Ecosystems

3. process by which bacteria convert nitrates into nitrogen gas
4. process used by plants to capture light energy and use it to convert carbon dioxide and water into oxygen and carbohydrates
5. an organism that relies on other organisms for energy
7. chemical substance that an organism needs to sustain life
8. material made up of decaying bits of plant and animal material
9. network of complex interactions formed by the feeding relationships among the various organisms in an ecosystem
12. tiny algae found near the ocean's surface
14. the relative amounts of energy or matter contained within each trophic level
15. process in which elements, chemical compounds, and other forms of matter are passed from one organism to another and from on part of the biosphere to another
16. process in which chemical energy is used to produce carbohydrates
17. total amount of living tissue within a given trophic level
18. first producer of energy-rich compounds that are later used by other organisms

1. organism that gets energy from eating other animals
2. single essential nutrient that limits productivity in an ecosystem
6. a series of steps in an ecosystem in which organisms transfer energy
10. organism that can capture sunlight or chemicals as energy to make its own food
11. process of converting nitrogen gas into nitrogen compounds that plants can absorb and use
13. each step in a food chain or web