| A | B |
|---|
| acceleration | speeding up, slowing down, or changing direction |
| acid rain | water in the air reacts with certain chemicals for form acids that fall as rain causing chemical weathering |
| adaptation | any characteristic that helps an animal stay alive in its environment |
| air pressure | the weight of air pressing on all sides of an object |
| air temperature | the hotness or coldness of the air |
| anemometer | a tool used to measure wind speed |
| anther | the tip of a stalk on the stamen of a flower where pollen grains, which hold male part cells, are produced |
| atmosphere | gases surround the planet |
| atom | the smallest particle of a substance. Atoms contain electrons and protons. |
| axis | the imaginary line that goes through the center of the planet. Earth rotates or turns in its axis. |
| bacteria | single celled organisms that get energy by breaking down, or decomposing the remains of dead organisms. |
| balanced forces | equal forces acting on an object. |
| barometer | a tool used to measure air pressure |
| beaker | a container used to measure the volume of a liquid. |
| bedrock | the layer of rock beneath the subsoil |
| behavioral adaptation | the way in which an organism acts in response to its environment |
| bile | a chemical made by the liver that aids in digestion |
| biomass | energy released when plant materials and wastes, such as wood, peat, and dung, are burned |
| biome | ecosystems that have similar characteristics |
| cartilage | a tough and flexible tissue that covers and protects the ends of bones |
| cell | the smallest structure in an organism. All living organisms are made of this. |
| chemical energy | the energy stored in molecules |
| chemical reaction | when a substance changes chemically into another substance. |
| clorophyll | a green pigment in a plant that captures the energy in sunlight and gives leaves and stems their color. |
| cold front | the front edge of a mass of cold air. |
