
fuse
A short piece of metal that acts as a safety device in an electric circuit by melting and stopping the current from flowing if a dangerously high current passes through the circuit.
fetus
a developing mammal from nine weeks to birth.
follicle
in human females, group of epithelial cells that surround a developing egg cell.
ethylene
plant hormone that promotes the ripening of fruits.
flagella
long projections composed of microtubules; found on some cell surfaces; they help propel cells and organisms by a whiplike motion.
experiment
A set of controlled observations that test the hypothesis.
fungus
group of unicellular or multicellular heterotrophic eukaryotes that do not move from place to place; absorb nutrients from organic materials in the environment.
gas
A form of matter that flows to conform to the shape of its container, fills the container's entire volume, and is easily compressed.
first law of thermodynamics
States that the change in thermal energy of an object is equal to the heat that is added to the object, minus the work done by the object.
fuel cell
A voltaic cell in which the oxidation of a fuel, such as hydrogen gas, is used to produce electric energy.
focus
Point of the initial fault rupture where an earthquake originates that usually lies at least several kilometers beneath Earth's surface.
front
Boundary between two air masses of differing densities; can be cold, warm, stationary, or occluded and can stretch over large areas of Earth's surface.
frequency
The number of waves that pass a given point per second.
fault
Fracture or system of fractures in Earth's crust that occurs when stress is applied too quickly or stress is too great; can form as a result of horizontal compression (reverse fault), horizontal shear (strike-slip fault), or horizontal tension (normal fault).
fertilization
fusion of male and female gametes.
extrusive
Fine-grained igneous rock that is formed when molten rock cools quickly and solidifies on Earth's surface.
feather
lightweight, modified scale found only on birds; provides insulation and enables flight.
fossil fuel
Nonrenewable energy resource formed over geologic time from the compression and partial decomposition of organisms that lived millions of years ago.
fatty acid
A long-chain carboxylic acid that usually has between 12 and 24 carbon atoms and can be saturated (no double bonds), or unsaturated (one or more double bonds).
fluids
Materials (liquids and gases) that flow and have no definite shape of their own.
gamma rays
High-energy radiation that has no electrical charge and no mass, is not deflected by electric or magnetic fields, usually accompanies alpha and beta radiation, and accounts for most of the energy lost during radioactive decay.
eutrophication
Process by which lakes become rich in nutrients from the surrounding watershed, resulting in a change in the kinds of organisms in the lake.
evolution
gradual change in a species through adaptations over time.
ester
An organic compound with a carboxyl group in which the hydrogen of the hydroxyl group is replaced by an alkyl group; may be volatile and sweet-smelling and is polar.
fission
Process in which heavy atomic nuclei split into smaller, lighter nuclei.
fusion
Process in a star's core in which lightweight hydrogen nuclei combine into heavier helium nuclei.
evaporation
The process in which vaporization occurs only at the surface of a liquid.
freezing point
The temperature at which a liquid is converted into a crystalline solid.
food chain
simple model that shows how matter and energy move through an ecosystem.
esophagus
muscular tube that connects the mouth to the stomach; moves food by peristalsis.
eukaryotes
unicellular or multicellular organisms, such as yeast, plants, and animals, composed of eukaryotic cells, which contain a true nucleus and membrane-bound organelles.
exosphere
Outermost layer of Earth's atmosphere that is located above the thermosphere and contains light gases such as helium and hydrogen.
exoskeleton
hard covering on the outside of some animals, including spiders and mollusks.
ferromagnetism
The strong attraction of a substance to a magnetic field.
fruit
seed-containing ripened ovary of an anthophyte flower; may be fleshy or dry.
filtration
A technique that uses a porous barrier to separate a solid from a liquid.
fuel
Material, such as wood, peat, or coal, burned to provide power or heat.
floodplain
Broad, flat, fertile area extending out from a stream's bank that is covered with water during floods.
fossil
Remains or evidence of a once-living plant or animal.
extinction
the disappearance of a species when the last of its members dies.
exothermic
A chemical reaction in which more energy is released than is required to break bonds in the initial reaction.
gametes
male and female sex cells; sperm and eggs.
exotic species
nonnative species in an area; may take over niches of native species in an area and eventually replace them.
exocytosis
active transport process by which materials are secreted or expelled from a cell.
fermentation
The process in which glucose is broken down in the absence of oxygen, producing either ethanol, carbon dioxide, and energy (alcoholic fermentation) or lactic acid and energy (lactic acid fermentation).
force
A push or pull exerted on an object that causes a change in motion; has both direction and magnitude and may be a contact or a field force.
exponential growth
Pattern of growth in which a population of organisms grows faster as it increases in size, resulting in a population explosion.
estuary
coastal body of water, partially surrounded by land, in which freshwater and salt water mix.
fracture
Ability of a mineral to break into pieces with arclike, rough, or jagged edges.
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half-life
The time required for one-half of a radioisotope's nuclei to decay into its products.
gravitational field
The field that surrounds any object with mass; equals the universal gravitational constant, times the mass of the object, divided by the square of the distance from the object's center.
hemoglobin
iron-containing protein molecule in red blood cells that binds to oxygen and carries it from the lungs to the body's cells.
host cell
living cell in which a virus replicates.
geothermal energy
Energy produced from Earth's own internal steam and hot water.
Global Positioning System (GPS)
Satellite-based navigation system that permits a user to pinpoint his or her exact location on Earth.
haploid
cell with one of each kind of chromosome; is said to contain a haploid or n, number of chromosomes.
genetic engineering
method of cutting DNA from one organism and inserting the DNA fragment into a host organism of the same or a different species.
hormone
chemical produced in one part of an organism and transported to another part, where it causes a physiological change.
Homo sapiens
Species to which humans belong.
heredity
passing on of characteristics from parents to offspring.
gland
in mammals, a cell or group of cells that secretes fluids.
germination
beginning of the development of an embryo into a new plant.
glycolysis
in cellular respiration, series of anaerobic chemical reactions in the cytoplasm that breaks down glucose into pyruvic acid; forms a net profit of two ATP molecules.
highlands
Light-colored, mountainous, heavily cratered areas of the Moon, composed mostly of lunar breccias.
halogen
A highly reactive group 7A element.
homogeneous mixture
One that has a uniform composition throughout and always has a single phase; also called a solution.
gestation
time during which placental mammals develop inside the uterus.
heterogeneous mixture
One that does not have a uniform composition and in which the individual substances remain distinct.
global warming
The rise in global temperatures, which may be due to increases in greenhouse gases, such as CO2.
gem
Rare, precious, highly prized mineral that can be cut, polished, and used for jewelry.
gene splicing
in recombinant DNA technology, the rejoining of DNA fragments by vectors and other enzymes.
heterotrophs
organisms that cannot make their own food and must feed on other organisms for energy and nutrients.
grounding
The process of removing excess charge by touching an object to Earth.
gizzard
sac with muscular walls and hard particles that grind soil before it passes into the intestine.
hardness
Measure of how easily a mineral can be scratched, which is determined by the arrangement of a mineral's atoms.
geologic time scale
Record of Earth's history from its origin to the present used to correlate geologic events, environmental changes, and development of life-forms that are preserved in rocks.
hair follicle
narrow cavities in the dermis from which hair grows.
hominids
Group of upright, bipedal primates, including Homo sapiens.
geyser
Explosive hot spring that erupts regularly.
genotype
combination of genes in an organism.
homeostasis
organism's regulation of its internal environment to maintain conditions suitable for survival; a characteristic of all living things.
genus
first word of a two-part scientific name used to identify a group of similar species.
grasslands
biome composed of large communities covered with rich soil, grasses, and similar small plants; receives 25-75 cm of precipitation annually.
gene
segment of DNA that controls the protein production and the cell cycle.
harmonics
Higher frequencies, which are odd-numbered multiples of the fundamental frequency; give certain musical instruments their own unique timbre.
group
A vertical column of elements in the periodic table; also called a family.
greenhouse effect
Natural heating of Earth's surface by certain atmospheric gases, which helps keep Earth warm enough to sustain life.
habitat
place where an organism lives out its life.
genetic drift
alteration of allelic frequencies in a population by chance events; results in disruption of genetic equilibrium.
gravitational force
The attractive force between two objects that is directly proportional to the mass of the objects.
glacier
Large, moving mass of ice that forms near Earth's poles and in mountainous regions at high elevations.
gene pool
all of the alleles in a population's genes.
gene therapy
insertion of normal genes into human cells to correct genetic disorders.
heat
A form of energy that flows from a warmer object to a cooler object.
gastrula
animal embryo development stage where cells on one side of the blastula move inward forming a cavity of two or three layers of cells with an opening at one end.
hibernation
state of reduced metabolism occurring in animals that sleep during parts of cold winter months; an animal's temperature drops, oxygen consumption decreases, and breathing rate declines.
growth
increase in the amount of living material and formation of new structures in an organism; a characteristic of all living things.
homozygous
when there are two identical alleles for a trait.
ground state
The lowest allowable energy state of an atom.
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impulse
The product of the average net force on an object and the time interval over which the force acts.
hypothalamus
portion of the brain that connects the endocrine and nervous systems, and controls the pituitary gland by sending messages to the pituitary, which then releases its own chemicals or stimulates other glands to release chemicals.
inner transition metal
A type of group B element that is contained in the f-block of the periodic table and is characterized by a filled outermost s orbital, and filled or partially filled 4f and 5f orbitals.
immigration
movement of individuals into a population.
ionization energy
The energy required to remove an electron from a gaseous atom.
hypertonic solution
in cells, solution in which the concentration of dissolved substances outside the cell is higher than the concentration inside the cell; causes a cell to shrink as water leaves the cell.
ion
An atom or bonded group of atoms with a positive or negative charge.
hygrometer
Weather instrument used to measure relative humidity.
hypotonic solution
in cells, solution in which the concentration of dissolved substances is lower in the solution outside the cell than the concentration inside the cell; causes a cell to swell and possibly burst as water enters the cell.
image
The combination of image points in a plane mirror from which the reflected object seems to originate.
infectious disease
any disease caused by pathogens in the body.
index fossils
Remains of plants or animals that were abundant, widely distributed, and existed briefly that can be used by geologists to correlate or date rock layers.
ionizing radiation
Radiation that is energetic enough to ionize matter it colides with.
hot spot
Unusually hot area in Earth's mantle that is stationary for long periods of time, where high-temperature plumes of mantle material rise toward the surface.
hypothesis
explanation for a question or a problem that can be formally tested.
igneous rock
Intrusive or extrusive rock formed from the cooling and crystallization of magma; can be classified as felsic, mafic, intermediate, and ultramafic, according to its mineral composition.
humidity
Amount of water vapor in the air.
human genome
map of the approximately 80 000 genes on 46 human chromosomes that when mapped and sequenced, may provide information on the treatment or cure of genetic disorders.
intrusive
Coarse-grained igneous rock that is formed when molten rock cools slowly and solidifies inside Earth's crust.
hybrid
offspring formed by parents having different forms of a trait.
intertidal zone
portion of the shoreline that lies between high tide and low tide lines.
insulator
A material, such as glass, through which a charge will not move easily.
involuntary muscle
muscle in which contractions are not under conscious control.
inelastic collision
A type of collision in which the kinetic energy after the collision is less than the kinetic energy before the collision.
ice age
Period of extensive glacial coverage, producing long-term climatic changes.
invertebrate
animal that does not have a backbone.
inertia
The tendency of an object to resist change.
imprinting
learned behavior in which an animal, at a specific critical time of its life, forms a social attachment to another object; usually occurs early in life and allows an animal to recognize its mother and others of its species.
hydrocarbon
Simplest organic compound composed only of the elements carbon and hydrogen.
interphase
cell growth phase where a cell increases in size, carries on metabolism, and duplicates chromosomes prior to division.
hydrothermal vent
Hot-water, deep-sea vent that has the energy and nutrients needed for the beginnings of life.
hydrogen bond
weak chemical bond formed by the attraction of positively charged hydrogen atoms to other negatively charged atoms.
immiscible
Describes two liquids that can be mixed together but separate shortly after you cease mixing them.
interference
Results from the superposition of two or more waves; can be constructive (wave displacements in the same direction) or destructive (waves with equal but opposite amplitudes).
insight
type of learning in which an animal uses previous experiences to respond to a new situation.
inertial mass
A measure of an object's resistance to any type of force.
infiltration
Process by which precipitation that has fallen on land surfaces enters the ground and becomes groundwater.
independent variable
Factor that is manipulated by the experimenter in an experiment.
intermediate
A substance produced in one elementary step of a complex reaction and consumed in a subsequent elementary step.
innate behavior
an inherited behavior in animals; includes automatic responses and instinctive behaviors.
inhibitor
A substance that slows down the reaction rate of a chemical reaction or prevents a reaction from happening.
instinct
complex innate behavior pattern that begins when an animal recognizes a stimulus and continues until all parts of the behavior have been performed.
interferons
host-cell specific proteins that protect cells from viruses.
hydrate
A compound that has a specific number of water molecules bound to its atoms.
hot spring
Thermal spring with temperatures higher than that of the human body.
hydrolysis
Chemical reaction of water with other substances.
International Date Line
The 180° meridian, which serves as the transition line for calendar days.
hydrosphere
All the water in Earth's oceans, lakes, seas, rivers, and glaciers plus all the water in the atmosphere.
incubate
process of keeping eggs laid outside of the body warm; also involves periodic turning of the eggs to ensure proper development.
insoluble
Describes a substance that cannot be dissolved in a given solvent.
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longitude
Distance in degrees east and west of the prime meridian.
lava
Magma that flows out onto Earth's surface.
lithosphere
Earth's rigid outer shell, including the crust and the solid, uppermost part of the mantle.
labor
physiological and physical changes a female goes through during the birthing process.
larva
in insects, the free-living, wormlike stage of metamorphosis, often called a caterpillar.
Lewis structure
A model that uses electron-dot structures to show how electrons are arranged in molecules. Pairs of dots or lines represent bonding pairs.
lithification
Transformation of sediments into rock through compaction and cementation.
isomers
Two or more compounds that have the same molecular formula but have different molecular structures.
macrophages
type of phagocyte that engulfs damaged cells or pathogens that have entered the body's tissues.
lens
A piece of transparent material, such as glass or plastic, that is used to focus light and form an image.
keratin
protein found in the exterior portion of the epidermis that helps protect living cells in the interior epidermis.
leaf
the plant organ that grows from a stem in which photosynthesis usually occurs.
limiting factor
any biotic or abiotic factor that restricts the existence, numbers, reproduction, or distribution of organisms.
limiting reactant
A reactant that is totally consumed during a chemical reaction, limits the extent of the reaction, and determines the amount of product.
lymph node
small mass of tissue that contains lymphocytes and filters pathogens from the lymph; made of a network of connective tissue fibers that contain lymphocytes.
kidneys
organs of the vertebrate urinary system; remove wastes, control sodium levels of the blood, and regulate blood pH levels.
latitude
Distance in degrees north and south of the equator.
lunar eclipse
Occurs only during a full moon, when Earth passes between the Sun and the Moon, and Earth's shadow falls on the Moon.
large intestine
muscular tube through which indigestible materials are passed to the rectum for excretion.
law of conservation of energy
States that in any chemical or physical process, energy may change from one form to another but it is neither created nor destroyed.
joints
point where two or more bones meet; can be fixed or facilitate movement of bones in relation to one another.
magnetic field
The area around a magnet, or around any current-carrying wire or coil of wire, where a magnetic force exists.
lever arm
The perpendicular distance from the axis of rotation to the point where force is exerted.
kilogram
The SI base unit for mass; about 2.2 pounds.
magma
Molten material found beneath Earth's crust that forms minerals with large crystals when it cools slowly and forms minerals with small crystals when it cools rapidly.
Le Système International D'Unités (SI)
Modern version of the metric system based on a decimal system using the number 10 as the base unit; includes the meter (m), liter (L), second (s), and kilogram (kg).
mammary glands
modified sweat glands in female mammals, which produce and secrete milk to feed their young.
kinetic energy
The energy of an object, resulting from its motion.
magnitude
Measure of the energy released during an earthquake, which can be described using the Richter scale.
lipids
large organic compounds made mostly of carbon and hydrogen with a small amount of oxygen; examples are fats, oils, waxes, and steroids; are insoluble in water and used by cells for energy storage, insulation, and protective coatings, such as in membranes.
kelvin
The SI base unit of temperature.
liver
large, complex organ of the digestive system that produces many chemicals for digestion, including bile.
ketone
An organic compound in which the carbon of the carbonyl group is bonded to two other carbon atoms.
kingdom
taxonomic grouping of similar phyla or divisions.
isotopes
Atoms of the same element that have different mass numbers and the same chemical properties.
isotonic solution
in cells, solution in which the concentration of dissolved substances in the solution is the same as the concentration of dissolved substances inside a cell.
laser
A device that produces powerful, coherent, directional, monochromatic light that can be used to excite other atoms; the acronym stands for light amplification by stimulated emission of radiation.
latent heat
Stored energy in water vapor that is not released to warm the atmosphere until condensation takes place.
law of conservation of mass
States that mass is neither created nor destroyed during a chemical reaction but is conserved.
ligament
tough band of connective tissue that attaches one bone to another; joints are often held together and enclosed by ligaments.
machine
A tool that makes work easier (but does not change the amount of work) by changing the magnitude or the direction of the force exerted to do work.
lake
Natural or human-made body of water that can form when a depression on land fills with water.
joule
The SI unit of heat and energy.
isolated system
A closed system on which the net external force is zero.
jet stream
High-altitude, narrow, westerly wind that occurs above large temperature contrasts and can flow as fast as 185 km/h.
magnification
The amount that an image is enlarged or reduced in size, relative to the object.
lymphocyte
type of white blood cell stored in lymph nodes that defends the body against foreign agents.
landslide
Rapid downslope movement of a mass of loose soil, rock, or debris that has separated from the bedrock; can be triggered by an earthquake.
luminosity
Energy output from the surface of a star per second; measured in watts.
law
Basic fact that describes the behavior of a natural phenomenon.
Section 12
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molting
in arthropods, the periodic shedding of an old exoskeleton.
microtubules
thin, hollow cylinders made of protein that provide structural support for eukaryotic cells.
momentum
The product of the object's mass and the object's velocity; is measured in kgm/s.
mineral
Naturally occurring, inorganic solid with a specific chemical composition and a definite crystalline structure that forms from magma or from supersaturated solution.
neurons
basic unit of structure and function in the nervous system; conducts impulses throughout the nervous system; composed of dendrites, a cell body, and an axon.
negative feedback system
internal feedback mechanism in which a substance is fed back to inhibit the original include hormones in the endocrine system.
mutualism
a symbiotic relationship in which both species benefit.
monotreme
subclass of mammals that have hair and mammary glands but reproduce by laying eggs.
mass spectrometer
Device that uses both electric and magnetic fields to measure the masses of ionized atoms and molecules and can determine the charge-to-mass ratio of an ion.
narcotic
type of pain-relief drug that affects the central nervous system.
migration
instinctive seasonal movements of animals from place to place.
mole
The SI base unit used to measure the amount of a substance, abbreviated mol; one mole is the amount of a pure substance that contains 6.02 X 1023 representative particles.
mesoderm
middle cell layer in the gastrula, between the ectoderm and the endoderm; develops into the muscles, circulatory system, excretory system, and in some animals, the respiratory system.
natural selection
mechanism for change in popula tions; occurs when organisms with favorable variations survive, reproduce, and pass their variations to the next generation.
mixture
combination of substances in which individual components retain their own properties.
mole ratio
In a balanced equation, the ratio between the numbers of moles of any two substances.
mutagen
any agent that can cause a change in DNA; includes high- energy radiation, chemicals, or high temperatures.
mechanical energy
The sum of kinetic and gravitational potential energy of a system.
meteor
Streak of light produced when a meteoroid falls toward Earth and burns up in Earth's atmosphere.
microchip
An integrated circuit consisting of thousands of diodes, transistors, resistors, and conductors.
net force
The vector sum of all the forces on an object.
mutation
any change or random error in a DNA sequence.
nebula
Large cloud of interstellar gas and dust that collapses on itself, due to its own gravity, and forms a hot, condensed object that will become a new star.
metabolism
all of the chemical reactions that occur within an organism.
mitosis
period of nuclear cell division in which two daughter cells are formed, each containing a complete set of chromosomes.
molarity
The number of moles of solute dissolved per liter of solution; also known as molar concentration.
menstrual cycle
in human females, the monthly cycle that includes the production of an egg, the preparation of the uterus to receive an egg, and the shedding of an egg if it remains unfertilized.
mitochondria
eukaryotic membrane-bound organelles that transform energy stored in food molecules; has a highly folded inner membrane that produces energy-storing molecules.
moment of inertia
The resistance to rotation.
melanin
pigment found in cells of the interior layer of the epidermis; protects cells from solar-radiation damage.
measurement
A comparison between an unknown quantity and a standard.
mechanical advantage
The ratio of resistance force to effort force.
mold
Fossil that can form when a shelled organism decays in sedimentary rock and is weathered away, leaving a hollowed-out impression.
nephron
individual filtering unit of the kidneys.
metamorphosis
in insects, series of chemically-controlled changes in body structure from juvenile to adult; may be complete or incomplete.
map legend
Key that explains what the symbols on a map represent.
meiosis
type of cell division where one body cell produces four gametes, each containing half the number of chromosomes as a parent's body cell.
meteorology
Branch of Earth science that studies the air that surrounds our planet; study of atmospheric phenomena such as fog, clouds, snow, rain, and lightning.
mass number
Combined number of protons and neutrons in the nucleus of an atom.
map scale
Ratio between the distances shown on a map and the actual distances on Earth's surface.
molar mass
The mass in grams of one mole of any pure substance.
meteorite
meteoroid that does not completely burn up in Earth's atmosphere and strikes Earth's surface, sometimes causing an impact crater.
natural resources
Resources provided by Earth, including air, water, land, all living organisms, nutrients, rocks, and minerals.
moraine
Ridge of mixed debris deposited by a melting glacier.
microclimate
Localized climate that differs from the surrounding regional climate.
molecular formula
A formula that specifies the actual number of atoms of each element in one molecule or formula unit of the substance.
mass extinction
Occurs when an unusually large number of organisms become extinct over a relatively short period of geologic time.
marsupial
subclass of mammals in which young develop for a short period in the uterus and complete their development outside of the mother's body inside a pouch made of skin and hair.
metaphase
short second phase of mitosis where doubled chromosomes move to the equator of the spindle and chromatids are attached by centromeres to a separate spindle fiber.
mechanical weathering
Process that breaks down rocks and minerals into smaller pieces but does not involve any change in their composition.
Section 13
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nuclear equation A type of equation that shows the atomic number and mass number of the particles involved.
orogeny
Cycle of processes that form all mountain ranges, resulting in broad mountain belts, most of which are associated with plate boundaries.
organism
anything that possesses all the characteristics of life; all organisms have an orderly structure, produce offspring, grow, develop, and adjust to changes in the environment.
oxidation
The loss of electrons from the atoms of a substance; increases an atom's oxidation number.
ozone layer
layer of the atmosphere that helps to protect living organisms on Earth's surface from damaging doses of ultraviolet radiation from the sun.
osmosis
The diffusion of solvent particles across a semipermeable membrane from an area of higher solvent concentration to an area of lower solvent concentration.
parallel circuit
A type of electric circuit in which there are several current paths; its total current is equal to the sum of the currents in the individual branches, and if any branch is opened, the current in the other branches remains unchanged.
Newton's third law
States that all forces come in pairs and that the two forces in a pair act on different objects and are equal in strength and opposite in direction.
object
A luminous or illuminated source of light rays that are to be reflected by a mirrored surface.
nonmetals
Elements that are generally gases or dull, brittle solids that are poor conductors of heat and electricity.
normals
Standard values for a location, including rainfall, wind speed, and temperatures, based on meteorological records compiled for at least 30 years.
oviduct
in females, the tube that transports eggs from the ovary to the uterus.
Newton's second law
States that the acceleration of an object is proportional to the net force and inversely proportional to the mass of the object being accelerated.
neutral
An atom whose positively charged nucleus exactly balances the negative charge of the surrounding electrons.
order
taxonomic grouping of similar families.
organization
orderly structure of cells in an organism; a characteristic of all living things.
neutron
A neutral subatomic particle in an atom's nucleus that has a mass nearly equal to that of a proton.
organic compounds All compounds that contain carbon with the primary exceptions of carbon oxides, carbides, and carbonates, all of which are considered inorganic.
octet rule
States that atoms lose, gain, or share electrons in order to acquire a full set of eight valence electrons (the stable electron configuration of a noble gas).
organelles
membrane-bound structures with particular functions within eukaryotic cells.
ovule
in seed plants, the sporophyte structure surrounding the developing female gametophyte; forms the seed after fertilization.
opposable thumb
primate characteristic of having a thumb that can cross the palm and meet the other fingertips; enables animal to grasp and cling to objects.
nucleotides
subunits of nucleic acid formed from a simple sugar, a phosphate group, and a nitrogenous base.
osteocytes
newly formed bone cells.
ozone
A gas, formed by the addition of a third oxygen atom to an oxygen molecule, that exists in a layer in the atmosphere and absorbs ultraviolet radiation from the Sun.
neurotransmitters
chemicals released from an axon that diffuse across a synapse to the next neuron's dendrites to initiate a new impulse.
ovary
in plants, the bottom portion of a flowers's pistil that contains one or more ovules each containing one egg.
normal
The line in a ray diagram that shows the diretion of the barrier and is drawn at a right angle, or perpendicular, to the barrier.
oxidation number
The positive or negative charge of a monatomic ion.
nucleic acid
A nitrogen-containing biological polymer that is involved in the storage and transmission of genetic information.
parallax
Apparent positional shift of an object caused by the motion of the observer.
osmotic pressure
The additional pressure needed to reverse osmosis.
noble gas
An extremely unreactive group 8A element.
ovulation
in females, the process of an egg rupturing through the ovary wall and moving into the oviduct.
open circulatory system
system where blood moves through vessels into open spaces around the body organs.
nitrogen fixation
The process that converts nitrogen gas into biologically useful nitrates.
nuclear reaction
A reaction that involves a change in the nucleus of an atom.
normal force
The perpendicular contact force exerted by a surface on another object.
nymph
stage of incomplete metamorphosis where an insect hatching from an egg has the same general appearance as the adult insect but is smaller and sexually immature.
nonrenewable resource
Resource that exists in Earth's crust in a fixed amount and can be replaced only by geological, physical, or chemical processes that take hundreds of millions of years.
nucleus
The extremely small, positively charged, dense center of an atom that contains positively charged protons, neutral neutrons, and is surrounded by empty space through which one or more negatively charged electrons move.
organ system
multiple organs that work together to perform a specific life function.
Newton's first law
States that an object at rest will remain at rest, and a moving object will continue moving in a straight line with constant speed, if and only if the net force acting on that object is zero.
niche
role or position a species has in its environment; includes all biotic and abiotic interactions as an animal meets its needs for survival and reproduction.
organ
group of two or more tissues organized to perform complex activities within an organism.
neutron star
Collapsed, dense core of a star that forms quickly while its outer layers are falling inward, has a radius of about 10 km, a mass 1.5 to 3 times that of the Sun, and contains only neutrons.
node
The stationary point where two equal wave pulses meet and are in the same location, having a displacement of zero.
ore
A material from which a mineral can be extracted at a reasonable cost.
Newton's second law for rotational motion
States that the angular acceleration of an object is directly proportional to the net torque and inversely proportional to the moment of inertia.
parasitism
symbiotic relationship in which one organism benefits at the expense of another, usually another species.
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pollination
from male reproductive organs to female reproductive organs of plants, usually within the same species.
physical property
A characteristic of matter that can be observed or measured without changing the sample's composition—for example, density, color, taste, hardness, and melting point.
plasma membrane
flexible boundary between the cell and its environment; allows materials such as water and nutrients to enter and waste products to leave.
pH
The negative logarithm of the hydrogen ion concentration of a solution; acidic solutions have pH values between 0 and 7, basic solutions have values between 7 and 14, and a solution with a pH of 7.0 is neutral.
peripheral nervous system (PNS)
division of the nervous system made up of all the nerves that carry messages to and from the central nervous system.
pheromones
chemical signals given off by animals that signal animals to engage in specific behaviors.
permeability
Ability of a material to let water pass through, which is high in material with large, well-connected pores and low in material with few pores or small pores.
photovoltaic cells
Thin, transparent wafers that convert sunlight into electrical energy and are made up of layers of boron- and phosphorus- enriched silicon.
pathogens
disease-producing agents such as bacteria, protozoans, fungi, viruses, and other parasites.
phylogeny
evolutionary history of a species based on comparative relationships of structures and comparisons of modern life forms with fossils.
periodic law
States that when the elements are arranged by increasing atomic number, there is a periodic repetition of their chemical and physical properties.
percent yield
The ratio of actual yield (from an experiment) to theoretical yield (from stoichiometric calculations) expressed as a percent.
period
A horizontal row of elements in the modern periodic table.
period
In any periodic motion, the amount of time required for an object to repeat one complete cycle of motion.
pascal
The SI unit of pressure; one pascal (Pa) is equal to a force of one newton per square meter.
population
group of organisms all of the same species, which interbreed and live in the same place at the same time.
pepsin
enzyme found in gastric juices; begins the chemical digestion of proteins in food; most effective in acidic environments.
platelets
small cell fragments in the blood that help blood clot after an injury.
petals
leaflike flower organs, usually brightly colored structures at the top of a flower stem.
plankton
small organisms that drift and float in the waters of the photic zone; includes both autotrophic and heterotrophic organisms, their eggs, and the juvenile stages of many marine animals.
pistil
female reproductive organ of a flower.
pendulum
A device that can demonstrate simple harmonic motion when its bob (a massive ball or weight), suspended by a string or light rod, is pulled to one side and released, causing it to swing back and forth.
phylum
taxonomic grouping of similar classes.
polyatomic ion
An ion made up of two or more atoms bonded together that acts as a single unit with a net charge.
pharynx
in planarians, the tubelike, muscular organ that extends from the mouth; aids in feeding and digestion.
passive transport
movement of particles across cell membranes by diffusion or osmosis; the cell uses no energy to move particles across the membrane.
plastic
A polymer that can be heated and molded while relatively soft.
polymer
large molecule formed when many smaller molecules bond together.
pigments
molecules that absorb specific wavelengths
physical change
A type of change that alters the physical properties of a substance but does not change its composition.
peptide
A chain of two or more amino acids linked by peptide bonds.
parasympathetic nervous system (PNS)
division of the automatic nervous system that controls many of the body's internal functions when the body is at rest.
pitch
The highness or lowness of a sound wave, which depends on the frequency of vibration.
periodic table
A chart that organizes all known elements into a grid of horizontal rows (periods) and vertical columns (groups or families) arranged by increasing atomic number.
placental mammals
mammals that give birth to young that have developed inside the mother's uterus until their body systems are fully functional and they can live independently of their mother's body.
plate tectonics
geological explanation for the movement of continents over Earth's thick, liquid interior.
permafrost
layer of permanently frozen ground that lies underneath the topsoil of the tundra.
phenotype
outward appearance of an organism, regardless of its genes.
photosynthesis
The complex process that converts energy from sunlight to chemical energy in the bonds of carbohydrates.
period
Third-longest time unit in the geological time scale, measured in tens of millions of years to hundreds of millions of years, and defined by life-forms that were abundant or became extinct.
photon
A particle of electromagnetic radiation with no mass that carries a quantum of energy.
perigee
Closest point in the Moon's elliptical orbit to Earth.
perennial
anthophyte that lives for several years.
placenta
organ that provides food and oxygen to and removes waste from young inside the uterus of placental mammals.
peristalsis
series of involuntary smooth muscle contractions along the walls of the digestive tract that move food through the digestive tract.
photic zone
portion of the marine biome that is shallow enough for sunlight to penetrate.
polarization
For a magnet, describes the property of having two distinct, opposite ends, one of which is a north-seeking pole and the other of which is a south-seeking pole.
plasma
Hot, highly ionized, electrically conducting gas.
pollutant
Substance that disrupts Earth's geochemical cycles and can harm the health of living things or adversely affect their activities.
plasma
fluid portion of the blood that makes up about 55 percent of the total volume of the blood; contains red and white blood cells.
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reaction rate
The change in concentration of a reactant or product per unit time, generally calculated and expressed in moles per liter per second.
pupa
stage of insect metamorphosis where tissues and organs are broken down and replaced by adult tissues; larva emerges from pupa as a mature adult.
quantitative data
Numerical information describing how much, how little, how big, how tall, how fast, etc.
reduction
The gain of electrons by the atoms of a substance; decreases an atom's oxidation number.
primary color
Red, green, and blue, which can be combined to form white light and mixed in pairs to produce the secondary colors
radioactivity
The process in which some substances spontaneously emit radiation.
receptors
binding sites on target cells that bind with specific hormones.
quasars
Starlike, very bright, extremely distant objects with emission lines in their spectra.
pyroclastic
flow Swift-moving, potentially deadly clouds of gas, ash, and other volcanic material produced by a violent eruption.
refraction
The change in direction of waves at the boundary between two different media.
reflecting telescope
A type of telescope that uses mirrors to focus visible light.
positron
A particle that has the same mass as an electron but an opposite charge.
posterior
tail end of bilaterally symmetric animals.
red blood cells
round, disk-shaped cells in the blood that carry oxygen to body cells; make up 44 percent of the total volume of the blood.
recessive
trait of an organism that can be masked by the dominant form of a trait.
proton
A subatomic particle in an atom's nucleus that has a positive charge of 1.
qualitative
data Information describing color, odor, shape, or some other physical characteristic.
reducing agent
The substance that reduces another substance by losing electrons.
pulse
surge of blood through an artery that can be felt on the surface of the body.
primary
wave Seismic wave that squeezes and pulls rocks in the same direction that the wave travels, causing rock particles to move back and forth.
product
A substance formed during a chemical reaction.
protein
large, complex polymer essential to all life composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur; provides structure for tissues and organs and helps carry out cell metabolism.
reclamation
Process in which a mining company restores land used during mining operations to its original contours and replants vegetation.
quantum
The minimum amount of energy that can be gained or lost by an atom.
refracting telescope
A type of telescope that uses lenses to focus visible light.
projectile
An object shot through the air, such as a football, that has independent vertical and horizontal motions and, after receiving an initial thrust, travels through the air only under the force of gravity.
reactant
The starting substance in a chemical reaction.
primate
Mammal that developed specialized traits, such as opposable thumbs and two eyes directed forward, primarily because of arboreal ancestry.
reflex
simple, automatic response in an animal that involves no conscious control; usually acts to protect an animal from serious injury.
ray
A line that can show the direction a wave is traveling and is drawn at a right angle to a wave's crest.
quarks
Tiny particles that make up protons, neutrons, and pions.
recharge
Process by which water from precipitation and runoff is added to the zone of saturation.
prion
a virus-like infectious agent composed of only protein, with no genetic material
prokaryotes
unicellular organisms, such as bacteria, composed of prokaryotic cells. Prokaryotic cells lack internal membrane- bound structures.
primary succession
colonization of barren land by pioneer organisms.
radioisotopes
Isotopes of atoms that have unstable nuclei and emit radiation to attain more stable atomic configurations.
redox reaction
An oxidation-reduction reaction.
precipitate
A solid produced during a chemical reaction in a solution.
pressure
Force applied per unit area.
position
The separation between an object and the origin; it can be either positive or negative.
radiation
The rays and particles—alpha and beta particles and gamma rays—that are emitted by radioactive materials.
radioactive decay
A spontaneous process in which unstable nuclei lose energy by emitting radiation.
precision
Refers to how close a series of measurements are to one another; precise measurements show little variation over a series of trials but may not be accurate.
protozoan
unicellular, heterotrophic, animal-like protist.
precession
Wobble in Earth's rotational axis.
radial symmetry
an animal's body plan that can be divided along any plane, through a central axis, into roughly equal halves.
prime meridian
Imaginary line representing 0° longitude, running from the north pole, through Greenwich, England, to the south pole.
porosity
Percentage of open spaces between grains in a rock; is highest in well-sorted sediments.
prophase
first and longest phase of mitosis where chromatin coils into visible chromosomes.
power
The work done, divided by the time needed to do the work.
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sexual reproduction
pattern of reproduction that involves the production and subsequent fusion of haploid sex cells.
runoff
Water that flows downslope on Earth's surface and may enter a stream, river, or lake.
saturated solution
Contains the maximum amount of dissolved solute for a given amount of solvent at a specific temperature and pressure.
series circuit
A type of electric circuit in which all current travels through each device and is the same everywhere; its current is equal to the potential difference divided by the equivalent resistance.
sediments
Solid particles deposited on Earth's surface that can form sedimentary rocks by processes such as weathering, erosion, deposition, and lithification.
ribosomes
nonmembrane-bound organelles in the nucleus where proteins are assembled.
sessile
organism that is permanently attached to a surface.
renewable resource
Natural resource, such as fresh air and most groundwater, than can be used indefinitely without causing a reduction in the available supply.
rhizome
thick, underground stem of a fern and other vascular plants; often functions as an organ for food storage.
seismogram
Record produced by a seismometer that can provide individual tracking of each type of seismic wave.
seminal vesicles
in males, pair of glands located at the base of the urinary bladder that secrete a mucouslike fluid into the vas deferens.
scales
thin bony plates that come in a variety of shapes and sizes formed from the skin of many fishes and reptiles.
rods
receptor cells in the retina that are adapted for vision in dim light; also help detect shape and movement.
seed
a plant organ of seed plants consisting of an embryo, a food supply, and a protective coat; protects the embryo from drying out and also can aid in dispersal.
residual soil
Soil located above its parent bedrock.
resultant
A vector that results from the sum of two other vectors; it always points from the first vector's tail to the last vector's tip.
rock cycle
Continuous, dynamic set of processes by which rocks are changed into other types of rock.
Richter scale
Numerical scale used to measure the magnitude of an earthquake, using values based on the size of the earthquake's largest seismic waves.
secondary succession
sequence of changes that take place after a community is disrupted by natural disasters or human actions.
short circuit
Occurs when a very low resistance circuit is formed, causing a very large current that could easily start a fire from overheated wires.
root
plant organ that absorbs water and minerals usually from soil; contains vascular tissues; anchors plant; can be a storage organ.
response
an organism's reaction to a change in its internal or external environment.
scalars
Quantities, such as temperature or distance, that are just numbers without any direction.
retina
thin layer of tissue found at the back of the eye made up of light receptors and sensory neurons.
sex chromosomes
in humans, the 23rd pair of chromosomes; determine the sex of an individual and carry sex-linked characteristics.
scientific notation
A type of shorthand used by scientists in which a number is expressed as a multiplier and a power of 10.
scientific methods
procedures that scientists use to gather information and answer questions; include observing and hypothesizing, experimenting, and gathering and interpreting results.
retrograde motion
A planet's backward motion in the sky.
Saffir-Simpson hurricane scale
Classifies hurricanes according to air pressure in the center, wind speed, and property damage potential on a scale ranging from Category 1 to Category 5.
semen
combination of sperm and fluids from the seminal vesicles, prostate gland, and bulbourethral glands.
reproduction
production of offspring by an organism; a characteristic of all living things.
relative humidity
Ratio of water vapor contained in a specific volume of air compared with how much water vapor that amount of air actually can hold.
scientific law
Describes a relationship in nature that is supported by many experiments.
shield volcano
Broad volcano with gently sloping sides built by nonexplosive eruptions of basaltic lava that accumulates in layers.
resonance
A special form of simple harmonic motion that occurs when small forces are applied at regular intervals to an oscillating or vibrating object and the amplitude of the vibration increases.
second law of thermodynamics
States that natural processes go in a direction that maintains or increases the total entropy of the universe.
regeneration
replacement or regrowth of missing body parts.
resistance
A property that determines how much current will flow; is equal to voltage divided by current.
semiconductors
Conductive materials, such as silicon or germanium, which, when made into solid-state devices, can amplify and control weak electric signals through electron movement within a tiny crystalline space.
selective permeability
feature of the plasma membrane that maintains homeostasis within a cell by allowing some molecules into the cell while keeping others out.
scavengers
animals that feed on animals that have already died.
secondary color
Yellow, cyan, and magenta, each of which is produced by combining two primary colors.
sex-linked traits
traits controlled by genes located on sex chromosomes.
resonance
Condition that occurs when more than one valid Lewis structure exists for the same molecule.
resistor
A device with a specific resistance; may be made of long, thin wires; graphite; or semiconductors and often is used to control the current in circuits or parts of circuits.
ribonucleic acid (RNA)
a nucleic acid that forms a copy of DNA for use in making proteins.
second
The SI base unit for time.
season
Short-term period of climatic change caused by regular variations in temperature, hours of daylight, and weather patterns that are due to the tilt of Earth's axis as it revolves around the Sun, causing different areas of Earth to receive different amounts of solar radiation.
salt
An ionic compound made up of a cation from a base and an anion from an acid.
secondary wave
Seismic wave that causes rock particles to move at right angles to the direction of the wave.
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solenoid
A long coil of wire with many loops; fields from each loop add to the fields of the other loops, creating a greater total field strength.
small intestine
muscular tube about 6 m long where digestion is completed; connects the stomach and the large intestine.
stratosphere
The atmospheric layer above the troposphere and below the mesosphere; contains an ozone layer, which forms a protective layer against ultraviolet radiation.
stress
Forces per unit area that act on a material— compression, tension, and shear.
stoichiometry
The study of quantitative relationships between the amounts of reactants used and products formed by a chemical reaction; is based on the law of conservation of mass.
specific gravity
Ratio of the weight of a substance to the weight of an equal volume of H2O at 4°C.
sperm
haploid male sex cells produced by meiosis.
sonar
Use of sound waves to detect and measure objects underwater.
strong acid
An acid that ionizes completely in aqueous solution.
stomach
muscular, pouchlike enlargement of the digestive tract where chemical and physical digestion take place.
states of matter
The physical forms in which all matter naturally exists on Earth—most commonly as a solid, a liquid, or a gas.
spring
Natural discharge of groundwater at Earth's surface where an aquifer and an aquiclude come in contact.
soluble
Describes a substance that can be dissolved in a given solvent.
soil horizon
A distinct layer within a soil profile.
steroids
Lipids that have multiple cyclic rings in their structures.
solar eclipse
Occurs when the Moon passes between Earth and the Sun and the Moon casts a shadow on Earth, blocking Earth's view of the Sun; can be partial or total.
silicate
Mineral that contains silicon (Si) and oxygen
spectrum
Arrangement of visible light ordered according to wavelength.
smog
Yellow-brown, photochemical haze that occurs when solar radiation acts on air polluted with hydrocarbons and nitrogen oxides from automobile exhausts.
smooth muscle
type of involuntary muscle found in the walls of internal organs and blood vessels; most common function is to squeeze, exerting pressure inside the tube or organ it surrounds.
significant figures
The number of all known digits reported in measurements plus one estimated digit.
subduction
Process by which one tectonic plate slips beneath another tectonic plate.
solid
A form of matter that has its own definite shape and volume, is incompressible, and expands only slightly when heated.
speciation
process of evolution of new species that occurs when members of similar populations no longer interbreed to produce fertile offspring within their natural environment.
solvent
The substance that dissolves a solute to form a solution.
storm surge
Occurs when powerful, hurricane-force winds drive a mound of ocean water toward shore, where it washes over the land, often causing enormous damage.
solute
A substance dissolved in a solution.
sinkhole
Depression in Earth's surface formed when a cave collapses or bedrock is dissolved by acidic rain or moist soil.
stamen
male reproductive organ of a flower consisting of an anther and a filament.
streak
Color a mineral leaves when it is rubbed across an unglazed porcelain plate or when it is broken up and powdered.
simple harmonic motion
A motion that occurs when the restoring force on an object is directly proportional to the object's displacement from equilibrium.
spore
type of haploid (n) reproductive cell with a hard outer coat that forms a new organism without the fusion of gametes.
strain
Deformation of materials in response to stress.
sound wave
A pressure variation transmitted through matter as a longitudinal wave; it reflects and interferes and has frequency, wavelength, speed, and amplitude.
steady-state theory
Proposes that the universe is the same as it has always been.
stem
plant organ that provides support and growth; contains tissues that transport food, water, and other materials; organ from which leaves grow. Can serve as a food storage organ; green stems can carry out photosynthesis.
spawning
method of reproduction in fishes and some other animals where a large number of eggs are fertilized outside of the body.
stimulus
anything in an organism's internal or external environment that causes the organism to react.
specific heat
The amount of heat required to raise the temperature of one gram of a given substance by one degree Celsius.
solution
A uniform mixture that may contain solids, liquids, or gases; also called a homogeneous mixture.
skeletal muscle
a type of voluntary muscle that is attached to and moves the bones of the skeleton.
stalagmite
Mound-shaped dripstone deposit of calcium carbonate that forms on a cave's floor beneath a stalactite.
soil
Loose covering of weathered rock and decayed organic matter overlying Earth's bedrock that is characterized by texture, fertility, and color and whose composition is determined by its parent rock and environmental conditions.
somatic nervous system
portion of the nervous system composed of cranial nerves, spinal nerves, and all of their branches; voluntary pathway that relays information mainly between the skin, the CNS, and skeletal muscles.
solar flare
Violent eruption of radiation and particles from the Sun's surface that is associated with sunspots.
stalactite
Cone-shaped or cylindrical dripstone deposit of calcium carbonate that hangs like an icicle from a cave's ceiling.
solubility
The maximum amount of solute that will dissolve in a given amount of solvent at a specific temperature and pressure.
species
group of organisms that can interbreed and produce fertile offspring in nature.
solar wind
Wind of charged particles that flows throughout the solar system and begins as gas flowing outward from the Sun's corona at high speeds.
stomata
openings in leaf tissues that control gas exchange.
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substance
A form of matter that has a uniform and unchanging composition; also known as a pure substance.
suspension
A type of heterogeneous mixture whose particles settle out over time and can be separated from the mixture by filtration.
trajectory
The path of a projectile through space.
surfactant
A compound, such as soap, that lowers the surface tension of water by disrupting hydrogen bonds between water molecules; also called a surface active agent.
supercell
Extremely powerful, self-sustaining thunderstorm characterized by intense, rotating updrafts.
temperature
A measure of the average kinetic energy of the particles in a sample of matter.
surface current
Wind-driven movement of ocean water that primarily affects the upper few hundred meters of the ocean.
succession
orderly, natural changes, and species replacements that take place in communities of an ecosystem over time.
thermocline
Transitional ocean layer that lies between the relatively warm, sunlit surface layer and the colder, dark, dense bottom layer and is characterized by temperatures that decrease rapidly with depth.
tsunami
Large, powerful, ocean wave generated by the vertical motions of the seafloor during an earthquake; in shallow water, can form huge, fast-moving breakers exceeding 30 m in height that can damage coastal areas.
tornado
Violent, whirling column of air in contact with the ground that forms when wind direction and speed suddenly change with height, is often associated with a supercell, and can be extremely damaging.
system
In thermochemistry, the specific part of the universe containing the reaction or process being studied.
telophase
final phase of mitosis during which new cells prepare for their own independent existence.
thermonuclear reaction
A nuclear fusion reaction.
sunspot
Dark spot on the surface of the photosphere that typically lasts two months, occurs in pairs, and has a penumbra and an umbra.
supersaturated solution
Contains more dissolved solute than a saturated solution at the same temperature.
synthesis reaction
A chemical reaction in which two or more substances react to yield a single product.
transverse wave
A mechanical wave that vibrates perpendicular to the direction of the wave's motion.
sublimation
Process by which a solid slowly changes to a gas without first entering a liquid state.
transition elements
Groups of elements in the modern periodic table that are designated with a B (1B through 8B) and are further divided into transition metals and inner transition metals.
synapse
tiny space between one neuron's axon and another neuron's dendrites over which a nerve impulse must pass.
thermal energy
A measure of the internal motion of an object's particles.
thermometer
Weather instrument used to measure temperature that contains a column of mercury or alcohol that expands and rises when heated and contracts and falls when cooled.
troposphere
The lowest layer of Earth's atmosphere where weather occurs and in which we live; has temperatures that generally decrease with increasing altitude.
topographic map
Map that uses contour lines, symbols, and color to show changes in the elevation of Earth's surface and features such as mountains, bridges, and rivers.
theoretical yield
In a chemical reaction, the maximum amount of product that can be produced from a given amount of reactant.
superconductor
A material with zero resistance that can conduct electricity without a loss of energy.
titration
The process in which an acid-base neutralization reaction is used to determine the concentration of a solution of unknown concentration.
symmetry
a term that describes the arrangement of body structures.
trough
Lowest point of a wave.
theory
An explanation based on many observations during repeated experiments that is valid only if it is consistent with observations, makes predictions that can be tested, and is the simplest explanation of observations.
technology
The practical use of scientific information.
tension
The specific name for the force exerted by a rope or a string.
torque
A measure of how effectively a force causes rotation; is equal to the force times the lever arm.
taxonomy
branch of biology that groups and names organisms based on studies of their shared characteristics; biologists who study taxonomy are called taxonomists.
transformer
A device that can decrease or increase the voltages in AC circuits with relatively little energy loss.
surface tension
The energy required to increase the surface area of a liquid by a given amount; results from an uneven distribution of attractive forces.
summer solstice
Occurs when the Sun is directly overhead at 23.5° north latitude, around June 21, and results in the maximum number of daylight hours for the northern hemisphere and the minimum number for the southern hemisphere.
supernova
Massive explosion that occurs when the outer layers of a star are blown off.
superposition
Principle stating that in an undisturbed rock sequence, the oldest rock layers are at the bottom and each successive layer is younger than the layer beneath.
trade winds
Global wind system that flows at 30° north and south latitude, where air sinks, warms, and returns to the equator in a westerly direction.
temperature inversion
Increase in temperature with height in an atmospheric level, which inverts the temperature-altitude relationship and can worsen air pollution problems.
thermosphere
Layer of Earth's atmosphere that is located above the mesopause and contains only a minute portion of the atmosphere's mass.
transistor
A simple device made of doped semiconducting material that can act as an amplifier, converting a weak signal to a much stronger one.
tropics
Area of Earth that receives the most solar radiation, is generally warm year-round, and extends between 23.5° south and 23.5° north of the equator.
taiga
biome just south of the tundra.
tide
Periodic rise and fall of sea level caused by the gravitational attraction among Earth, the Moon, and the Sun.
sympathetic nervous system
division of the automatic nervous system that controls many of the body's functions during times of stress.
symbiosis
permanent, close association between two or more organisms of different species.
tropical cyclone
Large, low-pressure, rotating storm that gets its energy from the evaporation of warm ocean water and the release of heat.
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