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 adaptation | A characteristic that enables a living thing to survive in its environment. |
| chlorophyll | A green chemical in plant cells that allows plants to use the Sun's energy for making food. |
| conifer | evergreen, cone-bearing tree |
| deciduous | a name for trees which lose their leaves every year |
| evergreen | a tree that does not lose its leaves in the winter, and stays green all year round |
| fungi | the familiar molds and mushrooms which help decompose dead organisms |
| organism | Any living thing |
| parasitism | the relation between two different kinds of organisms in which one receives benefits from the other by causing damage to it (usually not fatal damage) |
| photosynthesis | process by which plants use the sun's energy to convert water and carbon dioxide into sugars |
| predator | animal that hunts and eats other animals |
| transpiration | loss of water from a plant through its leaves |
| abiotic factor | all the non living things in an ecosystem |
| biome | A large region characterized by a specific type of climate and certain types of plants and animals communities |
| biotic factor | all the living things in an ecosystem |
| carbon cycle | the movement of carbon from the nonliving environment into living things and back |
| carnivore | organism that obtains energy by eating animals |
| carrying capacity | The largest population that an area can support. |
| climax community | The last or final stage of succession in a community |
| commensalism | a symbiotic relationship in which one member is benefited and the second is neither harmed nor benefited |
| community | all of the populations of different species that live and interact in an area |
| consumer | an organism that obtains energy by feeding on other organisms |
| decomposer | organism that breaks down the wastes or remains of other organisms |
| desert | A type of biome characterized by low moisture levels and infrequent and unpredictable precipitation. Daily and seasonal temperatures fluctuate widely |
| ecological succession | the change in an ecosystem that happens when one community replaces another as a result of changing abiotic and biotic factors |
| ecology | The study of how living things interact with each other and their environment |
| food web | network of all the food chains in an ecosystem |
| habitat | the place where an organism lives |
| herbivore | organism that obtains energy by eating only plants |
| host | an organism on which a parasite lives |
| humus | dark soil that contains decaying remains of plants and animals |
| limiting factor | any factor in the environment that limits the size of a population |
| mutualism | symbiotic relationship in which both species benefit from the relationship |
| niche | organism's role, or job, in its habitat |
| nitrogen cycle | The movement of nitrogen gas from compounds in the soil to the air. |
| omnivore | an animal that eats both plants and animals |
| parasite | an organism that lives on or in a host and causes harm to the host |
| permafrost | layer of permanently frozen subsoil in the tundra |
| pioneer species | the first species to populate an area |
| population | group of the same kind of organism living in a certain place |
| prey | animal hunted or caught for food |
| producer | an organism that makes its own food |
| scavenger | a carnivore that feeds on the bodies of dead organisms |
| symbiosis | Any relationship in which two species live closely together |
| conserve | to save by using carefully |
| crop rotation | the system of growing a different crop in a field each year to preserve the fertility of the land |
| crust | the outer layer of the Earth |
| delta | flat, low-lying land built up from soil carried downstream by a river and deposited at its mouth |
| density | the amount of matter in a given space |
| deposition | process in which sediment is laid down in new locations |
| elevation | the height of land above sea level |
| erosion | the wearing away of soil and rock particles by waves, wind, running water, or glaciers |
| flood plain | flat land near the edges of rivers formed by mud and silt deposited by floods |
| fossil fuel | a nonrenewable energy resource formed from the remains of organisms that lived long ago; examples include oil, coal, and natural gas |
| geologist | a scientist who studies the earth |
| groundwater | water held in rocks and soil below the surface |
| meander | a looplike bend in the course of a river |
| nonrenewable resource | a resource that cannot be replaced |
| ozone layer | a layer of ozone gas in the atmoshpere that screens out much of the Sun's UV rays |
| pollution | Release of harmful materials into the environment |
| reservoir | a storage area for fresh water supplies |
| run off | water from rain or melted snow that flows along Erath's surface into bodies of water |
| sediment | particles of rock and soil that are picked up and moved by erosion and deposition |
| strip farming | Planting different kinds of crops in alternating strips along land contours; when one crop is harvested, the other crop remains to protect the soil and prevent water from running straight down a hill. |
| water cycle | the continuous cycle of the transfer of water through an ecosystem, which involves evaporation, transpiration, condensation, and precipitation |
| watershed | the area of land that is drained by a river |
| weathering | The breaking down of rocks and other materials on the Earth's surface. |
| air pressure | the weight of air pressing down on an area |
| anemometer | measures wind speed |
| barometer | an instrument used to measure air pressure |
| cirrus cloud | A high-altitude cloud with a featherlike shape, made of ice crystals |
| climate | the average weather conditions in an area over a long period of time |
| cold front | the front edge of a moving mass of cold air that pushes beneath a warmer air mass like a wedge |
| Coriolis effect | The way Earth's rotation makes winds in the Northern Hemisphere curve to the right and winds in the Southern Hemisphere curve to the left. |
| cumulus cloud | big, puffy clouds that have fair weather. is made when warm air rises (generally low altitude) |
| downdraft | a rapidly moving current of cool air that flows downward in a thunderstorm |
| evaporation | the process by which a liquid changes into a gas |
| fog | droplets of water vapor suspended in the air near the ground |
| front | (meteorology) the atmospheric phenomenon created at the boundary between two different air masses |
| high pressure system | generally brings clear skies and calm air or gentle breezes |
| humidity | amount of water vapor in the air |
| hurricane | a severe tropical cyclone usually with heavy rains and winds moving a 73-136 knots (12 on the Beaufort scale) |
| inertia | the tendency of an object to resist any change in its motion. |
| insolation | The solar radiation (energy from the sun) that reaches Earth. |
| land breeze | movement of air from land to sea at night, created when cooler, denser air from the land forces up warmer air over the sea |
| low pressure system | Pressure system with counterclockwise and inward winds that brings cloudiness and stormy weather |
| mountain breeze | this dense, cool air then flows downward along the surface toward valleys and lower ground as a gentle wind |
| precipitation | the falling to earth of any form of water (rain or snow or hail or sleet or mist) |
| sea breeze | movement of air from sea to land during the day when cooler air from above the water moves over the land, forcing the heated, less dense air above the land to rise |
| stratus cloud | A flat, low-lying cloud that covers sky like a blanket; can produce rain or snow |
| troposphere | the layer closest to Earth, where almost all weather occurs; the thinnest layer |
| water vapor | Water in the form of gas. |
| condensation | the process by which a gas changes to a liquid |
| kinetic energy | the energy an object has because of its motion |
| potential energy | energy stored in an object due to its position |
| acceleration | A change in speed or direction |
| action | the force one object applied to a second object |
| balanced forces | equal forces acting on an object in opposite directions |
| effort arm | the part of a lever on which an effort force is applied |
| force | a push or pull exerted on an object |
| friction | a force that opposes the motion of objects that touch as they move past each other |
| fulcrum | the fixed point around which a lever pivots |
| gravity | the force that pulls objects toward earth |
| lever | a simple machine consisting of a rigid object that pivots about a fixed point |
| reaction | (mechanics) the equal and opposite force that is produced when any force is applied to a body |
| resistance arm | The part of a lever that applies a force to an object |
| speed | the distance an object travels in one unit of time |
| velocity | the speed of an object in a particular direction |
| work | the transfer of energy |
| ecosystem | all the living and nonliving things that interact in an area |
| estuary | A habitat in which the fresh water of a river meets the salt water of the ocean. |
| food chain | A diagram which shows the flow of energy from organism to organism. |
| primary consumer | an herbivore; an organism in the trophic level of an ecosystem that eats plants or algae. |
| secondary consumer | A member of the trophic level of an ecosystem consisting of carnivores that eat herbivores |
| tertiary consumer | a member of the trophic level of an ecosystem consisting of carnivores that eat mainly other carnivores. |
| deforestation | The process of stripping the land of its trees |
| abrasion | The grinding away of rock by other rock particles carried in water, ice, or wind |
| valley | Lower land between hills or mountains |
| canyon | a deep valley with steep sides often carved from the earth by a river |
| tributary | a stream or river that flows into a larger river |
| slope | A hillside. A gradient, inclined surface |
| dam | a structure built across a river to control the river's flow |
| weather | The condition of Earth's atmosphere at a particular time and place. |
| cloud | a collection of small water droplets or ice crystals suspended in the air, which forms when the air is cooled and condensation occurs |
| nimbus | cloud from which rain is falling |
| air mass | a huge body of air having relatively uniform temperature and humidity and covering hundreds or thousands of square kilos |
| meteorologist | A scientist who studies weather |
| valley breeze | the movement of air created by warm air rising and flowing up the slope of the mountain |
| position | The location of an object |
| energy | the ability to do work |
| machine | a device that makes doing work easier |
| unbalanced force | result when some forces acting on an object are stronger than others, producing motion |
| momentum | the product of a body's mass and its velocity |
| simple machine | a machine with few or no moving parts |