Ecosystem

2. process by which bacteria convert nitrates into nitrogen gas.
4. organism that obtains food by consuming other living things; also called a consumer.
5. total amount of living tissue within a given trophic level.
9. single essential nutrient that limits productivity in an ecosystem.
10. network of complex interactions formed by the feeding relationships among the various organisms in an ecosystems.
12. illustration of the relative amounts of energy or matter contained within each trophic level in a given food chain of food web.
14. photosynthetic algae found near the surface of the ocean.
16. process used by plants and other autotrophs to capture light energy and use it to power chemical reactions that convert carbon dioxide and water into oxygen and energy-rich carbohydrates such as sugars and starches.
18. organism that relies on other organisms for its energy and food supply; also called a heterotroph.

1. first producer of energy-rich compounds that are later used by other organisms.
3. Process in which elements, chemical compounds, and other forms of matter are passed from one organism to another and from one part of the biosphere to another.
6. organism that is able to capture energy form sunlight or chemicals and use it to produce its own food from inorganic compounds; also called a producer.
7. a series of steps in a ecosystem in which organisms transfer energy by eating and being eaten.
8. process of converting nitrogen gas into nitrogen compounds that plants can absorb and use.
11. material made up of decaying bits of plant and animal material.
13. process in which chemical energy is used to produce carbohydrates.
15. each step in a food chain of food web.
17. chemical substance that an organism needs to sustain life.