A

Abduction - A muscle movement that takes an appendage laterally from the midline.

Abiotic - Nonliving.

Absolute zero - The lowest possible temperature.

Abyssal zone - The floor of the deep-ocean plane from about 4000 meters down to about 6000 meters.

Acaulescent - Plants with basal leaves and a leafless flower stalk.

Acceleration - The rate of change in velocity.

 Acccelerators - Large, complicated machines used to shoot high energy particles into atoms for atomic research.

Accessory fruit - A fruit composed of the plant ovary wall plus other flower parts.

Accuracy - Refers to how close a measurement is to the true value of the quantity.

Achene - A dry fruit with more than one carpel, a single seed, and the fruit coat free from the seed coat.

Acid - A substance that produces the hydronium ion, H3O + in solution.

Acid anhydride - An oxide that produces an acid when dissolved in water.

Acid rain - Rain containing sulfuric acid (H2SO4) produced by the burning of fossil fuels with a high sulfur content.

Acoustics - The science of sound.

Activated complex - Formed when molecules collide with enough kinetic energy to cause changes in the electron clouds of both molecules, allowing a reaction to proceed.

Activation energy - The energy needed to start a chemical reaction.

Adaptation - Any trait giving an organism an advantage in a certain environment.

Adaptive radiation - Many species appear to be related to a single ancestral species.

Addiction - A dependence on a substance.

Adduction - Moves an appendage toward the midline.

Adenine - One of two double carbon ring nitrogen bases in DNA.

Adipose - Fleshy or fatty.

Adventitious root - A root that grow from a plant's stem or leaves.

 Aerobic - Refers to the use of molecular oxygen.

 Aggregate fruit - Derived from more than one pistil on one flower.

Agonists - Muscles primarily responsible for an action due to their contraction.

AIDS - Acquired immunodeficiency syndrome.

Alcohols - Organic compounds containing the hydroxyl group.

Algae - Plant-like protists that carry on photosynthesis.

Alimentary canal - The tube containing food as it passes through the body.

Alkali Metals - Elements in Group 1 on the periodic table.

Alkaline Earth Metals - Elements in Group 2 on the periodic table.

Alkanes - Saturated hydrocarbons with only single bonds.

Alkenes - Unsaturated hydrocarbons with at least one double bond.

Alkynes - Unsaturated hydrocarbons with at least one triple bond.

Allantosis - The amniote egg membrane that stores embryonic wastes.

Allele - Any of the several alternative forms of a gene.

Allele frequency - The percentage of a specific allele of a gene in the gene pool.

Alloy - Any mixture of two or more substances, as long as at least one is a metal.

Alpha particle - A helium nucleus given off by the nucleus of a larger atom.

Altair 8800 - The first personal computer, produced in kit form in 1975.

Alternating current - AC electricity whose current flow changes direction periodically.

Alternation of generations - The alternation between diploid and haploid cells or organisms.

Altricial - Birds that lay few eggs and incubate them for a short period.

ALU - The arithmetic logic unit that performs calculations in computers and calculators.

Alveoli - Small sacs that increase the surface area of the lungs.

Amino acids - The 20 nitrogen-containing organic compounds used to build proteins.

Ammocoete - The filter-feeding larval stage of a lamprey.

Ammonification - Bacteria decomposers breaking down amino acids from dead animals and animal wastes into NH4OH.

Amnion - The membrane enclosing the fluid in which an embryo developes.

Amorphous - A substance whose particles have no regular pattern.

Ampere - A measure of the amount of electric current flowing past a given point per second.

Amphetamine - A type of stimulant.

Amphoteric - A substance that acts as either acid or base, depending on what it reacts with.

Amplitude - The maximum distance molecules are displaced from their rest position in a wave.

Anaerobic - Refers to the absence of molecular oxygen.

Anaphase - The stage of mitosis in which the chromosomes move to opposite ends of the cell.

Androecium - A term for all the stamens of a flower together.

Angiosperms - The flowering plants.

Anhydrous - Without water.

Animal - A multicellular, eukaryotic, heterotrophic organism.

Anions - Ions with a negative charge.

Annuals - Herbaceous plants that live for only one year.

Antagonists - Muscles that relax to smooth the action of the agonists.

Antenna pigments - The bulk chlorophyll molecules that collect and channel energy to the reaction centers..

Anterior - Refers to the front end of an organism.

Anther -The part of the plant stamen that produces pollen grains

 Antibiotics - Natural chemicals that inhibit the growth of some bacteria.

Anticoagulin - A chemical in snake venom that thins the blood.

Antimatter - Matter composed of antiparticles.

Anti-oncogene - A gene that suppresses tumor growth.

Antiparticles - Particles that have exactly the same mass but opposite charges.

Antlers - Solid bone extensions from the skull of most species of deer.

Aorta - The body's major artery leading from the left ventricle of heart to the body.

Aphotic zone - A zone of deep, permanently dark ocean water.

Apical meristem - Located at the tips of stems and roots, this meristem produces growth in length known as primary growth.

Apomixis - The process by which plants form seeds without gamete formation or fertilization.

Appendicular skeleton - The part of a vertebrate skeleton containing the skull, spine, and ribs.

Applied science - The practicle use of scientific information; technology.

Aqueous - Having to do with water.

Aquifer - A layer of relatively porous and permeable underground rock, allowing water to move through it.

Arachnid - A term commonly used as a group name for spiders and their close relatives.

Arachnoid layer - The middle layer of the three protective tissues of the brain, consisting of a web-like elastic tissue.

Archaebacteria A relatively small kingdom of bacteria.

Archimedes' Principle - The buoyant force of an object is equal to the weight of the fluid displaced by the object.

Aromatic hydrocarbons - Hydrocarbons containing benzene, C6H6.

Arrhenius Theory - One of the three common acid/base theories.

Arteries - Thick-walled blood vessels that carry blood under high pressure away from the heart.

Arthropod - An animal characterized by an exoskeleton and jointed appendages.

Asexual reproduction - Producing offspring without the use of gametes.

Asphyxiant - A gas or vapor that causes injury by reducing the amount of oxygen available for breathing.

Astronomy - The study of objects in the universe.

Asymmetrical - Having no definate shape and cannot be divided into equal parts.

Atom - The smallest particle of an element.

 Atomic number - Represents the number of protons in an atom.

ATP - Adenosine triphosphate is the molecule most organisms can actually use for energy.

 Atrium - The collecting chamber of the heart.

Autonomic nervous system - Nerves that control involuntary muscles.

Autotrophic - Organisms that are able to produce their own food.

Auxins - A group of plant hormones that promote cell elongation, apical dominance, and rooting.

Avogadro's Number - 6.02 X 10 23

Avogadro's Principle - At equal temperature and pressure, equal volumes of gases contain the same number of molecules.

 Axial skeleton - The part of a vertebrate skeleton containing the arms, shoulders, legs, and pelvis.

Axon - An elongated extension of the neuron body that carries impulses away from the cell.

 Azimuth - A direction from one place toward another expressed as degrees on a compass.

 B

Bacilli - A term used to indicate rod-shaped bacterial cells.

Background radiation - Radiation found naturally in the environment.

Bacteria - Single-cell organisms with no nucleus.

Bacteriophage - A virus that commonly infects bacteria.

Balanced equation - A chemical equation with the same number of each type of atom on both sides.

Barbiturate - A type of depressant.

Bark - The tissues outside the wood and the cambial layer of woody stems.

Barometer - A device used to measure atmospheric pressure.

Baryons - Regular subatomic particles composed of three quarks.

Base - A substance that produces the hydroxide ion, OH - in solution.

Basic anhydride - An oxide that produces a base when dissolved in water.

Batesian mimicry - A harmless species mimicing the warning coloration of a dangerous species.

Bathyal zone - The ocean floor from the continental shelf down to about 4000 meters.

Battery - A series of connected electrochemical cells.

Beaker - The most versatile piece of glassware in the chemisty lab.

Becquerel - The unit for the measure of decay in radioactive nuclides.

Benign - Refers to a tumor whose cells remain attached to the parent tumor.

Benthic zone - The ocean floor.

Bernoulli's Principle - The pressure in a moving stream of fluid is less than the pressure in the surrounding fluid.

Berry - A fleshy fruit composed of more than one carpel with few to many seeds.

Beta particle - An electron given off by the nucleus of an atom.

Bicuspids - Teeth with two points for shearing and shredding.

Biennials - Short-lived herbaceous plants that produce only vegetative growth the first year, then bloom the second year.

 Big Bang Theory - A theory explaining the formation and operation of the Universe.

Binary acid - An acid composed of hydrogen and one other element.

Binary compounds - Compounds composed of two elements.

Binary fission - DNA replicates and then the cell pinches inward and splits in two.

Binomial nomenclature - A two name system for writing scientific names.

Biochemistry - The study of the chemical reactions of life.

 Biodegradable - Subject to decay by microorganisms.

Biogeochemical cycles - The process by which abiotic materials move from the atmosphere or soil into organisms and back again.

 Biology - The study of living things.

Biomass - The weight of living matter in a particular area.

Biomaterials - Mechanical devices used as replacements for various parts of the human body.

Biome - A large geographical area described by its climate, soil, flora, and fauna.

 Biosphere - The total of all ecosystems on Earth.

Biotic - Living.

Biotic potential - The maximum growth rate of which a population is physiologically capable.

Bit - A single electronic switch.

Bivalve - A filter-feeding mollusk with two shells.

Black hole - A concentration of matter which has a gravitational field strong enough to curve spacetime completely around upon itself so that nothing can escape, not even light.

Blastopore - The point where a blastula begins to fold inward.

Blastula - A hollow sphere of cells formed as zygote cells divide.

Blight - A quickly developing decay or discoloring of leaves, stems, or flowers caused by plant parasites.

 Boiling point - The temperature at which the vapor pressure of a liquid is equal to standard atmospheric pressure; changing a liquid into a gas.

Boiling point elevation - The addition of a nonvolatile solute making a solution boil at a higher temperature.

Bones - The hard, mineral structures making up the skeleton of most vertebrates.

Bosons - The force carriers in atoms.

Boyle's Law - The volume of a fixed amount of gas varies inversely with the pressure of the gas.

Brain stem - Connects the cerebrum with the spinal cord.

Bronchi - The two branches of the trachea leading to the lungs.

Bronchioles - The smallest branches of the bronchial tubes.

Bronsted - Lowery Theory - One of the three common acid/base theories.

BTU - British Thermal Unit - One BTU is the amount of thermal energy necessary to raise the temperature of one pound of liquid water by one degree Fahrenheit

 Buffer - A solution that can absorb moderate amounts of acid or base without a significant change in pH.

 Bulb - Fleshy, upright, underground stems with fleshy leaves or scales.

 Buoyancy - The force of a fluid that pushes up on an object in the fluid.

Buret - A graduated pipet with a dispensing device at one end.

Bursa - A fluid-filled sac in the knee and shoulder joints to cushion the bones.

Byte - A string of eight bits.

 C

C3 plants - The most common type of plant, producing 3-carbon organic acids as their first stable products.

 C4 plants - Plants that produce 4-carbon organic acids as their first stable products, with photosynthetic energy conversion efficiency as much as 50% higher than in C3 plants.

Calculator - An electronic device used for manipulating numbers.

Calorimeter - An insulated container used for measuring temperature changes.

Calyx - A term that refers to all the sepals of a flower together.

Calorie - The amount of heat needed to raise the temperature of one gram of water by one Celsius degree; a measure of the energy available in food.

Cancer - Uncontrolled division of cells.

Candela - The SI base unit for light intensity.

Canines - Pointed teeth for puncturing and tearing.

Capillaries - Small blood vessels that connect arteries and veins.

Capillary rise - The rise of a liquid in a tube of small diameter due to adhesion forces.

Capillary water - Water found in the smaller pores of soil that is most often available to plant roots.

Capsule - A thick, gel-like, protective coating on some bacteria cells; a dry fruit with several carpels, splitting lengthwise when ripe.

Carapace - The dorsal shell of turtle-like animals.

Carbohydrate - Organic compounds composed of carbon, hydrogen, and oxygen.

Carbon-Oxygen Cycle - The movement of carbon and oxygen in the Earth's biosphere.

Carcinogen - An agent that leads to the production of a cancer cell.

Carcinoma - Cancer of the skin or nerve cells.

Carnivores - Consumers that eat only animals.

Carrying capacity - The maximum population density that an environment can support for an extended time.

Caryopsis - Grain, a dry fruit with 1-seed, the fruit coat fused with seed coat.

Catalyst - A substance that changes the rate of a chemical reaction without being changed in the reaction.

Cations - Ions with a positive charge.

Catkin - A spike or raceme composed of unisexual flowers without petals.

 Caudal - Refers to the tail.

 Caulescent - Ordinary plant structure with leafy stems and flowers growing at their nodes.

Cell membrane - A complex barrier of lipid molecules separating a cell from its external environment.

Cell theory - A theory relating to the importance of cells in living things.

Cellulose - A complex polysaccharide forming the cell wall in plant cells.

Celsius - The SI temperature scale used in most scientific measurements.

Cementum - The material that binds the enamel to the dentine of a tooth.

Centi - The SI prefix for 1/100.

Central nervous system - Includes the brain and spinal cord.

Centrifugal force - An apparent force that appears only in rotating frames of reference.

 Centripetal acceleration - Acceleration toward the center of a circular path.

 Cephalization - The concentration of sensory and brain structures in the anterior end of an animal.

Cephalothorax - The fused head and thorax region of some segmented animals.

Cerebellum - The lower back of the brain, responsible for muscle coordination and balance.

 Cerebrum - The largest portion of the human brain, responsible for major brain functions.

Charles' Law - The volume of a fixed amount of gas varies directly with the temperature of the gas.

Chelicerae - Pincer-like mouthparts; arachnid fangs.

Chemical digestion - Breaking complex chemicals into simple ones.

Chemical equilibrium - A dynamic system in which chemical changes are taking place in such a way that there is no overall change in the composition of the system.

Chemical property - Any characteristic that describes how one material interacts with another material.

Chemical reaction - A process in which substances change into other substances.

Chemical symbol - A one or two letter shorthand used to represent elements.

Chemistry - The study of the structure and properties of matter.

Chemoautotrophs - Bacteria that use energy from chemical reactions to make their own food.

Chemoreceptors - Function as organs of smell and taste in earthworms and some other organisms.

Chemotherapy - Using chemicals injected into the blood to kill cancer cells.

Chemotropism - A plant growth response to chemicals.

Chitin - A tough calcium containing compound forming the exoskeleton of arthropods; forms the cell wall of fungi cells.

Chlorophyll - The green, light-absorbing pigment that makes photosynthesis possible in plants.

Chloroplasts - The sites of photosynthesis in plants.

Chorion - The amniote egg membrane that lines the shell.

Chromatid - One of two identical halves of a chromosome.

 Chromatophores - Structures containing pigment to provide color patterns.

Chromosome - A coiled, double rod-shaped form of condensed DNA that forms during cell division.

 Chromosome mutation - A mutation involving some piece of a chromosome.

Chrysalis - The protective case in which a butterfly pupa becomes an adult.

Circuit breaker - A switch that flips open when too much current flows.

Cladistics - A system of phylogenetic classification that uses shared derived characters to establish theoretical evolutionary relationships.

Cladogram - A phylogenetic tree based on a cladistic analysis.

Classification - The grouping of organisms based on characteristics.

Clevage - A term representing the rapid division of zygote cells.

Climate - The long-term average conditions of the atmosphere.

Climax community - The community that will remain stable in a given area.

Cloaca - A cavity which collects deposits from intestine, urinary bladder, and sex organs.

Clone - An artificial duplication of genes.

 Cocci - A term used to indicate round bacterial cells.

Cocoon - The protective case in which a moth pupa becomes an adult.

Cochlea - The coiled, fluid-filled cavity of the human inner ear.

Coefficients - The large numbers in front of chemical formulas in a chemical equation, representing the number of molecules.

Coelacanth - A fish that has paddle-like fins with a fleshy base.

Coelom - An animal body cavity.

Coevolution - Two or more species changing because of changes in a species with which they are interacting.

Collenchyma - Elongated plant cells with uneven, flexible cell walls.

Colloid - A homogeneous mixture with solute particles larger than a solution, but smaller than a suspension.

Colon - Another name for the large intestine.

Combined Gas Law - A gas law used for calculations when both temperature and pressure change.

Combustion reaction - A hydrocarbon reacts with oxygen, producing carbon dioxide and water.

Commensalism - A symbiotic relationship in which one organism benefits from another organism while that organism neither benefits nor is harmed.

Common Ion Effect - The addition of a substance containing an ion already at equilibrium in a saturated solution will shift the equilibrium toward the undissolved substance.

Community - A group of interacting populations.

Competition - Organisms using resources and reducing the availability of those resources to other organisms.

Competitive Exclusion Principle - The competition between populations of two species for the same limiting resource eventually leads to the elimination of one of the species populations.

Complete flower - A flower with sepals, petals, stamens, and pistils.

Compound eye - An eye composed of many individual lenses.

Compound leaf - A leaf with more than one blade on a single petiole.

Compounds - Pure substances made up of more than one element.

Computer - An electronice device that processes information.

 Concentrated - A solution with a large amount of solute.

Concentration - A comparison of the amount of solute dissolved in an amount of solvent.

Condensation - The changing of a gas to a liquid.

Conduction - The movement of heat from one substance to another by direct contact of molecules.

Conductors - Materials that easily allow the flow of an electric current; nerve cells that transmit information from receptors to the central nervous system.

Cones - Nerve cells in the eye that are sensitive to a particular primary color.

Conjoined twins - Twins that share some body parts.

Conjugate acid - The particle formed when a Bronsted-Lowery base accepts a proton.

Conjugate base - The particle that remains after a Bronsted-Lowery acid gives up a proton.

 Conjugation - The process by which two single cell organisms exchange a portion of their DNA across a bridge formed between the cells.

Constellation - A group of stars forming a pattern as viewed from Earth.

Consumers - Heterotrophic organisms that cannot make their own food.

Contraception - Preventing live sperm and egg from coming together.

Control group - A group used for a comparison in an experiment.

Controlled substance - A legal classification for drugs that have a potential for abuse.

Convection - The movement of heat from one place to another in a liquid or gas as molecules move in currents caused by density differences.

Convergent evolution - Unrelated species becoming more and more similar in appearance because of a shared environment.

Conversion factor - A fraction used to change one type of unit to another.

Coriolis effect - Winds veer to the right in the northern hemisphere and to the left in the southern hemisphere because of the Earth's rotation.

Cork - Closely packed cells protecting the stem in woody plants.

Corm - Fleshy, upright, underground stems with papery modified leaves or scales.

Corolla - Refers to all the petals of a flower together.

Coronary - Refers to the heart.

Corrosive material - A substance capable of causing visable and irreversible damage to human skin tissue at the site of contact.

Cortex - The tissue outside the central vascular bundles of herbaceous stems and roots.

Corymb - A flat-topped inflorenscence with the pedicels of different length.

Cosmology - The study of the universe as a whole.

Coulomb - The quantity of electricity produced by a current of one ampere flowing for one second.

Covalent bond - Electrons are shared between atoms to form a compound.

CPU - The central processing unit controlling a computer.

Cranial nerves - Connect major sense organs directly to the brain.

Critical length - The length of daylight above or below which a species of plant will flower.

Critical temperature - The temperature above which no amount of pressure will liquify a vapor.

Critical thinking - The disciplined process of actively conceptualizing, analyzing, and applying information as a guide to action.

Crop - An expandable organ in the digestive system of some animals that stores food for processing.

Cross-pollination - The transfer of pollen from one plant to another of the same species.

Crystal - A true rigid solid whose particles are arranged in a regular, repeating pattern.

Cultivars - Plants that are grown specifically for food.

Cumulus - Towering clouds formed by rising hot winds.

Cuticle - The outermost layer of the epidermis

Cyanobacteria - Bacteria that are photosynthetic, carrying on the same chemical processes as green plants.

Cyclotrons - Large, circular machines used to shoot high energy particles into an atomic nucleus.

Cytokinesis - Division of the cytoplasm of a parent cell during the cell cycle.

Cytokinins - A group of plant hormones that promote cell division.

Cytoplasm - A thick, aqueous solution of salts surrounding the organelles of a cell.

Cytoplasmic streaming - The constant motion of cytoplasm in a cell.

Cytosine - One of two single carbon ring nitrogen bases in DNA.

 D

Dalton's Law - The total pressure in a container is the sum of the partial pressures of all the gases in the container.

Dalton's Theory - The first atomic theory, in 1803.

Daughter cell - The new cell formed when a cell divides.

Day-neutral plants - Plants whose flowering is not affected by the length of days and nights.

Decapod - An animal with ten feet, five pairs of legs.

Deceleration - A term commonly used to mean a decrease in speed; negative acceleration.

Decomposers - Organisms that break down dead organic matter into smaller organic materials and ultimately into inorganic matter.

Decomposition reaction - One complex substance breaks down into two or more simple substanes.

Dehiscent - A dry fruit that opens when ripe.

Dehydration - A term referring to a multitude of cellular problems that develop as the amount of water in the body begins to get too low.

Deliquescent - A solid so strongly hygroscopic that it will dissolve in air.

Dendrite - A finger-like projection from the neuron body that receives impulses.

 Dendrochronology - The study of climate history using tree rings.

Denitrification - Anaerobic bacteria break down nitrates, releasing N2 into the atmosphere.

Density - Mass per unit of volume.

Dental formula - An expression of the number of each type of tooth on one side of the upper jaw over the number of each type of tooth on one side of the lower jaw.

 Dentine - The porous, bone-like foundation of a tooth.

Dependent variable - The variable in an experiment that changes with the independent variable; the variable plotted on the Y axis of a graph; the variable listed on the right side of a data table.

Depressants - Drugs that slow down nerve action, heart rate, and lower blood pressure.

Derived units - Combinations of basic SI units.

Desiccant - An anhydrous substance used to remove water from other substances.

Diadelphous - A flower whose stamens are attached by their filaments into two groups.

Diaphragm - The breathing muscle located below the ribs in mammals.

Diatomic molecules - Seven elements existing in pure form in nature only as two atoms covalently bonded.

 Dichasium - A peduncle bearing a terminal flower and a pair of branches producing lateral flowers.

Dichotomous key - A device to use to identify organisms.

Dicots - Plants with two seed leaves.

Diffraction - The bending of waves around the edge of a barrier.

Diffusion - The movement of particles from an area of high concentration to an area of low concentration.

Digestion - The two-part process that changes food into a form usable by body cells.

 Dihybrid cross - A genetic cross involving two traits.

Dilute - A solution with a small amount of solute.

Diode - The basic, one-way gate for electrons in electronic devices.

Dipeptide - Two amino acids bonded together.

Diphyodont - Having two sets of teeth.

Diploid - Refers to a cell that contains both chromosomes of a homologous pair.

Dipole - A polar molecule.

Dipole-induced dipole forces - A dipole transforms a nonpolar molecule into a dipole and an attraction occurs.

Direct current - DC electricity whose current flows in one direction only.

Disaccharide - A double sugar composed of two simple sugars.

Dislocation - A fault in which unit cells of a crystal are joined improperly.

Dispersal unit - Refers to any detached plant part serving as a vehicle for seed dispersal.

 Dispersion forces - The attraction of two nonpolar molecules.

Dissociation - The separation of ions from a compound during solution.

Distillation - Removing dissolved substances from a liquid or separating a mixture of liquids that have different boiling points.

Divergent evolution - Two or more similar species becoming more and more dissimilar because of environmental adaptations.

DNA - Deoxyribonucleic acid stores and transmits the genetic information in cells.

Doping - Adding impurities to a semiconductor to increase its conductivity.

Doppler effect - A change in the frequency and pitch of a sound due to the motion of either the sound source or the observer.

Dorsal - Refers to the top surface of an organism.

Double displacement reaction - Different atoms in two different compounds replace each other.

Double helix - The spiral shape of a DNA molecule.

Drug - Any substance taken into the body that alters normal body processes.

Drupe - A fleshy fruit composed of one carpel with a single seed, fleshy outer and inner stony layers.

Dry cell - An electrochemical cell in which all reactants are solids.

 Dry gas - A gas with no water vapor.

Dry fruit - A fruit with papery or leathery walls.

Dura mater - The outer layer of the three protective tissues of the brain, consisting of connective tissues, blood vessels, and nerves.

Dysphotic zone - Middle layers of ocean water consisting of twilight that does not support alga growth.

  E

Eardrum - A tightly stretched membrane in the outer ear that vibrates as the sound waves strike it.

E. Coli - Common bacteria living in our intestinal tract.

Ecological pyramid - A chart representing trophic level numbers within an ecosystem.

Ecology - The study of the interactions between organisms and the living and nonliving components of their environment.

Ecosystem - A functional environmental unit, consisting of a biotic community and the abiotic factors on which the organisms depend.

Ectocarp - The outermost layer of the pericarp, exocarp.

Ectoderm - The outer layer of cells of a gastrula that becomes the body covering.

Ectoparasite - A parasite living on the external surface of its host.

Ectothermic - Body temperature is determined by the environment; cold-blooded.

Effectors - Nerve cells that receive information from the central nervous system and transmit to muscles and glands.

Efficiency - A comparison of work output to work input.

 Effort force - The force applied to a machine.

Elastic collision - A collision in which the momentum and kinetic energy of the colliding particles are exactly the same after the collision as before.

Electricity - The energy associated with charged particles.

Electric circuit - A complete, closed path for an electric current.

Electric field - An area around a charged particle in which forces of attraction or repulsion are noticeable.

Electric motor - A device that converts electrical energy into mechanical energy.

Electrochemical cell - A device that changes chemical energy into electrical energy.

Electrolysis - The process by which an electric current produces a chemical change.

Electrolytes - Substances that produce ions in solution.

Electrolytic conduction - Movement of ions in solution from an area of high energy toward an area of low energy, producing a current.

Electromagnet - A temporary magnet produced by direct current running through a coil of wire wrapped around a soft iron core.

 Electromagnetic force - The force of attraction or repulsion between charged particles.

Electromagnetic induction - When a conducting wire cuts across magnetic lines of force, producing an electric current.

Electromagnetic spectrum - An arrangement of all electromagnetic waves by decreasing wavelength, and therefore increasing frequency.

Electromotive force - Another term for volts.

Electron - A subatomic particle with a negative charge normally found in energy levels outside the nucleus of an atom; discovered by J. J. Thomson in 1897.

Electron affinity - The tendency of an atom to attract electrons.

Electron cloud repulsion - The natural repulsion of the electrons of two different atoms that keeps most atoms from reacting.

Electron configuration - A way to indicate the location of every electron in an atom.

Electron-dot diagram - A way of drawing the outer energy level electrons of an atom.

 Electronic balance - A scale for measuring the mass of matter.

Electronics - The study of the release, behavior, and effects of electrons in useful devices.

 Electron microscope - Produces magnification by bending streams of electrons with magnets.

Electron volt - A measure of energy equal to the energy gained by a single electron when it is accelerated across an electric potential difference of 1 volt: 1 eV = 1.602 X 10 -19 joules.

Elementary crystal - Any crystal bonded by normal electrostatic (ionic) forces.

Elements - The simplest pure substances, composed of the same type of atoms.

Embryo - The mass of cells formed by the divisions of a zygote.

Emigration - The movement of individuals out of a population.

 Empirical formula - The simplest formula that represents the whole number ratio between the elements in a compound.

Enamel - A hard, smooth covering to protect the crown of a tooth.

Endochondral bone - Dense bone that forms by replacing cartilage and has a system of Haversian canals through which blood vessels can pass.

Endoderm - The inner layer of cells of a gastrula that becomes the lining of the gut.

Endoparasite - A parasite living inside its host.

Endoplasmic reticulum - A membrane system of folded sacs and tunnels in the cytoplasm of a cell.

Endospores - A protective envelope formed by bacteria and some other organisms to survive adverse conditions.

End point - When a neutralization reaction becomes neutral, neither acid nor base, during a titration.

Endocarp - The inner layer of the pericarp.

Endosperm - The food reserve in a seed derived from fertilized polar nuclei.

Endothermic - A reaction that releases energy; body temperature holds at a constant level.

Energy - The ability to do work.

Energy level - An area around the nucleus of an atom where electrons are found.

Enthalpy - Heat content in matter.

Enthalpy of formation - The change in enthalpy when one mole of a compound is produced from the free elements.

Entropy - Disorder in matter.

Environmental resistance - The combination of factors that tend to prevent exponential growth.

Enzymes - Proteins that act as catalysts in the chemical reactions of cells.

Epicotyl - The part of a plant embryo that will form the leaf of the new plant.

Epidermis - The outer layer of cells.

Epigynous - A flower in which the ovary is situated below the calyx.

Epipetalous - A flower whose stamens are attached to the corolla.

EPR paradox - The Einstein Podolsky Rosen paradox is a thought experiment originally formulated in 1935 by Albert Einstein, Boris Podolsky, and Nathan Rosen to demonstrate (as they thought) the logical impossibility of quantum mechanics.

Equilibrium - When there is no net change in a system.

Equivalent - The amount of an acid (or base) that will give one mole of hydrogen (or hydroxide) ions.

Erosion - The physical removal and transportation of materials on the Earth's surface by wind and water.

Erythrocytes - Red blood cells.

Escape velocity - The velocity needed to escape the orbital gravity of a planet.

 Essay - A short, written communication about a certain topic.

Estivation - A period of inactivity during the dry summer.

Estuary - A tide-influenced ecological system where a river meets the sea and fresh water mixes with salt water.

Ethics - A system defining right and wrong behaviors.

Eubacteria - The kingdom of bacteria commonly referred to as germs.

Eukaryotes - Cells that contain a nucleus and organelles surrounded by a membrane.

Euphotic zone - Upper, well lighted areas of open ocean water supporting photosynthetic algae.

Euryecious species - A widely distributed species with a high tolerance for many environmental factors.

Eustachian tube - Connects the middle ear with the mouth cavity.

Eutherians - Placental mammals.

Eutrophic - Refers to an environment with many nutrients supporting a variety of life.

Eutrophication - The increase of nutrients in an environment.

Evaporation - Random molecules leaving the surface of a liquid.

Evolution - The process by which living things change over a period of time.

Excretion - The process of removing metabilic wastes from the body.

Exocarp - The outermost layer of the pericarp, ectocarp.

Exothermic - A reaction that releases energy.

Exoskeleton - An external skeleton providing support and protection.

Experimental error - A comparison of an experimental value to a known value.

Explosive - A chemical that produces a sudden release of pressure, gas and/or heat when subjected to sudden shock, pressure or high temperature.

External respiration - The exchange of gases between atmosphere and blood.

Extrapolate - Extending a graph, along the same slope, above or below measured data.

 F

Facilitator - Someone who makes things run smoothly.

Factor label - A unit conversion process.

Facultative anaerobes - Bacteria that can live with or without atmospheric oxygen.

Fahrenheit - The temperature scale in every-day use in the United States.

Family of elements - A group of elements with similar characteristics, usually determined by the number of electrons in the outer electron energy level.

Faraday's Laws - Two laws related to electrolysis reactions.

Farsighted - The eyeball is too thin, causing the image to focus behind the retina; a person can see distant objects clearly, but has difficulty with near objects.

Fatty acid - An unbranched carbon chain with the carboxyl group at one end that combines to make lipids.

Feathers - Provide insulation and lift for flight in birds.

Fermentation - The breaking down of pyruvic acid without using molecular oxygen.

Fermions - A group of subatomic particles including quarks and leptons.

Ferns - Vascular plants that reproduce sexually by forming spores, not seeds.

Fertilization - The joining of sperm and egg in sexual reproduction.

Fetus - An embryo developed to the point that it begins to resemble the mature organism.

Fiber optics - The transfer of light through long, thin, flexible optical fibers by total internal reflection.

Fibrinogen - A soluble protein in blood that reacts with thrombin to form fibrin for clotting.

Fire blanket - A fire-resistant blanket used to extinguish buring clothing.

Fire extinguisher - A portable device used to put out small fires.

Fission - A nuclear reaction in which a very heavy nucleus is split into fragments.

Flagella - Long protein structures that turn to propel some single-cell organisms.

Flammable - A substance that is easily ignited and continues to burn after the source of ignition is removed.

Flash Point - The minimum temperature at which a substance produces enough vapor to be ignited.

Flask - One of several types of pear-shaped pieces of glassware used to contain chemical reactions in the lab.

Fleshy fruit - A fruit with soft, usually moist walls.

Flicker-fusion - The number of frames per second at which sequential images are no longer seen as separate.

Floral formula - A way of representing the structure of a flower using letters, numbers, and symbols.

Flower - A plant organ of sexual reproduction.

Fluorescent light - Electricity causes phosphors inside a glass tube to glow.

Fluid - Any substance that flows; liquids and gases.

Focal point - The point at which light rays come together after passing through a convex lens.

Follicle - A dry fruit with 1 carpel that splits along only one side when ripe.

Food chain - The specific sequence in which organisms obtain energy within an ecosystem.

Food web - Interrelated food chains within an ecosystem.

Forb - Herbaceous flowering plants with broad leaves.

Force - Any push or pull which causes motion.

Forces of nature - The four forces known to operate between elementary particles.

Formula mass - The sum of all the atomic masses in a chemical formula.

Fosssil - Any trace of a long-dead organism.

Fosssil fuel - Fuel made from the remains of long-dead organisms.

Frame-shift mutation - The addition or deletion of a nitrogen base, causing the gene sequence to read out of order.

 Frasch process - The physical process used to mine sulfur.

Fraternal twins - Formed from two egg cells fertilized by two sperm cells.

Freezing - Changing a liquid into a solid.

 Freezing point depression - The addition of a nonvolatile solute making a solution freeze at a lower temperature than the pure solvent.

Frequency - The number of complete waves passing a point in a given period of time.

Friction - A force that opposes motion.

Frond - A fern leaf.

Frontal lobe - Part of the brain involved in reasoning, speech, movement, and emotions.

Fruit - A ripened ovary with seeds.

Fruticose - Shrubby stems that are woody more or less throughout and commonly have several main stems but no main trunk.

Fulcrum - The point around which a lever moves.

Fume hood - A safety glass-front cabinet with an exhaust fan.

Functional group - The non-hydrocarbon part of an organic molecule.

Funiculus - The stalk attaching a seed to the plant fruit placenta.

Fuse - An emergency swith containing a wire that will melt when too much current flows.

Fusion - A nuclear reaction in which two or more small nuclei are forced together to form one larger nucleus.

  G

Galaxy - A large aggregate of gravitationally bound stars, plus an interstellar medium of gas and dust.

Galvanometer - An instrument for detecting electric current.

Gamete - A sex cell, either sperm or egg.

Ganglion - A mass of nerve cells outside the central nervous system.

Gas - A substance whose particles have enough kinetic energy to break all intermolecular forces of attraction.

Gas Laws - Calculations used to describe the characteristics of a gas as conditions change.

Gastrulation - The specialization of embryo cells forming the three germ layers found in all vertebrates.

Gene - A segment of DNA on a chromosome that controls a particular trait.

Gene flow - The process of genes moving from one population to another.

Gene mutation - A mutation involving a nitrogen base in DNA.

Gene pool - Refers to all the genes that can be shared by reproduction within a population.

Generator - A device that converts mechanical energy to electrical energy.

Gene therapy - Treating a genetic disorder by introducing a gene into a cell or by correcting a defect in a cell's genome.

Genetic drift - The changing of allele frequencies in a population.

Genetic engineering - The application of molecular genetics for practical purposes.

Genetic equilibrium - Allele frequencies in a population do not change from generation to generation.

Genetics - The study of the traits of organisms.

Genotype - The genetic makeup of an organism.

 Germination - When a seed begins to grow into a new plant.

Germ layers - The layers of specialized tissues found in multicellular organisms.

Germ mutation - A mutation in gametes.

Gestation period - The period of development in the placenta.

Gibberellins - A group of plant hormones that primarily stimulate elongation growth.

Gibbs Free Energy - A comparison of the changes of enthalpy and entropy during a chemical reaction; the chemical potential of a substance.

 Gills - External tissue rich with blood vessels to exchange gases with the water.

Gizzard - A muscular organ in the digestive system of some animals that grinds food.

Glottis - A slit-like opening from the throat to the lungs.

Glucose - The product of photosynthesis, C6H12O6, that stores the sun's energy in chemical form.

Gluons - Particles exchanged between quarks to bond them together.

Glycolysis - A cellular process that splits the 6-carbon glucose molecule into two 3-carbon pyruvic acid molecules and 2 ATP molecules.

Golgi apparatus - A stack of membranes or sacs that acts to prepare substances for export from a cell.

GPE - Gravitational potential energy.

Graduated cylindar - The basic piece of glassware use to measure the volume of liquids.

Graham's Law - The relative rates at which two gases diffuse under identical conditions vary inversely as the squareroots of their molecular masses.

Gram stain - A special way of staining bacteria cells to determine the effectiveness of antibiotics on them.

Grand Unified Theory (GUT) - Any gauge theory that attempts to combine the description of the electromagnetic force, the weak nuclear force, and the strong nuclear force in one mathematical package.

Granum - The complex network of stacked sacs found inside chloroplasts.

Graph - A way to visually represent data.

Gravitational water - Water that drains freely through the largest pores in the soil.

Graviton - The gravity force carrying particle.

Gravitropism - A plant growth response to gravity.

Gravity - The force of attraction between all objects in the universe; the weakest of the known natural forces.

Gray - An amount of radiation equal to the transfer of one joule of energy to one kilogram of living tissue.

Gray matter - Nerve cell bodies in the brain.

Group - A vertical column on the Periodic Table; family.

Guanine - One of two double carbon ring nitrogen bases in DNA.

Guard cells - Two specialized epidermal cells which open and close a stomata pore.

Gymnosperms - Seed plants that produce cones instead of flowers.

Gynandrous - A flower whose stamens are attached to the pistil.

 H

Haber process - The chemical process used to make ammonia.

Habitat - The physical area in which an organism lives.

Hadal zone - The floor of the deepest ocean trenches down to 10,000 meters.

Hadrons - Massive subatomic particles composed of quarks.

Half-life - The length of time it takes for one-half of the atoms of a radioactive nuclide to disintegrate.

Half-reaction - One half of an oxidation-reduction reaction.

Hall-Heroult process - The chemical process used to extract aluminum from bauxite ore.

Hallucinogens - Drugs that disrupt nerve actions causing altered senses.

Halogens - Elements in Group 17 on the periodic table.

Halophiles - "Salt-loving" bacteria living in environments with a very high salt concentration that would kill other bacteria.

Haploid - Refers to a cell containing only one chromosome of a pair.

Hard water - Water with a high mineral content, usually calcium.

Hardy-Weinberg Principle - A population will remain in genetic equilibrium if, and only if, a certain set of conditions are met.

Haversian canals - Pores in bones through which blood vessels can pass.

Head - A rounded or flat-topped cluster of sessil flowers.

Heartwood - The dark center of most trees, consisting of clogged xylem cells.

Heat - The motion of the particles of matter.

 Heat engine - A machine that burns some type of fuel to produce heat, then convert the heat energy into mechanical energy.

Heat of fusion - The amount of heat needed to change one gram of a substance from the solid phase to the liquid phase.

Heat of vaporization - The amount of heat needed to change one gram of a substance from the liquid phase to the gas phase.

Heat transfer - Heat flowing from an area of high heat to an area low in heat.

Helix - A spiral; a twisted spiral called a double helix is the basic shape of the DNA molecule.

Hemorrhagin - A chemical in snake venom that causes lysis (breaking down) of cells in the capillaries causing hemorrhaging in skin and mucous membranes.

Hemotoxin - Venom proteins that destroy red blood cells and disrupt blood clotting.

Herbaceous - Plants whose stems have very little sclerenchyma tissue, making them soft.

Herbarium - A humidity and temperature controlled container or room that protects a scientific collection of plants from insect infestation.

Herbivores - Consumers that eat only plants.

Heredity - The passing of traits from one generation to the next.

Hermaphroditic - Being able to produce both sperm and egg cells.

Hertz - The units of wave frequency.

 Hesperidium - A fleshy fruit with a tough rind, numerous carpels separable as 'sections'.

Hess's Law - The Enthalpy change for a reaction is the sum of the enthalpy changes for a series of reactions that add up to the overall reaction.

Heterodont - Having several types of teeth.

Heterogeneous - Not identical throughout.

Heterotrophic - Organisms that are not able to produce their own food.

Heterozygous - Refers to things that are different.

 Hibernation - A period of inactivity during the winter.

Hilum - The funicular scar on a seed coat.

HIV - Human immunodeficiency virus, the virus responsible for AIDS.

Hologram - A three-dimensional image produced with laser light.

Holotype - The original specimen designated by the author in a scientific collection.

Homeostasis - A stable level of internal conditions in living things.

 Homogeneous - Identical propertics throughout.

Homologous chromosomes - The two members of each pair of chromosomes in regular body cells.

Homozygous - Refers to things that are the same.

Horns - Extensions from the skull of all species of bovids.

Horsepower - A unit of power equal to 745.56 Watts.

Hotwater bath - A lab technique used to heat something slowly and evenly.

HTML - Hypertext markup language, used for constructing webpages.

Human genome - All the genes found on human chromosomes.

Humus - The organic matter in the soil.

Hund's Rule - Electrons will enter empty orbitals of equal energy, when they are available.

Hybrid - An organism produced by crossing individuals with different traits.

Hybrid vigor - Hybrid organisms are more successful than those that are produced from a very limited gene pool.

Hydrated crystal - A crystal in which water molecules have become chemically bonded to the ions.

Hydraulics - The study of the pressure exerted by fluids.

Hydrocarbon - A substance composed of only hydrogen and carbon.

Hydrogen bond - A covalent bond between hydrogen and a highly electronegative atom.

Hydrolysis - The reaction of a salt with water to form an acid or base solution.

Hydronium ion - Formed by a hydrogen ion and a water molecule, H3O +.

Hygroscopic - A substance that will capture water molecules out of the air.

Hygroscopic water - Water that is tightly bound to the soil particles and unavailable to plant roots.

Hydrotropism - A plant growth response to water.

Hypanthium - The cup of the receptacle from which all flower parts arise.

Hypha - The vegetative filament of a fungus.

Hypocotyl - The part of a plant embryo that will form the stem of the new plant.

Hypogynous - A flower with the ovary situated above the calyx with no floral cup around it.

  I

Ideal gas - A theoretical gas that has mass but no volume.

Identical twins - Formed from one egg cell fertilized by one sperm cell.

Immigration - The movement of individuals into a population.

Imperfect flower - A flower with either stamens or pistils, but not both.

Implantation - The blastocyst attaches to the uterine lining.

Incandescent light - Electricity passes through a wire filament making it glow.

Incisors - Knife-edged teeth for biting and cutting.

Inclined plane - A slanted surface used to raise an object.

Incomplete flower - A flower missing one of more of the four basic parts.

Indehiscent - A dry fruit that does not open when ripe.

 Independent variable - The variable in an experiment controlled by the experimentor; the variable plotted on the X axis of a graph; the variable listed on the left side of a data table.

Index of refraction - A comparison of the speed of light in air with the speed of light in another material.

Indicators - Compounds that show a color change in an acid or base.

 Induction - A neutral object acquires a charge from a charged object close by without contact being made.

Inelastic collision - A collision in which only the momentum, not the kinetic energy, of the colliding particles is exactly the same after the collision as before.

Inertia - The resistance of an object to changes in motion.

 Inflorescence - An arrangement of several flowers on a single stalk.

Inhalants - Toxic substances that are inhaled for the rush.

Inhibitor - A substance that ties up a reactant in a complex, so that it will not react.

Inner ear - Contains the cochlea, and is responsible for hearing and balance.

Insect - An arthropod with three body parts and six legs.

Insertion - The point of movable attachment of a skeletal muscle.

Insoluble - A substance does not dissolve in a solvent.

Insulators - Materials that do not easily allow the flow of heat or electric current.

Integrated circuit - Combines diodes and transistors on a thin slice of silicon crystal.

Integument - The body covering, skin, of an organism.

Interference - The interaction of two or more waves to produce a single new wave.

Interferon - A protein produced by cells when exposed to a virus.

Intermembranous bone - Flat bone that develops between two layers of fibrous connective tissue without the cartilage stage and has no system of Haversian canals.

Internal combustion engine - A heat engine in which fuel is burned inside the engine.

Internal respiration - The exchange of gases between blood and body cells.

Internodes - The intervals between nodes on a plant stem.

Interphase - The period of normal growth and activity in the cell cycle.

Interpolate - Predicting data between two measured points on the graph.

Intertidal zone - Shore areas that are alternately covered and uncoverd by the tide.

Invasive species - A species that moves into an area and pushes native species out.

Invertebrate - An animal with no vertebral column.

Irregular flower - A flower with petals and sepals that are dissimilar, the flower is not symmetrical.

Ion - An atom or group of atoms with a charge.

Ionic bond - Electrons are transferred between atoms to form a compound.

Ionization - The process of removing an electron from an atom to form an ion.

Ionization energy - The energy needed to remove an electron from an atom.

Iris - The muscular, colored area around the eye's pupil that controls the amount of light entering the eye.

Isobaric - Taking place at a constant pressure.

Isothermal - Taking place at a constant temperature.

Isotopes - Atoms of the same element with different amounts of neutrons.

Isotype - Any specimen from the original collection used to duplicate the holotype.

  J

Joint - A place where two bones meet.

 Joule - A unit of work, Newton-meter.

  K

Kaon - A subatomic particle composed of a quark and an antiquark.

Karyotype - An arrangement of the pairs of chromosomes of an organism, from largest to smallest.

K-capture - An atomic nucleus captures an electron from its own innermost energy level.

Kelvin - The temperature scale used in all gas law calculations.

Ketones - Organic compounds containing the carbonyl group.

Kepler's Laws - Three laws of planetary motion that serve as the foundation of celestial mechanics.

Kilo - Metric system unit for 1000.

Kinetic energy - Energy an object has because of its motion.

Kinetic Theory - Explains the effects of temperature and pressure on matter.

Kingdom - The largest classification grouping of organisms.

Krebs Cycle - An aerobic cellular process that produces 2 ATP molecules, 10 carrier molecules, and CO2 from each glucose molecule.

K-selected species - A species with more or less stable populations adapted to exist at or near carrying capacity in relatively stable habitats.

  L

Lambda Convention - A formal system used to determine the chemical formulas of organic compounds.

Larva - An early stage of metamorphosis that looks nothing like the adult.

Laser - Coherent light of only one frequency.

Latitude - Describes north or south of the equator.

Lateral line - A row of scales with sensory depressions down each side of the fish.

Lateral meristem - Located around the outer edge of stems and roots, this meristem produces growth in circumference known as secondary growth.

Law of Conservation of Matter and Energy - The total matter and energy in the universe is always conserved.

Law of Superposition - Successive layers of rock or soil have been deposited on top of one another by wind or water.

Le Chatelierës Principle - If stress is applied to a system at equilibrium, the system will tend to readjust so that the stress is reduced.

Left-hand Rules - Two rules related to current flow and poles in electromagnets.

Legume - A dry fruit with 1 carpel that splits along both sides when ripe.

Lens - A curved, transparent object that bends light rays.

Lentic ecosystem - A freshwater ecosystem composed of standing water like lakes, ponds, marshes, and swamps.

Leptons - Lightweight elementary particles not composed of quarks.

Leukemia - The uncontrolled production of white blood cells.

Leukocytes - White blood cells.

Lever - A bar which can move freely around a fixed position, or fulcrum.

Lewis Theory - One of the three common acid/base theories.

Lichen - A symbiotic association between a fungus and a photosynthetic partner, usually a cyanobacterium or green alga.

 Ligament - Tough, flexible bands of connective tissue holding bones together at joints.

Ligand - A negative ion or polar molecule bonded to the central ion in a complex.

 Light - A form of energy produced by excited atoms.

Light microscope - Produces magnification by bending light rays with lenses.

Limbic system - A combination of the thalamus and hypothalamus that work together in the brain to regulate emotions.

Limiting reactant - The reactant that is completely consumed in a chemical reaction.

Lipids - Large organic molecules with a higher ratio of carbon and hydrogen atoms to oxygen atoms than carbohydrates; fats.

Liquid - A substance whose particles have enough kinetic energy to stretch the intermolecular forces of attraction.

Liquid crystal - A crystal without a sharp melting point temperature.

Littoral zone - The highly variable intertidal zone of the ocean.

Litmus - A common paper acid/base indicator.

Loam - Soil containing a combination of sand, silt, and clay.

Locules - The chambers of a plant ovary.

Long-day plants - Plants that flower only when exposed to day lengths longer than their critical length.

Longitude - Describes east or west of the prime meridian.

Longitudinal wave - The medium particles move parallel to the direction of wave travel.

Lotic ecosystem - A freshwater ecosystem composed of flowing water like rivers and streams.

Lungfish - A small group of fish that have lungs as well as gills.

Lytic cycle - The reproductive cycle of a virulent virus.

Lymph - An intercellular fluid found in body tissues.

Lymphoma - Cancer of the lymph cells.

Lysogenic cycle - The reproductive cycle of a temperate virus.

 Lysosome - Digestive centers of a cell.

 M

Machine - A device that changes the size and direction of a force.

Macromolecule - A crystal with covalent bonds; network crystals.

Macronutrients - Elements organisms require in relatively large amounts.

Magnetic field - The area around a magnet where magnetic forces act.

Magnetic induction - The process by which a material is made into a magnet.

Magnetic pole - The concentration of force at the end of a magnet.

Magnetism - A force of attraction or repulsion due to an arrangement of electrons.

Magnetosphere - The Earth's magnetic field.

Malignant - Refers to a tumor whose cells break away from the parent tumor.

Mandible - The lower jaw in vertebrates; a chewing mouth part in arthropods.

Marine ecosystems - Because of the ocean's size, marine ecosystems consist of zones marked by differences in depth and light penetration.

 Marsupials - Pouched mammals.

Mass - The amount of matter in an object.

 Mass number - Represents the sum of the protons and neutrons in an atom.

Mass percent - A solution concentration describing the percent of a solution's total mass that is solute.

 Matter - Anything that has inertia.

Maxilla - The upper jaw in vertebrates.

Mechanical advantage - The number of times a machine multiplies an effort force.

Medulla oblongata - The part of the brain stem that controls heart rate, breathing rate, and flow of blood through the blood vessels.

 Medusa - A bell-shaped body form, specialized for swimming

Mega - The Metric system prefix for 1 million.

Meiosis - The process of nuclear division in gametes that reduces the number of chromosomes by half.

Melting - Changing a solid into a liquid.

Meninges - Refers to the three protective layers covering the brain and spinal cord.

Meniscus - The curve of the surface of a liquid confined in a cylindar.

Menstrual cycle - The 28 day hormone cycle of human females.

Meristems - Growing regions where cells divide in plants.

Mesoderm - The middle layer of cells of a gastrula that forms the muscles and interior organs.

Mesons - Hadrons composed of a quark and an antiquark.

Messenger RNA - mRNA, a single uncoiled strand that transmits information from DNA to the ribosomes during protein synthesis.

Metallic bond - Electrons are distributed equally through a metallic crystal.

Metallic conduction - The movement of electrons in metals from an area of high potential to an area of low potential energy.

Metalloids - Elements touching either side of the metal-nonmetal line on the table having properties of both metals and nonmetals.

 Metals - Elements that normally lose electrons to comply with the octet rule; elements on the left side of the periodic table.

Metaphase - The stage of mitosis when chromosomes line up across the middle of the cell.

Metamerism - Refers to the segmentation of the body.

Metamorphosis - A series of developmental changes.

Metastasize - The breaking away of cells from a tumor, spreading tumors to other parts of the body.

Methanogens - Bacteria to which oxygen is a poison, so they must live in anaerobic conditions.

Micronutrients - Trace elements needed only in minute amounts.

Micropyle - The small opening in a plant ovule through which the sperm reaches the egg cell.

Microscope - An optical device that enlarges images of very small objects.

Midbrain - Part of the brain stem that controls reflexes.

 Middle ear - Contains three bones, hammer, anvil, and stirrup, connecting the eardrum of the outer ear to the cochlea of the inner ear.

Migration - The movement of animals to escape poor weather and food supply.

Milky Way - The name of our galaxy.

Milli - The SI prefix for 1/1000.

Millibar - A unit of pressure equal to 100 Newtons/m2.

 Milt - The fuid containing the sperm in fish.

Minerals - Naturally occurring inorganic solids with a more or less definite chemical composition and an orderly structure; pure elements needed in small amounts by the body.

Mirror - A surface that reflects light, forming an image.

Miscible - Refers to two liquids that will dissolve in each other.

Mitochondria - Respiration centers of a cell.

Mitosis - The process by which chromosomal DNA is duplicated and divided into two identical sets during cell division.

Mixture - Two or more substances mixed together but not chemically combined.

Molality - A concentration in moles of solute per kilogram of solvent.

Molarity - A concentration in moles of solute per dm3 of solution.

Molars - Flattened teeth for grinding and crushing.

Molar volume - At STP, 22.4 dm3 of any gas contains one mole of molecules.

 Mole - 6.02 X 1023 of anything; the formula mass of a substance in grams.

Molecule - The smallest particle of a compound.

Mole fraction - A solution concentration that compares the number of moles of one substance to the total number of moles in the solution.

Molting - The shedding of an exoskeleton.

Momentum - The product of the mass of an object and its velocity.

Monadelphous - A flower whose stamens are attached by their filaments into a single group.

Monochasium - A peduncle bearing a terminal flower and , below it, one branch producing a single lateral flower.

 Monocots - Plants with one seed leaf.

Monoecious - A plant with both male and female flowers.

 Monohybrid cross - A genetic cross involving only one trait.

Monophyletic - A phylogenetic group of animals including an ancestral form and all of its recognized descendant species.

Monosaccharide - A simple sugar with the general formula CH2O.

Monotremes - Egg-laying mammals.

Morphology - A comparison of internal and external structures of organisms.

Mortality - The ratio of the number of deaths in a given time to the total population.

Moss - A small terrestrial plant with no vascular tissues.

Motion - A change in position, measured by distance and time.

MSDS - Material Safety Data Sheet; an information document that contains relevant information about a specific chemical.

Mullerian mimicry - Several dangerous species having similar patterns of warning coloration.

Multiple fruit - Derived from several flowers, an inflorescence.

Muon - A type of "heavy" electron.

Museum mount - The preserved skin of a mammal or bird for a scientific collection.

Music - Sound with a pleasing quality, an identifiable pitch, and a repeated rhythm.

Mutagen - Anything that causes a mutation.

Mutation - Any change in the DNA of an organism.

Mutualism - A symbiotic relationship in which both organisms benefit equally.

Mycelium - A mat of interwoven fungi hyphae.

Mycorrhiza - A symbiotic association between a fungus and plant roots.

  N

Narcotics - Drugs that are derived from opium.

Natality - The ratio of the number of births in a given time to the total population.

Natural Selection Theory - Organisms with favorable variations survive and reproduce at the highest rates.

Nearsighted - The eyeball is too thick, causing the image to focus in front of the retina; a person can't see distant objects, but can see near objects well.

Nematode - A general term for roundworms, based on their phylum name Nematoda.

Nematocysts - Specialized stinging cells for defense and capturing food.

Neoteny - The prolonged retention of larval body features to the point where reproduction occurs in larva-like individuals.

Neotype - A specimen selected to serve as a substitute for the holotype when all material on which the name was based is missing.

Neritic zone - Highly productive ocean areas lying over continental shelves.

Nerves - Groups of related neurons.

Net ionic equation - An equation that attempts to show only the exact particles involved in the reaction.

Network crystal - A crystal with covalent bonds; macromolecules.

Neurons - Cells composing the nervous system.

 Neurotoxin - Venom proteins that disrupt nerve transmission.

Neurotransmitters - Chemical messangers that carry nerve impulses across a synapse.

Neutralization - The reaction of an acid with a base to form a salt and water.

 Neutrino - An elementary particle not composed of quarks.

Neutron - A subatomic particle with an AMU of one and no charge, found in the nucleus of an atom; discovered in 1935 by Sir James Chadwick.

Newton - The SI unit of weight.

Newtonian Physics - The physics of regular, visible objects traveling at normal speeds.

Newton-meter - A unit of work, the Joule.

Newton's Law of Universal Gravitation - All objects in the universe attract each other by the force of gravity.

 Newton's Laws of Motion - Three laws explaining forces and the motion of matter.

NFPA - National Fire Protection Association.

Niche - The place that an organism occupies in an ecosystem.

Nictitating membrane - A clear membrane that protects the eye of most amphibians.

Nitrification - Chemosynthetic bacteria oxidize NH4OH to produce nitrates and nitrites.

Nitrogen cycle - Converts atmospheric nitrogen, N2 , into a form plants and animals can use.

Noble Gases - Elements in Group 18 on the periodic table.

Nomenclature - Applying names to organisms.

Nondisjunction - A pair of chromosomes fail to separate during cell division.

Nonmetals - Elements that normally gain electrons to comply with the octet rule; elements on the right side of the periodic table.

Normal boiling point - The temperature at which the vapor pressure of a liquid is equal to standard atmospheric pressure.

Normal melting point - The temperature at which the vapor pressure of a solid and the vapor pressure of its liquid phase are equal.

Normality - A concentration in equivalents of solute per dm3 of solution.

Notochord - A firm, flexible rod of specialized cells that becomes the endoskeleton in vertebrates.

Nuclear reactions - Reactions involving the atomic nucleus.

Nucleotide - One of the monomer molecules that link together to form DNA and RNA molecules.

Nucleus - The positively charged center of an atom, containing almost all the atom's mass; the control center of a cell where DNA is normally found.

Nut - A dry fruit with one seed and a thick hard wall, surrounded by a cup or husk.

Nutrition - Refers to the combination of nutrients and minerals in the diet.

Nymph - An immature form that looks similar to the adult but does not have wings or sexual parts.

 O

Obligate aerobes - Bacteria that cannot survive without atmospheric oxygen.

Obligate anaerobes - Bacteria that cannot survive in the presence of atmospheric oxygen.

Occipital lobe - Part of the brain controling vision.

Ockham's razor - If there are two possible explanations for something, and one explanation is simpler than the other, the simpler explanation should be preferred.

 Octet Rule - The maximum number of electrons in the outer electron energy level of an atom is eight.

Ohm - A measure of the resistance to the flow of electric current.

Ohm's Law - The current in a wire is equal to voltage divided by resistance.

Olfactory lobes - The part of the brain of lower vertebrates that respond to smell.

Oligotrophic - Refers to an environment with a low nutrient content.

Omnivores - Consumers that eat both plants and animals.

 Oncogene - A gene that causes cancer or other uncontrolled cell division.

Opaque - Light does not pass through a material.

Open circulatory system - A system in which the blood is not always contained in vessels.

Operculum - The gill cover of a fish.

Optic lobes - The part of the brain of lower vertebrates responsible for processing visual and auditory information.

Optimal foraging - Behaviors that bring a predator the maximum net food energy gain.

Orbital - An area in a sublevel that can hold up to two electrons.

Orbital-filling diagram - A way to represent the spin of electrons in the outer energy level of an atom.

Orbital motion - One object orbiting another has both a horizontal and vertical velocity.

Organ - A group of tissues with a common function.

Organism - Any complete living thing.

Organic acids - Organic compounds containing the carboxyl group.

Origin - The point of stationary attachment of a skeletal muscle.

Osmoregulation - The removing of excess water in freshwater species and conserving of water in marine and terrestrial species.

Osmosis - The movement of particles through a membrane from an area of high concentration to an area of low concentration.

Ossification - The gradual transition from a soft template to bone.

Ostwald process - The chemical process used for the commercial production of nitric acid.

Ovary - The female structure in both plants and animals that produces egg cells.

Oviparous - Eggs hatch outside the body of the female.

Ovoviviparous - Fertilized eggs carried inside female body until hatched.

Ovules - Structures in plant ovaries that produce an egg cell.

Oxidation - The combination of oxygen with other substances; the loss of electrons from an atom or ion.

Oxidation number - The number of electrons gained or lost by an atom to comply with the octet rule; valance.

Oxidizer - A chemical that promotes combustion in other materials.

Oxidizing agent - The reactant that gains electrons during a chemical reaction.

Oxygen - The most abundant element in the earth's crust and in your body.

Ozone - A relatively unstable molecule composed of three oxygen atoms, O3.

  P

Panicle - An elongated inflorencence with branched branches along the central axis.

Parallel circuit - An electric circuit with more than one path for the electrons to take.

Paraphyletic - A phylogenetic group of animals including an ancestral form and some of its recognized descendant species.

Parasitism - A symbiotic relationship in which one organism obtains its nutrition from another organism to the harm of the host.

 Paratype - Any specimen, other than the holotype, referred to in the original publication of the taxon.

Parenchyma - Large, loosely packed, rectangular plant cells with thin cell walls.

Parietal lobe - Part of the brain that controls the feeling of touch, pressure, temperature, and pain

Pascal - A unit of pressure equal to one Newton/m2.

Pauli Exclusion Principle - No two electrons in an atom have the same set of four quantum numbers.

Pectoral girdle - Bone structure supporting the forelimbs.

Pedigree - A history of the traits of several generations.

Pedipalps - Appendages in arachnids that hold and chew food.

Peduncle - The main supporting stalk of an inflorescence.

Pelagic zone - The open ocean.

Pelvic girdle - Bone structure supporting the hindlimbs.

Penicillin - An antibiotic that interferes with cell wall synthesis in bacteria.

Pentadactyl - Having five digits.

Pepo - A fleshy fruit with a leathery-skin and one carpel with 3 lines of ovules.

Percentage composition - The percentage of the formula mass represented by each element in a compound.

Perennials - Herbaceous plants that live for an indefinite period of years, and bloom every year after the first.

Perfect flower - A flower with both stamens and pistils.

Perianth - A flower's sepals and petals together.

Pericarp - The plant fruit wall.

Perigynous - A flower with the ovary situated within (and free from) a floral cup or hypanthium.

Period - A horizontal row on the Periodic Table.

Periodic Law - The physical and chemical properties of the elements are periodic functions of their atomic numbers.

Periodic table - A chart of the known elements arranged by increasing atomic number.

Peripheral nervous system - Nerves that connect the central nervous system to the rest of the body.

Peristalsis - Muscular contractions that push food through parts of the alimentary canal.

Permanent magnets - Materials that are hard to magnetize, but tend to stay magnetized.

Petiole - The leaf stalk connecting the leaf blade to the plant stem.

pH - A measure of the H3O + concentration in a solution.

Pharynx - A muscular organ at the back of the throat.

Phase change - The physical change of matter from one state to another because of particle motion.

Phase diagram - A graph showing the phases of a substance as they relate to temperature and pressure.

 Phenolphthalein - A common liquid acid/base indicator.

Phenotype - The external appearance of an organism.

Pheromones - A type of chemical messenger produced by some organisms.

Phloem - Straw-like tubes conducting food downward in a plant.

Photoautotrophs - Organisms that use sunlight as a source of energy.

Photoelectric effect - The production of electrons by the photons of light.

Photon - The massless, electromagnetic force carrier.

Photoperiodism - Plant response to changes in the length of days and nights.

Photoreceptors - Function as eyes in earthworms and some other organisms by detecting differences in light intensity.

Photosynthesis - The chemical process by which green plants use light energy to produce food.

Photosynthetic unit - A unit of several hundred antenna pigment molecules plus a reaction center.

Phototropism - A plant growth response to light.

Phylogenetic tree - A hypothetical model of an animal's evolutionary history.

 Phylogeny - Inferred evolutionary relationships amoung organisms.

Physical digestion - Breaking large pieces of food into smaller ones.

Physical property - Any characteristic of a material that can be observed without changing the substances that make up the material.

 Physical state symbols - Letters written as subscripts in a chemical equation to indicate physical state.

Physics - The study of the relationships between matter and energy.

Phytoplankton - Microscopic plants and animals that are the foundation of aquatic food chains.

Pia mater - The inner layer of the three protective tissues of the brain, consisting of blood vessels and nerves.

Pigments - Chemicals that reflect certain wavelengths of light and absorb the others.

Pion - A subatomic particle composed of a quark and an antiquark.

Placenta - A region of attachment of seeds on a plant fruit wall; the nutritive sac surrounding a developing mammal embryo.

Pili - Short, hairlike protein structures on the surface of some bacteria that help them stick to host cells.

Pion - A particle composed of quarks found only in cosmic rays.

Pioneer species - The first species to colonize a new haitat.

Pipet - A piece of glassware used for exact measurement of liquid volumes.

Pistil - The female organ of a flower.

Pitch - Refers to the frequency of sound waves.

Pith - A central core of parenchyma tissue in a herbaceous plant stem.

Planck's constant - A fundamental constant, denoted by h, which relates the energy of a photon to its frequency.

Plant - A multicellular, eukaryotic, autotrophic organism.

Plasma - The straw-colored liquid part of blood; a special form of gas that has a charge.

Plasmid - A ring of DNA.

Plastid - Pigment producing organelle in cells.

Plastron - The ventral shell of turtle-like animals.

Platelets - The part of the blood involved in clotting.

pOH - A measure of the OH - concentration in a solution.

Point defect - A change in a crystal unit cell.

Polar molecule - A molecule whose charge is not equally balanced over its surface.

Polarized light - Light with all waves vibrating in the same plane.

Pollen grain - The male gametophyte of Gymnosperms and Angiosperms.

Pollen tube - A pathway for the sperm cells to reach the ovule of a flower.

Pollination - The transfer of pollen from anther to stigma.

Pollution - Impurities producing an undesirable change in an ecosystem.

Polyatomic ion - A group of covalently bonded atoms with an overall charge.

Polygenic trait - A trait controled by two or more genes.

Polymer - A very large molecule made up of small, repeating units.

Polyp - A vase-shaped body form, specialized for a sessile life.

Polypeptide - A very long chain of bonded amino acids.

Polyphyletic - A phylogenetic group of animals including the descendants of more than one ancestral form.

Polyprotic acid - An acid with more than one ionizable hydrogen.

Polysaccharide - A complex molecule composed of three or more monosaccharides.

Pome - A fleshy accessory fruit with a cartilaginous core.

Pons - Part of the brain stem that relays signals between the cerebrum and cerebellum.

Population - A group of interacting individuals of the same species.

Portfolio - A collection of student work.

Posterior - Refers to the back end of an organism.

Potential energy - Energy stored in an object due to its position.

Power - The rate at which work is done.

PPE - Personal protective equipment.

Precipitate - An insoluble substance that crystallizes out of solution.

 Precision - Refers to how close a set of measurements for a quantity are to one another.

Precocial - Birds that lay many eggs and incubate them for a long period.

Predation - Refers to the relationship between a predator and its prey.

Pressure - A force that acts over a certain area; the force of particles striking a surface.

Primary colors - The three colors of light that can be mixed to produce white light.

Primary consumers - Herbivores that eat only primary producers.

Primary growth - The growth in length of a plant stem produced by the apical meristem.

Primary producers - Green plants, the foundation of all ecosystems.

Primary root - The first root to grow out of a seed.

Principle of Priority - The first validly published name of a species, or other taxon, becomes its accepted scientific name.

Prism - An object that forms a spectrum as light passes through it.

Producers - Autotrophic organisms that use solar or chemical energy to produce all the organic nutrients for an ecosystem.

Productivity - The rate of assimilation of chemical energy into organic matter within an ecosystem.

Proglottids - The body segments of a tapeworm.

Projectile - Any object thrown in the air.

Prokaryotes - Cells with no nucleus or organells with membranes.

Pronation - Rotating the palm of the hand downward.

Prophage - A segment of virus DNA that becomes part of the host cell's genome.

Prophase - The first stage of mitosis, when DNA condenses into chromosomes.

Protective coloration - The coloring of organisms to match their environment.

Protein - An organic compound composed of carbon, hydrogen, oxygen, and nitrogen.

Protocells - Cell-like organisms believed to the the ancestors of organized cells.

Proton - A positive subatomic particle found in the nucleus of atoms.

Proto-oncogene - A gene that, when altered by mutation, becomes an oncogene.

Protozoa - Single-celled microorganisms noted for their ability to move independently.

Pseudopods - Cytoplasmic streaming used for locomotion in amoeba.

Puberty - The physical and psychological changes caused by sex hormones.

Pulley - A belt, rope, or chain wrapped around a wheel.

Pulmonary - Refers to the lungs.

Punnett square - A chart drawn to determine the probable results of a genetic cross.

Pupa - A stage of metamorphosis in which a larva changes into the adult form.

Pupil - The opening through which light enters the eye

Pure science - The gathering of information that adds to the body of human knowledge.

Purines - The double carbon ring nitrogen bases in DNA and RNA.

PVC - Polyvinyl chloride, a plastic used for packaging and pipes.

Pyloric sphincter - The valve at the bottom of the stomach that regulates the passage of food.

Pyrimidines - The single carbon ring nitrogen bases in DNA and RNA.

Pyrophoric material - A substance that will ignite spontaneously in air at a temperature below 130 oF.

 Q

Qualitative - Characteristics that can be described without measurements.

Quantitative - Characteristics that must be described with measurements, including numbers and standard units.

Quantum - The smallest amount of something that it is possible to have.

Quantum chemistry - Describes the way atoms combine to form molecules and the way molecules interact with one another, using the rules of quantum physics.

Quantum mechanics - The term 'quantum mechanics' is essentially synonymous with 'quantum physics'.

Quantum numbers - The four numbers used to describe the electrons in an atom.

Quantum physics - Describes the behavior of the world on very small scales, the scale of molecules, atoms, and below.

Quarks - Subatomic particles making up protons, neutrons, and other particles.

  R

Raceme - An elongated inflorencence with simple pedicels along the central axis.

Radiation - The movement of heat through empty space in the form of infrared rays.

Radicle - The part of a plant embryo that will form the root of the new plant.

 Radula - A flexible tongue-like strip covered with chitinous teeth in snails.

Rain shadow - The lack of precipitation on the lee side of a mountain range.

Raptors - Birds that have hooked beaks for tearing flesh.

Rare-Earth Metals - The two rows below the main body of the Periodic Table.

Rate expression - A mathematical equation used to calculate the rate of a chemical reaction.

Rate of solution - Refers to how quickly a solute dissolves in a solvent.

Reaction center - One in about 250 chlorophyll molecules that actually processes light energy.

Reaction mechanism - The series of steps that must occur for a reaction to go to completion.

 Reaction rate - The rate at which products form or reactants are used up.

Reactors - Large devices used to control nuclear chain-reactions.

Real image - One that can be projected onto a screen.

Realized intrinsic growth rate - The difference between natality and mortality in a population.

Receptacle - The swollen tip of a plant stalk supporting a flower.

 Receptors - Nerve cells that receive information from internal and external stimuli.

Receptor sites - Specific places one a host cell where viruses attach.

Recombinant DNA - A combination of DNA from two or more sources.

Rectifier - A device that changes AC electricity to DC electricity.

Reducing agent - The reactant that gives up electrons during a chemical reaction.

Reduction - The gaining of electrons by an atom or ion.

 Redox reaction - A reaction in which atoms or ions undergo changes in electron structure.

Reference point - A point assumed to be unmoving by which motion is described.

 Reflection - The bouncing back of a wave after it strikes a boundary.

Refraction - The bending of a wave due to a change in speed.

Refractory period - The period of time it takes a neuron to return to its resting potential after being stimulated.

 Regular flower - A flower with petals and sepals that are similar in size and shape.

Replication - The process of duplicating a DNA molecule.

Research paper - A comprehensive written communication about a specific topic.

Resistance force - The force applied by a machine.

Resistor - A device that allows a limited amount of current to pass through it.

Resolution - The ability of an optical device to show details clearly.

Resonance - The ablility of an object to vibrate by absorbing energy of its own natural frequency.

Resonance structure - An average representation of a molecule in which there are several possible ways for its atoms to be linked.

Respiration - The breaking down of pyruvic acid using molecular oxygen within cells to release energy; the exchange of carbon dioxide for oxygen in the lungs.

Restriction enzymes - Bacterial enzymes used to cut DNA molecules at specific sites.

Reticulate - Another term for net-veined leaves.

Retina - The lining of the back of the eye containing nerves that transfer images to the brain.

Reverberation - A combination of many reflected waves.

Reversible reaction - A chemical reaction that can reach equilibrium with the reaction continuing at the same rate in both directions.

Ribosomal RNA - rRNA, a globular form of RNA that is the major constituent of the ribosomes.

Ribosome - The site of protein synthesis in a cell.

Rhizome - Horizontal, underground stems that produce new shoots at their tips.

 RNA - Ribonucleic acid, a single uncoiled strand that transmits information from DNA to the ribosomes during protein synthesis.

 Rods - Nerve cells in the eye that are sensitive to light and dark.

Root cap - A shield of parenchyma cells covering and protecting the apical meristem at the root tip.

Root hairs - Small extensions of a root, greatly increasing the surface area of the root for absorption.

r-Selected species - A species capable of very rapid population growth, approximating an exponential growth pattern, followed by a crash in the adult population.

Rubric - A tool used for evaluation.

R-value - A measure of the efficiency of insulation.

  S

Saliva - A mixture of water, mucus, and the digestive enzyme called salivary amylase.

Salt - A crystalline compound composed of the positive half of a base and the negative half of an acid.

Salt bridge - A solution connecting the two half-cells of a voltaic cell, allowing ions to move between the half-cells.

Samara - A dry fruit with 1-seed and winglike outgrowths.

Sand - Soil made of the largest particles, from 2mm down to 0.05mm (50 micrometers) in diameter.

Saprophytes - Bacteria that feed on dead or decaying organic matter.

Sapwood - The light-colored wood of a tree, consisting of active xylem cells.

 Sarcoma - Cancer of the bone or muscle cells.

Saturated solution - A solution containing all the solute it is possible to dissolve under a given set of conditions.

Schr–dinger's Cat - The shorthand name for a hypothetical experiment dreamed up by Erwin Schr–dinger in 1935 to demonstrate the absurdity of the Copenhagen interpretation of quantum mechanics.

Science - A never ending search for truth.

Scientific calculator - Calculators that have trig and log functions and work in scientific notation.

Scientific law - A description of a natural phenomena that does not vary.

Scientific method - A process of logically finding solutions to problems.

Scientific name - A three part formal name for an organism accepted by scientists around the world.

Scientific notation - A way to write very large or very small numbers.

Scientific theory - A generally accepted explanation of a concept or a broad explaination of a natural phenomena.

Sclerenchyma - Short-lived plant cells with thick cell walls.

Scolex - The head of a tapeworm.

Screw - An inclined plane wrapped around a cylinder.

Scutes - Tough, transparent plates protecting the bones of the shell of turtle-like animals; the belly scales of snakes.

Secondary consumers - Animals that eat primary consumers.

Secondary growth - The growth in diameter of a plant stem produced by the lateral meristem.

Seed - A matured ovule.

Self-pollination - The transfer of pollen between flowers on the same plant.

Semipermeable - A membrane that allow some things to easily pass through and blocks other things.

Sepal - The outer floral structures protecting a flower.

Septum - A wall dividing a chamber, found in reptiles and fungi.

Sessile - Attached to some object; non-moving.

Setae - Hair-like bristles of some annelids used for locomotion.

Sex-influenced - Traits with genes located on autosomes, but express themselves differently in the sexes because of sex hormones.

Sex-linked - Traits with genes located on a sex chromosome.

Sexual reproduction - Producing offspring by the joining of gametes.

Schr–dinger - The person who developed an equation using quantum numbers to described an atomic model with electrons in three dimensions.

Series circuit - An electric circuit with only one path for the electrons to take.

Short-day plants - Plants that flower only when exposed to day lengths shorter than their critical length.

Shrub - A woody plant with several stems growing from the ground.

SI - An abbreviation for the International System of Measurement, used for all scientific data.

Sieverts - Units indicating the dose of radiation absorbed by living tissue.

Significant digit - A number indicating an actual measurement.

Silt - Soil made up of particles ranging in size from 50 micrometers down to 2 micrometers in diameter.

Silique - A dry fruit with 2 carpels and lose outer walls.

Simple fruit - A fruit derived from a single pistil of one flower.

 Simple leaf - A leaf with a single blade on a single petiole.

Simple machine - Machines that do work with one movement.

Single displacement reaction - A single element replaces an element in a compound.

Slide rule - A mechanical device used to perform calculations.

Snow - Formed by a gas changing directly into a solid

Soft water - Water with a low mineral content.

Soil - A mixture of organic parts and materials formed by the weathering of loose rock and mineral fragments at the surface of the Earth.

Solar system - All the planets and other objects orbiting the Sun.

Solar tracking - The phototropism of leaves or flowers as they follow the sun's daily movement.

Solid - A substance whose particles have a low kinetic energy, allowing the intermolecular forces of attraction to hold them tightly packed.

Solubility - A measure of how much of a solute can be dissolved in a given amount of solvent under certain conditions.

Solubility Rules - Rules used to predict the solubility of salts in water.

Solute - The least abundant substance in a solution.

Solvent - The most abundant substance in a solution.

Somatic - Refers to a regular body cell.

Somatic mutation - A mutation in body cells.

Somatic nervous system - Nerves that control voluntary movement of the skeletal muscles.

Sound - Longitudinal waves in matter composed of a series of compressions and rarefactions.

Space lattice - The three-dimensional arrangement of unit cells repeated over and over giving a crystal its overall geometric shape.

Spadix - A spike with a thickened, fleshy axis.

Spawning - The process by which fish eggs are externally fertilized.

Speciation - The formation of a new species from an existing one.

 Species - A group of organisms that mate and produce fertile offspring.

 Specific gravity - A ratio of the mass of a substance to the mass of an equal volume of water.

Specific heat - The number of calories needed to raise the temperature of one gram of a substance one Celsius degree.

 Spectator ion - An ion that appears on both sides of a chemical equation.

 Speed - The distance traveled by a moving object per unit of time.

 Spike - An elongated inflorencence with flowers along the central axis that are sessil

 Spinal nerves - Connect internal organs and muscles to the spinal cord.

Spirilli - A term used to indicate spiral-shaped bacterial cells.

Spirochetes - Gram-negative, spiral-shaped, heterotrophic bacteria that move with a corkscrew-like rotation.

Sputnik - The first artificial earth satellite.

Stable compound - A compound that does not spontaneously decompose in air.

 Stamen - The male organ of a flower.

Standard pressure - One atmosphere, 760 mm Hg, or 101 kPa measured at sea-level.

Standard reduction potential table - A table showing the voltage of reduction half-reactions.

Standard solution - Any solution for which the concentration is precisely known.

Standard temperature - Zero degrees Celcius or 273 Kelvins.

Staphylo - A prefix used with the shape name to indicate a cluster of bacterial cells.

Static electricity - Electricity with high voltage and low power output.

Steel - A metallic alloy using iron as the base element.

STD - Sexually transmitted disease.

Stenoecious species - A species with a low tolerance for many environmental factors and therefore a narrow distribution.

Steroid - An atypical lipid formed of four fused carbon rings and various functional groups.

Stigma - The open top of a flower pistil.

Stimulants - Drugs that increase nerve action, heart rate, and blood pressure.

Stipules - A pair of appendages located at the base of the petiole of some leaves.

Stoichiometry - A quantitative study of chemical changes.

Stolons - Stems trailing above ground, which often root at their nodes and tend to produce new plants if the stem is broken.

 Stomata - Openings in leaves that regulate gases passing into and out of the plant.

STP - Standard temperature and pressure, o0 Celcius and 1 atmosphere.

Stratus - Layers of clouds shaped by cold horizontal winds.

Strepto - A prefix used with the shape name to indicate a filament of bacterial cells.

String Theory - A class of theories in physics that describes the fundamental particles and their interactions in terms of tiny one-dimensional entities - strings.

Stroma - The complex mixture of enzymes and water found in chloroplasts.

Strong force - Opposes the electromagnetic repulsion between protons in the nucleus; the strongest of the known natural forces.

Structural formula - A way to show all the atoms and bonds in an organic molecule.

Style - The hollow tube leading from the flower stigma to the ovary.

Subatomic particle - Any of the particles composing atoms.

Sublevel - An area within an electron energy level.

Sublimation - A solid changing into a gas without going through the liquid phase.

Sublittoral zone - The relatively shallow, highly productive floor of the continental shelf.

Subscripts - Small numbers to the lower right of chemical symbols, representing the number of atoms of that element in a compound.

Substrate - A molecule upon which an enzyme acts to yield a product.

Succession - The gradual replacement of populations in an area.

Succulent - Plants with thick, fleshy tissues in the leaves or stems for storing water.

Suction - A result of unequal pressure.

Suffrutescent - Semi-shrubby stems that turn woody in the lowest parts and remain alive over the winter when the higher parts die back.

Supersaturated solution - An unstable solution that has been forced to dissolve more solute than should be possible under a given set of conditions.

Supination - Rotating the palm of the hand upward.

Surface tension - The apparent elasticity of the surface of a liquid.

Suspension - A heterogeneous mixture in which the solute particles are large enough to be seen.

Symbiosis - The close association between two dissimilar organisms.

Symmetry - The way body parts are arranged around a point or central axis.

Synapse - A gap between each nerve cell.

Syngenesious - A flower whose stamens are attached by their filaments forming a ring.

Synthesis reaction - Two or more substances combine to form one complex substance.

 Syntype - One of two or more specimens used by the author of a taxon if no holotype was designated, or one of two or more specimens designated as Types simultaneously in the original publication.

Syrinx - The "song box" of birds.

  T

Taproot - A primary root that grows much larger than the other roots of a plant.

Tau - A type of "heavy" electron.

Taxidermy - Preserving a vertebrate in a life-like form.

Taxonomy - The branch of biology that names and groups organisms according to their characteristics and evolutionary history.

Technology - Putting scientific knowledge to practical use; applied science.

Telophase - The stage of mitosis when the chromosomes disappear and the nuclear membrane reforms.

Temperate - Not immediately disease causing.

Temperature - A measure of the average kinetic energy of molecules.

Temporal lobe - Part of the brain involved in hearing and memory.

Temporary magnets - Materials that are easy to magnetize, and loose their magnetism quickly.

Tendon - Tough, inflexible bands of connective tissue attaching muscle to bone.

Teratogen - Anything that can cause malformations of an embryo or fetus.

Terminal velocity - The point at which air resistance offsets the weight of a falling object, stopping its acceleration.

Ternary acid - An acid composed of hydrogen, oxygen, and another element.

Terrapins - Semi-aquatic animals, equally at home in water or on land.

Tetrad - The set of four haploid cells formed from one cell during meiosis.

Tetrapod - An animal with four appendages.

Tertiary consumers - Animals that eat secondary consumers.

Thecodont - Having teeth rooted in the jaw bone.

Theory of Everything (TOE) - Any theory which attempts to combine gravity and some form of grand unified theory in one package.

Thermal expansion - The expansion of a substance due to an increase in the motion of its molecules because of heat.

Thermoacidophiles - Bacteria that live in extremely acidic environments (pH less than 2) that have extremely high temperatures (up to 110 oC).

 Thermodynamics - The study of the flow of energy in matter.

Thermometer - An instrument for measuring temperature.

Thermostat - A device that uses heat changes to turn a current on and off automatically.

Thigmotropism - A plant growth response to contact with a solid object.

Thorn - A sharp and stunted stem branch, sometimes modified leaves or leaf parts.

 Thought experiment - An experiment which is not intended to be carried out as a practical reality, but is "all in the mind".

Thrombase - A chemical in snake venom that causes local thrombosis, the coagulation of blood in the blood vessels at the site of the bite.

Thromboplastin - Released by platelets to react with calcium and prothrombin in the blood plasma to produce thrombin in the first stages of clotting.

Throughfare channels - Vessels that allow blood to bypass a capillary bed.

Thylakoid - Each of the flattened sacs which make up the granum of chloroplasts.

Thymine - One of two single carbon ring nitrogen bases in DNA.

Timbre - The quality of sound produced by the blending of pitches.

Tincture - A solution with alcohol as a solvent.

Tissue - A group of cells that perform a common function.

Titration - An analytical procedure in which a standard solution is used to determine the concentration of another solution.

 Tolerance - The body becoming less and less responsive to a physically addictive drug.

Topographic map - A map that models the Earth's surface geology.

Torr - A unit of pressure used to indicate mm Hg.

Tortoises - Terrestrial, poor swimming animals with a shell and stumpy legs.

Toxins - Substances that disrupt the metabolism of organisms.

Trachea - A non-muscular tube leading from the pharynx to the lungs, sometimes called the windpipe.

 Transcription - The process of forming mRNA from DNA.

Transfer RNA - tRNA, a single folded RNA strand that bonds with a specific amino acid.

Transformer - A device used to increase or decrease the voltage of alternating current.

Transistor - A sandwich of three semiconductor crystals used to amplify an electric current.

Transition Metals - Elements in Groups 3-12 on the periodic table.

Translation - Assembling of protein molecules from information encoded in mRNA.

Translocation - The movement of water and photosynthetic products through the vascular tissues of a plant.

Translucent - Light passes through a material but is scattered so you cannot see clearly.

Transmutation - A change in the number of protons in a nucleus producing an atom with a different atomic number.

 Transparent - Light passes through a material so you can see clearly.

Transpiration - The evaporative loss of water from leaf stomata.

Transverse wave - The medium particles move at right angles to the direction of wave travel.

Tree ring - Formed by the contrast in size of cambium cells grown under differing moisture conditions.

Trichinella - A roundworm that causes trichinosis from eating undercooked pork.

Triglyceride - Three molecules of fatty acid combined with one molecule of glycerol.

Triple-beam balance - A device with three movable tares to measure the mass of matter.

Triple point - The temperature and pressure at which all three phases of a substance can exist in equilibrium.

Trochophore - The pear-shaped larva of Mollusks.

Tropism - A plant movement toward or away from an environmental stimulus.

True fruit - A fruit composed of only the plant ovary wall.

Tuber - Thick, fleshy underground stems that serve as organs for food storage and reproduction.

 Tumor - A mass of cells resulting from uncontrolled, abnormal cell division.

Turtle - Marine animals with a shell and paddle-like appendages.

Tympanic membrane - A circular "eardrum" behind each eye of amphibians and reptiles.

Type specimen - The original specimen designated by the author in a scientific collection; the Holotype.

  U

Umbel - An inflorescence having several branches arising from a common point at the end of the peduncle.

Unit cell - The simplest repeating unit in a crystal.

Universe - The volume of space including all the planets, stars, and material between them.

Unsaturated solution - A solution containing less solute than is possible to dissolve under a given set of conditions.

Uracil - One of two single carbon ring nitrogen bases in RNA.

Urea - The most common mammalian metabolic waste, CH4N2O.

  V

Vacuole - Storage sites within a cell.

Valence - The number of electrons gained or lost by an atom to comply with the octet rule; oxidation number.

Valence electrons - Electrons in the outer energy level of an atom.

Van de Graaff Generator - A device used to produce large quantities of static electricity.

Van der Waals forces - Intermolecular attraction between the electrons of one atom and the protons of another.

Vapor - The gaseous phase of a substance that is not a gas at room temperature.

 Vaporization - The changing of a liquid to a gas.

Variety - A classification division of a species, used most often in plants.

Vascular tissue - The conducting tissues of vascular plants.

Vector - A quantity that has both magnitude and direction.

Veins - Thin-walled blood vessels that carry blood under low pressure toward the heart.

Velocity - Speed in a given direction.

Venation - The arrangement of the principal veins in a leaf blade.

Ventral - Refers to the bottom surface of an organism.

Ventricle - The pumping chamber of the heart.

Viability - The ability of a seed to germinate in the future.

Virtual image - One that appears behind the surface of the mirror.

Virulent - Disease causing.

Visceral - Derived from or associated with the gut or coelom.

Viscosity - The resistance of a fluid to flow.

Vitamins - Complex organic molecules that assist many chemical reactions within the body.

Viviparous - The developing young is nourished inside the body of the female.

Voltaic cell - A device that changes chemical energy into electrical energy.

Volatile - A liquid that readily evaporates at room temperature.

Voltage - The electric potential difference between two points.

Voltmeter - An instrument to measure the potential difference between two half-cells in a voltaic cell.

Volume - The amount of space an object takes up.

Vomerine teeth - Two rough pads in the roof of the mouth of some amphibians.

  W

Warning coloration - The bold, bright color patterns that make dangerous or poisonous animals clearly recognizable and warn predators away.

Water cycle - Water moving from the atmosphere to the Earth's surface and back.

Watts - Units of power, Joules per second.

Wave - A disturbance that transfers energy through matter or space.

Wavelength - The distance between two consecutive crests of a wave.

Wax - A long fatty acid chain combined with a long alcohol chain.

Weather - Short-term changes in the state of the atmosphere.

Weak force - The force responsible for radioactive decay.

Weathering - The chemical decomposition or physical disintegration of rocks and minerals.

Wedge - A moving inclined plane.

Weight - A measure of the pull of gravity on an object.

Wheel and axle - A lever that rotates in a circle around a fulcrum.

White matter - Nerve cell fibers in the brain.

Wilting - The loss of water pressure in the tissues of a plant.

Withdrawal - The physical or mental reaction to lack of a drug.

Wood - Plant stem xylem cells with thick cell walls.

Work - A force acting through a distance.

  X

Xylem - Straw-like tubes conducting water and minerals upward in a plant.

  Y

 Z

Zooplankton - Made up of protists, it is a primary source of energy in aquatic ecosystems.

Zygote - Formed when sperm and egg cells join in sexual reproduction.