Desert Adaptations

Desert, term applied to regions on the earth that are characterised by less than about 250mm of annual rainfall, and, in many cases an evaporation rate that exceeds precipitation, and a high average temperature. Because of the lack of moisture in the soil and the low humidity in the atmosphere, most of the sunlight penetrates to the ground. Daytime temperatures have reached 57.8 Degrees Celsius on the 13th of September 1922, this was the highest ever recorded in Libya. On the other hand at night the temperature can drop to near freezing. Deserts are found in ever continent throughout the globe from Africa to the cold plains of Northern China.

Hot deserts extend all around the world in two belts, to the north and south of the tropical zone around the world's equator. Further from the equator, north and south are the cold deserts, and even further are the ice-covered polar deserts. Some deserts receive almost no rainfall, for example in southern Egypt, there are many years when rainfall is at an absolute zero. However when it does rain the downpour can be torrential. Thunderstorms quickly dampen the soil surface, then further water runs off the wet surface, creating flash-floods. 250 people passed-away from floods in Morocco in 1997, in the Atlas Mountains.

Desert areas in some continents have formed because the "Prevailing winds", are far removed from areas of water and have lost most of their moisture by the time they reach those regions of the world. An example of these types of deserts is the "Gobi" and "Takla Makan", of Asia.

Compared to the Earth's grand age of 4.5billion years, some of our planet's deserts are very young. The Great Basin in the USA has only been classified as a desert for around 12,000 years. In the deserts, winds blast rocks literally, into unusual shapes and "Sand Dunes." In the Sahara desert, these dunes are typical features which are found. Sand Dunes are visible from winds blowing from a single direction. Also the "Star"shaped Dunes are seen in regions where winds are blown from all directions, these are found in the "Namid" Desert.

Plant adaptation.

Plants need to be tough to survive in the desert. They have to deal with the daytime temperatures, which soar up to 57 degrees Celsius, and at night time temperatures that plunge to freezing and below. Also, they have to protect themselves from animals, to cope through this, they use all types of clever "Adaptations." Throughout the rest of the world, plants gather as much of the suns energy as they can, but in the desert plants are bathed in more sunlight than they can utilize. Many people wear light-coloured clothes in summer because the light-colours reflect the suns rays and help keep you cool. Desert plants use the same method, many of them are a pale green or silvery grey colour.

Water

Plants get most of their water through their roots. However in the desert there is little water to be found, the plants that grow there need to send their roots very deep to get as much water as possible. While deserts maybe very dry at the surface most of the time there is often water deep underground. To get at this water, some desert plants have a long thick central root named a "Taproot." This can go down 15metres (50ft).

Water from the air

Other desert plants take water from their leaves. The leaves can take in tiny droplets of water from the sea fogs that come in from the Atlantic Ocean in the early morning, this is the only regular source of water in the Namib desert.

Storing Water

Desert plants, when they obtain their water require a place to store it, as their might not be any more for a long time. Many types of plants are good at storing water inside themselves, these plants are called "Succulents", this means juicy. When it rains, Cacti plants suck in huge amounts of water and swell up like huge balloons. The organ-pipe cactus, which grows 3 times taller than an average person, can hold up to 380 litres in its stem. This is enough to fill 6 standard bath tubs. This amount of water, can get the Cacti through 4 months of drought.

Plants don't have to be large to be good at surviving through dry periods. For example, the wild tulips of the deserts of central Asia live through most of the year as small underground bulbs. When the spring rain comes, the bulbs quickly send up leaves and flowers. The bulbs store enough food and water to last until next spring.

Preventing water loss

Once a plant has built up a good store of water, it needs to prevent water loss. However no plant can avoid losing some water- it's a part of the way they keep themselves alive. All plants give off water vapour into the air. Most of the water vapour escapes through tiny pores (Holes) in the leaves, which plants have to keep open to survive. This is because the pores serve to take in carbon dioxide, a vital gas that they use to make food. So to receive carbon dioxide, plants have to lose a bit of water. Losing water can sometimes be an advantage because it makes their roots suck up more water from the ground, bringing up more useful chemicals with it. The soaring temperatures of the desert, water evaporates from leaves too easy, and there's very little water in the ground to replace it. Most plants after this would shrivel up and die, but desert plants have "Adapted" to stop this from happening.

Self defence

In deserts, plants which are poisonous is one sure way that a plant can protect itself from being eaten. A well known example of chemical defence is the "Creosote bush" its leaves contain poisonous oil that smells like "Creosote", the foul smelling chemical that people use to preserve timber. Desert plants have more visible defences for example Cacti and Agaves are all armed with sharp spines.

Plant

Acacias

Milkweed

Window plantAdaptation - for self defence.

Covered with Vicious thorns.

Long ribs, between leaves, sharp cage when plant is dead.

This plant has the ability to "Hide" underground.

Animal adaptation

Many people think of deserts as empty places, where no animals live. However, a large variety of animals are in the deserts, ranging from tiny insects to large mammals like antelopes and camels. Even elephants occupy a few deserts!

All land animals, depend on plants for food either they eat plants, or they eat other animals that feed on plants. In the driest deserts there are hardly any plants, so plant-eating animals can survive only by eating seeds or other bits of plants blown into the desert by the wind. This food is enough for only very small animals such as insects.

Wetter deserts have a wider range of plants, including grasses, cacti, shrubs or even scattered trees. Deserts that are rich in plant life provide enough food for large animals such as rabbits and camels.

Finding water

Many desert animals do not need to drink such as the "Gerenuk" this is because it gets all the water it needs from the leaves it consumes. All animals can also make their own water inside their bodies via a chemical reaction. This water comes from the chemical process that releases energy from food.

Other desert animals can go without drinking for a long time. Camels can survive for a week without drinking when they are working and for several months when they're not. When they do drink they take in over 100 litres.

The humps on camels DO NOT store water, it is just full of fatty tissues. Camels use this as an "emergency" food supply, and it can be broken inside the camel's body to release water. Large animals like antelopes travel long distances to get to water holes where they can drink. Some animals can break dry ground with their "Hooves", if they are horses to get some small amounts of water from the surface. Animals lose water when they urinate to get rid of the waste products in the body. To reduce water loss, camels and other desert animals have very concentrated urine.

Surviving hot and cold

Many deserts are very hot during the day, but at night the temperature can plummet to freezing. To avoid the heat during the days small animals shelter under rocks. Some animals only come out at night when it's cooler. Sometimes it gets too cold to go out at night, therefore animals like the Kangaroo rat come out of their shelters mainly at dawn and dusk, when the temperature is most comfortable. The western Diamondback has little pits under its eyes that can detect infrared radiation (Heat). This helps it see its prey, normally warm blooded rodents in the dark.

Cold blooded animals, such as snakes don't need to keep their bodies at a steady temperature. They can spend most of their time cold and inactive using very little energy, because of this, reptiles can live with a tenth of the food mammals and birds need. This gives an advantage in deserts when food is scarce.