Across
- 4. Replaceable by natural means in a short period of time.
- 7. Something that is needed by organisms and is not infinite in its abundance in the environment; if it is exhausted, then the organisms that need it cannot survive.
- 8. The layer of gas surrounding a planet that is held in place by gravity.
- 9. A source or supply of energy that can be used to generate electric power to meet people's needs.
Down
- 1. Any natural process that happens to Earth's surface, such as weathering, erosion, or plate tectonics.
- 2. Not replaceable by natural means within a short period of time.
- 3. Resources that exist in the environment without human intervention.
- 5. The sum of all living matter on Earth.
- 6. Water that collects in cracks and pores in underground soil and rock layers.