Studying the details of plant life in the desert is a fascinating topic for botanists. All desert flora exhibit certain characteristics adaptability, which play a crucial role for survival in extreme climatic conditions.
Everyone knows the basic concept that plants need water and/or moist soil throughout their life cycle. Thus, when we think about dry habitats and plants, it is difficult to relate these concepts to each other. Considering high temperature and prolonged droughts are common in desert areas, there are no stable factors to maintain vigorous vegetation. So what allows desert plants to thrive in extreme conditions? In this article we will try to learn about the life of desert plants and the features of their adaptation to an arid climate.
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Desert biome
An elementary example of desert flora is the cactus. We often visualize several thorny cacti with one. Indeed, certain types of cactus constitute the predominant number of species among plants in desert regions. Other desert plants include: Encelia powdery, jumping choli, Joshua tree, yucca, Arizona ironwood and creosote bush. These plants are xerophytes and have adaptive abilities that are responsible for their survival in arid environmental conditions in which other plants are unable to survive.
Adaptability of Desert Plants
There is no clear evidence for the evolution of adaptive features of desert plants. In fact, we have no cactus fossils at all, despite their widespread occurrence. Consequently, it is still unknown when these plants developed their adaptation to desert conditions. Scientists believe that they acquired certain adaptive functions millions of years ago, in response to changing environmental conditions. In other words, they were forced to develop adaptations for growth in the least favorable conditions. As soon as the rain begins, plants in the dry regions of the planet begin to quickly germinate, grow, bloom and bear fruit, thereby completing life cycle in a very short time period. Next, we will consider some adaptive features that allow flora thrive in the desert.
Desert plant root system
A typical desert plant has a deep root system, which represents a specific physical mechanism. As the roots grow deep into the soil, they absorb groundwater, which subsequently hydrates the upper parts of the plant. Plant species adapted to extreme conditions environment with the help of very long roots, called phreatophytes (for example, a mesquite tree with roots more than 20 meters in length). In contrast to phreatophytes, some plants, including cactus, have small roots that extend radially to absorb as much moisture as possible during the rainy season. Some xerophytes actually have both radial and deep root systems that absorb moisture.
Desert plant stem
One of the most important characteristics plants in arid habitats is their ability to store water in any of the body parts - roots, stems and leaves. Let's take a cactus as an example; they store moisture in green, flattened, succulent stems called phyllocladia. These stems serve food production and function in the same way as the leaves of most plant species. They also have a thick layer of waxy coating that helps retain moisture longer and protects the plants from the heat. According to plant evolution studies, the cactus is believed to be a xerophytic version of the rose family.
Desert plant leaves
Desert plants have small leaves with a waxy coating to minimize the process of transpiration (loss of water through the pores), which in turn helps conserve vital moisture. The foliage of succulents (plants with specialized tissues to retain water) provides another example of a moisture-storing adaptation. In addition, the pores of some xerophytes remain closed during the day and open at night, thereby reducing the rate of transpiration. Cacti do not have true leaves. Most likely, their function is performed by prickly spines to reduce moisture loss and protect against animals. In addition to cacti, many other plant species have adapted to life in the desert with the help of spines.
Even though plants require optimal conditions to grow in the average range, they develop certain adaptive properties to survive in the existing environment. Perennial plants in dry habitats remain dormant during hot dry periods and become active with the onset of the rainy season. While annual plants absorb water from rain and complete their life cycle very quickly. the main problem A threat to desert vegetation is the loss of nitrogen from the soil due to increasing aridity.
List, description and photo of 10 desert plants
The plants from the table below are among the few representatives of desert flora that have found their home in the kingdom of eternal sands.
| Name and photo of the plant | a brief description of |
 Wollemia |
Wollemia - conifer tree, also known as a living fossil and one of the most rare species plants in the world. This unnatural tree grows only in the desert region of Australia. The appearance of Wollemia is mysterious, and its trunk has the shape of an ascending chain. It is one of the oldest plant species on the planet with a history of about 200 million years. Wollemia has good adaptive abilities and can tolerate low temperatures down to -12° Celsius. Each Wollemia tree has both male and female cones. |
 Cleistocactus Strauss |
The silver cleistocactus, native to Bolivia and Argentina, is also called the woolly torch due to its unusual appearance. It reaches a height of up to 3 meters and has upright gray-green stems. Interestingly, cleistocactus is grown in winter at a temperature of -10° Celsius, due to which the plant is in a dormant period. Each rib is dotted with small areolas white, which are spaced 5mm apart and create a woolen look. The cactus blooms in late summer and has dark red cylindrical flowers. |
 Desert Ironwood |
Ironwood can be found in the Sonoran Desert in North America. It grows like a bush or tree and reaches a height of about 10 meters, and the average trunk diameter is about 60 cm; in exceptional places, it bigger size and more massive. In young trees, the bark is gray, shiny and smooth; in older trees it is fibrous. This tree is an evergreen, but may lose its leaves if the temperature drops below 2° Celsius. In constant drought conditions, leaves also fall off. Flowering occurs from late April/May to June. The flowers can be purple, purplish-red, pale pink or white. Desert Ironwood is very hard and heavy. Its density is greater than that of water, and therefore it sinks. Its wood is used to make knife handles, as it is ideally hard, fibrous and has a suitable color. |
 Euphorbia obese |
Euphorbia obese is commonly known as the “baseball plant” due to its shape. Its diameter ranges from 6 to 15 cm depending on age. Young plants are spherical in shape, but become cylindrical with age. Almost always, fat milkweed has 8 ribs, on which there are small cones. It has a reservoir to store water for a long time. The flowers of this plant are called cyathia. Fat spurge is common in the Karoo Desert of South Africa. |
 Cylindropuntia |
Cylindropuntia, also known as cholla, is native to the southwestern United States and the Sonoran Desert. This is a perennial plant covered with silver prickly needles measuring 2.5 cm in size. This type of plant grows densely in a certain area, which creates the impression small forest. The thick trunk helps the plant survive in the hot desert climate. Cylindropuntia blooms from February to May with greenish flowers. |
 Carnegie |
Carnegia is a plant from a monotypic genus Carnegie, which can grow up to 15 meters in height. Its homeland is the Sonoran Desert in Arizona, USA. This mysterious desert plant has no leaves and blooms in spring time. The Carnegia cactus flower is the national flower of Arizona. Thick spines help them conserve water. Life expectancy is from 75 to 150 years. The spines help redirect wind throughout the plant. |
 African Hydnora |
African Hydnora is the strangest desert plant native to Africa. It is difficult to identify as a plant due to its unnatural appearance. Hydnora is completely leafless and has a deep brown stem. This plant becomes more visible only during flowering. Its flowers are spherical, brown on the outside and orange on the inside. Hydnora also produces a pungent odor to attract beetles to collect pollen. |
 Barrel cactus |
Barrel cactus is a plant from the southwestern deserts of America. The plant has an unnatural cylindrical shape. The barrel cactus is the largest cactus in the American deserts and has thick spines. The Barrel cactus grows up to 1 meter in height and has a shallow root system. It can store water. The flowers are yellowish or orange, located on the upper part of the trunk. |
 Velvichia |
Its homeland is rocky, African desert Namib. This plant has only two leaves, which are divided into many ribbon-like parts, about 1.5 meters long. They create shade and retain moisture, so necessary in arid climates. The lifespan of this plant can reach 1500 years. Incorrectly, they call Velvichia herbaceous plant, but it is a tree, about 80 cm high, half of which is underground and about 120 cm in diameter. |
 Baobab |
Baobab is the most common type of tree from the genus Adansonia, native to the African continent. These long-lived trees are typically found in the arid, hot sub-Saharan region where they dominate the landscape, and help reveal the presence of watercourses from afar. Their growth rate is determined by the number groundwater or sediments, and their maximum age, which is still the subject of much debate, is about 1500 years. Baobabs have traditionally acted as a source of food, water, medicine or shelter, and are also shrouded in a host of legends and superstitions. Explorers used to carve their names into the baobab trees, and many of the trees have been defaced by modern graffiti. |
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In an effort to survive, they adapt to environmental conditions. Adaptation, or adaptability, is the result of long-term interaction of all living things with external environment. She helped life spread throughout the world. By adapting, a living organism changes its habits and even its structure.
Can be found in deserts vivid examples adaptation of organisms to very harsh living conditions. In deserts, plants and animals, each in their own way, adapted to hot and dry conditions, learned to store water and food reserves in their bodies for a long time and cooled their bodies more intensively. The Australian desert is the largest in the world sandy desert after the Sahara. There are many diverse desert landscapes, depending on the climate and local rocks. The indigenous people of Australia, the aborigines, have adapted to living conditions in the steppe and desert over thousands of years. Until recently, Aboriginal groups lived a traditional nomadic lifestyle, obtaining food by hunting and gathering. The malga tree has enlarged cuttings instead of leaves, thanks to which its crown evaporates less moisture. Marsupial mice hide from the heat of the day in deep burrows and come out at night to look for food. In case of hunger, they have fat in their tails. There are many other examples of adaptations to life in hot deserts. Thus, instead of leaves, cacti have developed spines to reduce moisture loss. And the North American hare has very long ears. Long ears North American hare, covered with blood vessels, seem to “release” excess and cool the body.
Desert Advance
Often arise as a result of human activity - for example, during deforestation or intensive cattle breeding; then the arid ones can become real deserts. Nowadays, the threat of turning into deserts hangs over many territories. Costs of protective measures and restoration of drylands, compared with income from Agriculture on these lands are very small. But nevertheless, soil protection measures are almost not applied, and many agricultural countries suffer severely from the onset of deserts.
How to make a cactus garden
Fill a flat clay pot with sandy soil and decorate with pebbles. That's all you need for your cactus garden. You can buy cacti or grow them from cuttings. To do this, cut off one of the shoots from a large cactus. Let it dry out for a few days and then plant it in the ground. Once they take root, cacti require almost no watering or care. They just need as much sun as possible.
Ice deserts
Environmental conditions in icy snowy deserts polar regions just as severe as in hot weather sandy deserts. In winter, ice and snow completely cover the huge continent and its surface. coastal seas, as well as the Arctic. But even there you can find animals that have adapted to life in these harsh conditions. In winter, polar bears take refuge in dens under a thick layer of snow and hibernate. Thick fur on the paws prevents them from falling into the snow. Only warm-blooded animals whose bodies are constant can survive in extreme cold. Thick layers of fat and fur allow them to retain heat. Residents of the North, Eskimos, grease their faces in the winter cold and wear warm fur clothes.
Polar summer
During the short polar summer, snow and ice melt, exposing the tundra. A variety of plants and small animals inhabiting it instantly wake up. Plants survive long winters either in seeds or without freezing at all (many of them contain their own “antifreeze”). They develop quickly and manage to produce seeds during the short northern summer. In hot dry deserts there are also short periods lush vegetation. This happens after the rain, when the long-awaited seeds are brought back to life. Plants in deserts are mostly ephemeral, able to germinate and produce seeds in a very short time.
Protective coloration and mimicry
Protective coloring is the ability of animals or plants to camouflage themselves in environment to become almost invisible. This saves them from predators. But sometimes predators also use mimicry to sneak up on their victims unnoticed. Mimicry is a useful method of camouflage for animals when they become very similar to some other creatures or objects surrounding nature. The fur color of the Arctic fox changes depending on the time of year; In winter it is snow-white, in summer it is red-brown. This is one example of mimicry. Flounder, changing its color, becomes almost invisible to predators. The flowers of the bee orchid are very similar to bees, this attracts real bees to the flowers, who are looking for a friend. They carry pollen on their paws and pollinate flowers.
Seed research
Not only the plants themselves, but also their seeds adapt to environmental conditions, which gives them a much better chance of survival. Most often, seeds adapt to flying with the wind, collect as much as possible more seeds different types and consider how varied their shapes and sizes are. Then toss them outside and watch how long each seed flies before falling.
Unbearable heat during the day, very cold at night. There is only dried earth, sand or cracked stones around. Not a single green tree nearby. Instead of trees there are dry trunks or “swaying” bushes. How and what does the desert live on? More precisely, how do plants and animals survive in these harsh desert conditions?
There are areas in nature where there is little or no vegetation and very few animals. Such natural areas are called deserts. They are on all continents globe and occupy about 11% of the land surface (about 16.5 million sq. km).
A prerequisite for the formation of a desert on the surface of the earth is uneven distribution heat and moisture. Deserts form where there is little rainfall and dry winds prevail. Many are located nearby or are already surrounded by mountains, which prevent precipitation.
The desert is characterized by:
- - Aridity. The amount of precipitation per year is approximately 100-200 mm, and in some places it does not happen for decades. Often, even these small precipitations, evaporating, do not have time to reach the surface of the earth. And those precious drops that fall into the soil will replenish groundwater reserves;
- - Winds arising from excessive heating and associated air flows that reach 15 - 20 m/s or more;
- - Temperature, which depends on where the desert is located.
Desert climate
The climate in Putin is affected by geographical position. There can be either a warm or dry climate. When the air is dry, it practically does not protect the surface from solar radiation. During the day the air warms up to + 50 °C, and at night it quickly cools down. During the day, the sun's rays, without lingering in the air, quickly reach the surface and heat it. Due to the lack of water, there is no heat transfer, which is why it is so hot during the day. And at night it’s cold for the same reason - lack of moisture. There is no water in the soil, therefore there are no clouds to retain heat. If daily fluctuations in desert temperatures tropical zone are 30-40° C, then temperate zone 20 ° C. The latter are characterized by hot summers and Cold winter(up to - 50° C with light snow cover).
Desert flora and fauna
Few plants and animals can survive in such difficult climatic conditions. They are characterized by:
- - Long roots to extract moisture in deep layers of soil;
- - Small, hard leaves, and in some they are replaced by needles. Everything for less moisture evaporation.
Desert inhabitants vary depending on the location of the desert. Wormwood, saxaul, solyanka, koslosnyak, dzhuzgun are characteristic of the desert of the temperate zone, in subtropical and tropical deserts Africa and Arabia, succulents (cacti) are added. Lots of light, poor soil, lack large quantity water is all that cacti need. Cacti have adapted perfectly: the spines do not allow unnecessary waste of moisture, developed root system collects morning dew and night soil moisture.
Deserts North America and Australia is much richer and more diverse (low-growing acacia, eucalyptus, quinoa, twig, etc.). In oases and large river valleys in the temperate zone of Asia, trees grow: jida, willow, elm, turango poplar; in subtropical and tropical - evergreen palm, oleander. And this small list is very valuable in the desert. The plants serve as food for camels and for warmth on cold nights.
The fauna is not picky about food and water, and the color is close to the color of the earth's surface. Characteristic for many night life, during the day they sleep.
The most famous and widespread is the camel, the only one that can eat camel thorn and get by for a long time without water. All thanks to its hump, which contains a supply of nutrients.
Reptiles also live: lizards, agamas, and monitor lizards. The length of the latter can reach one and a half meters. A variety of insects, arachnids, and mammals (jerboas, gerbils) make up the desert fauna.
What is the secret of scorpion survival in deserts?
Scorpios are representatives arachnid. And this is surprising, since they are not at all like spiders. Scorpions prefer dry and hot deserts, but even some of their species have adapted to humid ones. tropical forests. These arachnids also live in Russia. For example, the yellow scorpion can be found in the forests of Dagestan and Chechnya. In the Lower Volga region, the motley scorpion lives in wastelands and dried desert areas, and the Italian and Crimean scorpion is found on the Black Sea coasts.
Because respiratory system These arachnids are poorly adapted to dry and hot climates; this feature forces the insect to take refuge from the heat in various gorges, cracks, under stones, and bury itself in sand or soil. There they find at least some moisture. That is why scorpions are nocturnal animals: during the day they sleep, waiting out the heat, and at night they are good-natured. Desert scorpions can do practically without water, feeding on various insects, and large individuals can eat a lizard or not. large rodent. Cases have been recorded where a scorpion survives after starvation for 0.5 to 1.5 years. In the desert, scorpions mainly obtain moisture from food, but sometimes suck it from wet sand.
For any animal and plant in the desert, the main difficulty is the lack of moisture, the lack of water. It is this feature that gives the world such bizarre forms of life. Some people have adapted not to drink, but to limit themselves to moisture obtained from food. Some people often change their location in search of water. Someone is moving to dry time years closer to the water. Some people produce metabolic water during their metabolism. Somehow, desert animals have found a way to survive in the harsh desert climate.
In addition, see documentary BBC from the Forces of Nature series, the film explains in detail the features of desert branding
December 8th, 2014
Life in the desert is not easy. In addition to the arid climate and lack of water, its inhabitants have to adapt to very large daily temperature changes: during the day it rises above 40 ° C, and at night it drops below zero. But, despite all these difficulties, thousands of animals live in deserts with different climatic characteristics.
Let's remember these features...
For example, the Sahara, the most famous of all deserts, consists of many dunes and oases lost between them. The deserts of the southwestern United States have clayey soil, and the vegetation there is dominated by cacti. Desert inhabitants: foxes, bats, snakes, and rodents have developed curious physiological and behavioral mechanisms that facilitate survival in such harsh conditions. For example, they only leave their burrows at night when the temperature drops.
When it gets too hot and the vegetation becomes too dry, some animals, such as the ground squirrels found in the deserts of Mexico and the United States, enter a hibernation similar to that of animals inhabiting cold regions of the planet. Turkey vultures, for example, urinate on their own feet to cool off. When a liquid evaporates, it takes some heat with it.
For the same reason, many desert mammals lick their paws. Desert inhabitants have also developed mechanisms to help them survive in conditions of water scarcity. Many of them, especially cacti, are able to absorb the entire required volume of liquid from food.
When living in such conditions, every drop is important. For example, desert kangaroo rats live in burrows underground with no exits to the outside. A microclimate favorable for life is created there. The moisture exhaled along with the air does not leave the hole, and animals can use it thanks to the special shape of the nasal sinuses.
Cooling through the ears
The black-tailed hare, also called the California hare, uses disproportionately large and containing many blood vessels ears for heat dissipation while resting in the shade. The size of the ears even among representatives of the same species living in regions with different temperatures, will be different.
Recirculation of urine in the body
On the one hand, desert kangaroo rats, small rodents just like mice, live in underground burrows, which is already a kind of protection from the harsh desert climate. On the other hand, they have another means of survival - their kidneys are very efficient, they contain microscopic tubes that remove most water present in urine, causing water to return to the body.
Ability to save water
The California ground cuckoo is one of the most famous animals of the American deserts. This bird can adsorb water contained in the stool before defecation. In addition, excess salt in her body is eliminated with the help of the nasal glands, and not through the secretion of urine, as most other animals do. This helps preserve precious fluid in the body.
Miracle- fish
It's hard to believe, but there is a fish that can live in the desert. One of these rare cases is a desert carp – colorful gold fish 6 cm long, living in springs and ponds with hot water. When winter approaches and the water gets colder, this fish goes into hibernation, burrowing into the soil at the bottom of the pond, and remains there until early spring.
Fast running lizard
Desert lizards remain active even during the hottest times of the day. To reduce contact with hot soil, which can exceed 60°C, they move at high speed. Thus, the collared desert iguana has a rare skill for this type of reptile; it stands up on two hind legs and runs only on them.
Twice protected animal
The western desert gopher is able to withstand higher temperatures due to its ability to dig holes and hide in them. Representatives of this species spend up to 95% of their lives in these burrows. In addition, these animals do not tolerate cold well and go into a kind of hibernation in winter time of the year. At the same time, all physiological mechanisms work more slowly, saving energy.
The absence of clouds over deserts has two consequences. Their land not only does not receive rain, but during the day it is deprived of any protection from sun rays, and at night - a cover that prevents heat loss. Even though the desert is hot during the day, at night the temperature can drop below zero. Such huge fluctuations in living conditions over the course of one day subject the animals that have chosen the desert as their home to severe trials.
Many find the simplest way out of the situation and hide from both the highest and the most low temperatures. Small mammals During the day they hide in the darkness of burrows and under stones. In these shelters it is much cooler than under the scorching sun, and the humidity, partly due to the breathing of the inhabitants, is several times higher than outside, and therefore the animals lose noticeably less moisture. They spend a significant part of the day in their shelters and leave them when the sun disappears below the horizon.
In the Sahara, as soon as it gets dark, mouse-like gerbils and jerboas timidly climb to the surface. These are vegetarians. The tufts of grass there are few in number and sparsely scattered, but they are still there, albeit stunted. And the wind carries seeds, leaves and twigs there from greener areas, so these little ones have something to snack on. Geckos scurry across the cooling stones in search of beetles and other insects. Fennecs, miniature foxes, pricking up their huge triangular ears, run silently among the stones. With their noses lowered to the ground, they catch smells that can tell when, who and where passed here. The trail leads to a gerbil. A jump - and the fennec ate for the first time that day, and the gerbil will never have to eat again. Caracals, representatives of the cat family, and striped hyenas appear as if out of nowhere, and in the deserts of the Middle East there are also wolves, which are noticeably smaller than their northern relatives and are dressed in lighter and not very thick hair. The deserts of the New World also have their vegetarians and their carnivores: kangaroo rats hop around looking for seeds, and dwarf foxes and coyotes hunt them.
After the first hunger is satisfied, activity noticeably stops. The temperature continues to drop. Geckos, losing body heat, climb into crevices. Mammals that generate their own heat can continue searching for seeds and hunting even when the night gets very cold, but they also return to their dens and burrows long before dawn.
As the sun emerges from the eastern horizon, other groups of animals appear. In the deserts of the American West, Gila snakes go hunting at this hour. Apart from their close relatives, the Mexican escarpion, they are the only venomous lizards in the world. They are about a third of a meter long with relatively thick short tail and are dressed in shiny, tuberous, bead-like scales - coral pink and black. At dawn, the movements of the vultures are slow, but as the sun warms their body, they become more and more mobile - they grab insects, bird eggs and chicks. The poisonous tooth can climb into the nest of desert mice and devour not only the young, but also the adults. In Australia, a small Moloch lizard comes out to eat ants: it settles down near some ant path and collects them over and over again with a lightning-fast movement of its tongue, and the ants keep walking and walking past, not noticing anything. In deserts, turtles crawl out of holes and holes everywhere, having spent the night there quietly under the protection of their shells.
But this explosion of activity does not last long. The sun rises higher and higher, and the desert again turns into a blazing inferno. Overheating is no less dangerous for reptiles than for mammals, and four or five hours after dawn the heat becomes unbearable for them too. A hot haze sways over the stones. They burn the hand of a person who carelessly touches them. The air is so dry and hot that a person does not even notice that he is sweating - the sweat evaporates so quickly. If he stays under open air without water all day, death awaits him. Even slight muscle movement generates heat. And now no one moves, unless he is forced to do so. And the sun pours and pours merciless heat from the hot sky.
Heat is just as dangerous to plants as it is to animals. And they die of thirst if evaporation takes away too much water from them. In the American deserts, Defontania prickly grows in places where there is not the slightest shade. She has adapted to reduce the amount of sunlight due to the fact that its narrow leaves are turned at an angle of 70° to the vertical, and most of the day the sun's rays fall only on their edges. Only in the morning, when the air is still cool and the sun is low above the horizon, its rays hit the leaf plate, supplying them with the necessary energy for photosynthesis. In addition, defontania leaves secrete salt, which the roots absorb from the soil. The sap delivers salt to the leaves, and it coats their surface with a fine crystalline powder that reflects some of the heat rays, like white clothing.
Some animals still remain on the surface and under the midday sun. In the Kalahari, ground squirrels turn their fluffy tail into a sun umbrella: they bend it over their head, fluffing out their hair, and turn it so that their body remains in the shade all the time. Other animals cool their bodies using radiators. Desert hares in America, one of the hedgehogs in the Gobi Desert and a bandicoot in Australia all use the same adaptation as the fennec in the Sahara: big ears. Undoubtedly, large ears help to catch every sound in the desert, but all of them have ears that are too large for acoustic needs alone. Very close to the surface of the skin, both in front and behind them, a network of tiny blood vessels pierces them, and the wind blowing on these ears cools the blood washing them.
http://dic.academic.ru/dic.nsf/enc_animals/502/%D0%9F%D1%83%D1%81%D1%82%D1%8B%D0%BD%D1%8F
And I’ll remind you of something else about deserts: it happens, for example, it happens. And here it is The original article is on the website InfoGlaz.rf Link to the article from which this copy was made -
The absence of clouds over deserts has two consequences. Their land not only does not receive rain, but during the day it is deprived of any protection from the sun's rays, and at night - a cover that prevents heat loss. Even though the desert is hot during the day, at night the temperature can drop below zero. Such huge fluctuations in living conditions over the course of one day subject the animals that have chosen the desert as their home to severe trials.
Many find the simplest way out of the situation and hide from both the highest and lowest temperatures. Small mammals take refuge during the day in the darkness of burrows and under stones. In these shelters it is much cooler than under the scorching sun, and the humidity, partly due to the breathing of the inhabitants, is several times higher than outside, and therefore the animals lose noticeably less moisture. They spend a significant part of the day in their shelters and leave them when the sun disappears below the horizon.
In the Sahara, as soon as it gets dark, mouse-like gerbils and jerboas timidly climb to the surface. These are vegetarians. The tufts of grass there are few in number and sparsely scattered, but they are still there, albeit stunted. And the wind carries seeds, leaves and twigs there from greener areas, so these little ones have something to snack on. Geckos scurry across the cooling stones in search of beetles and other insects. Fennecs, miniature foxes, pricking up their huge triangular ears, run silently among the stones. With their noses lowered to the ground, they catch smells that can tell when, who and where passed here. The trail leads to a gerbil. A jump - and the fennec ate for the first time that day, and the gerbil will never have to eat again. Caracals, representatives of the cat family, and striped hyenas appear as if out of nowhere, and in the deserts of the Middle East there are also wolves, which are noticeably smaller than their northern relatives and are dressed in lighter and not very thick hair. The deserts of the New World also have their vegetarians and their carnivores: kangaroo rats hop around looking for seeds, and dwarf foxes and coyotes hunt them.
After the first hunger is satisfied, activity noticeably stops. The temperature continues to drop. Geckos, losing body heat, climb into crevices. Mammals that generate their own heat can continue searching for seeds and hunting even when the night gets very cold, but they also return to their dens and burrows long before dawn.
As the sun emerges from the eastern horizon, other groups of animals appear. In the deserts of the American West, Gila snakes go hunting at this hour. Apart from their close relatives, the Mexican escarpion, they are the only venomous lizards in the world. They are about a third of a meter long with a thick, relatively short tail and are covered in shiny, tuberous scales resembling beads - coral pink and black. At dawn, the movements of the vultures are slow, but as the sun warms their body, they become more and more mobile - they grab insects, bird eggs and chicks. The poisonous tooth can climb into the nest of desert mice and devour not only the young, but also the adults. In Australia, a small Moloch lizard comes out to eat ants: it settles down near some ant path and collects them over and over again with a lightning-fast movement of its tongue, and the ants keep walking and walking past, not noticing anything. In deserts, turtles crawl out of holes and holes everywhere, having spent the night there quietly under the protection of their shells.
But this explosion of activity does not last long. The sun rises higher and higher, and the desert again turns into a blazing inferno. Overheating is no less dangerous for reptiles than for mammals, and four or five hours after dawn the heat becomes unbearable for them too. A hot haze sways over the stones. They burn the hand of a person who carelessly touches them. The air is so dry and hot that a person does not even notice that he is sweating - the sweat evaporates so quickly. If he remains out in the open all day without water, he will die. Even slight muscle movement generates heat. And now no one moves, unless he is forced to do so. And the sun pours and pours merciless heat from the hot sky.
Heat is just as dangerous to plants as it is to animals. And they die of thirst if evaporation takes away too much water from them. In the American deserts, Defontania prickly grows in places where there is not the slightest shade. It has adapted to reduce the amount of sunlight it receives due to the fact that its narrow leaves are turned at an angle of 70° to the vertical, and most of the day the sun's rays fall only on their edges. Only in the morning, when the air is still cool and the sun is low above the horizon, its rays hit the leaf plate, supplying them with the necessary energy for photosynthesis. In addition, defontania leaves secrete salt, which the roots absorb from the soil. The sap delivers salt to the leaves, and it coats their surface with a fine crystalline powder that reflects some of the heat rays, like white clothing.
Some animals still remain on the surface and under the midday sun. In the Kalahari, ground squirrels turn their fluffy tail into a sun umbrella: they bend it over their head, fluffing out their hair, and turn it so that their body remains in the shade all the time. Other animals cool their bodies using radiators. Desert hares in America, one of the hedgehogs in the Gobi Desert, and a bandicoot in Australia all use the same adaptation as the fennec in the Sahara: large ears. Undoubtedly, large ears help to catch every sound in the desert, but all of them have ears that are too large for acoustic needs alone. Very close to the surface of the skin, both in front and behind them, a network of tiny blood vessels pierces them, and the wind blowing on these ears cools the blood washing them.
Other animals increase the cooling power of the wind by wetting parts of their bodies with some liquid. Physical process The transition of a liquid into a gaseous state is accompanied by the absorption of heat. Therefore, when water evaporates, it takes away heat from the objects it comes into contact with. This is why sweating cools mammals. Like puffing as air moves back and forth over moist mucous membranes oral cavity: Saliva evaporates and the blood in the capillaries cools. Turtles, when they get too hot (above 40.5°), wet their head and neck with a copious stream of saliva. And sometimes they take even more drastic measures, releasing a large supply of fluid contained in the bladder onto the hind legs. In Australian kangaroos, under the armpits, near the surface of the skin, there is a special network of capillaries. When the heat becomes unbearable, the kangaroo vigorously rubs saliva, literally whipping foam, into the fur above these capillaries, and the evaporation cools the blood flowing through them.
Birds are better able to withstand heat than most animals. Of course, in the majority geographical areas their plumage helps them retain body heat. However, heat insulators do not allow heat to pass through, regardless of which side it is located on, and just as reliably do not allow external heat to pass through to the body as they save its own. With the protection of their feathers, many birds can remain in the hot desert sun all day long. But even they sometimes need cooling and use more effective form puffing breath than mammals. They vibrate the windpipe. This saves the muscle effort required to move the chest vigorously while still creating sufficient air flow over the moistened oral surface.
David Attenborough. LIVING PLANET. PUBLISHING HOUSE “MIR”. Moscow 1988
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