The age of a rock given as the number of years since the rock formed.
The brightness a star would have if it were at a standard distance from Earth.
The rate at which velocity changes.
A substance that tastes sour, reacts with metals and carbonates, and turns blue litmus red.
An inherited behavior or physical characteristic that helps an organism survive and reproduce in its environment.
A vertebrate whose body temperature is determined by the temperature of its environment, and that lives its early life in water and its adult life on land.
To study something closely in order to determine the nature of its parts and how they work together.
The brightness of a star as seen from Earth.
The process by which humans breed only those organisms with desired traits to produce the next generation; selective breeding.
One of the rocky objects revolving around the sun that are too small and numerous to be considered a planet.
A unit of distance equal to the average distance between Earth and the sun, about 150 million kilometers.
The basic particle from which all elements are made; the smallest particle of an element that has the properties of that element.
The average mass of all the isotopes of an element.
The number of protons in the nucleus of an atom.
An organism that is able to capture energy from sunlight or chemicals and use it to produce its own food.
An imaginary line that passes through a planet’s center and its north and south poles, about which the planet rotates.
A substance that tastes bitter, feels slippery, and turns red litmus paper blue.
The initial explosion that resulted in the formation and expansion of the universe.
The temperature at which a liquid boils.
A principle that describes the relationship between the pressure and volume of a gas at constant temperature.
Maintaining consistency between two variables; as one variable increases or decreases, the other variable does the same.
The series of events in which a cell grows, prepares for division, and divides to form two daughter cells.
To show an equivalent value using a different unit of measurement.
A statement that demonstrates equality between two mathematical or chemical expressions.
To make an exact copy.
How slowly or quickly something happens.
When one substance completely disappears into another substance to form a solution.
The process in which oxygen and glucose undergo a complex series of chemical reactions inside cells, releasing energy.
To use a combination of materials and processes to create something new.
A principle that describes the relationship between the temperature and volume of a gas at constant pressure.
A change in which one or more substances combine or break apart to form new substances.
A characteristic of a substance that describes its ability to change into different substances.
A one- or two-letter abbreviation for an element.
A green photosynthetic pigment found in the chloroplasts of plants, algae, and some bacteria.
The structure formed when a chromosome divides during meiosis.
A threadlike structure within a cell’s nucleus that contains DNA that is passed from one generation to the next.
The middle layer of the sun’s atmosphere.
An organism that is genetically identical to the organism from which it was produced.
A system in which no matter is allowed to enter or leave.
The process by which two species evolve in response to changes in each other over time.
A mixture containing small, undissolved particles that do not settle out.
A loose collection of ice and dust that orbits the sun, typically in a long, narrow orbit.
The struggle between organisms to survive as they attempt to use the same limited resources in the same place at the same time.
Something that completes, enhances, or improves something else.
A substance made of two or more elements chemically combined in a specific ratio or proportion.
The change of state from a gas to a liquid.
The transfer of energy from one particle of matter to another within an object or between two objects that are in direct contact.
When nothing is lost or gained; to remain constant.
A pattern or grouping of stars that suggest the outline of a figure or object.
The transfer of thermal energy by the movement of a fluid.
The effect of Earth’s rotation on the direction of winds and currents.
The outer layer of the sun’s atmosphere.
Term used to describe acids that react with some metals by wearing away the metal.
A chemical bond formed when two atoms share electrons.
A large stream of moving water that flows through the oceans.
The act of a compound breaking down into simpler products.
The measurement of how much mass of a substance is contained in a given volume.
Deoxyribonucleic acid; the genetic material that carries information about an organism and is passed from parent to offspring.
An allele whose trait always shows up in the organism when the allele is present.
A term used to describe a material that can be pulled out into a long wire.
The partial or total blocking of one object in space by another.
An abnormal climate event that occurs every two to seven years in the Pacific Ocean, causing changes in winds, currents, and weather patterns for one to two years.
The energy transferred through space by electromagnetic waves.
A wave that can transfer electric and magnetic energy through the vacuum of space.
A tiny, negatively-charged particle that moves around the outside of the nucleus of an atom.
A substance that contains one kind of atom and cannot be broken down into a simpler form.
An oval shape, which may be elongated or nearly circular; the shape of the planets’ orbits.
The young organism that develops from a zygote.
A relationship in which one organism lives inside another organism’s cells.
A reaction that absorbs energy.
Either of the two days of the year on which neither hemisphere is tilted toward or away from the sun.
The process by which molecules at the surface of a liquid absorb enough energy to change to a gas.
Information or data that is used to support a conclusion.
Information or data that is gathered using one of the five senses—sight, touch, hearing, taste, or smell.
Change over time; the process by which modern organisms have descended from ancient organisms.
A reaction that releases energy, usually in the form of heat.
Term used to refer to a group of related organisms that has died out and has no living members.
The process by which cells release energy by breaking down food molecules without using oxygen.
How well an organism can survive and reproduce in its environment.
A push or pull exerted on an object.
The preserved remains or traces of an organism that lived in the past.
All the fossils that have been discovered and what scientists have learned from them.
The temperature at which a liquid freezes.
The number of complete waves that pass a given point in a certain amount of time.
The force that two surfaces exert on each other when they rub against each other.
A huge group of single stars, star systems, star clusters, dust, and gas bound together by gravity.
A state of matter with no definite shape or volume.
To move back and forth slightly.
The process of replacing an absent or faulty gene with a normal working gene to treat a medical disease or disorder.
The transfer of a gene from the DNA of one organism into another organism, in order to produce an organism with desired traits.
The complete set of genetic information that an organism carries in its DNA.
An organism’s genetic makeup, or allele combinations.
Term describing a model of the universe in which Earth is at the center of the revolving planets and stars.
A record of the geologic events and life forms in Earth’s history.
The attractive force between objects; the force that moves objects downhill.
The trapping of heat near a planet’s surface by certain gases in the planet’s atmosphere.
Elements in the same vertical column of the periodic table; also called family.
A drawing or image of an actual thing.
Term describing a model of the solar system in which Earth and the other planets revolve around the sun.
The passing of traits from parents to offspring.
An organism that cannot make its own food, but gets food by consuming other living things.
Structures that are similar in different species and that have been inherited from a common ancestor.
A compound that changes color in the presence of an acid or a base.
The tendency of an object to resist a change in motion.
To develop an evidence-based idea that can be tested by experimentation or investigation.
An animal without a backbone.
An atom or group of atoms that has become electrically charged.
The attraction between ions with opposite charges.
An atom with the same number of protons and a different number of neutrons from other atoms of the same element.
Band of high-speed winds about 10 kilometers above Earth’s surface.
A climate event in the eastern Pacific Ocean in which surface waters are colder than normal.
The flow of air from land to a body of water.
The rule that energy cannot be created or destroyed.
The principle that the total amount of matter remains the same, regardless of any chemical or physical change.
The geologic principle that states that in horizontal layers of sedimentary rock, each layer is older than the layer above it and younger than the layer below it.
The scientific law that states that every object in the universe attracts every other object.
The distance that light travels in one year; about 9.46 trillion kilometers.
A state of matter that has no definite shape but has a definite volume.
The way a mineral reflects light from its surface.
A term used to describe material that can be hammered or rolled into flat sheets.
A vertebrate whose body temperature is regulated by its internal heat, and that has skin covered with hair or fur and glands that produce milk to feed its young.
A measure of how much matter is in an object.
When entire species of living things die off at the same time.
The sum of protons and neutrons in the nucleus of an atom.
An idea that has been studied and investigated and is supported by a vast and diverse array of evidence.
Anything that has mass and takes up space.
The natural process by which something takes place.
The process that occurs in the formation of sex cells (sperm and egg) by which the number of chromosomes is reduced by half.
The temperature at which a substance changes from a solid to a liquid; the same as the freezing point, or temperature at which a liquid changes to a solid.
Type of RNA that carries copies of instructions for the assembly of amino acids into proteins from DNA to ribosomes in the cytoplasm.
A streak of light in the sky produced by the burning of a meteoroid in Earth’s atmosphere.
A chunk of rock or dust in space, generally smaller than an asteroid.
The second stage of the cell cycle, during which the cell’s nucleus divides into two new nuclei and one set of DNA is distributed into each daughter cell.
Two or more substances that are together in the same place but their atoms are not chemically bonded.
A neutral group of two or more atoms held together by covalent bonds.
A natural satellite that orbits a planet.
The state in which one object’s distance from another is changing.
Any change in the DNA of a gene or a chromosome.
Anything naturally occurring in the environment that humans use.
The process by which organisms that are best adapted to their environment are most likely to survive and reproduce.
The tide with the least difference between consecutive low and high tides.
A large cloud of gas and dust in space.
The overall force on an object when all the individual forces acting on it are added together.
A reaction of an acid with a base, yielding a solution that is not as acidic or basic as the starting solutions were.
A small particle in the nucleus of the atom, with no electrical charge.
A unit of measure that equals the force required to accelerate 1 kilogram of mass at 1 meter per second.
A covalent bond in which electrons are shared equally.
The central core of an atom, which contains protons and neutrons.
A system in which matter can enter from or escape to its surroundings.
The path of an object as it revolves around another object in space.
A tool that geneticists use to map out the inheritance of traits.
The part of a shadow surrounding the darkest part.
A horizontal row of elements in the periodic table.
An arrangement of the elements showing the repeating pattern of their properties.
One of the different shapes of the moon as seen from Earth.
An organism’s physical appearance, or visible traits.
The inner layer of the sun’s atmosphere that gives off its visible light; the sun’s surface.
The process by which plants and other autotrophs capture and use light energy to make food from carbon dioxide and water.
A change that alters the form or appearance of a material but does not make the material into another substance.
A characteristic of a pure substance that can be observed without changing it into another substance.
An object that orbits a star, is large enough to have become rounded by its own gravity, and has cleared the area of its orbit.
A covalent bond in which electrons are shared unequally.
An ion that is made of more than one atom.
A long chain of molecules made up of repeating units.
Any form of water that falls from clouds and reaches Earth’s surface as rain, snow, sleet, or hail.
The force pushing on a surface divided by the area of that surface.
A number that describes how likely it is that a particular event will occur.
A series of changes that happen over time and lead to an expected result.
A substance formed as a result of a chemical reaction.
A huge, reddish loop of gas that protrudes from the sun’s surface, linking parts of sunspot regions.
Large organic molecule made of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.
The process by which amino acids link together to form proteins.
A small, positively-charged particle that is found in the nucleus of an atom.
A contracting cloud of gas and dust with enough mass to form a star.
The transfer of energy by electromagnetic waves.
The process of determining the age of an object using the half-life of one or more radioactive isotopes.
The process in which the nuclei of radioactive elements break down, releasing fast-moving particles and energy.
A substance that enters into a chemical reaction.
The ease and speed with which an element combines, or reacts, with other elements and compounds.
An allele that is hidden whenever the dominant allele is present.
A place or object used for comparison to determine if an object is in motion.
The age of a rock compared to the ages of other rocks.
When one variable is dependent on another variable.
A vertebrate whose temperature is determined by the temperature of its environment, that has lungs and scaly skin, and that lays eggs on land.
The movement of an object around another object.
The spinning motion of a planet on its axis.
An ionic compound made from the neutralization of an acid with a base.
1. An object that orbits a planet. 2. Any object that orbits around another object in space.
A well-tested explanation for a wide range of observations or experimental results.
The flow of cooler air from over an ocean or lake toward land.
A substance that can conduct electric current under some conditions.
A type of natural selection that acts on an organism’s ability to get the best possible mate.
To support results with data.
The steepness of a graph line; the ratio of the vertical change (the rise) to the horizontal change (the run).
An eruption of gas from the sun’s surface that occurs when the loops in sunspot regions suddenly connect.
The system consisting of the sun and the planets and other objects that revolve around it.
A stream of electrically-charged particles that emanates from the sun’s corona.
A state of matter that has a definite shape and a definite volume.
Either of the two days of the year on which the sun reaches its greatest distance from the equator.
A measure of how much solute can dissolve in a given solvent at a given temperature.
The part of a solution that is dissolved by a solvent.
A mixture containing a solvent and at least one solute that has the same properties throughout; a mixture in which one substance is dissolved in another.
The part of a solution that is usually present in the largest amount and dissolves a solute.
A group of similar organisms that can mate with each other and produce offspring that can also mate and reproduce.
The range of wavelengths of electromagnetic waves.
The distance an object travels per unit of time.
The tide with the greatest difference between consecutive low and high tides.
A ball of hot gas, primarily hydrogen and helium, that undergoes nuclear fusion.
The change in state from a solid directly to a gas without passing through the liquid state.
To maintain a position off the ground, with unseen support.
A single kind of matter that is pure and has a specific set of properties.
A large, gaseous body at the center of the solar system.
A dark area of gas on the sun’s surface that is cooler than surrounding gases.
The brilliant explosion of a dying supergiant star.
The result of an inward pull among the molecules of a liquid that brings the molecules on the surface closer together, causing the surface to act as if it has a thin skin.
A mixture in which particles can be seen and easily separated by settling or filtration.
Created or manufactured by humans; not found occurring in nature.
A group of parts that work together as a whole.
An optical instrument that forms enlarged images of distant objects.
How hot or cold something is; the measure of the average kinetic energy of the particles in a substance.
Stress that stretches rock so that it becomes thinner in the middle.
The total kinetic and potential energy of all the particles of an object.
The periodic rise and fall of the level of water in the ocean.
Type of RNA in the cytoplasm that carries an amino acid to the ribosome during protein synthesis.
The darkest part of a shadow.
A gap in the geologic record that shows where rock layers have been lost due to erosion.
All of space and everything in it.
The electrons that are in the highest energy level of an atom and that are involved in chemical bonding.
The change of state from a liquid to a gas.
Any difference between individuals of the same species.
Speed in a given direction.
An animal with a backbone.
A liquid’s resistance to flowing.
Electromagnetic radiation that can be seen with the unaided eye.
The amount of space that matter occupies.
The distance between two corresponding parts of a wave, such as the distance between two crests.
A measure of the force of gravity acting on an object.
The degree to which one action influences or affects another action.
The blue-white hot core of a star that is left behind after its outer layers have expanded and drifted out into space.
The horizontal movement of air from an area of high pressure to an area of lower pressure.
Qualities that describe an individual or a thing; or qualities that describe a group of similar individuals or things.
Fixed; unlikely to change.
When something has been moved through space or between two mediums.
Something found in nature that enhances the lives of plants, animals, and humans.
To cause a change in something using artificial means.
Observable traits that stand out and set an object or organism apart from others.
Divided among; passed out or spread out.
An explanation that is based on information or data given in a chart, table, graph, or other medium.
To move from one person, place, or object to another without changing form.
The individual objects or parts that combine or work together to form a whole.
To separate liquids by boiling them.
The act of showing or making known; representing.
Doing something with no obvious plan, pattern, or necessity.
The different ways that living things communicate with, act toward, and influence each other.
A value that falls directly in the middle of other related values.
A letter or symbol that represents a number that can change.
The place where something can be taken from; a source.
To make a conclusion based on prior knowledge or evidence.
One of the three long units of geologic time between the Precambrian and the present.
To make something neat; to put things in order.
To make changes or improvements to something based on new information or data.
Something that leads to or causes a specific result.
An undefined space or location; can be large or small.
An exact copy of something on a much smaller scale.
To take in; to swallow up.
A forceful, damaging contact.
To move or change slowly.
To arrive at an answer by doing research.
Energy-rich substance formed from the remains of organisms.
The place where something comes from; the point where something begins.
A gas in Earth’s atmosphere that absorb heat leaving Earth’s surface.
A sudden or gradual change in Earth’s climate.
A gradual increase in the Earth’s average temperature.
An unforeseen chain of events caused by a disturbance in a system.
Clean energy sources that do not come from fossil fuels.
A discussion in which people present a difference in opinion.
To give specific details about a person, place, thing, event, or phenomenon.
The average annual conditions of temperature, precipitation, winds, and clouds in an area.
Term used to describe a volcano that is no longer active and unlikely to erupt again.
The pair of chromosomes carrying genes that determine whether a person is biologically male or female.
The 22 pairs of chromosomes that are not sex chromosomes.
A gene carried on a sex chromosome.
Describes an estimate of a value that is very close to the exact value.
Features that help to identify something.
To be able to tell one object from another by identifying key differences.
Not affected, harmed, or destroyed by something.
Remaining in one place for an extended period of time.
To combine information or data from many sources.
A set of pieces or parts that are arranged in a certain way within a larger object, system, or body.
The job or purpose of a specific structure or organ within an organism.
A series of connected events that happen in a specific order.
To draw a connection between two or more things.