Science

2. a person, company, or country that makes, grows, or supplies goods or commodities for sale
4. an animal that feeds on plants
8. the principle by which the total value of a physical quantity or parameter remains constant in a system which is not subject to external influence
11. the process of change by which an organism or species becomes better suited to its environment
12. An energy pyramid is a graphical model of energy flow in a community
14. an animal that is hunted and killed by another for food
16. a person who purchases goods and services for personal use
18. relating to or resulting from living organisms
19. a series of organisms each dependent on the next as a source of food.
20. an animal that feeds on other animals
21. a series of events that are regularly repeated in the same order

1. an organism which lives in or on another organism (its host) and benefits by deriving nutrients at the other's expense
3. able to be maintained at a certain rate or level
5. the surroundings or conditions in which a person, animal, or plant lives or operates
6. an animal or person that eats a variety of food of both plant and animal origin
7. the strength and vitality required for sustained physical or mental activity
9. a substance that provides nourishment essential for the maintenance of life and for growth
10. the dependence of two or more people or things on each other
13. physical rather than biological; not derived from living organisms
15. an animal that naturally preys on others
17. a system of interlocking and interdependent food chains