Crossword Puzzle

3. The process of increasing in size.
5. The conversion of a vapor or gas to a liquid.
7. Type of symbiotic interaction in which one species benefits while the other is not hurt or aided in any way.
8. Power derived from the utilization of physical or chemical resources, especially to provide light and heat or to work machines.
11. The preying of one animal on others.
13. A disorder of structure or function in a human, animal, or plant, especially one that produces specific symptoms or that affects a specific location and is not simply a direct result of physical injury.
15. Rain, snow, sleet, or hail that falls to or condenses on the ground.
18. A process that reduces nitrate and nitrite to gaseous forms of nitrogen.
19. The interaction between two different organisms living in close physical association.
20. Attraction between unlike molecules.
21. A measure of the quantity of some physical property (usually mass) per unit length, area, or volume.

1. The relationship between two species of plants or animals in which one benefits at the expense of the other, sometimes without killing the host organism.
2. A series of events that are regularly repeated in the same order.
4. All the variety of life that can be found on Earth.
6. The process by which a liquid turns into a gas.
9. (of an increase) becoming more and more rapid.
10. When a population's growth rate decreases as population size approaches a maximum imposed by limited resources.
11. A substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource.
12. Attraction for other molecules of the same kind.
14. Any nutritious substance that people or animals eat or drink or that plants absorb to maintain life and growth.
16. When two organisms “work together” each benefiting from the relationship.
17. The quantity of rain falling within a given area in a given time.