Desert

A desert is an area where little or no life exists because of a lack of water. Scientists estimate that about one-fifth of the earth's land surface is desert. Deserts can be found on every continent except Europe. There are two different kinds: hot and dry (such as the Arabian and Sahara deserts) and cold and dry (such as Antarctica and the Gobi desert).

In North America, there are four major deserts: the Great Basin, the Mojave, the Sonoran, and the Chihuahuan. All but the Great Basin are hot deserts located in Mexico and the southwestern part of the United States. The Great Basin covers parts of Idaho, Nevada, Oregon, and Utah, and is considered a cold desert.

Special features:

The lack of water and intense heat or cold make this biome inhospitable to most life forms. Most of the plants you'll see in the desert are species of cactus. You might come across yucca, aloe, octillo plants, or the tall saguaro cacti. A few animals—mainly reptiles, like snakes and lizards, and amphibians, like frogs and toads—are well adapted to the hot desert. Another famous desert animal is the camel, which can make water from the fat it stores in its hump. The Emperor and Adélie penguins are well-known animals living at the edge of the Antarctic desert.

Desert Biome

  • A desert is a place that gets just a bit of rain every year.
  • Some deserts get almost no rain at all.
  • A desert can be very hot in daytime and cold at night.
  • Some deserts are cold all the time.

A desert is a dry area where less than 50 cm of rain falls each year. About one fifth of the Earth's surface is desert.

Deserts can be hot or cold. The AustralianDesert is one example of a hot desert, and the GobiDesert in Mongolia is an example of a cold desert. Antarctica is the world's largest desert.

The Atacama Desert of Chile and the Sahara Desert in Africa receive less than 1.5 cm a year, if at all.

Although rain doesn't fall very often in deserts, sometimes not for years, there can be sudden, heavy rains that cause flooding.

Deserts can be found along coastlines, such as the Atacama Desert, or in the interior of continents, such as the Great Basin Desert of North America.

The location of the desert and of mountain ranges help determine what type of desert it is. Coastal deserts are located on west coasts of continents.The winds blow in an easterly direction and prevent the moisture from moving onto the land. Some deserts, like the GobiDesert, are affected by high mountain ranges that produce a rainshadow effect, which means the mountains prevent moisture from reaching an area. The Himalaya Mountains prevent rainfall from reaching the GobiDesert .

Because they are dry, deserts have wide variations in temperature each day. In the daytime when there is little moisture in the air to block the sun's rays, it becomes very hot. When the sun goes down, the heat absorbed by the ground during the day quickly evaporates into the air and the temperature becomes very cold.

This variation of temperatures is one of the things that makes survival in the desert very difficult.

Arctic Tundra

The Arctic tundra is a cold, vast, treeless area of low, swampy plains in the far north around the Arctic Ocean. It includes the northern lands of Europe (Lapland and Scandinavia), Asia (Siberia), and North America (Alaska and Canada), as well as most of Greenland. Another type of tundra is the alpine tundra, which is a biome that exists at the tops of high mountains.

Special features:

This is the earth's coldest biome. Since the sun does not rise for nearly six months of the year, it is not unusual for the temperature to be below -30°F in winter. The earth of the Arctic tundra has a permanently frozen subsoil, called permafrost, which makes it impossible for trees to grow. Frozen prehistoric animal remains have been found preserved in the permafrost.

In summer, a thin layer of topsoil thaws and creates many pools, lakes, and marshes, a haven for mosquitoes, midges, and blackflies. More than 100 species of migrant birds are attracted by the insect food and the safe feeding ground of the tundra. Other animals that live in this biome include polar bears, Arctic foxes, caribou, and grey wolves. Plants that you might find include small shrubs and cushion plants, and the lichen which cover the many rocks on the tundra's terrain. The Arctic is also famous for the beauty of its flowers during early autumn.

Tundra Biome

  • The tundra is near the North Pole.
  • Trees do not grow there.
  • Winters are very cold.
  • Summers last for a very short time.
  • Under the soil the earth is frozen and never melts.

About 1/5 of the Earth is tundra. Tundra is the coldest of all the biomes. The word comes from a Finnish word and means 'treeless plain'. There is arctic tundra and alpine tundra.

The winter is long and very cold, with a short summer.

Arctic tundra is in the northern hemisphere, around the north pole, stretching south to the taiga. The summer growing season lasts about 50 to 60 days. Winter temperatures average -34° C , but the summer temperatures average 3-12° C, which is warm enough for plants and animals to reproduce and grow.

Rainfall varies around the Arctic, but on average yearly rain and snow is 15 cm to 25 cm.

About a metre under the top layer of soil there is ground that is permanently frozen, called permafrost. In the very short summers, the top level of soil thaws just long enough for plants to grow and reproduce, then become dormant (hibernate) over winter. But the permafrost layer never thaws. Because of this, tundra plants do not have deep root systems. When water soaks the upper soil surface, bogs and ponds may form and provide moisture for plants and small life forms.

Plants in the tundra are low-growing, and include:
low shrubs, sedges, mosses, liverworts, and grasses;400 varieties of flowers;lichens

Plants group together to withstand the strong winds and cold temperatures. They are protected by the winter snows. They have adapted so that photosynthesis (getting food from sunlight) can occur in the low light and cold temperatures.

Animals found in the Arctic include:
Herbivorous (plant eating) mammals such as lemmings, voles, caribou, arctic hares and squirrels
Carnivorous (meat eating) mammals such as arctic foxes, wolves, and polar bears
Migratory birds such as ravens, falcons, loons, ravens, sandpipers, terns and snow birds
Insects such as mosquitoes, flies, moths, grasshoppers, blackflies and arctic bumble bees

Animals in the tundra have adapted to survive the long cold winters. They have an extra layer of fat to keep them warm, and in winter their fur is longer and thicker. Many hibernate during the winter when food is hard to find. Others migrate to warmer places to avoid the tundra winter. This means that animal populations in the tundra fluctuate with the seasons. Animals breed and raise their young in the short summer. There are few reptiles and amphibians in the tundra because of the cold .

Grasslands

Grasslands are places with hot, dry climates that are perfect for growing food. They are known throughout the world by different names. In the U.S. they are called prairies and extend from the Midwest to the Rocky Mountains. In South Africa, grasslands are called the veld. Hot, tropical grasslands called savannas are found in South America and Africa. In Eurasia, temperate zone grasslands are called steppes; in South America, pampas.

Special features: This inland biome is made of vast areas of grassy field. It receives so little rain that very few trees can grow. The U.S. prairies are used to graze cattle and to raise cereal crops. There is little variety of animal life. Some original prairie animals like the wolf and bison have come close to being eliminated from the habitat by hunters. Today, some of the most common grassland animals include the prairie dog and the mule deer in North America, the giraffe and the zebra in Africa, and the lion in Africa and Asia.

  • Grasses are the main kind of plant in grasslands.
  • There are not many trees in grasslands.
  • Some grasslands are hot all year round.
  • Some grassland areas have hot summers and very cold winters.
  • Grasslands have different names in different places.
  • Grasslands are big open areas that get between 25 and 75 cm of rain per year. This is less rain than a forest gets and more than a desert gets.
  • Grasslands are found on every continent except Antarctica. About one quarter of the Earth's land is in the grasslands biome. Grasslands have different names in different countries, such as pampas (South America), prairies (North America), savannahs (Africa), or steppes (Asia).
  • The main plants of a grassland are of course grasses, with a few low shrubs and occasional trees. In grasslands, trees are more commonly found near rivers and streams. There are many wildflowers that grow in grasslands.
  • Therefore, when you look out over a grassland, what you see is a large, open, continuous piece of land with lots and lots of grass. The roots of the grasses and small plants make the soil rich and good for farming.

There are 3 types of grassland:

Tall grasslands have very tall grass, up to 152 cm tall, and up to 80cm of rain a year.
Mixed grasslands have grasses that grow around 60-90 cm high and about 40-60 cm of rain each year.
Short grasslands have short grasses and receive very little rainfall each year, less than 15 cm.

Grasslands around the world are becoming extinct as people make farms and towns.
Grasslands plants and animals are becoming endangered.

Tropical grasslands are those closest to the equator. They are hot all year long.

Temperate grasslands are those further from the equator, with hot summers and harsh winters.They once stretched across much of North and South America, and they were common in Europe and Asia.

Rainforests

Tropical rainforests are found in Asia, Africa, South America, Central America, and on many of the Pacific islands. They are often found along the equator. Almost half of the world's tropical rainforests are in the South American country Brazil.

There are other types of rainforests around the world, too. For example, northern Australia has a “dry rainforest” that experiences a dry season each year, and the rainy Pacific Northwest in the United States has a “temperate rainforest” that is made up of evergreen trees.

Special features:

Tropical rainforests receive at least 70 inches of rain each year and have more species of plants and animals than any other biome. Many of the plants used in medicine can only be found in tropical rainforests. The combination of heat and moisture makes this biome the perfect environment for more than 15 million plants and animals. The thick vegetation absorbs moisture, which then evaporates and completes the cycle by falling again as rain.

A rainforest grows in three levels. The canopy, or tallest level, has trees between 100 and 200 feet tall. They block most of the sunlight from the levels below. The second level, or understory, contains a mix of small trees, vines, and palms as well as shrubs and ferns. The third and lowest level is the forest floor, where herbs, mosses, and fungi grow.

Rainforests are an endangered biome. People have cut the trees and sold the wood for firewood, building materials, and paper. Parts of the rainforest have been burned to make space for grazing and farming. Every minute, approximately 30 acres of rainforest are destroyed. The large amounts of carbon dioxide that are released due to the cutting and burning of rainforests contribute to the greenhouse effect.

Some of the animals of the tropical rainforest are the anteater, jaguar, brocket deer, lemur, orangutan, marmoset, macaw, parrot, sloth, and toucan. Among the many plant species are bamboo, banana trees, rubber trees, and cassava.

Rainforest Biome

Rainforests are thick, warm and wet forests.

There are two kinds of rainforest: tropical and temperate

Tropical rainforests are millions of years old

Another name for tropical rainforest is jungle

Rainforests are thick, warm and wet forests. They are forests that get at least 250 cm a year of rain, often more. There are two kinds of rainforest: tropical and temperate. Both kinds are endangered.
Tropical rainforests are millions of years old, and temperate rainforests are about 10,000 years old.

Tropical rainforests are located close to the equator, in 85 different countries, and most are in Central and South America, Africa, Asia and Australia. The largest tropical rainforest in the world is the South American Amazon rainforest, much of which lies in Brazil. The world's largest river, the Amazon, flows through the rainforest.

The equator is an imaginary line around the widest part of the earth (not pole to pole), dividing it into two halves, a northern and southern. The equator is where the sun shines most directly onto the earth, and the area in a wide band on either side of the equator is called the tropics. Tropical weather is always very warm and humid.

Only about 40% of forests in the tropics are rainforests. Only places with high rainfall throughout the year that are warm and frost free with little variation in temperature are rainforests. The tropical forests that are not rainforests are in places that have rainy and dry seasons, and the trees often drop their leaves in the dry season. Some forests in mountain areas may get snow and frost even though close to the equator.

Temperate rainforests are found near coastal areas and there are fewer of them than tropical rainforests. Temperate rainforests are found along the Pacific coast of Canada and the USA, and in New Zealand, Tasmania, Chile, Ireland, Scotland and Norway.

In Australia both tropical and temperate rainforests can be found.

Tropical Rainforest Layers
A tropicalrainforest grows in four main layers, with different trees, flowers, and other plants in each layer.
The layers are:
The Top Layer (called the emergent layer)
Huge trees rising high above the rest of the forest, therefore receiving the most sunlight.
The second layer (called the canopy)
Tall trees growing close together so that their tops are close, forming a fairly continuous cover.
The third layer (called the understorey)
Smaller trees, bushes, and plants such as ferns, form the understorey. Not much sunlight reaches here, because the canopy blocks the sun.
The fourth layer (called the forest floor)
Few plants grow on the forest floor because almost no sunlight reaches it. The leaves and plants that drop from the upper layers provide food and shelter for animals and insects that inhabit the forest floor.

Temperate rainforests have just two layers, the canopy and floor.

Coniferous Forest

The coniferous forest biome is south of the Arctic tundra. It stretches from Alaska straight across North America to the Atlantic Ocean and across Eurasia. The largest stretch of coniferous forest in the world, circling the earth in the Northern Hemisphere, is called the “taiga.” It supplies the bulk of the world's commercial softwood timber, which is used to make paper.

Special features:

These forests consist mainly of cone-bearing trees such as spruce, hemlock, and fir, which are well suited to the cold climate. The soil is not very fertile, however, because there are no leaves to decompose and enrich it. Some animals that thrive in this biome are the ermine, the moose, the red fox, the snowshoe rabbit, and birds such as the crossbill and the great horned owl.

Taiga Biome

Taiga, also called boreal forests, is the largest land biome.These forests are found in a broad belt across Europe, Asia and North America : about two thirds are in Siberia, and the rest are in Scandinavia, Alaska and Canada.

In this biome, summers are short and mild and the winters are long, cold and dry.