Presentation on the topic "tropical deserts". Presentation on the topic "tropical deserts" Presentation on the topic tropical deserts of Africa
Geographical location The space from the Atlantic Ocean to the Red Sea and from the foot of the Atlas Mountains and the Mediterranean coast to the northern borders of the savannas, occupied by tropical deserts, is called the Sahara. In South Africa, the desert zone occupies the Atlantic coast. This is where the Namib Desert is located.
Climate The annual precipitation in the Sahara is less than 50 ml. In the interior parts of the desert there is sometimes no rain for several years. Clouds are a rare phenomenon, so the sun's rays heat the earth's surface especially strongly. In summer, the daytime heat reaches + 40 C in the shade.
Flora The vegetation of the Sahara is extremely sparse, and in some places, especially in the central part, it is completely absent. Here and there isolated tufts of grasses and thorny bushes grow. Desert plants have a highly developed root system, with which they collect water from great depths and from vast spaces (for example, camel thorn). Many plants have very small leaves to reduce evaporation, and sometimes spines grow instead of leaves. Some plants appear only after rain and grow unusually quickly, bloom and bear fruit, and then dry out. Lichens are common in the rocky desert, and saltwort and wormwood are common on saline soils.
Flora The Namib Desert is characterized by a peculiar Welwitschia plant. Its short thick trunk rises above the ground only 50 cm. Two dense leathery leaves extend from its top, reaching a length of up to 3 m. The leaves grow continuously from the stem, dying off gradually at the ends. The age of Velvichia can exceed 150 years. The deserts of South Africa to the east and north turn into semi-deserts, where prickly cushion-shaped plants predominate, as well as milkweed, aloe, and wild watermelons with juicy fruits, which often replace water for the local population and animals.
Fauna Animals of the Sahara are adapted to desert climate conditions. Thus, antelopes are capable of running long distances in search of water and food. Lizards, turtles and snakes can go without water for a long time. Various beetles, locusts, and scorpions are also numerous. On the outskirts of the desert there are hyenas and lions.
Soils In deserts, due to the poor vegetation cover, there is very little organic matter in the soil. Desert tropical soils form here. They contain very little humus, but clay deserts contain mineral salts necessary for plant life. Due to the lack of rain, the salts are not washed out. Large areas of rocky and sandy deserts are devoid of soil cover.
Economic activities of people In the conditions of a tropical desert climate, agriculture in the Sahara is possible only in oases. Therefore, the local population is mainly engaged in animal husbandry and leads a nomadic lifestyle, raising goats, sheep and camels. Nomads live in large tents - tents covered with coarse woolen fabric or sheep and goat skins.
Sources V.A. Korinskaya, L.D. Prozorov, V.A. Shchenov. Geography textbook for 7th grade. Moscow education Kondratyev B.A., Matreveli P.M. Geography lessons: 6th grade. – Education, 1990 Photo gallery “Animal World” - thematic selection and software shell Absolut soft, 2002
Animals and plants of tropical deserts School No. 657 2 A 1st grade Plotnikov Sergey
The hot and extremely dry climate of tropical deserts is extreme for living organisms. However, the animals living in these places managed to adapt to such conditions. They may not drink for long periods of time and travel great distances in search of water. During the hottest season of the year in tropical deserts, many invertebrates go into suspended animation, and reptiles and rodents hibernate. Some animals spend almost their entire lives underground, and ungulates and most bird species migrate from hot regions in the summer. Many desert animals are nocturnal. They crawl out of their burrows only for a short period of time between the cold of the night and the scorching heat of the day, and some animals during the daytime hide in the shade of bushes or climb onto high branches, away from the hot ground.
In tropical deserts, jerboas, voles, mole rats, hyenas, cheetahs, desert cats, turtles, and miniature foxes are common; ungulates are represented by antelopes, donkeys, mountain sheep; birds - sandgrouses, larks. When rare rains fall, the desert comes to life: plant bulbs and seeds wake up, grasses turn green, and after the plants, animals come to the surface.
The fennec fox is a small reddish or golden fox that is found in the deserts of North Africa and the Arabian Peninsula. The fennec cat's body length is about 40 cm, and its weight is 1-1.5 kg. The fenech has the largest ears (15 cm) among predatory animals. The fox easily moves along the hot sand on its hairy feet, and in the most intense heat it can bury itself in the sand. The fennec cat has small teeth, so it does not hunt large prey, but feeds on rodents, rabbits, gerbils, lizards, insects, eggs, and eats the roots and fruits of plants. Fenechs live in groups and during the daytime occupy one hole; they are talkative - they bark and purr. Twice a year, fennec cats give birth to puppies, which live with their parents for about 12 months.
The one-humped camel (dromedary) is often called the “ship of the desert” for its endurance and reliability. The dromedary was once found only in the arid regions of the Middle East, northern India and northern Africa, but dromedary camels were later introduced to central Australia. Brownish or sandy-gray dromedaries weigh from 300 to 690 kg and reach a height of 2 m, sometimes black and white individuals are found. The dromedary has a long, curved neck, a narrow chest and a single hump made up of fat deposits - food reserves. The size of the hump varies depending on the amount of food and the time of year. Dromedar feeds on dry grass and young shoots of bushes, chewing each portion of food thoroughly (40-50 times). It needs salt to maintain its water supply.
Typical desert birds - sandgrouses - have long and sharp wings, adapted for fast flight. They feed on the seeds of grasses and shrubs, and when they fly to a watering hole, they moisten their belly feathers, which have a special structure. In the crop and wet feathers, hazel grouse carry water to the chicks. The nest of the hazel grouse is made on the ground, and the parents take turns incubating the 3 laid eggs. Bustards and desert sparrows listed in the Red Book are also found in deserts.
In arid deserts, even insects were able to adapt to life. There are scorpions, darkling beetles and many others.
Over many millions of years, desert plants have developed certain adaptations for existing in these incredibly difficult conditions. As soon as winter ends in the desert and the first spring rains pass, the dull sands are covered with delicate greenery and a luxurious colorful carpet of flowers. With the onset of dry, hot summer, the desert is covered with low, bright green bushes with small leaves and a mass of thorns. This is yantak, camel thorn. The plant is characterized by its long roots, growing up to 10-20, and sometimes more, meters, with which it draws moisture from great depths, often reaching groundwater. Many desert plants have leaves covered with either fluff or a waxy coating, which reduces the area of leaf evaporation, and sometimes they even change their shape. A typical desert tree is saxaul.
Tropical deserts of Africa Teacher: Moroz Svetlana Anatolyevna Geography - 7th grade MBOU Verkhneoblivskaya oosh Tatsinsky district Rostov region Objectives of the lesson: - consider the natural zone of deserts - as a zonal natural complex. - characterize the natural complex of tropical deserts; - identify cause-and-effect relationships of the complex; - understand new concepts and terms; - learn to work with an electronic geographical dictionary; Exercise 1. From the proposed words and expressions, create definitions of concepts: A natural zone is ... (temperature conditions and moisture, a large natural complex, soils with common vegetation and fauna). (Answer: A natural zone is a large natural complex that has common temperature and moisture conditions, soils, vegetation and fauna).
“Deserts - a pattern or anomaly on the face of the Earth”?
Table 1 “Natural zones Tropical deserts “Namib” - means “shield” Kalahari - “Land of Thirst”; Sahara - "as-sahra" - desert steppe, or translation of the word "reddish", "red". Dunes and dunes Desert types Sandy deserts are called Ergi. Hamada - rocky surfaces excavated from bedrock and covered with crushed stone. Regs - sand and pebble deserts Tropical climate zone Samum "The wild wind in the desert is the second ruler." N. Gumilyov
SAMUM (Arabic) - a sultry dry wind (“breath of death” among local residents) in the deserts of North Africa, carrying hot sand and dust. Raised “clouds” of sand obscure the Sun. In the Algerian Sahara it happens up to 40 times a year.
Make a logical chain about the reasons for the formation of the Sahara Desert, using the following information: high pressure area, tropical zone, air contains little moisture, downward air currents, high temperatures, low precipitation, practically does not protect the land from solar radiation, dry tropical deserts). Cause-and-effect relationships Tropical zone High pressure area Downdrafts Low rainfall Poor vegetation Oasis in the desert. Oasis– a site in a zone of hot deserts with rich flora and fauna compared to the environment. Desert animals Date palm. Economic activities of people In the tropical desert climate, farming in the Sahara is possible only in oases. Therefore, the local population is mainly engaged in animal husbandry and leads a nomadic lifestyle, raising goats, sheep and camels. Nomads live in large tents - tents covered with coarse woolen fabric or sheep and goat skins.
“The sun in our country makes even the stones scream”
Desertification “And, perhaps, there are only a few centuries left, when predatory flocks of sand will rush wildly onto our world, green and old, from the burning young Sahara.” N. Gumilev Self-test “5” - no errors “4” - 1-2 errors “3” - 3-4 errors “2” - more than 4 errors
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Reflection. "Stone Roses" of the Sahara Desert
1 rose - I understood everything, I can explain this material to another. 2 rose - I understood the material, I can explain it to someone else, but with the help of a teacher. 3 rose - I didn’t understand anything. Homework
- Find the answer to a problematic question: How could the Namib Desert form on the Atlantic coast?
- For inquisitive students, find the answer to the question: What is the “rose of the Sahara”?
- Thank you for your work!
Slide 3
Sahara Desert
Slide 4
- The Sahara is the greatest desert in the world.
- The word “Sahara” is associated with images of endless, glowing sand dunes with very rare emerald green oases. But in reality, here, in the vast expanses of the Sahara, you can find almost any type of desert landscape. In the Sahara, in addition to sand dunes, there are barren rocky plateaus strewn with stones; there are unusual fantastic geological formations; You can also see thickets of thorny bushes.
Slide 5
- The Sahara is the greatest desert on Earth and occupies 30% of the area of all of Africa. And this is half the territory of Russia, or the size of Brazil, the fifth largest country in the world.
- There are ten countries in the Sahara: Egypt, Algeria, Tunisia, Libya, Western Sahara, Mauritania, Niger, Morocco, Chad and Sudan.
Slide 6
- Local residents also call it “The Sea without Water”, because 5-10 thousand years ago there were many lakes, rivers and tropical forests.
- Interestingly, the dunes of the Sahara move at speeds from a few centimeters to hundreds of meters per year, reaching a height of 250 m.
Slide 8
The average daily temperature in the desert is +40 ° C, but during the day the sand sometimes warms up to +80 ° C. And at night the temperature can drop sharply to -15.
Slide 9
Rain in the Sahara
Rain in the Sahara is a very rare holiday. But there are frequent sandstorms caused by hot desert winds. Over the past 50 years, the number of sandstorms has increased by 10, and in some places by 40 times.
Slide 10
Population
Now 2.5 million people live in the Sahara. However, it used to be busier here. Caravans of traders often stretched across the Sahara, carrying gold, copper, slaves, and ostrich feathers. Just imagine, crossing the desert and back took 1.5 years!
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Fauna of the Sahara
- The fauna of the Sahara has 4 thousand species.
- Camels can live without water for two weeks, and without food for up to a month. These amazing animals can smell moisture from another 50 km away and can drink about 100 liters of water at a time. The interesting thing is that in such heat, camels do not sweat at all. Their large humps are fat, which allows the animals to go for a long time without food.
Slide 13
sand cat
The sand cat is the smallest representative of wild cats. Body length is only 65-90 cm, 40% of which is the tail. These babies are nocturnal, escaping the heat of the day in burrows.
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Ethiopian hedgehog
Another striking representative of the fauna of the Sahara is the Ethiopian hedgehog. By the way, he can go without food for up to 2.5 months.
Slide 15
fennec
Little fennec fox, the smallest fox in the world, also lives in the Sahara.
Slide 16
Oryx
The body temperature of oryxes can reach 45 ° C. Despite their good endurance (they can go without water for a long time), the Ooryxes are now facing complete extinction.
Slide 17
Kalahari Desert
Slide 18
The Kalahari is called a desert, although it is more like a semi-desert because its average annual rainfall is significantly higher than what would normally fall in a true desert. This is a plateau with an almost uniform topography.
Slide 19
The Kalahari Desert, the largest of the deserts in South Africa, covers an area of about 600 thousand square meters. km, and its territory extends into Botswana, South Africa and Namibia. Recently, due to an increase in area, it has been invading the territory of Angola, Zimbabwe and Zambia.
Slide 20
Climate of the Kalahari
The climate of the Kalahari is arid with summer maximum precipitation and mild winters, with aridity increasing towards the southeast. The Kalahari is one of the hottest regions of South Africa. Precipitation (up to 500 mm) is confined to the summer period (November - April), but its value varies significantly both in time and area.
Slide 21
The average maximum temperature is plus 29 °C, and the average minimum temperature is plus 12 °C, evaporation is 3 thousand mm/year. In the Kalahari territory there is the largest delta in the world of the Okovango River, which does not flow anywhere.
Slide 22
Surface of the Kalahari
The surface of the Kalahari is composed of Tertiary and Quaternary horizontally lying continental strata (Karru layers) of sandstones, pebbles and breccias.
Slide 23
The entire territory of the Kalahari is occupied by sand dunes, located, as a rule, in chains at a distance of 70-150 m from each other. The accumulation of longitudinal dunes - alab - is especially common in the vicinity of the Molopo and Kuruman rivers. There are several types of Kalahari sands here. The most common are red sands, the color of which can vary from bright pink to red to almost brown, due to the presence of iron oxides.
Slide 24
The soils are mainly red-brown and orange-brown, sandy, structureless, consisting mainly of coarse and fine sand, slightly acidic, with low fertility, which is caused by a lack of nitrogen and phosphorus. With depth, the color in more humid areas changes to yellow-brown, and the sand becomes denser.
Slide 25
Giraffe
The giraffe is the tallest animal in the world. His height is approximately equal to the height of a two-story house. An adult male can reach a height of 6 m and weigh from 550 to 1800 kg.
Slide 26
Zebra
Zebra (Equussp.) Zebras are a type of wild horse. All zebras have the same type of coloring - black and white stripes, but they depend on where they live: northern zebras have black and long stripes, southern zebras have brown and short stripes.
Slide 27
Cheetah
The cheetah is the fastest land mammal: in a short time it can reach speeds of up to 112-120 km/h (70 to 75 mph) and can accelerate to almost 100 km/h in three seconds. This is one of the few members of the cat family with semi-retractable claws
Slide 28
a lion
The lion is the second largest living cat after the tiger - some males can weigh up to 250 kg
Slide 29
Cobra
The cobra poses an undoubted danger to humans and animals, but unlike viper snakes it always warns of its presence. Only in case of an immediate threat does the cobra make several lightning-fast attacks towards the enemy, one of which, as a rule, ends with a targeted bite
Slide 30
Namib Desert
Slide 31
The only place where you can cut down trees that died a thousand years ago is the Namib Desert in Africa.
Slide 32
The Namib Desert is a coastal desert in southwestern Africa. The area of the Namib is over 100 thousand sq. km. The desert stretches 1900 km along the Atlantic coast from the city of Namibe in Angola, across the whole of Namibia
Slide 33
The South Atlantic blocks the path of the sandy waves of the Namib Desert, which stretches 2,000 km along the African coast.
Slide 34
An endless sea of sand dunes goes deep into the mainland, to the dry heart of the Namib Desert. At first glance, very few animals and plants live in this dry climate, however, just a sprinkle of rain, and the desert suddenly wakes up and a bright and active life begins.
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Slide captions:
NAMIB DESERT
The name "Namib" in the Nama language means "a place where there is nothing." SHORE OF MISTS SHORE OF SKELETONS SHORE OF GIANT DUNES
Most of the Namib is occupied by huge sand dunes, reaching three hundred meters in height. Nowhere else in the world are there such gigantic mountains of shifting sand. Above their tops you can almost always see plumes of sandy dust raised into the air, and it seems that the dunes are smoking like volcanoes. Closer to the ocean, dune ridges are white or yellowish in color, and further from the coast their color becomes darker, turning fiery red.
Life in the desert becomes active only in the short morning hours when the cold of the night recedes, but the surface of the sand dunes has not yet become hot from the sun. After all, at the height of the day, the sand heats up to seventy degrees, and the only salvation for beetles, lizards and other small living creatures is a relatively cool hole.
Only on the ocean coast is life in full swing all day long. Eared seals make their rookeries on the beaches at the foot of rocky capes. These hefty, two-hundred-kilogram animals feed on fish, which abound in the waters of the Benguela Current. It must be said that these are the only seals that live in the tropics. The abundance of marine mammals allows packs of brown hyenas to survive. Due to the lack of their main food - carrion - they completely switched to a marine diet and eat the bodies of dead seals thrown ashore. On the rocky islands the polyphonic din of bird colonies does not stop. Millions of pelicans, flamingos, cormorants and gulls make nests. Small spectacled penguins walk busily next to them.
Rainy weather is very rare in the Namib. Both plants and animals of the desert have learned to extract moisture from the night air. Insects manage to drink droplets of dew that settle on their bodies from the fog, and plants absorb condensation covering the leaves through stomata that are located on their surface.
The most unusual, one might say, amazing plant of the Namib is the dwarf Welwitschia tree. Its trunk is half hidden in the sand and rises above it by 20-30 centimeters, a maximum of half a meter, but reaches a thickness of one and a half meters. The main root of Velvichia goes 5-7 meters deep, and the side roots lie near the surface, greedily absorbing moisture from occasional rains and heavy dew.
Velvichia has only two leaves, but what leaves! Wriggling green ribbons, a meter wide, stretch in both directions from the trunk, reaching a length of six meters. Their green tongues trailing along the ground resemble tentacles, which is why Welwitschia is often called the “desert octopus.” Only thanks to this unique crown structure can this plant fully use coastal fog - the main source of moisture in the Namib. Welwitschia wood does not have annual rings. It burns well, producing almost no smoke. Velvichia lives for an unusually long time - up to two thousand years.
Another plant found almost exclusively in these parts is the wild Nara melon, which bears fruit only once every ten years. The juicy oval fruits of the bunk have more than once saved travelers who were dying of thirst.
People were brought to these uninhabitable regions for two reasons: greed and misfortune. Large diamonds of excellent quality are often found in the depths of coastal dunes and on beaches, and many adventurers have paid with their lives in pursuit of their deceptive brilliance.
And shipwreck victims have long cursed the fogs and sandy shoals of the treacherous Namib coast, which became the grave for hundreds of ships and thousands of sailors. Underwater ridges of sand, like dunes on land, shift day after day, subject to the whims of storm waves, so that not a single nautical map of this area can be considered completely reliable. It happened that a ship anchored in a bay, having completed repairs or waited out a storm, found itself cut off from the sea by a suddenly growing sand bar. The sailors who abandoned the useless ship walked along the shore in search of water, but few managed to escape.
