science

3. cycle A biogeochemical process through which nitrogen is converted into various forms, constantly passing from the atmosphere to organisms and back.
4. profile A vertical cross-section of the soil, made of layers running parallel to the surface.
6. cycle The continuous circulation of water in the Earth-atmosphere system.
10. The process in which deep, cold water rises toward the surface.
11. resource A resource that can be replenished naturally over time.
12. Water released from clouds in the form of rain, freezing rain, sleet, snow, or hail.
13. key A printed or computerized device that aids in the identification of biological entities.

1. equilibrium A population in which the allelic frequencies of its gene pool do not change through successive generations.
2. The study of organisms and how they interact with their environment.
5. resource Natural substances that are not replenished at the speed at which they are consumed.
7. cycle The processes through which the three main rock types transform from one into another.
8. energy The radiation from the Sun capable of producing heat, causing chemical reactions, or generating electricity.
9. cycle The movement of particles through a substance, transporting heat from hotter to cooler areas.