Acceleration

Any change in the speed or direction of motion of an object.

Acid

A substance with a pH less than 7.0 that releases hydrogen ions in a water solution; for example, vinegar.

Acid Rain

Rain that is highly acidic because of sulfur oxides, nitrogen oxides, and other air pollutants dissolved into it; can damage plant and animal life.

Activation Energy

The energy needed to enable a chemical reaction to take place.

Adaptation

A process that helps an organism survive and function in its environment.

Adequacy

Being satisfactory; being sufficient for a job.

Aging

The changes that bring about the decline of an organism.

Air Mass

A large body of air that has the same moisture and temperature throughout.

Air Pressure

The weight of the atmosphere.

Air Resistance

Friction caused by air.

Alimentary Canal

The tube that makes up the digestive canal.

Allele

A different form of a gene.

Alpha Particle

A radioactive particle made up of two protons and two neutrons bound tightly together.

Alternating Current

A current in which the electrons flow first in one direction and then in the opposite direction.

Alveoli

Small air sacs in the lungs at the end of the bronchioles where oxygen passes in the blood and carbon dioxide is released from the blood.

Amino Acids

The building blocks of proteins.

Amniocentesis

A procedure that is used to examine fetal cells to identify certain types of genetic disorders present in a fetus.

Amniotic Egg

A covering that protects and nourishes a developing embryo.

Amplitude

The distance between the rest position and crest of a wave.

Antibodies

Substances produced by the body's immune system that fight diseases.

Antigen

A protein on the surface of a pathogen.

Aorta

A large artery that carries oxygen-rich blood from the heart to other parts of the body.

Applying ideas

Taking information learned one set of circumstances and using it in another situation.

Artery

A blood vessel that carries blood away from the heart.

Asexual Reproduction

A method of reproduction in which an organism is produced from a single cell.

Assess

To determine the importance, adequacy, or significance of something.

Assumption

A belief that something is true without checking its validity.

Asteroid

A small celestial body, sometimes called a minor planet, that revolves around the sun.

Astronomy

The study of all celestial bodies in the universe.

Atmosphere

The layers of gases that surround the Earth.

Atom

The smallest particle of an element that can exist alone.

Atomic Mass

The sum of protons and neutrons in the nuclease of an atom.

Atomic Number

The number of protons in the atom.

ATP

A compound in which energy is stored for later use in a cell.

Atrium

One of the upper chambers of the heart (plural, atria)

Axis

The imaginary line running through Earth's center from the North Pole from the South Pole on which the planet rotates.

Backbone

A segmented column of bones.

Bacteria

A one-celled organism that has DNA.

Balanced Equation

A chemical equation in which the same number of each type of atom appears on both sides.

Base

A substance with a pH greater than 7.0 that releases hydroxide ions in a water solution; for example, milk of magnesia.

Behavior

An organism's actions or reactions to its environment.

Beta Particle

An electron emitted from the nuclease of a radioactive atom.

Bias

Anything that sways an experiment's results in a way that makes them inaccurate.

Big Bang Theory

The idea that the universe began with an explosion of a dense, hot, compact mass under extreme pressure.

Binary Fission

A method of reproduction in which a cell divides into two new cells.

Biodegradable

Organic materials that naturally decompose.

Biodiversity

A healthy variety of plant and animal species coexisting in an environment and making the environment more stable.

Biogenesis

The principle that living things only come from living things.

Biological Clock

An internal control of natural behavioral cycles.

Biological Process

A fundamental property that is common to all living organisms.

Biology

The study of all living things.

Biomass

The total mass of the living organisms in a particular place.

Black Hole

The collapsed leftovers of a supernova.

Blue Star

A massive, hot star that uses up its hydrogen quickly, expands, and turs into a giant or supergiant

Boiling Point

The temperature at which a liquid turns into a gas.

Bosons

Force-carrying subatomic particles.

Botany

The study of plants.

Brain Stem

The part of the human brain that controls automatic functions such as breathing and heartbeat.

Bronchi

The two tubes that lead from the trachea into each of the lungs.

Bronchioles

Tubes branching off the bronchi in the lungs and ending in alveoli.

Bud

The part of a plant where the new growth takes place.

Calorie

A measure of energy.

Camouflage

A coloring pattern that enables an animal to blend into their surroundings and not be seen by predators.

Capillaries

Very small blood vessels.

Carbohydrate

The main source of food energy.

Carbon Cycle

A process that keeps the carbon on Earth in balance.

Carbon-oxygen Cycle

The continuous circulation of carbon and oxygen through the biosphere primarily through the processes of photosynthesis, respiration, and decomposition.

Carnivore

An animal that eats other animals.

Carrying Capacity

The maximum population an ecosystem can support without losing resources.

Cartilage

A tough, flexible material that covers bones and joints.

Catalyst

A substance that provides a faster mechanism by which a reaction may take place.

Cause

Something that makes something else (an effect) happen.

Cause-and-Effect Relationship

Something that can make something else (a cause) happen results in another (an effect).

Cell

The smallest unit of life that can exist independently and that makes up all living organisms.

Cell Cycle

The process of division of a cell into new identical cells.

Cell Membrane

The soft, flexible covering that holds a cell together and separates it from other cells.

Cell Specialization

The process in which the cells of an organism develop in different shapes, structures, and functions.

Cell Wall

A tough, flexible covering that surrounds the cell membrane of a plant cell.

Cellular Respiration

The chemical process requiring oxygen by which living things convert food to energy.

Cerebellum

The part of the brain , which controls movement, coordination, and balance; located below the cerebrum at the base of the skull.

Cerebrum

The largest part of the human brain, which coordinates all higher functions such as perception, thinking, and conscious actually.

Chain Reaction

A reaction in which nuclei are split apart in a controlled way, resulting in a great quantity of nuclear energy.

Chemical Formula

A shorthand way of showing which elements are contained in a molecule.

Chart

A visual representation of data.

Chemical Bonding

The process though which atoms are combined.

Chemical Change

A change that produces a new substance.

Chemical Equation

A shorthand way of describing what happens in a chemical reaction.

Chemical Reaction

The process in which two or more substances combine to form one or more substances.

Chemical Weathering

Process that changes the composition of the rocks and occurs through chemical reactions.

Chlorophyll

The green substance in a plant cell that is used to capture light energy.

Chloroplast

An organelle in a plant cell that contains chlorophyll.

Chromatin

The part of a cell's nucleus that contains genetic information.

Chromosome

A structure in a cell that contains DNA.

Circadian Clock

A biological clock that controls daily activity.

Circular Argument

A form of faulty logic which a conclusion is supported by reasons that simply restate the conclusion.

Circulatory System

the system, consisting of the heart, blood vessels, and the blood, that carries nutrients and oxygen to the body's tissues removes carbon dioxide and waste products.

Climate

Average weather conditions in a particular region over a long period of time.

Cloning

The process of creating a genetically identical replica of an organism.

Closed Universe

The theory that the universe at some future time will begin to contract and collapse into its original state as a solar nebula.

Coal

A solid fossil fuel.

Codon

A combination of three bases.

Coefficient

A number added to the reactants and the products to balance a chemical equation.

Cold-Blooded

A classification of an organism that cannot control its own body temperature.

Colloid

A mixture in which fine particles are spread out throughout a second substance; for example, foam.

Collusion

When two or more moving objects run into one another.

Comet

A small object made of dust and frozen gas that orbits in a predictable path around the sun.

Commensalism

A relationship that benefits organism, while the other is neither harmed nor helped.

Common Ancestor

An individual in a species history to which all individuals in that species can be traced.

Compare

To identify how things are alike.

Complete Metamorphosis

a type of metamorphosis that takes place in four stages.

Complex Machine

Two or more simple machines put together.

Composting

The use of natural biological processes to aid in the decomposition of organic materials.

Compound

A group of molecules that each contain the atoms of two or more elements.

Concentrated

When a solution contains a large amount of solute.

Conclusion

A logical result or generalization.

Condensation

The change of a of a gas into a liquid.

Condense

To change from gas to a liquid; for example, from steam to water.

Conduction

Transfer of heat through direct contact.

Conductor

A substance through which electric current flows easily.

Conservation

The controlled use and preservation of natural resources.

Constancy

The tendency for things to remain unchanged.

Constellation

A pattern of stars in the sky that humans have observed and named.

Consumer

An organism that must eat other organisms to obtain energy.

Contaminants

Substances that harm the environment.

Context

The situation within which something is said or done.

Continental Drift

The movements of continents.

Contraction

A decrease in size of a substance due to its atoms moving closer together, often caused by a decrease in temperature.

Contrast

To identify how things are different.

Control Variable

A factor that is kept the same or constant during an experiment.

Convection

The movement of heat through a liquid or gas.

Convection Currents

Currents of molten rock the mantle that carry much of the heat to Earth's surface.

Copernican Theory

The idea that the Sun is at the center of the solar system

Core

The center of the Earth.

Coriolis Effect

The apparent change in motion of wind and water on Earth's surface due to rotation.

Covalent Bond

A bond in which electrons are shared by the bonded atoms of the molecule.

Crest

The high point of a wave.

Crust

The outermost layer of Earth.

Crustal Plates

The exterior layer of Earth's crust (surface); also called tectonic plates

Current

A large movement of water.

Cytoplasm

In a cell, the jellylike matter that surrounds the nucleus and contains cell structures (called organelles) that carry out the cell's activities.

Data

Information gathered during an experiment or investigation.

Daughter Cells

The cells produced as a result of cell division, each identical to the parent cell.

Decomposer

An organism that feed off the dead bodies of a once-living organism.

Dendrite

A branching fiber on a nerve cell the receives messages from another nerve cell.

Denitrification

The process by which certain bacteria in the soil change nitrates into gaseous nitrogen, returning it to the air.

Density

A measure of mass in relation to volume.

Dependent Variable

A factor is changed in response to the independent variable during an experiment.

Diagram

A picture or an illustration that shows information.

Diffraction

The process in which a waves spread out into a region behind or around a barrier.

Diffusion

Movement of a substance from a region of higher concentration to a region of lower concentration.

Digestion

The breaking down of food into nutrients that the body's cells can use.

Digestive System

The system of the body that breaks down food into nutrients the body can use and expels leftover wastes.

Dilute

A solution with the small amount of solute.

Direct Current

Electric current that moves in one direction only.

Dissolve

To become part of a solution.

Distillation

A process for separating liquids that have different boiling points.

DNA

The molecules that contains hereditary information and controls the activities of each cell; found in the chromosomes.

Dominant

An allele for which the phenotype will always be present.

Dominant Gene

One gene in a pair that determines the effect of the gene pair.

Dominant Trait

A trait that will appear in an offspring if one parent contributes it; dominant traits suppress recessive traits.

Double Blind

An investigation in which neither the researchers nor the patients know who is receiving placebos.

Drag

The force slowing or stopping the movement of an object through a gas or liquid.

Drawing Conclusions

Expressing unstated ideas that are logically connected to give information.