I.        Description and general information (such as location, why it is named what it

          is, what is the dominant plant life, etc.)

The Tropical Deserts of the southern Sahara in Africa have high year round temperatures and little rain fall. The tropical desert is an environment of extremes: it is the driest and hottest place on earth.  The dry conditions is caused by the yearly influence of sub-tropical high pressure. These deserts are usually found in the interiors of continents in the subtropics (between 15 and 30 degrees latitude). The flora of the tropical deserts include shallow root plants, shrubs, and many succulents. Animals that thrive in these deserts are rodents, lizards, birds, and many types of insects. Tropical deserts can be found in South America along the Pacific Coast, northern Africa (the Sahara), and Central Australia.

Deserts are, to many people, rather deserted. Hence the name "desert". One can avoid confusing "desert" with "dessert" by remembering that "dessert" has the letter "s" twice while "desert" has the letter only once, and "dessert" is twice as good as "desert". Which would you rather have?

II.       Climate, especially rainfall (discuss - give more than just a number) and 

           temperature (discuss - give more than just a number and be sure to include

           the climate zone) 

Rainfall is infrequent, averaging less than 100 cm a year. Average annual temperatures are above 10 degrees Celsius. Most subtropical deserts are near the equator (with exception of the deserts in Australia) which the explains the very hot, dry conditions.

III.      Define Biomass and Productivity.  Provide a discussion of the biome's rank in

           productivity to include its soil quality.

Out of all the biomes, the desert has by far the lowest productivity. In order to be productive and have a lot of living material standing around (biomass), an ecosystem has to have 4 basic necessities for plant life to thrive:

1. Sunlight

2. Nutrients

3. Warm temperatures

4. Water

If plant life is abundant, then consequently animal life will be abundant. The desert has a lot of sun which makes the soil very dry. Because the soil is dry, nutrients are still present in the soil which makes it more nutritious then soils in say the Tropical Rain Forest. The biggest problem with desert is, of course, the lack of water. Many plants have adapted new methods for surviving known as CAM photosynthesis (explained in VI.).

IV.     Discuss threats to the biome.

• Development
• Water supplied by irrigation projects have introduced sod which contributed to pollen (allergies)
• Mining can lead to salinization of soil
• Grazing animals
• Tumbleweed is a non-native invasive species
• Off-Road Vehicle use
• Firewood gathering can lead to desertification

V.      Choose 1 animal that lives in the biome and describe how it is adapted to live  

          there.

Animals in the desert must survive in a hostile environment. Intense heat, searing sun, and lack of water are just a few of the challenges facing desert animals. Animals that live in the hot desert have many adaptations. Some animals never drink, but get their water from seeds (some can contain up to 50% water) and plants. Many animals are nocturnal, sleeping during the hot day and only coming out at night to eat and hunt. Some animals rarely spend any time above ground. Spadefoot toads spend nine months of every year underground. A mammal that lives in the desert, the Fat Sand Rat, eats an abundant amount of food and stores the food as a thick layer of fat. It then lives of this fat when there is a shortage of food.

VI.     Choose 1 plant that lives in the biome and describe how it is adapted to live

          there.

Desert plants have two main adaptations that have allowed them to live in these harsh dry environments: the ability to control the collection and storage of water, and features that reduce water loss. One classic example of a plant that has these characteristics is the C4 (CAM) Plants. These plants fix carbon dioxide (CO₂) during the night, storing it as the four carbon acid malate. The CO₂ is released during the day and concentrated into an enzyme called RuBisCO. The CAM pathway allows stomata to remain shut during the day and open during the night to prevent water loss.  These plants also have a thick, waxy outer coating called a cuticle to prevent overtranspiration.