1. DESERT BIOMES DESERT – AN AREA WHERE EVAPORATION EXCEEDS PRECIPITATION

2. DESERT BIOMES SPARSE, WIDELY SPACED, MOSTLY LOW VEGETATION PRECIPITATION IS LESS THAN 25 CM (10 INCHES) PER YEAR COVER ABOUT 30% OF THE EARTH’S LAND SITUATED MAINLY BETWEEN TROPICAL AND SUBTROPICAL REGIONS NORTH AND SOUTH OF THE EQUATOR

3. DESERT BIOMES LARGEST DESERTS ARE IN THE INTERIORS OF CONTINENTS AIR THAT HAS LOST ITS MOISTURE OVER THE TROPICS FALLS BACK TO EARTH DESERT WARMS DURING THE DAY QUICKLY LOSES HEAT AT NIGHT BECAUSE OF LITTLE VEGETATION AND MOISTURE AND SKIES ARE CLEAR

4. 3 TYPES OF DESERTS TROPICAL DESERTS – TEMPERATURES ARE USUALLY HIGH YEAR-ROUND LITTLE RAIN ONLY 1-2 MONTHS EACH YEAR TYPICALLY HAVE FEW PLANTS AND HARD, WINDBLOWN SURFACES STREWN WITH ROCKS AND SOME SAND SAHARA DESERT IN AFRICA

5. 3 TYPES OF DESERTS TEMPERATE DESERTS – DAYTIME TEMPERATURES ARE HIGH IN SUMMER AND LOW IN WINTER PRECIPITATION OF 8-12 INCHES EACH YEAR MAY – AUGUST HAS MOST RAIN

6. TEMPERATE DESERTS SPARSE VEGETATION – MOSTLY OF WIDELY DISPERSED, DROUGHT- RESISTANT SHRUBS AND CACTI OR OTHER SUCCULENTS ANIMALS ARE ADAPTED TO THE LACK OF WATER AND TEMPERATURE VARIATIONS MOJAVE DESERT IN S.W. CALIFORNIA

7. COLD DESERTS GOBI DESERT IN CHINA COLD WINTERS WARM OR HOT SUMMERS 7-13 INCHES OF RAIN EACH YEAR

8. SEMIDESERT SEMIARID ZONES BETWEEN DESERTS AND GRASSLANDS DOMINATED BY THORN TREES AND SHRUBS PLANTS ADAPTED TO LONG DRY SPELLS FOLLOWED BY BRIEF, SOMETIMES HEAVY RAINS

9. DESERT SURVIVAL PERENNIAL SHRUBS SUCH AS MESQUITE AND CREOSOTE PLANTS GROW DEEP ROOTS TO TAP INTO GROUNDWATER DROP LEAVES TO SURVIVE IN A DORMANT STATE DURING LONG, DRY SPELLS

10. HOW DO DESERT PLANTS AND ANIMALS SURVIVE? SOME DESERT PLANTS ARE EVERGREENS WITH WAX-COATED LEAVES THAT MINIMIZE TRANSPIRATION (CREOSOTE BUSH) DESERT PERENNIALS HAVE SMALL LEAVES OR NO LEAVES WHICH HELPS THEM CONSERVE WATER

11. DESERT SURVIVAL OTHER PERENNIALS SUCH AS PRICKLY PEAR AND SAGUARO CACTUS USE WIDELY SPREAD, SHALLOW ROOTS TO COLLECT WATER AFTER BRIEF SHOWERS AND STORE IT IN THEIR SPONGY TISSUES HAVE SHARP SPINES TO KEEP HERBIVORES FROM FEEDING ON THEIR WATER-STORING, FLESHY TISSUE

12. DESERT SURVIVAL SPINES ALSO REDUCE OVERHEATING BY REFLECTING SOME SUNLIGHT SPINES PROVIDE SHADE AND INSULATION CREOSOTE BUSH AND SAGEBRUSH SECRETE TOXINS INTO THE SOIL TO REDUCE COMPETITION FOR WATER AND NUTRIENTS FROM OTHER PLANT SPECIES

13. DESERT SURVIVAL MANY DESERT PLANTS ARE ANNUAL WILDFLOWERS AND GRASSES THAT STORE MUCH OF THEIR BIOMASS IN SEEDS DURING DRY PERIODS AND REMAIN INACTIVE UNTIL THEY GET ENOUGH WATER TO GERMINATE

14. DESERT SURVIVAL MOSSES AND LICHENS CAN TOLERATE EXTREMELY HIGH TEMPERATURES THEY DRY OUT COMPLETELY, BECOME DORMANT UNTIL THE NEXT RAINFALL

15. HOW DO DESERT ANIMALS SURVIVE? MOST DESERT ANIMALS ARE SMALL SURVIVE THE HEAT AND REDUCE WATER LOSS BY EVAPORATIVE COOLING STAY IN COOL AREAS BY DAY COME OUT AT NIGHT OR EARLY MORNING

16. HOW DO DESERT ANIMALS SURVIVE? PHYSICAL ADAPTATIONS: INSECTS & REPTILES HAVE THICK OUTER COVERINGS TO MINIMIZE WATER LOSS THROUGH EVAPORATION REDUCE WATER LOSS BY HAVING DRIED FECES & EXCRETING A DRIED CONCENTRATE OF URINE

17. HOW DO DESERT ANIMALS SURVIVE? SPIDERS AND INSECTS GET THEIR WATER FROM THE DEW OR FROM THE FOOD THEY EAT SOME DESERT ANIMALS BECOME DORMANT DURING PERIODS OF EXTREME HEAT OR DROUGHT AND ARE ACTIVE ONLY DURING THE COOLER MONTHS OF THE YEAR

18. WHAT IMPACTS DO HUMAN ACTIVITIES HAVE ON DESERT ECOSYSTEMS? RAPID GROWTH OF LARGE DESERT CITIES IRRIGATION OF SOME DESERT AREAS TO GROW CROPS – AS THE WATER EVAPORATES, SALTS MAY ACCUMULATE IN TH SOIL AND LIMIT CROP PRODUCTIVITY DEPLETION OF UNDERGROUND WATER

19. HUMAN IMPACTS ON DESERTS DISRUPTION AND POLLUTION BY EXTRACTION OF OIL, MINERALS AND BUILDING MATERIALS SUCH AS ROAD STONE AND SAND USE OF REMOTE DESERT AREAS AS SITES FOR STORAGE OF TOXIC AND RADIOACTIVE WASTES, UNDERGROUND TESTING OF NUCLEAR WEAPONS AND MILITARY MANEUVERS

20. HUMAN IMPACTS ON DESERTS DESERTS TAKE A LONG TIME TO RECOVER FROM DISTURBANCES BECAUSE: SLOW PLANT GROWTH LOW SPECIES DIVERSITY SLOW NUTRIENT CYCLING WATER SHORTAGES

21. HUMAN IMPACTS ON DESERTS THE LARGEST AND MOST UNTAPPED RESOURCE OF DESERTS IS THE ABUNDANT SUNLIGHT IF SOLAR ENERGY IS USED MORE IN THE NEXT 50 YEARS, LARGE AREAS OF DESERTS WILL BE COVERED WITH SOLAR COLLECTORS AND SOLAR CELLS WHICH WILL DISRUPT THE DESERT ECOSYSTEMS