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2E1 Group 4: Desert

Page history last edited by 2E1group4 11 years, 5 months ago

Team members


Names / Roles:

  •       (Leader)
  •                                    (Writer)
  •         (Research)
  •              (Research)
  •                                              (Research) 




A desert is a landscape or region that receives very little precipitation. Deserts can be defined as areas that receive an average annual precipitation of less than 250 mm (10 in),for as areas in which more water is lost than falls as precipitation. IIn the Thornthwaite climate classification system, deserts would be classified as arid megathermal climates.


Physical Factors




Moisture of all kinds...rain, sweat, dew, pools, lakes, sap, breath evaporates very quickly in the hot, dry desert air.

  • Rain soaks into the sand and disappears in minutes or only hours.

    Swimsuits dry in minutes

  • Throats parch and leaves shrivel
  • The heat of the ground and the drying wind take most moisture before it can be used by plants and animals
  • Sometimes, rain evaporates before it even hits the ground.

Desert plants and animals conserve water. Because it is so scarce, most desert animals and plants are extremely thrifty in their use of water, and sometimes use very similar strategies to survive. The desert tortoise and barrel cactus are both water savers, with built-in storage capabilities. They spend their stores in drought conditions. Spadefoot toads and wildflowers lie dormant most of the time, then accelerate their life cycles to take advantage of rain. Both need just enough rain to make sure the next generation matures, and both go from egg or seed to adult in a matter of days. Coyotes dig deep "wells", a strategy similar to the mesquite tree, whose roots may drive 150 feet deep.



Mineral resources


Some mineral deposits are formed, improved, or preserved by geologic processes that occur in arid lands as a consequence of climate. Ground water leaches ore minerals and redeposits them in zones near the water table. This leaching process concentrates these minerals as ore that can be mined.

Evaporation in arid lands enriches mineral accumulation in their lakes. Lake beds known as Playas may be sources of mineral deposits formed by evaporation. Water evaporating in closed basins precipitates minerals such as gypsum, salts (including sodium nitrate and sodium chloride), and borates. The minerals formed in these evaporate deposits depend on the composition and temperature of the saline waters at the time of deposition.




Micronutrients, in addition to macronutrients, are necessary for all plant life, although micronutrients are required in much smaller amounts. There are 10 micronutrients that plants need. However, only four are regularly deficient from highly alkaline desert soils: Iron, zinc, copper and manganese.

Iron (Fe) is involved with the production of chlorophyll. Plants grown in alkaline soil (so prevalent in desert soils) can develop iron deficiencies, especially if they are sensitive. Yellowing of leaves is one symptom of iron deficiency or iron chlorosis.

Zinc (Zn) is necessary for energy production, the making of protein, and regulation of growth in plants. High pH levels prevent plants from zinc intake. Additionally, high levels of phosphorus in the soil can cause zinc deficiency.

Copper (Cu) is necessary for plants to metabolize carbohydrates. Copper deficiency symptoms are yellowing of leaves, stem and twig dieback, stunted growth and pale green, easily withered leaves.



The ph level of the desert is usually 7.5 and above.




Deserts are characterized by extreme heat and dryness, very hot in the daytime and chilly or even cold at night.

The average temperature is 100 degrees during the day and below 50 degrees at night.

The wettest desert does not get more than 10 inches of rain a year.

Deserts often get their names like "Death Valley" or "The place from where there is no return" because of their extreme conditions.

Classification of Living Organisms


A food chain is sequence of plants, herbivores and carnivores, through which energy and materials move within an ecosystem. Food chains are usually short and not more than three or four links. They usually consist of a producer, a consumer and a predator, with the predator being the top of the food chain. The top of the desert food chain does eventually die though, and is returned to the bottom of the chain as nutrients by decomposers.



Primary Producers

Food chains are divided into nutritional or trophic levels. The first trophic, or lowest level, is occupied by the primary producers, plants.

Plants produce energy from photosynthesis. Plants produce energy to use for survival, growth and to store when production resources are not available.


Primary Consumers

Primary consumers are the animals that eat the plants. These animals, including insects, occupy the second trophic level. Energy is transferred from the plants to the consumers as food for the consumers. Although primary consumers are for the most part herbivorous, this is where the line between the primary and secondary consumers begins to blur.

In a mammal, such as the desert pocket mouse, food is consumed and converted to energy. The mouse, being warm-blooded, uses this energy in several ways.


4th Trophic Level:

Tertiary Consumers


These are high level consumers, carnivores that will eat other carnivores.




3rd Trophic Level:

Secondary Consumers

Small Carnivores

The predators are the secondary consumers. They occupy the third trophic level. Again we see cold-blooded animals, such as snakes, insect-eating lizards, and tarantulas. In the harsher desert environments, they are the top predators.




2nd Trophic Level:

Primary Consumers


These animals are usually small and eat little. Many are insects, or reptiles, who are cold blooded and who use less energy to maintain their bodies than mammals and birds do.




Examples of primary consumers: Ants and other insects, rats and mice, some    reptiles the largest of which are the tortoise and chuckwalla.

1st Trophic Level:

Primary Producers


These are plants that make food through photosynthesis.




Examples of primary consumers:

Trees, shrubs, cactus, wildflowers, grasses






1. The mouse receives stored energy by eating food.

2. The mouse's metabolism converts stored energy from the food to available energy for its survival. To survive the mouse needs to grow, acquire more food, escape predators, etc). Some energy is lost to heat, but this heat can be helpful to keep the mouse's body at a normal temperature in cold weather.

3. Some energy is lost in the production and passing of waste as unprocessed nutrients.

4. About 90% of the energy the mouse converts from food is stored and used by the mouse. The remaining 10% is available for consumption by predators at the next trophic level.










A Food Pyramid in the Hot Desert Biome



Food Web 




Interrelationship in Ecosystem

Predator-prey relationship

 In ecology, predation describes a biological interaction where a predator (an organism that is hunting) feeds on its prey, the organism that is attacked. Predators may or may not kill their prey prior to feeding on them, but the act of predation always results in the death of the prey. The other main category of consumption is detritivory, the consumption of dead organic material (detritus). It can at times be difficult to separate the two feeding behaviors, for example where parasitic species prey on a host organism and then lay their eggs on it for their offspring to feed on its decaying corpse. The key characteristic of predation however is the predator's direct impact on the prey population. On the other hand, detritivores simply eat what is available and have no direct impact on the "donor" organism(s). (A juvenile Red-tailed Hawk eating a California Vole)


Parasitism is a type of symbiotic relationship between two different organisms where one organism, the parasite, takes from the host, sometimes for a prolonged time. In general, parasites are much smaller than their hosts, show a high degree of specialization for their mode of life, and reproduce more quickly and in greater numbers than their hosts. Classic examples of parasitism include interactions between vertebrate hosts and diverse animals such as tapeworms, flukes, the Plasmodium species, and scabs. Parasitism is differentiated from parasitoidism, a relationship in which the host is always killed by the parasite such as moths, butterflies, ants, flies and others.(Mites parasitising a harvestman)




Mutualism is a biological interaction between two organisms, where each individual derives a fitness benefit, for example increased survivorship. Similar interactions within a species are known as co-operation. It can be contrasted with interspecific competition, in which each species experiences reduced fitness, and exploitation, in which one species benefits at the expense of the other. Mutualism and symbiosis are sometimes used as if they are synonymous, but this is strictly incorrect: symbiosis is a broad category, defined to include relationships which are mutualistic, parasitic or commensal. Mutualism is only one type.

(Hummingbird Hawkmoth drinking from Dianthus. Pollination is a classic example of mutualism.)





Useful Links

Include the links of websites you took information from. 

For example:

Wild World @ nationalgeographic.com ( http://www.nationalgeographic.com/wildworld/terrestrial.html )


Comments (2)

nazrul_hadi_jamali@... said

at 11:48 am on Apr 4, 2009

Hi Group 4, i havent seen anything being put up yet.
remember to update your site as soon as possible, the deadline is near.

2E1group4 said

at 7:38 pm on Apr 6, 2009

Yes!!!!!!!!!!We finally finish it.

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