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8th Grade Vocabulary by Chapter

8th Grade Vocabulary Terms

Chapter 1 – Scientific Investigations and Reasoning

Analyze - examine methodically and in detail for purposes of explanation and interpretation

Conclusion - a short paragraph that states the results of an experiment and explains whether the hypothesis was correct or not

Constant – the factors in an experiment that stay the same

Control Group – the part of a controlled experiment that contains the same factors as the experimental group, but the independent variable is not changed

Controlled Experiment - a scientific test that is directly manipulated by a scientist, in order to test a single variable at a time

Critical Thinking – comparing what you already know about something to new information and deciding whether or not you agree with the new information

Dependent/Responding Variable - a variable whose value changes because of another variable; graphed on the y –axis

Experimental Group – the part of the controlled experiment used to study relationships among variables

Hypothesis – a possible explanation for an observation that can be tested by scientific explanations; an “if, then” statement

Independent/Manipulated Variable – the factor that is changed by the investigator to observe how it affects a dependent variable

Inference – a logical explanation of an observation that is drawn from prior knowledge or experience

International Unit - the standard units of measurement defined by the International System of Units

Model - a physical, conceptual, or mathematical representation of something that is difficult to observe directly

Observation – the act of using one or more of your senses to gather information and take note of what occurs

Opinion - a statement describing a personal belief or thought that cannot be tested (or has not been tested) and is unsupported by evidence

Prediction – a statement of what will happen next in a sequence of events

Prototype - a first full-scale and usually functional form of a new type or design of a construction

Qualitative – data is descriptive and conceptual; using words to describe something

Quantitative – data can be counted, measured, and expressed using numbers; using measurements to describe something

Research - the orderly investigation into and study of materials in order to establish facts and reach new conclusions  

Science – the exploration and investigation of natural events and the new information that comes from those investigations

Scientific Inquiry - the diverse ways in which scientists study the natural world and propose explanations based on the evidence from their work

Scientific Law – a rule that describes a pattern in nature; it happens the same way every time

Scientific Theory – an explanation of observations or event that is based on knowledge gained from many observations and investigations; not definitively proven

Skeptical - not easily convinced; having doubts or reservations

Variable – any factor that can have more than one value


Chapter 2 – Atoms and the Periodic Table


Atom – the smallest piece of an element that still represents that element

Atomic Number – the number of protons in an atom of an element

Average Mass Number - the average atomic mass of an element based on its isotopes and their natural abundance

Bohr’s Atomic Model - electrons travel in defined circular orbits around the nucleus

Chemical Bond – a force that holds two or more atoms together

Compound – a substance made of two or more elements that are chemically joined in a specific combination

Electron – a negatively charged particle that occupies the space in an atom outside the nucleus

Electron Cloud – the region surrounding an atom’s nucleus where one or more electrons are most likely to be found

Electron Dot Diagram/Lewis Dot Diagram – a model that represents valence electrons in an atom as dots around the element’s chemical symbol

Group/Family – a column on the periodic table where the elements have the same number of valence electrons

Isotope – atoms of the same element that have different numbers of neutrons

Modern Atomic Model - Electrons are in constant motion around the nucleus, protons and neutrons vibrate within the nucleus

Neutron – a neutral particle in the nucleus of an atom

Nuclear Decay - the process by which an unstable atomic nucleus loses energy by radiation

Nucleus (Chemistry) – the region in the center of the atom where most of an atom’s mass is found; contains protons and neutrons

Period – a row on the periodic table that shows the number of energy shells/levels/rings of an atom

Periodic - refers to trends or recurring variations in element properties with increasing atomic number

Periodic Table – a chart of the elements arranged by physical and chemical properties

Proton – a positively charged particle in the nucleus of an atom

Radioactive – an element that naturally emits radiation

Rutherford’s Atomic Model - the atom has a tiny, dense, positively charged core called a nucleus while negatively charged electrons circulate around the nucleus

Thomson’s Atomic Model - atoms are uniform spheres of positively charged matter in which electrons are embedded

Valence Electrons – the outermost electrons of an atom that are responsible for chemical bonding


Chapter 3 – Chemical Bonding and Chemical Reactions


Chemical Bond – a force that holds two or more atoms together

Chemical Change – a change in matter in which substances change into other substances with different chemical and physical properties

Chemical Equation – a description of a reaction using element symbols and chemical formulas

Chemical Formula – a group of chemical symbols and numbers that represent the elements and the number of atoms that make up a compound

Chemical Reaction – a process in which atoms of one or more substances rearrange to form one or more new substances

Coefficient - a number placed in front of an element symbol or chemical formula in an equation

Combustion – a chemical reaction in which a substance combines with oxygen and releases energy

Compound – a substance made of two or more elements that are chemically joined in a specific combination

Covalent Bond - a chemical bond formed when two atoms share one or more pairs of valence electrons

Decomposition – a type of chemical reaction in which one compound breaks down and forms two or more substances

Electron Sharing - when the electrons in the outermost shell from one atom can be used to complete the outermost shell of another atom without being permanently transferred

Electron Transfer - when an electron relocates from an atom or molecule to another

Element – a pure substance made of only one kind of atom

Ion – an atom that has gained or lost an electron and is no longer neutral

Ionic Bond - the attraction between positively and negatively charged ions in an ionic compound

Law of Conservation of Mass – the total mass of the reactants before a chemical reaction is the same as the total mass of the products of the reaction

Metallic Bond – a bond formed when many metal atoms share their pooled valence electrons

Molecule – two or more atoms that are held together by covalent bonds and act as a unit

Physical Change – a change of matter that does not change the matter’s identity

Polar Molecule – a molecule with a slight negative charge in one area and a slight positive charge in another area

Precipitate – a solid that forms when two liquids are combined

Product – a substance produced by a chemical reaction

Reactant – a starting substance in a chemical reaction; ingredient

Replacement – an atom or group of atoms replaces part of a compound; switched

Subscript - numbers that come after and below a symbol; tell you the number of atoms of that element

Substance – matter with a composition that is always the same

Synthesis – a chemical reaction in which two or more substances combine to form one compound


Chapter 4 – Speed, Velocity, and Acceleration


Average Speed – total distance divided by the total time of the trip

Constant Speed – an object moves the same distance over a given unit of time

Instantaneous Speed - the speed of an object at a particular moment (instant) in time when the speed of an object is constantly changing

Negative Acceleration/Deceleration – velocity is decreasing, the action of slowing down

Positive Acceleration – velocity is increasing, the action of speeding up

Speed – the distance an object is moving in a unit of time

Velocity – the speed and direction of a moving object

X-axis - the independent/manipulated variable is on the x-axis (horizontal)

Y-axis – the dependent/responding variable is on the y-axis (vertical)


Chapter 5 – The Laws of Motion


Action Force – Force exerted on an object in one direction

Air Resistance - the force that air exerts on objects moving through it

Balanced Forces – forces acting on an object that combine and form a net force of zero; no change in motion

Centripetal Force – in circular motion, a force that acts perpendicular to the direction of motion, toward the center of a curve

Contact - Touching

Elastic Collision - the kinetic energy before the collision and after the collision remains the same and is not converted to any other form of energy; objects collide and bounce off each other

Force – a push or a pull on an object

Force Pair - As in Newton’s 3rd law, the forces two objects apply to each other

Friction – a contact force that resists the sliding motion of two surfaces that are touching

Gravity – an attractive force that exists between all objects that have mass

Inertia – the tendency of an object to resist a change in its motion

Law of Conservation of Momentum – the total momentum of a group of objects stays the same unless outside forces act on the objects

Law of Universal Gravitation – all objects are attracted to each other by a gravitational force

Mass – the amount of matter in an object

Momentum – a measure of how hard it is to stop a moving object

Net Force – the sum of all forces acting on an object

Newton - force needed to move a mass of one kilogram with an acceleration of one meter per second2

Noncontact – a force that one object applies to another object without touching it

Reaction Force – A force exerted by an object in response to an action force

Reference Direction - the direction you must travel from the reference point toward an object

Sliding Friction - a contact force that resists the sliding motion of two objects or an object and a surface

Static Friction – a force between two surfaces that aren't moving relative to each other

Terminal Velocity - the highest velocity that can be achieved by an object that is falling through a fluid, such as air or water

Unbalanced Forces – forces acting on an object that combine and form a net force that is not zero and therefore results in a change in motion

Weight – the gravitation force on an object


Chapter 6 – Earth’s Motion


Astronomical Unit – a unit of measurement in space equal to 150 million km; the distance from Earth to the Sun

Crescent - the shape of the visible part of the moon when it is less than half full

Equator – an imaginary line at latitude 0o, separates the northern and southern hemispheres

Equinox – when Earth’s rotation axis is not tilted toward or away from the Sun; hours of daylight = hours of darkness

Gibbous - more than half but less than fully illuminated; a term used in describing Moon phases

Lunar Eclipse – an occurrence when the Moon moves into Earth’s shadow; occurs only in the full moon phase

Maria – the large, dark, flat areas on the moon

Moon Phase - the angle from which an observer on earth can see the moon illuminated by the sun as it orbits our planet

Orbit – the path an object follows as it moves around another object

Penumbra – the lighter part of a shadow where light is partially blocked; almost a complete shadow

Revolution – the orbit of one object around another object

Rotation – a spinning motion

Rotation Axis – the line on which an object rotates

Solar Eclipse – when the Moon is between the Sun and the Earth and blocks the sunlight

Solstice – when Earth’s rotation axis is tilted toward or away from the Sun causing the longest/shortest hours (days) of sunlight

Tide – the rhythmic rise and fall of the ocean’s surface that is caused by the gravity between the Earth, Moon, and Sun

Umbra – the central, darkest part of a shadow; light is completely blocked

Waning - to decrease in some way

Waxing – to increase in some way


Chapter 7 – The Universe


Absolute Magnitude - how bright the star appears at a standard distance of 32.6 light-years (roughly 10 trillion kilometers)

Apparent Magnitude - how bright a star appears from Earth

Astronomical Unit – a unit of measurement in space equal to 150 million km; the distance from Earth to the Sun

Aurora – curtains of light that appear when solar wind particles or coronal mass ejections interact with Earth’s magnetic field

Big Bang Theory – states that the universe began from one point and has been expanding and cooling since then

Binary System - consists of two stars that are gravitationally bound and orbit their common center of mass in elliptical or circular orbits.

Black Hole – an object whose gravity is so strong that no light can escape

Chromosphere – the orange-red layer above the photosphere of a star

Convection Zone – layer of a star where hot gas moved up toward the surface and cooler gas moves deeper into the interior

Corona – the wide, outermost layer of a star’s atmosphere

Dark Matter – matter the emits no light at any wavelength

Electromagnetic Spectrum - energy from the Sun that travels to Earth and ranges from very long-length radio waves to very short-length gamma rays

Flare – sudden increases in brightness near the Sun’s sunspots and prominences (looping clouds of gas)

Galaxy – a huge collection of stars, gas, and dust

Hertzsprung-Russell Diagram – a graph that plots luminosity and temperature of stars

Light Year - the distance light travels in one year

Luminosity – the true brightness of an object

Milky Way – a spiral galaxy that contains gas, dust, and the Solar system

Nebula – a cloud of dust and gas

Neutron Star – a dense core of neutrons that remains after a supernova

Nuclear Fusion – when the nuclei of several atoms combine into one larger nucleus

Parallax - when the position or direction of an object appears to differ when viewed from different positions

Photosphere – the apparent surface of a star

Prominence – clouds of gas that loop and jet into the Sun’s corona

Protostar – when gravity causes the densest parts of a nebula to collapse

Solar Wind – charged particles that are always moving away from the Sun

Spectroscope – a tool that spreads light into different wavelengths

Star – a large ball of gas held together by gravity with a core so hot that nuclear fusion occurs

Star Cluster – large groups of stars that are of similar age and distance from Earth

Stellar - relating to a star or stars

Sunspot – regions of strong magnetic activity on the Sun; dark spots on the Sun

Supernova – an enormous explosion that destroys a star; occurs when a star loses its internal energy source and the iron core collapses

White Dwarf – a hot, dense, slowly cooling sphere of carbon


Chapter 8 – Interpreting Maps


Antarctic Circle - latitude on the Earth at approximately 66.5 degrees south of the equator

Arctic Circle - latitude on the Earth at approximately 66.5 degrees north of the equator

Contour Interval – the elevation difference between contour lines that are next to each other on a map

Contour Line – a line on a topographic map that connects points of equal elevation

Equator - latitude on the Earth at 0 degrees; separates the Earth into the Northern and Southern Hemispheres

Geologic Map – a map that shows the surface geology of an area

Global Positioning System (GPS) - an accurate worldwide navigational and surveying system based on the reception of signals from many orbiting satellites

Index Line - the thickest/darker contour lines usually labeled with the elevation

International Date Line – the line of longitude 180 degrees west or east of the Prime Meridian

Latitude – the distance in degrees north or south of the Equator

Longitude – the distance in degrees east or west of the Prime Meridian

Map – a model of an area of land or sea showing physical features

Map Legend – a key that lists all the symbols used on a map

Map Scale – the relationship between a distance on the map and the actual distance on the ground

Map View/Plan View – a map drawn as if you were looking down on an area from above Earth’s surface

Prime Meridian – a reference point at 0 degrees longitude which runs through the original site of the Royal Observatory at Greenwich, England, and from which other longitudes are determined

Profile View – a drawing that shows a vertical section through the ground; a side view

Relief – the difference in elevation between the highest and lowest point in an area

Remote Sensing - the scanning of the earth by satellite or high-flying aircraft in order to obtain information about it

Slope – a measure of the steepness of the land

Time Zone –one of 24 areas on Earth’s surface where people use the same time

Topographic Map – a map showing the detailed shapes of Earth’s surface, along with its natural and manmade features

Topography - the arrangement of the natural and artificial physical features of an area

Tropic of Cancer - latitude 23°26ʹ north of the equator

Tropic of Capricorn - latitude 23°26ʹ south of the equator


Chapter 9 – Plate Tectonics


Abyssal – the bottom of the ocean

Basalt – a dense rock that forms oceanic crust; a fine-grained extrusive igneous rock

Compression - decrease in volume of any object or substance resulting from applied stress

Continental Crust – crust that is thicker than oceanic crust with a lower density causing it to ride higher on the mantle; formed from granite; contains the land masses

Continental Drift – the movement of Earth’s continents over time; theory proposed by Alfred Wegener

Continental Rift - a zone of the lithosphere that has become thinner due to extensional forces associated with plate tectonics; area of divergence

Convergent Plate Boundary – the boundary between two plates that move toward each other

Divergent Plate Boundary - the boundary between two plates that move away from each other

Dormant - is a period when physical activity has temporarily stopped

Fault Block Mountain – parallel ridge that forms where blocks of crust move up or down along faults

Fault Zone – an area of many fractured pieces of crust along a fault line

Folded Mountain – mountain made of layers of rocks that are folded

Granite – a rock that is less dense than basalt and forms continental crust; a coarse or medium-grained intrusive igneous rock

Island Arc - a curved chain of volcanic islands located at a tectonic plate margin

Magnetic Reversal – an event that causes a magnetic field to reverse direction

Mid-ocean Ridge – a long, narrow mountain range on the ocean floor; formed by magma at divergent plate boundaries

Normal Polarity – when magnetized objects orient themselves to North

Ocean Trench – a deep, underwater trough created by one plate subducting under another plate at a convergent plate boundary

Oceanic Crust - the relatively thin part of the Earth's crust which underlies the ocean; geologically young compared with the continental crust and consists of basaltic rock covered by sediments

Pangaea – name of a supercontinent that began to break apart 200 million years ago

Reversed Polarity – when magnetized objects reverse direction and orient themselves to South

Seafloor Spreading – the process where new oceanic crust forms at a mid-ocean ridge and older oceanic crust is pushed away from the ridge

Shear - a force acting in a direction that's parallel to a surface

Subduction – the process that occurs when one tectonic plate moves under another tectonic plate

Tension - the force that is transmitted on an object when pulled by forces acting from opposite sides; stretched

Transform Plate Boundary/ Transform Fault – the boundary where two tectonic plates slide past each other

Uplifted Mountain – mountain that forms when large regions rise vertically with little apparent change

Volcanic Arc – a curved line of volcanoes that forms parallel to a plate boundary

Volcanic Mountain - mountains formed by volcanoes; formed when lava erupts, piles upon the surface, and ash and lava cools to build a cone of rock


Chapter 10 – Interactions of the Atmosphere and Oceans


Conduction – the transfer of thermal energy due to collisions between particles

Convection – the transfer of thermal energy by the movement of particles from one part of a material to another

Coriolis Effect – the movement of wind and water to the right or left that is caused by Earth’s rotation

Downwelling/Density Current – carry water from the surface to deeper parts of the ocean; circulate thermal energy, nutrients, and gases

Great Ocean Conveyor Belt – a large global system of ocean currents that affects weather and climate around the Earth; may take 1000 years for one cycle

Greenhouse Effect – the natural process that occurs when certain gases in the atmosphere absorb and reradiate thermal energy from the Sun

Gyre – a large circular system of ocean currents

Infrared - a type of radiant energy that's invisible to human eyes but that we can feel as heat; radiation that Earth bounces back to the atmosphere

Jet Stream – a narrow band of westerly high winds located near the top of the troposphere

Land Breeze – a wind that blows from the land to the sea due to local temperature and pressure differences at the shore; occurs at night since land cools faster than water

Ocean Current – a large volume of water flowing in a certain direction

Polar Easterlies – cold winds that blow from the east to the west near the North and South Poles

Radiant Energy – energy that travels as electromagnetic waves; can travel through the vacuum of space

Sea Breeze - a wind that blows in from the sea due to local temperature and pressure differences at the shore; occurs in the day since land heats faster than water

Temperature Inversion – a temperature increase as altitude increases in the troposphere

Trade Winds – steady winds that flow from east to west between latitudes 30 degrees North and 30 degrees South

Tropics - between the latitude lines of the Tropic of Cancer and the Tropic of Capricorn

Ultraviolet - situated beyond the visible spectrum at its violet end; having a wavelength shorter than wavelengths of visible light and longer than those of X-rays

Unstable Air – warm air rises rapidly in the atmosphere and forms cumulonimbus clouds that produce thunderstorms

Upwelling – vertical movement of water toward the ocean surface

Westerlies – steady winds that flow from west to east between 30 degrees and 60 degrees in the northern and southern hemispheres

Wind - wind is moving air and is caused by differences in air pressure within our atmosphere


Chapter 11 – Weather


Air Mass – a large area of air that has uniform temperature, humidity, and pressure

Air Pressure – the force that a column of air exerts on the air, or a surface, below it

Blizzard – a violent winter storm characterized by freezing temperatures, strong winds, and blowing snow

Cirrus - cloud generally characterized by thin, wispy strands; high in the troposphere and do not produce rain or snow

Cold Front – area where a cold air mass replaces a warm air mass

Continental Polar – cold air mass that travels over land; cold and dry

Continental Tropical – warm air mass that travels over land; hot and dry

Cumulus – puffy white clouds with flat bases; indicate nice weather

Dew Point – temperature at which air is fully saturated; the atmospheric temperature below which water droplets begin to condense

Doppler Radar – used to detect precipitation and wind speed

Front – a boundary between two air masses

High Pressure System – a large body of circulating air with high pressure at its center; brings “happy” weather

Humidity – the amount of water vapor in the air

Hurricane – an intense tropical storm with winds over 119km/h (74mph)

Isobar – lines that connect all places on a map where pressure has the same value

Lightning – an electric discharge within a cloud, between clouds, or between a cloud and the ground

Low Pressure System – a large body of circulating air with low pressure at its center; brings “lousy” weather

Maritime Polar - cold air mass that travels over oceans; cold and moist

Maritime Tropical - warm air mass that travels over oceans; hot and humid

Occluded Front – a fast moving cold front catches up with a warm front, surrounds it and forces it up into the atmosphere; brings precipitation

Precipitation – any form of water that falls from the atmosphere

Relative Humidity – the amount of water vapor in the air compared to the maximum amount of water vapor the air could hold; a percentage of the water vapor that the air could hold

Station Model – a diagram that uses numbers and symbols to show local weather measurements

Stationary Front – a cold air mass and warm air mass meet and stop moving; brings cloudy days and light rain

Storm Warning – a storm is here, take cover

Storm Watch – the conditions are right for a storm to happen

Stratus – cloud that spreads across the sky and produces a light rain or drizzle; resembles a high fog

Surface Report – weather measurements made on Earth’s surface

Thunderstorm – a weather event that includes rain, strong winds, thunder, and lightning

Tornado – a violent, whirling column of air in contact with the ground

Upper Air Report – describes wind, temperature, and humidity above Earth’s surface

Warm Front – dense, warm air moves toward colder, dense air and rises above it

Weather –local atmospheric conditions, along with short-term changes, of a certain place at a certain time


Chapter 12 – Populations and Communities


Abiotic – non living

Atmosphere – layer of gases surrounding the Earth

Biosphere – all living organisms on Earth

Biotic – living or were once living

Biotic Potential – the possible growth of a population if it could grow in perfect conditions with no limiting factors

Birthrate – the number of offspring produced in a population over a given time period

Carnivore – an organism that eats flesh

Carrying Capacity – the largest number of members of a species that the environment can support

Commensalism – a symbiotic relationship that benefits one species but does not harm or benefit the other

Community – all the populations of different species that live together in the same area at the same time

Competition – the demand for resources, such as food, water, and shelter, in short supply in a community

Consumer – heterotroph; organisms that get energy by eating other organisms

Cryosphere - the places where water is in its solid form, where low temperatures freeze water and turn it into ice

Deathrate – the number of individuals in a population that die over a given time period

Decomposer - an organism, often a bacterium, fungus, or invertebrate that feeds on and breaks down dead plant or animal remains, making organic nutrients available to the ecosystem.

Detritivore/Scavenger – heterotrophs that eat dead plant and animal matter to obtain energy

Ecosystem – all the living and nonliving things in a given area

Endangered species – a species whose population is a risk of extinction

Energy Pyramid – a model that shows the amount of energy available in each link (trophic level) of a food chain

Extinct – a species that has dies out and no individuals are left

Food Chain – a model that shows how energy flows in an ecosystem through feeding relationships

Food Web – a model of energy transfer that can show hot the food chains in a community are interconnected

Geosphere – the solid part of the Earth

Habitat – the place within an ecosystem where an organism lives; provides the biotic and abiotic factors an organism needs to survive and reproduce

Herbivore – get their energy by eating plants; primary consumers

Host – the species that is harmed in parasitism

Hydrosphere – all the water that is on the surface of the planet, underground, and in the air

Limiting Factor – anything that restricts the size of a population

Migration – the instinctive seasonal movement of a population of organisms from one place to another

Mutualism – a symbiotic relationship in which both partners benefit

Niche - the role an organism plays in a community; all of the interactions of a species with the other members of its community and the ecosystem

Omnivore – heterotrophs that get their energy by eating plants and animals

Overpopulation – when the size of a population becomes larger than the ecosystem can support

Parasite - the species that benefits from harming its host

Parasitism – a symbiotic relationship that benefits one species and harms the other

Population – all the organisms of the same species living in an area

Population Density – the size of a population compared to the amount of space available

Predation - a biological interaction where one organism, the predator, kills and eats another organism, its prey

Producer - autotroph; an organism that can use chemical or radiant energy to produce its own food

Species – a group of organisms that have similar traits and are able to produce fertile offspring

Symbiosis – a close and long-term relationship between two species that involves an exchange of resources


Chapter 13 – How Organisms Affect Environments


Acquired Trait – a trait that an organism acquires or develops over time; not genetically determined

Adaptations – an inherited or learned trait that increases an organism’s chance of surviving and reproducing in a particular environment

Algal Bloom – when algae grow and reproduce in large numbers

Allele – a gene for a single trait

Asexual Reproduction – a type of reproduction in which one parent organism produces a genetically identical offspring

Camouflage – an adaptation that enables a species to blend in with its environment

Chromosome - microscopic threadlike part of the cell that carries hereditary information in the form of genes

Deoxyribonucleic acid (DNA) - a molecule that encodes an organism's genetic code; contains all of the information required to build and maintain an organism

Dominant - an allele or a gene that is expressed in an organism’s phenotype, masking the effect of the recessive allele

Fertilization – a reproductive process in which a sperm joins an egg

Gene – a section of DNA on a chromosome that has genetic information for one trait

Genotype – the alleles of all the genes on an organism’s chromosomes

Homoeostasis – an organism’s ability to maintain steady internal conditions when outside conditions change

Inheritance – the passing of traits from one generation to another

Marine - having to do with the ocean

Meiosis – a process in which one diploid cell divides to make 4 haploid sex cells

Mimicry - external resemblance of an animal or plant (or part of one) to another animal, plant, or inanimate object

Mitosis – a process during which the nucleus of a cell and its contents divide

Mutation – a permanent change in the sequence of DNA in a gene or chromosome

Natural Selection – the process by which organisms with variations that help them survive live to reproduce

Nonpoint Source – a source of pollution that cannot be easily identified; pollution that comes from many places, all at once

Nucleus (biology) – a part of a eukaryotic cell that directs cell activity and contains genetic information stored in DNA

Point Source - any single identifiable source of pollution from which pollutants are discharged, such as a pipe

Punnett Square - a square diagram that is a grid of usually four boxes and is used to calculate and depict all the possible combinations of the different genotypes and phenotypes among the offspring 

Recessive – genetic code that is not expressed if a dominant allele is present

Selective Breeding – the selection and breeding of organisms for desired traits

Sexual Reproduction – type of reproduction where the genetic material from two different cells (sperm and egg) combine to produce a unique offspring

Trait – a distinguishing characteristic of an organism

Variations – a slight difference in an inherited trait among individual members of a species