BIO 109 Home
Questions | Answers

1. A place where potential evapotranspiration is significantly higher than precipitation.

2. Index of Aridity. The index is 5 in Tucson, AZ.

3. Radiation (greater sunlight intensity = more), Temperature (higher = more), Wind Speed (higher = more), Plant Activity (higher = more), and Relative Humidity (lower = more).

4. Desert (precipitation; indicator species) below:

  • Great Basin Desert
    • most of Nevada, southern Oregon and Idaho
    • precipitation year-round, mostly snow
    • big sagebrush
  • Mojave Desert
    • southern Nevada (Las Vegas) and southeast California (Death Valley)
    • precipitation mostly winter rain
    • joshua tree
  • Sonoran Desert
    • southern Arizona and California and northwestern Mexico
    • precipitation winter and summer rain
    • columnar cacti and trees in Fabaceae family
  • Chihuahuan Desert
    • southern New Mexico, western Texas and north-central Mexico
    • precipitation mostly summer rain
    • tarbush

5. A series of biotic communities occurs as one goes up mountains. These biotic communities (e.g., Ponderosa Pine forest) are isolated from other such communities by the distance and inhospitable habitat separating mountain ranges. These isolated mountains and their biotic communities are referred to as sky islands.

6. Habitat occurring beside permanent and temporary streams (dry washes) and other sources of water.

7. These areas occupying less than 2% of the area but 70% of the threatened and endangered vertebrates in Arizona depend on riparian areas. Riparian areas are being lost for a variety of reasons, especially lowering the water table to supply agriculture and cities.

8. Elevation and Latitude

9. Hot air rises, cold air descends.

10. Rising air cools, descending air heats (that is why it is hotter in Tucson than on Mt. Lemmon).

11. Warm air holds more water potentially.

12. Specific humidity is the actual amount of water in the air (water vapor content).
Relative humidity (RH) is the actual amount of water in the air (water vapor content) as a percentage of the maximum amount of water the air could contain at that temperature (water vapor capacity).

13. When air cools, relative humidity increases. When air heats, relative humidity decreases.

14. When air rises, it cools, so relative humidity increases. When air descends, it heats, so relative humidity decreases.

15. When air rises, it is more likely to rain. When air descends, it is less likely to rain.

16. The temperature at which the relative humidity of the air becomes 100%.

17. More likely.

18. From the Pacific in winter, and from the Gulf of California and the Gulf of Mexico in summer.

19. Three causes of precipitation:

  • Convection: the sun heats the ground, the ground heats the air, the air rises, cools, relative humidity increases, chance of rain increases.
  • Orographic: wind blows air up the side of a mountain, the air cools, relative humidity increases, chance of rain increases.
  • Frontal: air rises as it is pushed up the leading edge of a cold front, the air cools, relative humidity increases, chance of rain increases.