environmental system

5. the envelope of gases surrounding the earth or another planet
6. the ratio of deaths to the population of a particular area or during a particular period of time
10. unusually warm ocean temperatures in the Equatorial Pacific
12. the action of clearing a wide area of trees
14. the weather conditions prevailing in an area in general or over a long period
16. a substance that pollutes something, especially water or the atmosphere
17. fog or haze combined with smoke and other atmospheric pollutants
18. a natural resource which will replenish to replace the portion depleted by usage and consumption
21. the specified extent or degree to which an area is or has been populated
22. capable of being decomposed by bacteria or other living organisms
24. an irregularly recurring upwelling of unusually cold water to the ocean surface along the western coast of South America
25. the number of people living in each unit of area

1. the total number of children that would be born
2. the process of making an area more urban
3. the regions of the surface, atmosphere, and hydrosphere of the earth
4. one of two types of biological and ecological succession of plant life
7. a colorless unstable toxic gas with a pungent odor and powerful oxidizing properties
8. any of a class of compounds of carbon, hydrogen, chlorine, and fluorine, typically gases used in refrigerants and aerosol propellants
9. a gradual increase in the overall temperature of the earth's atmosphere generally attributed to the greenhouse effect caused by increased levels of carbon dioxide
11. the action of coming to live permanently in a foreign country
13. ratio betw een the number of live-born births in the year and the average total population of that year
15. an area that was previously occupied by living things is disturbed, then re-colonized following the disturbance
19. the act of leaving one's own country to settle permanently in another
20. the factor that limits the reaction rate in any physiological process governed by many variables
23. a substance that pollutes something, especially water or the atmosphere