BIOMES OF THE WORLD

BIOMES OF THE WORLD

There are many different kinds of plants and animals on the Earth, but only certain kinds are naturally found at any particular place.For example, cacti are found in the desert, polar bears are found in the Arctic, and elephants are found in central Africa and India. So, why don't people living in south Texas have to be on the lookout for snow leopards, or why don't kids in Minnesota have to worry about finding giant boa constrictors in their back yards? It is because these animals are not adapted to live in the average weather conditions found in Texas or Minnesota. These average weather conditions, such as the range of temperature and rainfall that typically occur in a particular location like Minnesota, are called the climate of that location. Some climates are hot, some are cold, some are wet and some are dry. "Adapted" means that a plant or animal has inherited certain characteristics that enable it to live in one type of climate or another. For example, polar bears have a layer of fat under their skin and a heavy fur coat to help them withstand arctic cold. They would have a difficult time trying to survive in a hot climate. Plants and animals don't live in isolation, but they live together with other plants and animals in an interdependent group called  an ecological community. If you think about it for a moment, you will realize that  all of the plants and animals in a particular ecological community must be adapted to the same climate so that they can all live in the same location.

A distinct ecological community of plants and animals living together in a particular climate is called a "biome." Scientists have divided the broad spectrum of climates and ecological communities found on Earth into biomes in different ways - some with many divisions, some with only a few. Here is a commonly found grouping:

TERRESTRIAL BIOMES

TROPICAL RAIN FOREST

Tropical rainforests occur near the equator where the rainfall is abundant and occurs throughout the year. They are found in South and Central America particularly in and around the Amazon basin, West and Equatorial Africa, South-East Asia, Indonesia and North-east Australia as in Fig 1.11. This continual combination of warmth and moisture allows continuous plant growth to occur. The tropical rainforest is the richest biome in terms of number of species probably containing at least half of the species of terrestrial organisms. Contrary to popular belief, undisturbed tropical rainforest is not impenetrable. This is because so little light is able to get through to the forest floor that relatively few plants can grow there. Many trees in the canopy are covered by epiphytes (plants growing on other plants) and some other trees produce aerial roots which absorb nutrients just as roots in the soil do. Much of the animal life is confined for most of the time to the canopy. Fruits are found throughout the year and specialized fruit eaters have evolved among the insects, the birds and the primates. Some other animals concentrate on feeding on leaves for example, the species of sloth in tropical south American forests.

The tropical rainforest is a hot, moist biome found near Earth's equator. The world's largest

tropical rainforests are in South America, Africa, and Southeast Asia. Tropical rainforests

receive from 60 to 160 inches of precipitation that is fairly evenly distributed throughout the

year. The combination of constant warmth and abundant moisture makes the tropical

rainforest a suitable environment for many plants and animals. Tropical rainforests contain

the greatest biodiversity in the world. Over 15 million species of plants and animals live within

this biome.

The hot and humid conditions make tropical rainforests an ideal environment for bacteria and

other microorganisms. Because these organisms remain active throughout the year, they

quickly decompose matter on the forest floor. In other biomes, such as the deciduous forest,

the decomposition of leaf litter adds nutrients to the soil. But in the tropical rainforest, plants

grow so fast that they rapidly consume the nutrients from the decomposed leaf litter. As a

result, most of the nutrients are contained in the trees and other plants rather than in the soil.

Most nutrients that are absorbed into the soil are leached out by the abundant rainfall, which

leaves the soil infertile and acidic.

Tropical Rainforest: Animals

Tropical rainforests support a greater number and variety of animals than any other biome.

One of the reasons for this great variety of animals is the constant warmth. Tropical

rainforests also provide a nearly constant supply of water and a wide variety of food for the

animals. Small animals, including monkeys, birds, snakes, rodents, frogs, and lizards are

common in the tropical rainforest. Many of these animals and a multitude of insects never set

foot on the ground. The animals use the tall trees and understory for shelter, hiding places

from their predators, and a source of food.

Animal adaptation

Because there are so many animals competing for food, many animals have adapted by

learning to eat a particular food eaten by no other animal. Toucans have adapted by

developing long, large bill. This adaptation allows this bird to reach fruit on branches that are

too small to support the bird's weight. The bill also is used to cut the fruit from the tree.

The sloth uses a behavioral adaptation and camouflage to survive in the rainforest. It moves

very, very slowly and spends most of its time hanging upside down from trees. Blue-green

algae grows on its fur giving the sloth a greenish color and making it more difficult for

predators to spot.

Tropical Rainforest: Plants

Although tropical rainforests receive 12 hours of sunlight daily, less than 2% of that sunlight

ever reaches the ground. The tropical rainforest has dense vegetation, often forming three

different layers--the canopy, the understory, and the ground layer. Frequently, people think of

the tropical rainforest as a "jungle" where plant growth is dense even at ground level.

However, the canopy created by the tall trees (100-120 feet) and the understory, prevents

sunlight from reaching the ground. The soil is, therefore, always shaded, and very little

vegetation is able to survive at ground level.

Vegetation can become dense at ground level near riverbanks and on hillsides. Hillsides

have more plant growth because the angle of the growing surface allows sunlight to reach

lower layers of the forest. Riverbeds break up the forest canopy so that smaller plants can get

the needed sunlight.

Plant adaptation

Plant survival in a tropical rainforest depends on the plant's ability to tolerate constant shade

or to adapt strategies to reach sunlight. Fungus is a good example of a plant that flourishes in

warm, dark places created by the forest canopy and understory.

Competition for sunlight by plants is sometimes deadly. The strangler fig needs sunlight to

grow and reproduce. Seeds falling to the ground quickly die in the deep shade and infertile

soil of the tropical rainforest. So it has adapted. Its seeds are deposited on branches of host

trees by birds and small animals that have eaten the fruit of the strangler fig. The seeds

sprout and send a long root to the ground. This root rapidly increases in diameter and

successfully competes for the water and nutrients in the soil. As the strangler fig matures,

branches and leaves grow upwards creating a canopy that blocks sunlight from the host tree.

Additional roots are sent out and wrap around the host tree, forming a massive network of

roots that strangle and eventually kill the host.

TROPICAL SEASONAL FOREST

Close to tropical rain forests are tropical seasonal forests which occur in humid tropical climates with a clear dry season during which period trees lose their leaves. They are found in India, South-east Asia, West and East Africa, South and Central America and Northern Australia. The seasonality makes their habitat less diverse than the rain forests. Tropical seasonal forests are often found also where monsoons occur e.g. India. The monsoons provide seasonal rains as well.

SAVANNAH

Savannahs are tropical grasslands often with scattered trees. They are most extensive in Africa but are also found in Australia, South America and Southern Asia. Savannah is subjected to fire either from lightning or started by humans. Much of the African Savannah is burnt each year which has made savannah trees have thick bark which insulates the living cambium from the heat of the fire. The savannah or grassland of Africa is famed for its abundance of wildlife being inhabited by herds of grazing animal and their associated predators. The numerous herbivores including Zebra, Buffalo, gazelle and Giraffe support large numbers of mammalian carnivores like lion, Leopard, Cheetah and Spotted Hyena among others. On a global scale, the savannah biome is transitional between tropical rainforest and desert. Generally, it records rainfall of between 90 - 150 cm annually. Temperatures annually fluctuate more in this biome than in the tropical rain forest and there is seasonal drought. Savannahs have often been converted to agricultural purposes throughout the world and provide most of the agricultural products for many tropical and subtropical countries.

Tropical Savannah

The tropical savanna is a biome characterized by tall grasses and occasional trees. Large

regions of tropical savanna extend through the nations of Botswana, Namibia, and Kenya in

Africa, southern Brazil, India, and Australia. Surprisingly, the Everglades of southern Florida

in North America is also a tropical savanna.

Savannas exist in areas where there is a 6 to 8 month wet summer season and a dry winter

season. Annual rainfall in savannas varies depending on the geographic location. Some

savannas get as little as 10 inches of rain annually while others can get as much as 50

inches. The dry season is marked by months of drought and fire which are essential to the

maintenance of savannas. Without the period of drought and fire, some scientists believe that

tropical savannas would eventually change into tropical forests.

Savannas can result from either climate, soil conditions, animal behavior, or agricultural

practices, which limit the occurrence of trees. Humans create savannas by burning the

grasslands and felling the trees in order to plant crops. Large animals such as elephants can

turn a forest into a savanna by stripping the bark from the trees, knocking over trees, and

tramping on tree seedlings. 

Tropical Savannah: Animals

The species of animals in a savanna depends upon the geographic location of the biome.

The African savannah, the savannah with which most people are familiar, is home to a wide

variety of animals. A short list of some of those animals includes wildebeest, warthogs,

elephants, zebras, rhinos, gazelles, hyenas, cheetahs, lions, leopards, ostrich, mousebirds,

starlings, and weavers.

Animal adaptations 

During the rainy season, birds, insects, and both large and small mammals thrive in the

savannah, but the rainy season only lasts 6 to 8 months. During the dry season, surface

water from the rain is quickly absorbed into the ground because the soil is extremely porous.

Competition for water during the dry season is intense. Consequently, most birds and many

of the large mammals migrate during the dry season in search of water. Because drought

conditions are sometimes localized, the migration may be just to another area within the

savannah. When drought conditions exist for a long time and over a wide area, the animals

may migrate to another biome until the rainy season begins again.

Although elephants do migrate, they have a physical adaptation that allows them to access

water that is not available to other animals. Baobab trees store water in their large trunks.

The elephant's physical strength and anatomy allow it to tear open the trunk of the baobab

tree and to suck the water from it. An adaptation used by small burrowing animals is to

remain dormant during times of drought--much like bears do during the winter in other

biomes.

During the dry season, lightning frequently ignites the brown, dry grasses that cover the

savannah. Many of the animals have adapted to living with the fires. The ability to fly or to run

fast enables most birds and large mammals to escape the flames. Some birds, such as the

Fork-tailed Drongos, actually are attracted to the active fires. These birds feast on fleeing or

flame-roasted insects. Although small burrowing animals may not be able to outrun the

flames, they frequently survive the fire by digging beneath the soil and remaining there until

the flames pass by them.

Tropical Savannah: Plants

Grasses are the dominant plant life in the savanna. A wide variety of grasses grow in

savannas, but different varieties are found in different savannas. Some grasses grow 6 to 9

feet tall.

Trees growing alone or in small clusters are also part of the savanna biome. In fact, without

the trees, the savanna biome would be considered a prairie. The variety of trees in a

particular savanna is dependent upon the geographic location of the savanna. The acacia

and baobab trees are common in African savannas.

Plant adaptations

In order for the grasses to survive the dry season and the periodic fires, they have developed

an adaptation that allows them to grow quickly when there is adequate water. Then when

water becomes scarce, the grasses turn brown to limit water loss. They store necessary

moisture and nutrients in their roots while they await the return of the rainy season. With food

and water reserves stored below ground, the grasses are able to survive the effects of fire as

well. In fact, fire stimulates new growth and replenishes the soil with nutrients.

The baobab tree has adapted to the savanna biome by only producing leaves during the wet

season. When leaves do grow, they are in tiny finger-like clusters. The small size of the

leaves helps limit water loss. Another adaptation that enables the baobab tree to survive the

long months of drought is its ability to store water in its large trunk.

The acacia tree can survive drought conditions because it has developed long tap roots that

can reach deep, ground water sources. It is also fire resistant. Some varieties resprout from

the root crown when the above ground portion of the tree is damaged by fire. Fire is not the

only hazard faced by the acacia tree.

The acacia tree has developed very useful physical and behavioral adaptations to discourage

animals from eating its leaves. It developed long, sharp thorns and a symbiotic relationship

with stinging ants. The ants live in acacia thorns they have hollowed out, and they feed on the

nectar produced by the tree. When an animal takes a bite of leaves (and thorns), it also gets

a mouthful of angry, stinging ants. The ants defend their homes from other insects as well,

thus protecting the acacia tree.

Giraffes graze on the tops of the acacia, which results in the dome-shaped top characteristic

of acadia trees. A behavioral adaptation aimed at preventing giraffe grazing is a chemical

defense system that is triggered when the giraffe begins to munch on the leaves. First, a poisonous alkaloid that tastes nasty is pumped into the leaves. The giraffe only gets a couple

of mouthfuls of leaves before the remaining leaves become inedible. Then, the tree warns

other acacia trees in the area by emitting a chemical into the air. The other acacia trees

respond by pumping alkaloid into their leaves.

DESERT

Deserts are found throughout the world, mostly in the subtropical zone between 15 and 400 north and south of the equator. Deserts usually receive less than 50mm of rain a year and the rain is unpredictable. Because vegetation is sparse and the skies are usually clear, deserts radiate heat rapidly at night. This leads to large daily changes in temperature, sometimes exceeding 300c between day and night. Summer day time temperatures in deserts are extremely hot frequently exceeding 400c but nights are cool or cold. For most desert organisms the key to survival is being able to make use of the occasional heavy rainfall. Some ephemeral plants use the occasion to germinate, grow flower and produce seeds within the space of 20 – 30 days. Others survive as perennials as underground bulbs or corns with the above ground parts shooting out after heavy rain. Others like cacti are succulent with thick cuticles and sunken stomata which only open at night to minimize transpiration losses. Trees and shrubs that live in deserts often have deep roots that reach sources of water far below the surface of the ground. Animals in the desert face a formidable array of problems. A wide variety of mechanisms have evolved to deal with the problems. To avoid high temperatures, most desert vertebrates live in deep, cool and sometimes even somewhat moist burrows. Active ones only emerge at night when the temperatures are relatively cool. Camels can drink large quantity of water when it is available and can then safely withstand the loss of much of it as they can tolerate a 30% loss of their total water content. Most mammals die if 14% of their water is lost. Among the great deserts of the world are Namid and Kalahari deserts in the south of Africa, the Sahara desert in the north, the Arabian desert, the Gobi to the north of Himalayas and perhaps the driest of them all, the coastal Atacama desert of Peru and Chile in South America.

The defining characteristic of a desert is that it is dry. Depending on its geographical location, the annual precipitation in a desert varies from half an inch to as much as 15 inches. Rainfall is usually very localized, and although it is frequently seasonal, it is difficult to predict when or where it will occur. At times in the Atacama Desert in Chile, years have passed with no measurable rainfall at all. However, that is not generally the case. Deserts can be either hot such as the Australian Desert or cold such as the Gobi Desert. As with all biomes, the desert climate is determined by geographic conditions. Geographic conditions such as location, high atmospheric pressure, and proximity of mountain ranges

determine just what type of desert it is. Deserts may occur along the coast such as the Atacama and Namib deserts or in the interior of continents such as the Great Basin and Australian deserts, which are far from any source of water. Coastal deserts are located on west coasts of continents between 20° to 30° latitude. Prevailing winds blow in an easterly pattern and prevent the moisture from moving onto the land. Semiarid deserts, like the Great Basin Desert, are not only located far from moisture, but are frequently associated with high mountain ranges that produce a rainshadow effect. The rainshadow effect prevents available moisture from reaching the area. The great Gobi Desert of Mongolia has little rainfall because the Himalayan Mountains prevent rainfall from moving into this region. Because all deserts are dry, they have large daily temperature variations. Temperatures are high during the day because there is very little moisture in the air to block the Sun's rays from reaching Earth. Once the Sun goes down, the heat absorbed during the day quickly escapes back into space. High daytime emperatures and low nighttime temperatures make survival in the desert very difficult.

Desert: Animals

At first glance, deserts may appear to be without animal life. However, deserts are home to many reptiles, insects, birds, and small mammals. The kangaroo mice of North America and the bilby and red kangaroo of Australia are just a few examples of small mammals that live in the desert. Most large animals have not adapted to desert life. Their size prevents them from finding shelter from the Sun's heat and they are not able to store water for future use. Animals that do survive in the desert have developed a number of adaptations. Photo: Red Kangaroo.

Animal adaptations 

The most universal behavioral adaptation used by small mammals, reptiles, and insects to deal with high temperatures is staying in the shadow (shade) of plants or rocks, thus avoiding the direct rays of the Sun. These animals also seek shelter by burrowing into the ground. Just as a basement room is cooler than an above-ground room, a burrow, even a few feet underground, can decrease the temperature by several degrees. Another behavioral adaptation used by desert animals is to remain inactive during the hot daylight hours. They hunt at night when temperatures are cool and when there is less risk of losing precious body water. Animals that use this adaptation are referred to as nocturnal. Some animals get all of the water they need from the insects, bulbs, and seeds they eat. They will not drink water

even when it is available. Some animals have developed salt glands, a physical adaptation that allows the secretion of salt without the loss of water. The absence of sweat glands, and the concentration of urine are other physical adaptations made by desert animals. Because fat intensifies heat, a unique physical adaptation of some desert animals is the storage of fat in humps or tails, rather than throughout the entire body.

Desert: Plants

Short grasses, sagebrush, creosote bushes, and cacti are just a few of the plants that can be found in the desert. Plant abundance and variety are determined by the geographic location of the desert. Although short grasses can be found in nearly all desert locations, the saguaro cactus is unique to the Sonoran Desert, and the spiniflex is associated with the Australian Desert.

Plant adaptations 

Because of the dry climate, plants have developed a number of different methods of capturing water. Some plants have developed long (20-30 foot) taproots that go deep into the ground and tap into groundwater sources. Other plants have developed extensive horizontal root systems. These horizontal root systems lie just below the surface and extend far beyond the plant canopy. When it rains the numerous tiny roots capture the water. The mulga tree's root system lies close to the base of the tree. The tree survives because it has developed its own unique system of collecting water. The tree's numerous tiny leaves grow upward. When it rains the leaves capture the water and funnel it down along the branches to the center of the tree. The water then falls to the ground near the trunk of the tree where tree roots are concentrated. Another common physical adaptation is the ability of desert plants to store water in their roots, stems, leaves, or fruit. Plants that store water in this way are referred to as succulents, and they include cacti.Desert plants retain moisture by limiting water loss through their leaf surface. Many plants accomplish this by adapting the size, sheen, or texture of their leaves. Small leaves or spines limit the amount of surface area exposed to the drying heat. Glossy leaves reflect the Sun's radiant heat reducing leaf temperatures and evaporation rates. Waxy leaves prevent moisture from escaping. Water escapes from leaves through the stomata, or leaf pores. A behavioral adaptation used by some plants is to only open leaf pores during the night when air temperature is cool and evaporation rate is low.

TEMPERATE  RAINFORESTS

Temperate rainforests occur along the pacific coast of North America, New Zealand, Australia and Chile. Their climate is cool and maritime, lacking great variation in temperature and with abundant summer rain and much cloudiness and fog. Like with the tropical rainforest, they have rain throughout the year. Though at sometimes of the year, the so called rain is condensed fog. The trees in the temperate rainforests are the tallest in the world. In Australia, the dominant tree of these forests is the mountain ash (Eucalyptus regnans) which can grow to over 90m in height. In North America, the dominant tree is redwood (Sequoia sempervirens) which may be as high as 100m.

DECIDIOUS FOREST

The mid-latitude deciduous forest biome is located between the polar regions and the tropics. Because of its location, air masses from both the cold polar region and the warm tropical region contribute to the changes of climate in this biome. Mid-latitude deciduous forests have both a warm and a cold season Precipitation ranges from 30 to 60 inches and is evenly distributed throughout the year. Much of the human population lives in this biome. Although evergreens are found in this biome, this biome is characterized by an abundance of deciduous trees. "Deciduous" means to fall off, or shed, seasonally. Just as the name implies, these deciduous trees shed their leaves each fall. Lying on the forest floor, the leaves decay. As the leaves decompose, the nutrients contained in the leaves are absorbed by the soil. For this reason, the soils of this biome tend to be very fertile. Because this biome has fertile soil and a long, 5 to 6 month, growing season, many deciduous forests have been converted into agricultural

regions.

Deciduous Forest: Animals

A wide variety of mammals, birds, insects, and reptiles can be found in a deciduous forest biome. Mammals that are commonly found in a deciduous forest include bears, raccoons, squirrels, skunks, wood mice, and, in the U.S., deer can be found in these forests. While bobcats, mountain lions, timberwolves, and coyotes are natural residents of these forests, they have nearly been eliminated by humans because of their threat to human life. Other animals that were native to this biome, such as elk and bison, have been hunted to near extinction.

Animal Adaptations

Migration and hibernation are two adaptations used by the animals in this biome. While a wide variety of birds migrate, many of the mammals hibernate during the cold winter months when food is in short supply. Another behavioral adaptation some animals have adopted is food storage. The nuts and seeds that are plentiful during the summer are gathered by squirrels, chipmunks, and some jays, and are stored in the hollows of trees for use during the winter months. Cold temperatures help prevent the decomposition of the nuts and seeds.

Deciduous Forest: Plants

Trees of this biome include both broadleaf, deciduous trees, such as maple, oak, hickory, and beech, and evergreens, such as hemlock, spruce, and fir. A deciduous forest typically has three to four, and sometimes five, layers of plant growth. Tall deciduous trees make up the top layer of plant growth, and they create a moderately dense forest canopy. Although the canopy is moderately dense, it does allow sunlight to reach the forest floor. This sunlight allows plants in the other layers to grow. The second layer of plant growth includes saplings and species of trees that are naturally shorter in stature. A third layer (or understory) would include shrubs. Forest herbs, such as wildflowers and berries, make up a fourth layer. During the spring, before the deciduous trees leaf out, these herbs bloom and grow quickly in order to take advantage of the sunlight. A fifth layer would include mosses and lichens that grow on tree trunks.

Plant adaptations

In the spring, deciduous trees begin producing thin, broad, light-weight leaves. This type of leaf structure easily captures the sunlight needed for food production (photosynthesis). The broad leaves are great when temperatures are warm and there is plenty of sunlight. However, when temperatures are cold, the broad leaves expose too much surface area to water loss and tissue damage. To help prevent this damage from occurring, deciduous trees make internal and physical adaptations that are triggered by changes in the climate. Cooler temperatures and limited sunlight are two climatic conditions that tell the tree to begin adapting. In the Fall, when these conditions occur, the tree cuts off the supply of water to the leaves and seals off the area between the leaf stem and the tree trunk. With limited sunlight and water, the leaf is unable to continue producing chlorophyll, the "green" stuff in the leaves, and as the Chlorophyll decreases the leaves change color. The beautiful display of brilliant red, yellow, and gold leaves, associated with deciduous forests in the fall, is a result of this process. Most deciduous trees shed their leaves, once the leaves are brown and dry.

TEMPERATE DECIDUOUS FOREST

Temperate deciduous forests grow in continental climates of Northern hemisphere in areas with relatively warm summers and cold or severe winters. The biome covers large areas including much of Asia (Eurasia), eastern United States and Canada. Annual precipitation is generally from 750 to about 2500mm and is well distributed throughout the year but water is generally unavailable during the winter because it is frozen. Trees are the dominant life form and the most abundant species are the oaks. Where there is less precipitation, temperate deciduous forests are replaced by temperate grassland.

GRASSLANDS

 (including the tropical savannah, American prairies) - Grasslands are big open

spaces. There are not many bushes in the grassland. Trees are found only by rivers and

streams. The grassland seems like an endless ocean of grass. Grasslands receive about 10

to 30 inches of rain per year. If they received more rain, the grasslands would become a

forest. If they received less, they would become a desert. Grasslands are often located

between deserts and forests. Grassland soil tends to be deep and fertile. The roots of

perennial grasses usually penetrate far into the soil. In North America, the prairies were once

inhabited by huge herds of bison and pronghorns who fed on the prairie grasses. These

herds are almost gone now, and most of the prairies have been converted into the richest

agricultural region on earth. Crops grow well in the rich soil.

TEMPERATE GRASSLAND

Temperate grasslands are found across large areas of eastern Europe and Asia (Eurasia) where they are called steppe; Central North America where they are called prairie and Argentina where they are called pampas. The summers are hot and the winters cold with the continental climate moderately dry having between 200 to 750mm of rain each year. The flora of these temperate grasslands is dominated by perennial grasses.The Eurasian steppes lie between the forests to the north and the deserts to the south. Most of the steppe has now been devoted to the production of wheat. Much wheat is also produced in the prairies of North America as temperate grasslands are suited to agriculture when they receive enough precipitation.

BOREAL FOREST (TAIGA)

Boreal forest is also known as taiga. It extends from north-eastern Europe across Russia to the Pacific Ocean and right across North America from Alaska to Newfound land. To the North it merges into tundra; and to the south, it grades into temperate deciduous forest or grassland. It can be very cold in the taiga. In winter, taiga receives a deep blanket of snow and for much of the year, snow lies on the ground. Eastern Siberia is the coldest area in the northern hemisphere with a January temperature of – 50 to –60oc . Because of the latitude where boreal forest occurs the days are short in winter (as little as 6 hours) and correspondingly long in summer. The vegetation of boreal forest is dominated by coniferous trees primarily, spruce, hemlock and fir. Most trees tend to occur in dense stands of one or a few species. During summer, plants may grow rapidly and crops often attain a large size in a surprisingly short time. With the harsh winters, the taiga poses severe problems for the animals found in it. Some of the birds and mammals migrate, some remain active during the long dark winter, like the community of rodents and other animals beneath the thick cover of snow where they are completely protected from most predators and some of the mammals hibernate. Large animals that live here include herbivores like moose, deer and carnivores such as wolves, bear and lynx. This region is traditionally known for fur trapping and lumber producing.

The taiga biome is found in the northern hemisphere close to the polar region. This cold biome (see climograph) stretches across the northern portions of North America, Europe, and Asia. Large population centers, such as Moscow and Toronto, can be found in the southern portion of this biome, but the northern portion is relatively unpopulated. Within this biome, there is a wide range of temperatures between winter and summer seasons. Winters are long and cold, and the summers are short and cool. Precipitation is moderately high throughout the year with snow occurring during the winter months.Most of the taiga in North America was once covered with glaciers that have receded, leaving gouges and depressions in the topography. Since there is moderately high precipitation, these gouges and depressions are frequently filled with water, creating bogs and lakes. The soil found in the taiga is low in nutrients and high in acid. It also is rocky and covered with undecayed leaf litter. Patches of permafrost can also be found in areas of the taiga.

Taiga: Animals

The cold climate of the taiga prevents many animals from living there year-round. Some of the large animals found in the taiga include moose, deer, and bears. Examples of smaller animals that live in the taiga are bobcats, squirrels, chipmunks, ermine, and moles. The taiga is home to many insects and birds such as the bald eagle, chickadee, woodpeckers, and warblers. The bogs and ponds, found throughout the taiga during the summer, provide a wonderful breeding place for a wide variety of insects. Many migratory birds come to the taiga to nest and feed on the huge insect population.

Animal adaptations

Most animals migrate to warmer climates once the cold weather begins. Some animals have adapted to life in the taiga by hibernating when temperatures drop. Other animals have adapted to the extreme cold temperatures by producing a layer of insulating feathers or fur to protect them from the cold. In some instances, the adaptation of a seasonal change in color of feathers or fur protects the animal from its predators. The ermine, a small mammal, is a good example of this adaptation. Its dark brown summer coat changes to white in the winter. This adaptation helps the ermine blend into its surroundings and makes it more difficult for the ermine's predators to spot them.

Taiga: Plants

Because the climate of the taiga is very cold, there is not a large variety of plant life. The most common type of tree found in the taiga is the conifer--trees that have cones. Four kinds of conifers are common in the taiga. Three of the common conifers are evergreens; spruce, fir, and pine. The fourth common conifer is the tamarack, or larch, a deciduous tree. Under certain conditions, broadleaf trees, such as birch and aspen, are able to survive the harsh climate of the taiga.

Plant adaptations 

Evergreens use a wide variety of physical adaptations. Some of these adaptations include their shape, leaf type, root system, and color. Their name, evergreen, describes an important adaptation. They are always--or ever green. Because they don't drop their leaves when temperatures cool, they don't have to regrow them in the spring. Growing new leaves takes a lot of energy. Plants get their energy from the soil and from the Sun. Soil is a source of nutrients. Sunlight is necessary for photosynthesis to take place in the plant. The taiga soil doesn't contain many nutrients, and the Sun usually remains low in the sky. These two factors limit the amount of energy available to the tree. By keeping their leaves, the evergreens are able to use that limited energy for structural growth rather than producing leaves. Although the taiga has moderately high precipitation, the ground freezes during the winter months and plant roots are unable to get water. The adaptation from broadleaf to narrow needle-like structures limits water loss through transpiration. Evergreen needles do not contain very much sap. This limits the risk of needle damage from freezing temperatures. The needles do, however, contain a chemical that repels animals who would eat the needles. The dark green color of the needles absorbs the sunlight, and since the needles are always present, once temperature start to get warm, photosynthesis quickly begins. The conical shape of the evergreens allows the snow to slide off the branches rather than pile up. If the snow can't pile up on the branches, there is less risk of broken branches due to the weight of

the snow.

TUNDRA

Farthest north in Eurasia, North America and their associated Islands between the taiga and the permanent ice, occurs the open often boggy low treeless vegetation known as tundra. It is an enormous biome, extremely uniform in appearance that covers a fifth of the earths land surface. The growing season is too short, the winters too cold and dry and the soil too unstable to support trees. The trees present are small and are mostly confined to the margins of streams and lakes. In general, tundra is dominated by scattered patches of grasses and sedges (grass like plants) heathers, lichens and dwarf willows. The growing season is so short that few plants are annuals. When the short growing season does arrive, plant growth and flowering may be spectacular with enormous areas bathed in colour. The rapid growth of plants is with food stored underground by the plants. Tremendous numbers of insects suddenly appear and for a few weeks productivity is high before winter sets in again for most of the year. Large grazing animals including musk-oxen, caribou, reindeer and carnivores such as wolves, foxes and lynx live in the tundra which teems with life in the short summer.

Arctic Tundra

Arctic tundra is found across northern Alaska, Canada, and Siberia. This biome has long cold  winters and short cool summers. The Arctic tundra has low precipitation (less than 10 inches  per year) and dry  inds. These conditions make the Arctic tundra a desert-like climate One unique characteristic of the Arctic tundra is permafrost--ground that is permanently frozen. Because the permafrost has no cracks or pores, nothing can penetrate it--neither plant roots nor water. The surface layer above the permafrost thaws each summer. This layer is called the active layer. Thickness of the active layer depends on its location in the tundra. The more northerly the location, the thinner the active layer is. Curiously, during the summer Arctic tundra is characterized by lots of surface water. When snow melts, the water percolates through the active layer but is unable to penetrate the permafrost. Since the water has nowhere to go, the active layer becomes saturated and pools of water form on the surface. Another characteristic of the Arctic tundra is the limited amount of sunlight it receives due to the position of the Sun in the sky. Depending on the latitude, the Sun can remain below the horizon for up to 2 months, leaving the Arctic tundra in darkness. Although the sun remains in the sky 24 hours a day during the summer, it stays close to the horizon and provides only low intensity sunlight.

Arctic Tundra: Animals

Not many kinds of animals live year-round in the Arctic tundra. Most birds and mammals only use the tundra as a summer home. Mammals that do live year-round in the tundra include the musk ox, Arctic wolf, and brown bear; and each has its own way of adapting to the extreme climatic conditions. Animals need to find ways to stay warm and to provide nourishment for themselves in order to survive the long, cold, winter months.

Animal adaptations

Migration and hibernation are examples of behavioral adaptations used by animals in the Arctic tundra. The fact that many animals do not live year-round in the tundra means they leave or migrate for a length of time to warmer climates.Hibernation is a combination of behavioral and physical adaptations. For example, during the summer the brown bear's behavior is to eat just about anything it can find; then it hibernates, or sleeps, during the winter. The bear's physical adaptation allows the food eaten during the summer to be stored as a layer of fat underneath its skin. The layer of fat insulates the bear from the cold. While in hibernation the fat is slowly converted into energy that maintains life. A physical adaptation used by the Musk Ox is the growth of two layers of fur--one short and the other long. Air is trapped in the short layer of fur and is warmed by body heat. The warmed air, trapped close to the body, acts as insulation from the cold. The layer of long fur protects the Musk Ox from the wind and water. In addition to thick layers of fur, the Musk Ox relies on another physical adaptation to help it survive. The hooves of the Musk Ox are large and hard. During the winter months, this adaptation allows the Musk Ox to break the ice and drink the water underneath.

Arctic Tundra: Plants

Plants need warmth and sunlight to grow and reproduce. In the Arctic tundra, warmth and sunlight are in short supply, even in the summer. The ground is frequently covered with snow until June, and the Sun is always low in the sky. Only plants with shallow root systems grow in the Arctic tundra because the permafrost prevents plants from sending their roots down past the active layer of soil. The active layer of soil is free from ice for only 50 to 90 days. Arctic plants have a very short growing season. However, in spite of the severe conditions and the short growing season, there are approximately 1,700 kinds of plants that live in the Arctic tundra. Some of the plants that live in the Arctic tundra include mosses, lichens, lowgrowing shrubs, and grasses--but no trees. In fact, "tundra" is a Finnish words which means

"treeless".

Plant Adaptations

Growing close together and low to the ground are some of the adaptations that plants use to survive. This growing pattern helps the plant resist the effects of cold temperatures and reduce the damage caused by the impact of tiny particles of ice and snow that are driven by the dry winds. Plants also have adapted to the Arctic tundra by developing the ability to grow under a layer of snow, to carry out photosynthesis in extremely cold temperatures, and for flowering plants, to produce flowers quickly once summer begins. A small leaf structure is another physical adaptation that helps plants survive. Plants lose water through their leaf surface. By producing small leaves the plant is more able to retain the moisture it has stored.

TEMPERATE SHRUBLAND (MEDITERRANEAN)

This biome is noted for winter rainy season and summer drought. It has what is often called Mediterranean climate and is found around the Mediterranean area itself; California, central Chile, the Cape region of South Africa and Southwestern Australia. The annual rainfall is about 300 – 800mm and during the summer there is usually no rain for about four months. The vegetation is very similar in these separated regions even though the individual plant species differ greatly between the regions. This biome called Chaparral in California and Maquis in the Mediterranean region consists of evergreen often spiny shrubs and low trees between 1 - 5m high with small thick drought resistant leaves. Because of its relatively dry conditions, these shrubland are greatly affected by fire. California Chaparral is highly inflammable. Fires are often started by lightning. In recent times bush fires in this biome have caused so much havoc in both California and Australia.

ALPINE BIOMES

Increasing altitude produced many of the same changes in temperature and moisture as increasing latitude. The tops of the mountains, therefore, have a typical windswept vegetation similar in many respects to tundra. The difference between altitude and latitude however is that day length remains constant up a mountain while it changes with increasing latitude as you approach the poles. Among the biomes influenced by altitude are the following:

ALPINE SHRUBLAND

Alpine shrublands are sometimes found above the tree line on mountains. They occur in South America, Africa, the Himalaya and New Zealand. Above about 300m, frosts occur at night and the altitude marks the limit of the mountain forest or tree line. The vegetation in this high location is like that on the mountain of East Africa described as Afro-alpine of low growing treeless alpine type. The giant rosette plants (giant lobelias) Lobelia telekii up to 5-8m in height dominate the landscape. Hyrax, rat and mice abound in this alpine biome.

 ALPINE GRASSLAND

High up the mountain, the climate might be thought to be similar to the climate near the poles. However, with longer day length on the mountain than the poles and the fact that the mountain often receives more rain and snow than the poles, mountain vegetation differs significantly from the vegetation of the tundra. Alpine plants on the mountain are small and tend to grow slowly with beautiful delicate brightly coloured flowers. The alpine marmot (Marmota marmota) occurs throughout the Alps of central Europe. Marmots hibernate at least half the year when their heartbeats slow down and body temperature falls to enable them conserve energy.

AQUATIC BIOMES 

FRESHWATER BIOMES

Freshwater biomes are found in bogs, swamps, marshes, lakes, ponds, rivers and streams. Bogs are wetlands that only receive water from rainfall. Swamps and marshes form where water runs off the surrounding land and collects as a result of impeded drainage or where ground water lies close to the surface. In some cases, rivers and streams may also feed into the areas. It becomes a swamp if the dominant vegetation are trees and a marsh if the vegetation is mainly of grasses and reeds.

COOL TEMPERATE BOG

Bogs tend to be nutrient poor as they receive water only from the rain which has very little nutrient content. They are dominated by mosses the dominant species being of the genus Sphagnum. Bogs occur mainly in the temperate and boreal regions. Bog community is slow growing and short. Primary productivity is slow with only small populations of herbivores such as insects, hares and bog lemmings and few predators such as spiders and owls. Larger herbivores and predators like deer, caribou and bears roam over large areas and occasionally enter bogs.

TROPICAL FRESHWATER SWAMP FOREST

The best developed tropical fresh water swamp forests are those of the Amazon basin in South America. They are dominated by trees. Minerals in the waters and accompanying soils tend to be scarce so that primary production is low. As such, there are few animals in the biome.

TEMPERATE FRESH WATER SWAMP FOREST

The most famous swamp area of this biome is found in Florida (USA) called the Everglades. Here the very low-lying land is often flooded. Dominant tree species include the swamp cypress and water tupelo. With the floor of the forest under water most of the time several plant species have knee roots which may act as pneumatophores. Animals are abundant in this swamp forest. In the Everglades, there are about 250 species of birds, 240 of fish, 57 of reptiles 25 of mammals and 17 species of amphibians. Alligators are quite common in the swamp forest. Marshes which are dominated by grasses, sedges and reeds are common in temperate zones. The same genera of plants are common in marshes found in North America and Eurasia both in the northern hemisphere.

LAKES AND PONDS

The factors that influence the biome of lake or pond is the extent to which the water is present all the year round. A pond for example can be ephemeral or not. The nutrient abundance or lack of it is also important. Large lakes like the North American Great Lakes drain a huge area which in the past consisted of deciduous forest to the south and conifer forest to the north. Human activities have greatly affected the forests. Salmon fishing used to be a dominant business in the lakes. However, as a result of sawdust pollution of streams used by salmon for spawning and which flowed into the lakes, fishing ceased by 1900. In the absence of pollution, the presence of plankton in a lake should encourage the presence of many other organisms in the lake and increase productivity to man’s advantage.

A lake is a large body of fresh water. Lakes can range in size from small ponds to huge bodies of water such the Great Lakes in the U.S.  Lakes and rivers are closely tied. Some lakes are the source for some rivers. Important rivers, most often, originate from lakes. Some rivers end in lakes. Since both rivers and lakes are freshwater and flow in and out of each other, they share similar characteristics and many species reside in both habitats.  A pond is a body of water shallow enough to support rooted plants. Many times plants grow all the way across a shallow pond. Water temperature is fairly even from top to bottom and changes with air temperature. There is little wave action and the bottom is usually covered

with mud. Plants can, and often do, grow along the pond edge. The amount of dissolved oxygen may vary greatly during a day. In really cold places, the entire pond can freeze solid.  A lake is bigger than a pond, and is too deep to support rooted plants except near the shore. Some lakes are big enough for waves to be produced. Water temperatures in lakes during summer months is not uniform from top to bottom. Three distinct layers develop: The top layer stays warm at around 65–75 degrees F (18.8–24.5 degrees C). The middle layer dropsdramatically, usually to 45–65 degrees F (7.4–18.8 degrees C). The bottom layer is the coldest, staying at around 39–45 degrees F (4.0–7.4 degrees C). Since light does not

penetrate to the bottom, photosynthesis is limited to the top layer. Because of the warmer waters and more plentiful food supply, almost all creatures spend the summer months in the upper layer.  During spring and fall the lake temperature is more uniform. Fish and other animals are found throughout the layers of the lake.  Even in cold climates, most lakes are large enough so that they don't freeze solid, unlike ponds. During the winter months some creatures hibernate in the bottom mud. Some fish continue to feed, but less actively. A layer of ice can develop on the top of lakes during winter. The ice blocks out sunlight and can prevent photosynthesis. Without photosynthesis, oxygen levels drop and some plants and animals may die. This is called "winterkill." 

WETLANDS

Fresh water wetlands are found all over the world in lowland areas or along

rivers, lakes, and streams.   Some wetlands are temporary and seasonal. They occur for a few weeks at a time and then disappear until they are refilled with water. Other wetlands are always under water.  he term "wetlands" encompasses a wide variety of aquatic habitats including swamps, marshes,

bogs, prairie potholes, flood plains, and fen.   Natural wetlands are lands which, due to geological or ecological factors, have a natural supply of water—either from tidal flows, flooding rivers, connections with groundwater, or because they are perched above aquifers or potholes. Wetlands are covered or soaked for at least a part, and often all, of the year. This makes wetlands intermediaries between terrestrial and aquatic ecosystems. They are neither one or the other, and yet they are both.  

STREAMS AND RIVERS

Stream and rivers vary greatly. The large Amazon river with its huge mouth cannot be compared with a steep stream just taking off from a mountain side. As a stream or river flows from its source to its South, the speed decreases, the volume of water increases, oxygen level falls, the bed becomes less steep and composed of smaller particles and human influences increase. Streams and rivers unlike lakes are unidirectional with relatively rapid flow of water. This characteristic may be responsible for the virtual absence of plankton in them. The communities in rivers and streams are therefore, quite different from those of even adjacent lakes.

A watershed describes an area of land that contains a common set of streams and rivers that all drain into a single larger body of water, such as a larger river, a lake or an ocean. For example, the Mississippi River watershed is an enormous watershed. All the tributaries to the Mississippi that collect rainwater eventually drain into the Mississippi, which eventually drains into the Gulf of Mexico. Rainwater that falls on more than half of the United States subsequently drains into the Mississippi. 

OCEAN OR MARINE BIOMES

Marine biomes are found in the coastal and intertidal zones around the oceans of the world. The various types of marine biomes include:

MARINE ROCKY SHORE

Marine rocky shore can occur on any rocky coastline and are found in both temperate and tropical climates. They are found where waves or currents are particularly strong. Vascular plants and mammals are totally absent here. Photosynthetic organisms found here are multi-cellular algae or seaweeds. Most of the animals are invertebrates, a few fish and occasional visit of predatory birds. No organism here is large or obvious like oak trees because the energy of the waves crashing on the rock would probably break up and wash them off. Rock pools differ greatly from one another. A biological feature of a rock shore is zonation of organisms in littoral regions. Those low down on the shore spend almost all their time submerged by water, high up on the shore, they may be submerged only at certain times of the month remaining terrestrial at other times apart from the influence of sea spray. Besides the plants (species of seaweed), animals (sedentary barnacles and mobile periwinkles) also           show characteristic zonation too.

MARINE SANDY BEACH

Marine sandy beaches occur around the world in the littoral belt. They look inviting to humans but pose considerable problems for the organisms living there. Sand is abrasive and constantly on the move as such, no rooted plants can establish in the intertidal region. Except for some calcareous matter from seashells, sand is nutrient poor although diatoms and other algae can be found on surface layers. In the intertidal region, plankton and detritus brought in by the waves are what small animals depend on. Such animals include bivalve, mollusc, sea cucumber, crabs, worms and other wormlike or flattened invertebrates. The rich invertebrate life supports large numbers of wading birds with specialized beaks used to remove invertebrates from various depths of the sand.

MANGROOVE SWAMP

Mangrove swamps occur along the coastline of tropical or subtropical regions where strips of swampland are submerged every high tide with marine or brackish water. Wherever the wave action is not too strong to prevent regeneration, these coastal wetlands are densely vegetated with thickets of mangrove trees. There are about 70 species of mangrove plants around the world with Rhizophora and Avicennia being the most important genera. Mangroves are well adapted to salty conditions although they are capable of growing in fresh water. Mangrove swamps are influenced by tides as incoming tides bring in nutrients. Plant seeds are also dispersed by tides. The structure of the trees is unique and unusual as aerial roots arise quite high up on the trunk then, plunge into the mud beneath. A variety of animals live within the mangrove including fiddler crabs, mud skippers, alligators, crocodiles and in some mangroves big cats such as tigers.

CORAL REEF

Corals are coelenterates (invertebrates), relatives of the sea anemones. Most corals are colonial and secrete a limestone skeleton from which the polyps extend. The polyps have tiny tentacles which catch food and stuff it into a central mouth. At times of danger, the individual polyps pull themselves down into the skeleton out of harm’s way. A coral reef is made up of the limestone skeletons secreted by innumerable colonial coral polyps which are left behind one on top of another. Coral reefs are only found in clear seas within 50m of the surface where the temperature remains above 200C throughout the year. Many species of corals live together within a single reef. These corals support many other animals such as invertebrates the most well known being the crown-of-thorns star fish (Acanthaster planci) and many fishes. In terms of high productivity, the species diversity complexities of co-evolution and sheer beauty, coral reefs are the tropical rainforests of the ocean. They abound mainly in the pacific West Indies where we have some coral Islands.

Continental Shelf

The considerable continental shelves that surround many of the continents lie on average, 130m below sea level, so that in their shallower regions, benthic algae and plants can photosynthesise. Here are found the impressive Kelp forests of large brown algae such as Laminaria. Kelps are often found in areas where ocean currents and the action of waves ensure a plentiful supply of nutrients. Their productivity may be high but they enter the food web in the form of detritus as few animals feed on them. The continental shelf benthos supports large numbers of animals from a variety of phyla. These animals include polychaete worms, nemertine worms, mollusks, sea squirts, sponges, sea spiders crustaceans and echinoderms along with a number of fish.