AIM: SWBAT describe the desert /xeric shrubland biome

1. AIM: SWBAT describe the desert /xeric shrubland biome Please Do Now: What is an osmoregulator and why is that relevant to the study of estuaries?

2. Agenda • Do Now • Introduce Deserts • Desert Video • Talk about paper

3. Deserts Deserts are found on every continent, usually found on the leeward (downwind) side of mountain ranges

4. Brief description • Do on your own

5. Climate (Precipitation and Temperature) • Deserts are defined by their extremely low precipitation, less than 16 in a year • Deserts can exist in a wide range of temperatures (there are deserts in the Arctic and on Antarctica), but most are quite warm • There is usually a huge swing in temperatures from the daytime to the night in deserts

6. Soil • The soil in deserts is very low in organic content, usually high in salts • The soil is also mostly made up of sand and rocks, as smaller particles get blown away by winds without vegetation to hold them down • Bad for plants

7. Plant Life • Cactti, succulent plants, bushes, clumps of grasses • No trees

8. Plant Adaptations • Plants are highly efficient at acquiring, using, and storing water • Thick waxy layer (cuticle) to prevent water loss, small leaves, CAM photosynthesis, • Spines and thorns to protect from water-stealing animals • Huge roots to take advantage of rare rainfall

9. Seasonal Variation • Is low in most deserts, other than cold ones. Some have periods where the rare rains are more likely • The sporadic rainfalls are the important source of climatic variation, life has evolved to take advantage of brief wet spells

10. Limiting Factors and Adaptations • On your own (easy)

11. Other Physical Factors • Oases or exotic rivers sometimes exist in deserts, and are obviously a magnet for wildlife • When rainfall does occur, it is often heavy, and flash floods spring up in normally dry channels called arroyos

12. Deserts continued Please Do Now: Fill in the limiting factors section for the desert

13. Biodiversity and Productivity • Productivity is very low ( 3), because of a lack of water • Surprisingly, biodiversity in deserts is not as low as you would expect given the low productivity, but still pretty sparse; call it below average diversity

14. Succession • Competition is pretty low in the desert compared to other ecosystems, so succession is not very obvious • Creosote bushes, and other shrubs with slow growth, k-select tendencies are the climax community

15. Keystone Species • Cacti act like the “trees” of the ecosystem in some deserts, providing a microhabitat for all sorts of organisms

16. Video time We will discuss after video You look for during the video Trophic pyramid, example organisms, limiting factors and adaptations, famous examples • Migrations, symbioses, mating, conservation

17. Aim: Deserts continued Please Do Now: Why do you think that reptiles like snakes and lizards are so common in the desert, while amphibians are so rare?

18. Migrations • With low productivity, the larger animals that do live in the desert have to cover huge ranges to find enough food, but large scale migrations are uncommon since population densities are so low

19. Mating Systems • Lots of life emerges after the rare sudden rain, and does most of their life cycle in this time, which lends itself to promiscuous mating

20. Symbioses • Commensalism: young creosote bushes, often the dominant vegetation, need the shade of larger established bushes to survive to maturity • Creosote bushes and cacti are used by all kinds of animals for nesting sites

21. Conservation • Historically, deserts have been well preserved due to their low value to humans • Solar energy farms, as well as oil and mineral extraction are now competing with the conservation of deserts as wild spaces

22. Vocab • Xeric: having to do with deserts • Xerophyte: a desert plant • Succulent: plant that stores water in leaves • Xerocole, an animal that can go extended periods without water