inter1U8 a visit to the desert

skysome

地球上的几种地貌

Biomes on the earth
A biome is a large area characterized by its vegetation, soil, climate, and wildlife. There are five major types of biomes: aquatic, grassland, forest, desert, and tundra, though some of these biomes can be further divided into more specific categories, such as freshwater, marine, savanna, tropical rainforest, temperate rainforest, and taiga.

Aquatic biomes include both freshwater and marine biomes. Freshwater biomes are bodies of water surrounded by land—such as ponds, rivers, and lakes—that have a salt content of less than one percent. Marine biomes cover close to three-quarters of Earth’s surface. Marine biomes include the ocean, coral reefs, and estuaries.

Grasslands are open regions that are dominated by grass and have a warm, dry climate. There are two types of grasslands: tropical grasslands (sometimes called savannas) and temperate grasslands. Savannas are found closer to the equator and can have a few scattered trees. They cover almost half of the continent of Africa, as well as areas of Australia, India, and South America. Temperate grasslands are found further away from the equator, in South Africa, Hungary, Argentina, Uruguay, North America, and Russia. They do not have any trees or shrubs, and receive less precipitation than savannas. Prairies and steppes are two types of temperate grasslands; prairies are characterized as having taller grasses, while steppes have shorter grasses.

Forests are dominated by trees, and cover about one-third of the Earth. Forests contain much of the world’s terrestrial biodiversity, including insects, birds, and mammals. The three major forest biomes are temperate forests, tropical forests, and boreal forests (also known as the taiga). These forest types occur at different latitudes, and therefore experience different climatic conditions. Tropical forests are warm, humid, and found close to the equator. Temperate forests are found at higher latitudes and experience all four seasons. Boreal forests are found at even higher latitudes, and have the coldest and driest climate, where precipitation occurs primarily in the form of snow.

Deserts are dry areas where rainfall is less than 50 centimeters (20 inches) per year. They cover around 20 percent of Earth’s surface. Deserts can be either cold or hot, although most of them are found in subtropical areas. Because of their extreme conditions, there is not as much biodiversity found in deserts as in other biomes. Any vegetation and wildlife living in a desert must have special adaptations for surviving in a dry environment. Desert wildlife consists primarily of reptiles and small mammals. Deserts can fall into four categories according to their geographic location or climatic conditions: hot and dry, semiarid, coastal, and cold.

A tundra has extremely inhospitable conditions, with the lowest measured temperatures of any of the five major biomes with average yearly temperatures ranging from -34 to 12 degrees Celsius (-29 to 54 degrees Fahrenheit). They also have a low amount of precipitation, just 15–25 centimeters (six to ten inches) per year, as well as poor quality soil nutrients and short summers. There are two types of tundra: arctic and alpine. The tundra does not have much biodiversity and vegetation is simple, including shrubs, grasses, mosses, and lichens. This is partly due to a frozen layer under the soil surface, called permafrost. The arctic tundra is found north of boreal forests and the alpine tundra is found on mountains where the altitude is too high for trees to survive. Any wildlife inhabiting the tundra must be adapted to its extreme conditions to survive.

关于meerkat 猫鼬

Meerkats live in the deserts and grasslands of the southern tip of Africa.

They are extremely cute, with bushy, brown-striped fur, a small, pointed face, and large eyes surrounded by dark patches.

Meerkats only go outside during the daytime. Each morning, as the sun comes up, the mob emerges and begins looking for food. They use their keen sense of smell to locate their favorite foods, which include beetles, caterpillars, spiders, and scorpions. They'll also eat small reptiles, birds, eggs, fruit, and plants.

Back at the burrow, several babysitters stay behind to watch over newborn pups. This duty rotates to different members of the mob, and a sitter will often go all day without food. The babysitters' main job is to protect pups from meerkats in rival mobs, who will kill the babies if they can.

While the rest of the mob forages for food, one or more meerkats, called a sentry, will find a high point, like a termite mound, and perch on their back legs, scanning the sky and desert for predators like eagles, hawks, and jackals. A sentry who senses danger will let out a high-pitched squeal, sending the mob scrambling for cover. Meerkats eat mostly insects, but they also eat lizards, snakes, spiders, birds, plants, eggs and other small mammals.

The meerkats help each other. When the family is eating or playing together, one meerkat acts a sentry, and looks out for predators. If he or she sees one, then he gives a chirp and the group runs to a burrow to be safe.

关于沙漠

• 沙漠分布

When people think of a desert, they usually think of a sandy, hot, and dry place. But there are other types of deserts as well. A desert is any large region that gets very little rain each year. Very few plants or animals live in desert areas. Features
Deserts cover about 20 percent of Earth’s land surface. All the continents have them. Deserts differ greatly in their land features. They may include dunes of shifting sand, mountains, bare rock, and plains of gravel and boulders. Sand dunes are not as common in deserts as many people think. For example, they make up only about 10 percent of the Sahara of northern Africa. Some deserts are not sandy at all.

Types of Deserts
Deserts may be hot or cold. In hot deserts daytime temperatures are often above 100 ° F (38 ° C) in summer. The temperature drops sharply at night. The Sahara is the world’s largest hot desert. Other hot deserts include the Kalahari in southern Africa and those in the southwestern United States. Most hot deserts are in the region known as the tropics. This is a band of Earth on either side of the Equator.
Desert Facts for Kids
A desert receives less than 10 inches of rain a year
A lot of the animals that live in the desert are nocturnal
The Sahara is the largest hot desert on Earth
Antarctica is the largest cold desert on Earth
20 percent of the world’s land surface is desert
Animals have learned to adapt to desert conditions
Deserts land surfaces can be very different – some examples are stones, snow, and sand
The Sahara Desert is in northern Africa and spreads its sand across 12 countries.
The second-largest hot desert on Earth is the Arabian Desert in the Middle East.

• 沙漠的动物

Desert animals also have adaptations that help them survive without much water. Kangaroo rats in the Sonoran Desert get water from the seeds they eat. Some carnivores, such as desert foxes, get enough liquid from their prey.

Another trick? Most desert animals stay underground or beneath shady rocks during the day. Many of them come out to hunt for food at night, when it’s cool.
horn lizard

desert iguana

The iguana, like all lizards, is cold-blooded and relies on the sun to warm its system to optimum temperature . . . too much exposure, however, and it will overheat.

desert turtle
rattle snake
barn owl
hummingbird red-tailed eagle
fennec fox
mountain lion

jack rabbit长耳大野兔

The Rabbit vs. the Hare – Hares and rabbits are similar, but also distinctly different creatures. These animals both look and behave differently from one another. Hares have longer ears and stronger hind legs, while rabbits have shorter ears and smaller rear legs. Hares also live primarily above ground, while rabbits live in tunnels. Their large ears help them thermoregulate, making them well adapted to hot climates. These hares are herbivores, which means that they eat plants. They will feed on a variety of different types of plants, including shrubs, grasses, flowering plants, and small trees.

coyote bobcat

• 沙漠中的植物

Many plants that live in the desert have to go without water for years because rainfall is so sporadic. Some plants have extremely long roots that go a long way into the soil to find water. These roots are called ‘tap roots.’ Other plants find clever ways of storing the water in their leaves or stem to ensure it lasts them a long time - these plants are called succulents.

As a way of reducing water loss via transpiration, a lot of desert plants have also evolved to have very small leaves. The colour of a leaf can help reflect the heat of the sun. Plants with silvery leaves like dune plants absorb less heat than plants with darker leaves. Other plants have small hairs on their leaves to prevent further water loss.

Some plants, like cacti, store enough water in their stems to last until the next rain. Other plants, like mesquite grass, have very small leaves that curl up in the daytime to conserve the water they have. Some desert plants sprout and bloom only when it rains. Cacti make use of structural adaptations. They have shallow roots, persistent spines, and robust stalks.

Water stores in succulent plants’ leaves, stems, and roots. Cacti have adapted to endure the harsh, arid desert environment.