Lower Pottsgrove Elementary

5^th Grade Science Vocabulary

Abiotic factor – a nonliving part of an ecosystem.

Absorption – the disappearance of a sound wave into a surface.

Abyssal plain – the vast flat lands beyond the continental shelf that cover almost half of the deep ocean floor.

Acceleration – change in velocity with respect to time.

Acid – a substance that tastes sour and turns litmus paper red.

Acid rain - moisture that falls to Earth after being mixed with wastes from burned fossil fuels.

Acidity – the strength of an acid.

Action – the force one object applies to a second, as in Newton’s third law of motion, which states, “For every action, there is an equal but opposite reaction.”

Adaption – a characteristic that enables a living thing to survive in its environment .

Aerial root – a root that never touches the ground but can take in moisture from the air.

Aerosol – a type of colloid in which liquid drops or solid particles are spread throughout a gas.

Air mass – a large region of the atmosphere where the air has similar properties throughout.

Air pressure – the force put on a given area by the weight of the air above it.

Alkalinity – The strength of a base.

Alternative energy source – a source of energy other than the burning of a fossil fuel.

Amphibian – a vertebrate that lives part of its life in the water and part of its life on land.

Anemometer – a device that measures wind speed.

Aneroid barometer – a spring enclosed in a pleated metal can that expands or contracts to indicate changes in air pressure.

Angiosperm – a seed plant that produces flowers.

Aquifer - an underground layer of rock or soil filled with water.

Asexual reproduction – The production of a new organism from only one cell.

Asteroid – “minor planet” one of many small, rocky objects that orbit the Sun between the orbits of Mars and Jupiter.

Asteroid belt - region between Mars and Jupiter where most asteroids are found.

Atmosphere – the blanket of gases that surround the Earth.

Atom - the smallest unit of an element that retains the properties of that element.

Aurora – the northern or southern lights that appear in the night sky, especially in polar regions.

Bacterium – a member of either of two kingdoms of one-celled living things that have no nucleus, or center, in their cell body.

Balanced forces – forces that cancel each other out when acting together on a single object.

Barometer – a device for measuring air pressure.

Base – a substance that tastes bitter and turns red litmus paper blue.

Basin – the floor of an ocean, containing mountains, valleys and plains.

Bench mark – a plaque left by surveyors to tell the exact location and elevation of a place.

Benthos – organisms that live on the bottom in aquatic ecosystems.

Bird – a vertebrate that has both feathers and wings.

Biomass – energy from plant matter or animal waste.

Biome – one of Earth’s large ecosystems, with it’s own kind of climate, soil, plants, and animals.

Biotic factor – a living part of an ecosystem.

Boiling point – the particular temperature for each substance at which it changes state from a liquid to a gas.

Buoyancy – the upward push of a liquid on an object placed in it.

Cambium – the layer in plants that separates the xylem from the phloem.

Carbon cycle – the continuous exchange of carbon dioxide and oxygen among living things.

Carnivore – an animal that eats another animal.

Carrying capacity – the maximum population size that an area can support.

Cell - the smallest unit of living matter.

Chemical change – a change of matter that occurs when atoms link together in a new way, creating a new substance different from the original substances.

Chemical formula – a way to write a compound’s name using symbols. The letters tell what elements are in the compound, and the subscripts tell the number of particles in the compound.

Chemical reaction – another name for chemical change.

Chemosynthesis – in tube worms the process by which bacteria create nutrients from hydrogen sulfide and oxygen, using chemical reactions rather than light.

Chlorophyll – a green chemical in plant cells that allows plants to use the Sun’s energy for making food.

Cirrus cloud – a high-altitude cloud with a featherlike shape, made of ice crystals.

Classification – the science of finding patterns among living things.

Cleavage – the tendency of a mineral to break along flat services.

Climate – the average weather pattern of a region.

Climate zone – a region that has similar weather patterns based on temperature, precipitation, wind, distance from a coast, mountain ranges, ocean currents, and vegetation.

Climax community – the final stage of succession in an area, unless a major change happens.

Cold front – a front where cold air moves in under a warm air mass.

Colloid – a special type of mixture in which the particles of one material are scattered through another and block the passage of light without settling out.

Comet – a “dirty snowball” orbiting the Sun – a mixture of ices, frozen gases, rock, and dust left over from the formation of the solar system.

Commensalism – a relationship between two kinds of organisms that benefits one without harming the other.

Community – all the living things in an ecosystem.

Complete flower – a flower that has sepals, petals, stamens, and pistils.

Compound – any substance that is formed by the chemical combination of two or more elements and acts like a single substance.

Compression - 1. The part of a sound wave where molecules are crowded together. 2. A movement of plates that presses together or squeezes Earth’s crust.

Concave lens – a lens that is thinker at the edges than at the middle. As it curves inward, it spreads light rays apart, making images appear smaller.

Concave mirror – a mirror that curves in on the shiny side.

Condensation – the changing of a gas into a liquid.

Conduction – the passing of heat through a material while the material itself stays in place.

Conifer - any of a group of gymnosperms that produce seed in cones and have needlelike leaves.

Conserve – to save, protect, or use resources wisely.

Constellation – patterns formed by groups of stars in the night sky.

Consumer – any animal that eats plants or eats other plant-eating animals.

Continental rise – a buildup of sediment on the sea floor at the bottom of the continental slope. It is a zone of sand and mud that stretches from the slope down to the deep-sea floor.

Continental shelf – the underwater edge of a continent.

Continental slope – the steep slope leading down from the continental shelf toward the sea.

Contour plowing – preventing erosion by plowing across rather than up and down a slope.

Contract – to shrink, as when a material gets colder.

Convection – the flow of heat through a liquid or a gas, causing hot parts to rise and cooler parts to sink.

Convection cell – a circular pattern of air rising, air sinking, and wind.

Convex lens – a lens that is thicker at the middle than at the edges. As it curves outward, it brings light together, making images appear larger.

Convex mirror – a mirror that curves out on the shiny side.

Coquina – a sedimentary rock formed from seashell fragments.

Coriolis effect – the curving of the path of a moving object caused by Earth’s rotation.

Cortex – the layer of tissue just inside the epidermis of a plant’s roots and stems.

Cotyledon – a tiny leaflike structure, also called a seedleaf, inside the seed of an angiosperm.

Crop rotation – growing different crops each year so that the soil does not use up the same kinds of minerals year after year.

Crossbreeding – producing offspring by mating individuals from two distinct breeds or varieties of the same species.

Cross-pollination – the transfer of pollen from one flower to another.

Crust – the rocky surface that makes up the top of the lithosphere and includes the continents and the ocean floor.

Crystal – the geometric shape a mineral forms when its atoms and molecules get into fixed positions.

Cumulus cloud – a puffy cloud that appears to rise up from a flat bottom.

Current – an ocean movement; a large stream of water that flows in the ocean.

Cycad – one of the evergreen gymnosperms that resemble palms and have seed-bearing cones.

Decibel – a unit that measures loudness.

Deciduous – said of a plant that loses its leaves each fall.

Deciduous forest – a forest biome with many kinds of trees that lose their leaves each autumn.

Decomposer – any of the fungi or bacteria that break down dead plants and animals into useful things like minerals and rich soil.

Delta – fan-shaped region formed by deposits of sediments found at the mouth of a river.

Density – a measure of how tightly packed the matter in an object is.

Deposition – the dropping off of bits of eroded rock.

Desalination – getting fresh water from seawater.

Desert – a sandy or rocky biome, with little precipitation and little plant life.

Dicot – an angiosperm with two cotyledons in each seed.

Dinoflagellate – a protest containing chlorophyll that has two flagella for motion. When they over reproduce, they can cause “red tides”.

Distillation – the process of separating the parts of a mixture by evaporation and condensation.

Diversity – a wide variety of traits in individuals from the same population.

Doppler effect – the change in frequency (and pitch) as a source of sound moves toward or away from you.

Downdraft – a downward rush of air caused by the falling of rain during a thunderstorm.

Echo – a reflected sound wave.

Echolocation – finding an object by using reflected sound.

Ecological succession – the gradual replacement of one community by another.

Ecology – the study of how living and nonliving things interact.

Ecosystem – all the living and nonliving things in the environment, including their interactions with each other.

Effort arm – the part of a lever that applies force to the resistance arm.

Electromagnetic spectrum – all the wavelengths of visible and invisible light in order, from short (gamma rays) to long (radio).

Electromagnetism – the production of magnetism by electricity (and the production of electricity by magnets)

Electron – a particle in the space outside the nucleus of an atom that carries one unit of negative electric charge.

Element – a pure substance that cannot be broken down into any simpler substances.

Elevation – the height of a place above sea level.

Embryo – the immature plant inside a seed.

Emulsion – a type of colloid in which one liquid is spread throughout another.

Epidermis – an outermost layer of such plant parts as roots and leaves.

Erosion – the picking up and carrying away of pieces of rocks.

Evaporation – the slow changing of a liquid into a gas.

Evergreen – said of a gymnosperm that keeps its leaves for at least a few years.

Expand – to spread out , as when a material gets hotter.

Extinct – a species that has died out completely.

Fault – a crack in Earth’s crust whose sides show evidence of motion.

Fertilization – the joining of a sperm cell with an egg cell to make one new cell, a fertilized egg.

Fertilizer – a substance used to add minerals to the soil.

Fibrous root – one of the many hairy branching roots that some plants have.

Filament – the wire in a light bulb that gives off light and heat.

Fish – a vertebrate that lives its whole life in water.

Flood plain – land that is likely to be underwater during a flood.

Foam – a type of colloid in which a gas is spread throughout a liquid.

Fog – a cloud at ground level.

Fold mountain – a mountain made up mostly of rock layers folded by being squeezed together.

Food chain – the path of the energy in food from one organism to another.

Food web – the overlapping food chains in an ecosystem.

Force – a push or pull exerted by one object on another, causing a change in motion.

Fossil – any remains or imprint of living things of the past.

Fossil fuel – a fuel formed from the decay of ancient forms of life.

Fracture – the characteristic way some minerals break in uneven patterns.

Freezing point – the temperature at which a substance changes state from a liquid to a solid.

Frequency – the number of times an object vibrates per second.

Friction – a force that opposes the motion of one object moving past another.

Frond – the leaf of a fern.

Front – a boundary between air masses with different temperatures.

Fruit – the ripened ovary of a flowering seed plant.

Fulcrum – the pivot point of a lever.

Fundamental tendency – the lowest frequency at which an object vibrates .

Fungus – members of a kingdom that contains one-celled and many celled living things that absorb food from their environment.

Galaxy – a collection of billions of stars. Our Sun belongs to the Milky Way galaxy.

Gas – a form of matter that does not take up a definite amount of space and has no definite shape.

Gel – a type of colloid in which a solid is spread throughout a liquid.

Gem – a mineral valued for being rare and beautiful.

Geologist – a scientist who studies rocks to tell how they formed and to predict when an earthquake may occur.

Geothermal energy – Earth’s internal energy.

Germination – the sprouting of a seed into a new plant.

Ginkgo – a large gymnosperm with fan shaped leaves.

Gnetophyte – one of the gymnosperms that are closely related to flowering plants and live in both deserts and the tropics.

Grassland – a biome where grasses, not trees, are the main plant life. Prairies are one kind of grassland region.

Gravitropism – the response of a plant to gravity.

Gravity – the force of attraction between any two objects due to their mass.

Groundwater – precipitation the seeps into the ground and is stored in tiny holes, or pores, in soil and rocks.

Gymnosperms – a seed plant that does not produce flowers.

Habitat – the place where a plant or animal naturally lives and grows.

Hail – pellets made of ice and snow.

Hardness – how well a mineral resists scratching.

Herbivore – an animal that eats plants, algae, and other producers.

Heredity – the passing down of inherited traits from parents to offspring.

Hertz – a unit for measuring frequency.

Heterogeneous – differing in kind or nature: dissimilar; not homogeneous.

High-pressure system – a pattern surrounding a high pressure center, from which winds blow outward. In the Northern Hemisphere these winds curve to the right in a clockwise pattern.

Host – the organism a parasite lives in or on and is harmed by.

Humidity – the amount of water vapor in the air.

Humus – Decayed plant or animal material in the soil.

Hurricane – A very large, swirling storm with very low pressure at the center.

Hybrid – An organism produced by the crossing of parents that have different forms of the same trait.

Hydrocarbon – Compound made only of hydrogen and carbon atoms.

Hydrosphere – Earth’s water, found in continents and oceans, including the fresh water in ice, lakes, rivers, and underground water.

Hydrotropism – the response of a plant to a nearby source of water.

Hyperthermia – the overheating of the body that can be caused by over exposure in a hot, dry climate.

Igneous rock – a rock formed when melted rock material cools and hardens.

Image – a “picture” of the light source that light rays make in bouncing off a polished, shiny surface.

Imperfect flower – a flower with either a stamen or a pistil, but not both.

Incomplete flower – A flower that lacks sepals, petals, stamens or pistils.

Indicator – a substance such as litmus paper whose color changes when it is mixed with an acid or a base.

Inertia – the tendency of a moving object to keep moving in a straight line or of any object to resist a change in motion.

Inexhaustible resource – a resource that cannot be depleted or used up easily.

Inherited trait – a characteristic that is passed from parents to offspring.

Inner planet – a planet between the sun and the asteroid belt. The inner planets are Mercury, Venus, Earth and Mars.

Insolation – the amount of the sun’s energy that reaches the Earth at a given time and place.

Instinct – an inherited behavior, one that is not learned but is done automatically.

Insulate – to prevent heat from passing through.

Intertidal zone - the shallow section of the ocean ecosystem where the ocean floor is covered and uncovered as the tide goes in and out.

Invertebrate – an animal that does not have a backbone.

Ionized – electrically charged by radiation, as gas particles of auroras in the night sky.

Isobar – a line on a weather map connecting places with equal air pressure.

Kinetic energy - The energy of any moving object.

Land breeze - Wind that blows from land to sea.

Laser - A device that produces a thin stream of light of just a few close wavelengths.

Lava - Magma that reaches Earth’s surface.

Law of reflection - The angle between an incoming light ray and a surface equals the angle between the reflected light ray and the surface.

Lever - A simple machine made of a rigid bar and a fixed pivot point, called the fulcrum.

Light ray - A straight-line beam of light as it travels outward from its source.

Lightning - One of the huge electric sparks that leap from clouds to the ground in thunderstorms.

Limiting factor- Anything that controls the growth or survival of a population.

Liquid - A form of matter that takes up a definite amount of space and has no definite shape.

Lithosphere - The hard outer layer of Earth, about 100 km thick.

Long-day plant - A plant that blooms when there is much more daylight than darkness.

Low-pressure system - A pattern surrounding a low-pressure center, in which winds blow in toward the center. In the Northern Hemisphere, these winds blow to the right in a counterclockwise pattern.

Luster - The way light bounces off a mineral’s surface.

Magma - Hot, molten rock deep below Earth.

Magnetic - The property of a material like iron in which the particles line up pole to pole, causing it to be attracted or repelled by a magnet.

Mammal - a vertebrate that feeds its young milk.

Mare- (maria)- Dark-colored land on the Moon that is dry and flat and is surrounded by mountains and ridges.

Mass - A measure of the amount of matter in an object.

Matter - Anything that has mass and takes up space.

Meander - Bends or s-shaped curves in a river.

Melting point - The particular temperature for each substance at which it changes state from a solid to a liqud.

Membrane - a thin envelope surrounding the nucleus of a cell.

Metal - Any of a group of elements found in the ground that conducts heat and electricity.

Metamorphic rock - A rock formed under heat and pressure from another kind of rock.

Meteor - A chunk of rock from space that burns up as it travels through Earth’s atmosphere. A “shooting star.”

Meteorite - A chunk of rock from space that strikes the surface of Earth or the Moon.

Mid-ocean ridge - Chain of mountains that wind along all the world’s major oceans.

Mimicry - An adaptation in which an animal is protected against predators by its resemblance to another, unpleasant animal.

Mineral - A solid material of Earth’s crust with a definite composition.

Mixture - A physical combination of two or more substances that are blended together without forming new substances.

Molecule - A particle that contains more than one atom joined together.

Monocot - An angiosperm with one cotyledon in each seed. See dictot.

Mountain breeze - A cool night wind that blows down a mountain slope to replace the warmer air in the valley.

Mutualism - A relationship between two kinds of organisms that benefits both.

Neap tide - The slightest changes from high to low tide that occur when the Sun, the Moon, and Earth form a right angle or are perpendicular to each other.

Nekton - Organisms that swim through the water in aquatic ecosystems.

Neutral - Neither acid nor base.

Neutron - A particle in the nucleus of an atom that has no net electric charge.

Newton - A basic unit measuring the amount of pull or push a force produces.

NEXRAD - A new form of Doppler radar that is used to track storms. The word stands for NEXt generation of weather RADar.

Niche - The role of an organism in a community.

Nitrogen cycle - The continuous trapping of nitrogen gas into compounds in the soil and its return to the air.

Nonrenewable resources - A resource that cannot be replaced within a short period of time or at all.

Nonvascular - Containing no plant tissue through which water and food move.

Nucleus - 1. A dense structure inside the cell. 2. One of the airborne dust particles around which water condenses as droplets or ice crystals before falling as precipitation. 3. An atom’s dense center, where most of its mass is.

Omnivore - An animal that eats both plants and animals.

Opaque - Completely blocking light from passing through it.

Orbit - The path of a planet traveling around a star.

Ore - A mineral containing a useful substance.

Organ - A group of tissues that work together to do a certain job.

Organism - Any living thing that can carry out its life on its own.

Organ system - A group of organs that work together to do a certain job.

Outer planets - One of the five planets beyond the asteroid belt (Jupiter, Saturn, Uranus, Neptune, Pluto).

Ovary - A structure containing egg cells; the base of a pistil in a flower.

Overtone - One of a series of pitches that blend to give a sound its quality.

Ozone layer - A layer of ozone gas in the atmosphere that screens out much of the Sun’s UV (ultraviolet) rays.

Parasitism - A relationship in which one organism lives in or on another organism and benefits from that relationship while the other organism may be harmed by it.

Perfect flower - A flower with both male and female parts, that is, both a stamen and a pistil.

Permafrost - A layer of permanently frozen soil found in arctic and Antarctic regions.

pH - The scale that tells how acidic or basic a solution is.

Phloem - The tissue through which food from the leaves moves down through the rest of a plant.

Photon - The tiny bundles of energy by means of which light travels.

Photoperiodism -The flowering response of a plant to changing periods of daylight and darkness.

Photosynthesis- The food-making process in green plants that uses sunlight.

Phototropism- The response of a plant to changes in light.

Phylum- (phyla) – One of the large groups in the animal kingdom.

Physical change- A change of matter in size, shape, or state without any change in identity.

Pioneer community- The first community thriving in a once lifeless area.

Pitch- How high or low a sound is.

Planet- Any of the nine major objects that travel around the Sun and shine by reflecting its light.

Plankton- Organisms that float on the water in aquatic ecosystems.

Plate- One of the moving pieces of Earth’s crust that has been broken by upward pressure from the mantle.

Plate tectonics- A scientific theory that Earth’s crust is made of moving plates.

Polarization – Allowing light vibrations to pass through in only one direction.

Pollen- Dustlike grains in the flower of a plant that contain its male sex cells.

Pollination- The transfer of a pollen grain to the egg-producing part of a plant.

Pollute- To add harmful substances to Earth’s land, water, or air.

Population- All the members of one species in an area.

Potential energy- Stored energy.

Precipitation- Any form of water particles that falls from the atmosphere and reaches the ground.

Predator- An animal that hunts other animals for food.

Prey- A living thing that is hunted for food.

Primary color- Red, green, or blue. Mixing these colors can product all the colors of the spectrum.

Primary pigment- Magenta, cyan, or yellow. Materials with any of these colors absorb one primary color of light and reflect the other two.

Primary succession- The beginning of a community where few, if any, living things exist, or where earlier communities were wiped out.

Prism- A cut piece of clear glass (or plastic)with two opposite sides in the shape of a triangle or other geometric shape.

Producer- Any of the plants and algae that produce oxygen and food that animals need.

Product- A new substance produced by a chemical change.

Prop root- One of the roots that grow out of a plant’s stem-like main roots and help prop up the plant.

Property- A characteristic of matter that can be observed, such as mass, volume weight, or density.

Protective coloration- A type of camouflage in which the color of an animal blends in with its background, protecting it against predators.

Protein- A substance rich in nitrogen that the body uses for growth and the repair of cells.

Protist- A member of a kingdom that contains one-celled and many-celled living things, some that make food and some that hunt for food.

Proton- A particle in the nucleus of an atom that carries one unit of positive electric charge.

Quality- The difference you hear between two sounds of the same loudness and pitch.

Radar- A device for tracking the position and path of a distant moving object.

Radiation- The transfer of heat through electromagnetic rays,

Rarefaction- The part of a sound wave where molecules are spread apart.

Raw material- Material not yet refined, manufactured, or processed.

Reactant- An original substance at the beginning of a chemical reaction.

Reaction- The force with which an object responds to an action, as in Newton’s third law of motion.

Reflection- The bouncing of a sound wave off a surface.

Refraction- The bending of light rays as they pass from one substance into another.

Relative humidity- A comparison between how much water vapor is in the air and how much the air could hold at a given temperature if it were full, or saturated.

Renewable resources- A resource that can be replaced in a short period of time.

Reservoir- A storage area for fresh water supplies.

Resistance arm- The part of a lever that applies force to the load the machine acts against.

Resonance- In an instrument or object, a unique blend of the fundamental frequency and its overtones.

Resource- In an instrument or object, a unique blend of the fundamental frequency and its overtones.

Respiration- The release of energy in plants and animals from food (sugar).

Response- What a living thing does as a result of a stimulus.

Reptile- An egg-laying vertebrate with thick, dry skin.

Revolve- The move around, or orbit, another object.

Rhizoid- One of the hairlike fibers that anchor a moss to the soil and take in water from the soil.

Rhizome- The underground stem of a fern.

Rock- A naturally formed solid in the crust made up of one or more minerals.

Rock cycle- Rocks changing from one into another in a never-ending series of processes.

Root cap- A thin covering made up of cells that protect the root tip of a plant as it grows into the soil.

Root hair- Any of the threadlike projections from a plant root that absorb water and dissolved minerals from the soil.

Rotate- To make a complete spin on an axis, causing one day on a planet. A day differs in length from planet to planet.

Runoff- Precipitation that flows across the land’s surface or falls into rivers, and streams.

Savanna- A tropical grassland with some trees and shrubs.

Scanning tunneling microscope- A device that uses electric current flowing through a needle to trace the contours of atoms and magnify them as much as 30 million times.

Scavenger - A meat-eating animal that feeds on the remains of dead animals.

Sea breeze- Winds that blows from sea to land

Sea-floor vent - An opening in a mid-ocean ridge where mineral-saturated water boils up from the seafloor crust.

Seamount - A huge underwater volcanic mountain that may emerge from the ocean surface as an island.

Secondary succession - The beginning of a new community where an earlier community already exists.

Sediment- Pieces of material carried and deposited by water or wind.

Sedimentary rock - A rock made of bits of matter joined together.

Seed - An underdeveloped plant with stored food sealed in a protective covering.

Seed coat -The outer covering of a seed.

Seed dispersal - The movement of a seed from the flower to a place where it can sprout.

Self-pollination - The transfer of pollen from an anther to a stigma in the same plant.

Shear - A movement of plates that twists, tears, or pushes one part of Earth’s crust past another.

Short-day plant - A plant that blooms when there is more darkness and less daylight.

Simple machine - A machine with few moving parts, making it easier to do work.

Smog - A mixture of smoke and fog.

Solar system - The Sun and the objects that are traveling around it.

Solid - A form of matter that has a definite shape and takes up a definite amount of space.

Solubility - The ability of a substance to be dissolved by another substance.

Solute - A substance that is dissolved by another substance to form a solution.

Solution - A mixture of substances that are blended so completely that the mixture looks the same everywhere.

Solvent - A substance that dissolves one or more other substances to form a solution.

Sound wave - A vibration that spreads away from a vibrating object.

Spectrum - A band of colors produced when light goes through a prism.

Speed - How fast an object’s position changes with time at any given moment.

Spore - Cells in seedless plants that grow into new organisms.

Spring - A place where groundwater seeps out of the ground.

Spring tide - The greatest changes from high to low tide that occur when the Sun, the Moon, and Earth are lined up.

State of matter - One of the three forms that matter can take—solid, liquid, or gas.

Stimulus - (stimuli)- Something in the environment that causes a living thing to react.

Stomata (stoma)- Pores in a bottom of leaves that open and close to let in air or give off water vapor.

Storm surge - A great rise of the sea along a shore caused by low air pressure.

Stratus cloud - A cloud that forms in a blanket-like layer.

Streak - The color of the powder left when a mineral is rubbed against a hard, rough surface.

Strip farming - Trapping runoff by alternating tightly growing grasses with more widely spaced plants.

Subscript- A number in a chemical formula that tells the number of atoms in the compound.

Surveyor- A specialist who makes accurate measurements of Earth’s crust.

Suspension- A mixture in which suspended particles can easily be seen.

Symbiosis- A relationship between two kinds of organisms that lasts over time.

Taiga- A cool forest biome of conifers in the upper Northern Hemisphere.

Taproot- A root that has few hairy branches and grows deep into the ground.

Temperate- Free from extremes of temperature.

Tension- A movement of plates that stretches or pulls apart Earth’s crust.

Terracing- Shaping hillsides into steps so that runoff and eroded soil get trapped on the steps.

Texture- An identifying quality of a rock based on how coarse, fine, or glassy it is and on how angular or rounded it is.

Threatened species- A species that is in danger of becoming endangered.

Thunder- The noise caused by lightning-heated air during a thunderstorm.

Thunderhead- A cumulonimbus cloud in which a thunderstorm forms

Tissue- A group of similar cells that work together at the same job.

Topsoil- The dark, top layer of soil, rich in humus and minerals, in which many tiny organisms live and most plants grow

Tornado- A violent, whirling wind that moves across the ground in a narrow path.

Trade wind- A belt of winds around Earth moving from high pressure zones toward the low pressure at the equator.

Translucent- Letting only some light through, so that objects on the other side can be seen clearly.

Transparent- Letting all light through, so that objects on the other side can be seen clearly.

Transpiration- The loss of water through a plant’s leaves.

Trench- A deep valley in the sea floor.

Tropical rain forest- A hot biome near the equator, with much rainfall and a wide variety of life

Tropism- A response of a plant toward or away from a stimulus.

Troposphere- The layer of the atmosphere closest to Earth’s surface.

Tube worm- Large worm-like animals that live near the sea-floor vents and obtain their food through bacterial chemosynthesis

Tundra- Large, treeless plain in the artic regions, where the ground is frozen all year.

Ultrasonic- Said of a sound with a frequency too high to be heard by humans.

Unbalanced forces- Forces that do not cancel each other out when acting together on a single object.

Updraft- An upward rush of heated air during a thunderstorm.

Vacuum- A space through which sound waves cannot travel because it contains no matter.

Valley breeze- A cool wind that blows up a mountain slope and replaces the slope’s rising Sun-warmed air.

Variable- One of the changes in a situation that may affect the outcome of an experiment.

Vascular- Containing plant tissue through which water moves up and food moves down.

Velocity- The speed and direction of a moving object.

Vertebrate- An animal that has a backbone.

Vibration- A back-and-forth motion.

Volume- 1. A measure of how much space an object takes up.

2. The loudness or softness of a sound.

Warm front- A front where warm air moves in over a cold air mass.

Water cycle- The continuous movement of water between Earth’s surface and the air, changing from liquid to gas to liquid.

Water table- The top of the water-filled spaces in the ground.

Water vapor- Water in the form of a gas.

Watershed- Area from which water is drained; region that contributes water to a river or river system.

Weather- What the lower atmosphere is like at any given place and time.

Weathering- Breaking down rocks into smaller pieces.

Weight- The force of gravity between Earth and an object.

Well- A hole dug below the water table that water seeps into.

Wind- air that moves horizontally.

Work- The use of force to move an object a certain distance.

Xylem- The tissue through which water and minerals move up through a plant.

Year- The time it takes a planet to orbit the Sun. A year is different from planet to planet.