Climate and characteristics

Transcription

1 Climate and characteristics Desert climates have extreme temperature range. During the day the temperature may reach 50 C, at night however temperatures can fall to below 0 C. Deserts also have very little rainfall, with less than 250mm of rainfall per year. This rain can also be very unreliable. Desert soils tend to be sandy or stony with little organic matter and a lack of dense vegetation. The soils are dry but can soak up water rapidly after rainfall. Evaporation draws salts to the surface, often leaving a white residue on the ground. All this means that desert soils are not particularly fertile. There are three factors which form desert areas: 1. Mountain ranges to create rain shadows, meaning only very dry air moves beyond the mountains. 2. High pressure areas (due to sinking air), creating cloud free conditions. 3. Cold ocean currents. Living in the desert Page 1 of 6

2 Vegetation adaptations Plants have adaptations to help then survive (live and grow) in different areas. Adaptations are special features that allow a plant or animal to live in a particular place or habitat. These adaptations might make it very difficult for the plant to survive in a different place. This explains why certain plants are found in one area, but not another. For example, you wouldn t see a cactus living in the Arctic, nor would you see lots of really tall trees living in grasslands. Some desert plants have shallow roots to get water when it soaks into the surface. Other plants have very long tap roots to get to the water deep in the rocks as the soil on the surface is very dry. Some desert plants have small waxy leaves to reduce transpiration. Needles are also thin and mean there is less water loss so precious water is saved. Some desert plants flower directly after the rain to drop their seeds and then they disappear. Saguaro Cacti are well adapted for survival in the desert. They have: stems that can store water widespread root systems that can collect water from a large area spines instead of leaves, minimising the surface area and reducing water loss by transpiration spines to protect it from animals that might eat it Page 2 of 6

3 Hot desert location Hot deserts are generally located in dry continental interiors in belts following the 30 degrees north and 30 degrees south lines of latitude. These latitudes are where air that has risen at the equator descends forming a persistent belt of high pressure. This location is associated with a lack of cloud and rain and high daytime temperatures. This lack of cloud cover means very cold nights. In the United States, the largest desert in the Great Basin Desert. The Great Basin Desert is not the type of desert you would normally picture. It is unique because it receives most of its precipitation as snow! The Sahara Desert. Blanketing much of the northern third of the African continent, or some 3.5 million square miles, the Sahara Desert extends eastward from the Atlantic Ocean some 3,000 miles to the Nile River and the Red Sea, and southward from the Atlas Mountains of Morocco and the Mediterranean shores more than 1,000 miles to the savannah called the Sahel. More than 16 times the size of France, the Sahara Desert covers nearly all of Mauritania, Western Sahara, Algeria, Libya, Egypt and Niger, the southern half of Tunisia and the northern parts of Mali, Chad and Sudan Page 3 of 6

4 Animal adaptations Animals have to adapt to living in the desert. Camels have adapted to living in the desert in the following ways: long eyelashes keep out dust tough mouth for eating thorny plants large padded feet to stop sinking into the sand stores water in stomach tail scares flies away light colour to reflect heat hair on back for shade. Animals in the desert have evolved physically and behaviourally to survive. They must ensure they can avoid heat, find water, retain water and ensure survival against predators. The Jerboa mouse has adapted to living in the desert by: being active at night and sleeping during the day having huge ears to help it stay cool. The Thorny Devil lizard has adapted to living in the desert by: having sand coloured skin to camouflage into the sand growing hard spikes to stop other animals from eating it having spikes which helps it to get water (in the morning it rubs against dew drops and the moisture runs between the spikes along grooves that run directly into its mouth) Page 4 of 6

5 Climate and characteristics Vegetation adaptions Hot desert location Animal adaptions Page 5 of 6

6 Николай Усик / - Own work, CC BY-SA 3.0, Koppen_World_Map_Hi-Res.png: Peel, M. C., Finlayson, B. L., and McMahon, T. A. (University of Melbourne) derivative work: Me ne frego (Koppen_World_Map_Hi-Res.png) [CC BY-SA 3.0 ( via Wikimedia Commons, commons.wikimedia.org/wiki/file%3akoppen_world_map_bwh.png Page 6 of 6