Energy, Producers and Consumers

3. Network of complex interactions formed by the feeding relationships among the various organisms in an ecosystem.
6. Photosynthetic algae found near the surface of the ocean.
9. First producer of energy-rich compounds that are later used by other organisms.
10. Small pieces of dead or decaying plant or animal remains.
12. Illustration of the relative amounts of energy or matter contained within each trophic level in a food chain or food web.
13. A series of steps in an ecosystem in which organisms transfer energy by eating and being eaten.
16. Organism that relies on other organisms for its energy and food supply; also called a heterotroph.
17. 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. The total mass of living tissue within a trophic level.

1. Single essential nutrient that limits productivity in an ecosystem.
2. 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.
4. Organism that obtains food by consuming other living things; also called a consumer.
5. Each step in a food chain or food web.
7. Chemical substance that an organism needs to sustain life.
8. Process in which chemical energy is used to produce carbohydrates.
11. Process of converting nitrogen gas into nitrogen compounds that plants can absorb and use.
14. Organism that is able to capture energy from sunlight or chemicals and use it to produce its own food from inorganic compounds; also called a producer.
15. Process by which soil bacteria convert nitrates into nitrogen gas.