Nature

3. the process in which energy is emitted as particles or waves
4. extreme and general scarcity of food, as in a country or a large geographical area.
6. the gaseous envelope surrounding the earth; the air
9. falling products of condensation in the atmosphere, as rain, snow,or hail.
14. the introduction of harmful substances or products into the environment:
15. the process by which the surface of the earth is worn away by the action of water, glaciers, winds, waves, etc.
16. the air, water, minerals, organisms, and all other external factors surrounding and affecting a given organism at any time
17. a sudden and widespread disaster
18. the composite or generally prevailing weather conditions of a region, as temperature, air pressure, humidity, precipitation, sunshine, cloudiness, and winds, throughout the year, averaged over a series of years.
19. a state of equilibrium or equipoise

1. capable of decaying through the action of living organisms
2. an animal, especially a nonhuman
5. the act or fact of urbanizing, or taking on the characteristics of a city
7. no longer in existence; that has ended or died out:
8. diversity among and within plant and animal species in an environment
10. a period of dry weather, especially a long one that is injurious to crops
11. the part of the earth's crust, waters, and atmosphere that supports life
12. a system, or a group of interconnected elements, formed by the interaction of a community of organisms with their environment
13. an air mass of high temperature covering an extended area and moving relatively slowly.
16. the branch of biology dealing with the relations and interactions between organisms and their environment, including other organisms.