Crossword Puzzle Chapter 4

3. total ammount of living tissue within a given tropic level.
6. process by which bacteria convert nitrates into nitrogen gas.
7. each step in a food chain or food web.
9. process in which elements, chemical compounds, and other forms of matter are passed form one organism to another and from part of the biosphere to another.
12. a series of steps in an ecosystem in which organisms transfer energy by eating and being eaten.
14. single essential nutrient that limits productivity in an ecosystem.
15. network of complex interactions formed by the feeding relationships among the various organisms in an ecosystem.
16. organism that obtains food by consuming other living things; also called a consumer.
17. process used by plants and other autotrophs to capture lights 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. chemical substance that an organism needs to sustain life.

1. first producer of energy-rich compounds that are later used by other organisms.
2. illustration of the relative amounts of energy or matter contained within each tropic level in a given food chain or food web.
4. process of converting nitrogen gas into nitrogen compounds that plants can absorb and use.
5. organisms that relies on other organisms for its energy and food supply; also called a heterotroph.
8. process in which chemical energy is used to produce carbohydrates.
10. material made up of decaying bits of plant and animal material.
11. photosynthetic algae found near the surface of the ocean.
13. 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.