6 Major Biomes of the World – Discussed!

Some of the major biomes of the world are as follows:

1. Desert Biome 2. Grassland Biome 3. Rain Forest Biome 4. Deciduous Forest Biome 5. Taiga Biome 6. Tundra Biome.

1. Desert Biome:

A desert usually has less than 25 cm of rain per year. Deserts are also characterized by intense sunshine and very hot days (40°C and upward) at least during summer; and the evaporation rate is very high. Nights are generally cold, even in summers, and daily variations in temperature reach extremes found in no other environment. Desert life is usually well adapted to the dry weather.

Most annual plants in the desert are small. They grow rapidly, bloom and produce seeds all within a few days after a rain. Since the growing season is greatly restricted, such plants live relatively small. Many perennial desert plants have small leaves, or none at all, or their leaf surfaces are often reduced to spines and thorns, minimizing water loss by evaporation. Some have very long roots, reaching deeply buried water. Others, like the cacti, absorb water rapidly after a rain and store the same in spongy internal tissues.

Desert animals are also adapted to scarcity of water and extremes of temperature. In most deserts, the large homoeothermic mammals and birds are comparatively rare or are absent altogether because the maintenance of a constant body temperature is difficult or rather impossible under conditions of extreme heat and practically no water.

However, some animals like the camel are adapted to extreme desert conditions. Animals, which match their internal temperature to that of their environment, the so-called cold-blooded animals, live more easily in the desert. Desert animals are generally small, and they include many burrowing forms, which may avoid the direct heat of the Sun. In all deserts small rodents are numerous and almost all are burrowers. The kangaroo rat (Dipodomys) is a desert animal depending on bipedal, leaping locomotion. Snakes and lizards are common in all deserts.

2. Grassland Biome:

In a grassland biome, the vegetation is dominated by grasses, which may grow to about 2 m in the moist areas and 0.2 m in arid regions of the grassland biome. It is not an exclusively tropical biome but extends into much of the temperate zone as well. The more or less synonymous terms “prairie” (in North America), “pampas” (South America), “steppes” (in Central Asia) “puszta” (Hungary) and many other regional terms underscore the wide distribution of this biome.

The common feature of all grasslands is intermittent, erratic rainfall, amounting to about 4 to 16 cm annually. The irregularly of rain, porosity and drainage of the soil, or both factors together prevent a continuous or ample supply of water to plant roots. Grasses of various kinds are particularly adapted to irregularly alternating periods of precipitation and dryness. The environmental conditions vary greatly in different grasslands. There are also non-grass herbaceous species, which are called forbs.

Grassland biome probably supports more species of animals than any other terrestrial habitat. In all grasslands, the primary consumers are the large grazing mammals like the bisons, pronghoms (Antilocapra Americana ) and zebra (Equus zebra). African glass-lands support large herds of zebras and several species of grazing antelopes.

The grassland ungulates are cursorial. Hares and rodent are also common primary consumers in the grasslands. Many rodents, like the prairie dogs and other ground squirrels or the pocket gophers, are burrowing or fossorial animals. Australian grasslands have herbivores very different in appearance and relationships but ecologically similar.

These are large grazing cursorial kangaroos and small, burrowing, rodent-like pouched “mice”. Predators are adapted to the herbivore prey: wild dogs, lions, and the like preying on the ungulates; weasels, snakes, and others on the smaller herbivores. Herbivorous insects such as locusts and grasshoppers are also numerous. Grasslands also support some herbivorous predacious birds.

3. Rain Forest Biome:

They occur in those tropical and subtropical parts where torrential rains fall practically every day and where a well-defined rainy season characterizes the winter. Rain forests exhibit a communal coexistence of up to several hundred different species of trees. They cover much of Central Africa, South and Southeast Asia, Central America, and South America.

However, in contrast to rain forests in the tropics, the species diversity of temperate rain forests is quite low. A tropical rain forest generally has a hundred or more species of trees, and as many as 500 have been observed m one such forest. Two trees of the same species seldom stand near each other. However, the actual species present may be totally different in rain forests found in widely separated regions of the earth.

Tropical rain forest biome receives about 200 cm of precipitation during a year. The productivity of this biome is more than that of any other terrestrial biome. Because of high temperature and abundant moisture, plant litter decomposes quickly and the vegetation immediately takes up the nutrients released. A striking feature of a tropical rain forest is the vertical stratification of plant communities.

Trees in such forests are normally so crowded together that they form a continuous overhead canopy of branches and foliage, which cuts off practically all the sunlight, much of the rain water and wind. As a result, the forest floor is very humid and quite dark and, therefore, plants that require only a minimum of light populate it.

Apart from the forest trees themselves climbing Lianas and Epiphytes are quite characteristic of the tropical rain forests. Rooted in the dark forest floor, lianas are climbing vines, which use the standing trees as supports upon which they climb toward the canopy where they spread their leaves in the light. Epiphytes grow on other plants. Orchids, ferns, and many other epiphytes form veritable aerial gardens among the high branches of the trees of rain forests.

In rain forests animal communities too are stratified vertically into different habitats found between canopy and ground. A much larger proportion of animals live in the upper layers of the vegetation than in temperate forests where most of the life is near the ground level. For example, 31 to 59 species of mammals in British Guiana are arboreal and 5 are amphibious, leaving only 23, which live on the ground.

In addition to the arboreal mammals (monkeys, rodents, squirrels), there is an abundance of chameleons, iguanas, geckos, arboreal snakes, frogs, and birds. Ants, termites, beetles and the Orthopetra, as well as butterflies and moths are ecologically important. Frogs may be present in large numbers.

In the Old World rain forests, ground-dwelling herbivores include musk deer, small forest antelopes, and forest pigs. In both hemispheres partly arboreal carnivores, especially cats such as leopard and jaguar, kill the herbivores. Symbiosis between animals and epiphytes is widespread. Many animals of the rain forest are nocturnal.

4. Deciduous Forest Biome:

In the temperate zones such as Europe, eastern Asia, southern Canada and eastern part of United States, the most characteristic biome is the deciduous forest. Tropical deciduous forests also occur in many tropical parts of the world. The fundamental climatic conditions of a deciduous forest biome are cold winters, warm summers, and well spaced rains bringing about 75 to 100 cm of precipitation per year. The biome is also characterized by seasonal temperature variations, which are greater than daily variations.

Winter makes the growing season discontinuous, and the flora is adapted to this. The temperate deciduous forests cover many parts of the United States, the British Isles, Central Europe, China and south-eastern Siberia. Similar forests also occur in the Temperate Zone of South America, but they are not so widespread there.

The term “deciduous” implies the most obvious characteristic of this biome and the most obvious adaptation to it (i.e., trees shed their leaves and hibernate). Half the year or somewhat more is the growing season, when perennial plants put on their leaves and are active, while annual plants go through the whole cycle from seed to seed.

The rest of the year the trees are bare. Common trees of the deciduous forest are beech, tulip, sycamore, maple, oak, hickory, elm, poplar, and birch. Chestnuts were also formerly common. A deciduous forest differs from a rain forest in that trees are spaced at considerable distance from one another and there are only few species of trees. Compared with the hundreds of tree species in a rain forest, there may be only about 10 or 20 in a deciduous forest.

The most striking herbivorous mammals of a deciduous forest are the browsing deer, mainly the white-tailed deer in North America and other species in Eurasia and South America. In Eurasia wild pigs (or boars) are also found in this biome, but they do not occur native in America. The principal carnivores are the large cats including puma, mountain lion, cougar, or panther (all one species, Felis concolor) ranging into most of the environments of North and South America. Foxes are also common in them.

The arboreal martens are locally as common here as in the taiga, and the raccoon (absent in Eurasia) is especially abundant in deciduous forests of North America. Throughout the world these forests are also rich in tree squirrels. Among mammals of the North American deciduous forests, over a third of the species are mainly arboreal. Tree-nesting birds are also abundant and woodpeckers are characteristic of this biome. The leaf and mold-covered forest floor supports many species of invertebrates and fungi.

5. Taiga Biome:

North of the deciduous forests and the grasslands across northern Europe, Siberia, and Canada, stretches the taiga (northern coniferous forest biome). It is also called the boreal forest biome. This is a biome of long, severe winters and of growing seasons limited largely to the few months of summer. The vegetation is extremely frost-tolerant, as temperatures may fall to – 60° C during the winter. The precipitation is in the range of 40-100 cm. Hardy conifers, spruce in particular, are most representative of the flora; and moose, wolves, and bears of the fauna.

The taiga is largely a zone of forests, which differ from other types of forests in that they usually consist of single species of coniferous tree. Thus, over a large area, spruce, for example, may be the only kind of tree present. Among other coniferous trees, alder, birch, and juniper thickets are common. They might be found in an adjacent equally large area. Many of the larger herbivorous vertebrates, such as the moose (elk), snowshoe hare, and grouse depend on broad leaved developmental communities of spruce forest.

The seeds of conifers provide important food for many animals such as squirrels, siskins, and crossbills. In taiga, seasonal periodicity is pronounced and populations tend to oscillate. The snowshoe hare-lynx cycles are classic examples. Smaller mammals are much more varied than in the tundra. Black bears, wolves, and martens are more common in this biome that elsewhere.

Fishers, wolverines, lynex and some rodents such as the northern vole are practically confined to it. Squirrels and birds also thrive in coniferous forests. Most of the birds here, however, are summer breeders and migrate southward in the autumn. The many species of insects remain dormant during the severe winters.

6. Tundra Biome:

In Asia, Europe, and North America a vast northern zone encircling the Arctic Ocean is known as the tundra. This biome lies north of the taiga. The tundra has the arctic climate, which is cold, and there may be continuous night during the winter season and continuous daylight, of comparatively low intensity, during the summer. Some distance below the surface, the ground is permanently frozen.

This is called permafrost. Above the ground, frost can form even during the summer; plants often freeze solid and remain dormant up to the growing season. The latter is very brief, as in the deserts; but in the tundra the chief limiting factor is temperature, and not water supply. However, alpine tundra does not contain permafrost.

Precipitation is generally less than 50-60 cm but in low lying areas soils may remain saturated with water during most of the growing season. Plants are low, ground hugging forms, and frees are absent. Lichens (especially reindeer moss), mosses (especially Sphagnum) coniferous and other shrubby growths, and herbs with brilliantly coloured flowers, are characteristic of the habitat.

The warm-blooded animals of this biome are caribou, reindeer, musk ox, arctic hare, arctic fox, lemming, and polar bear. They are well protected by fur. Some of the resident birds, like the ptarmigan (an arctic grouse-like bird), and mammals, like the snowshoe hare, turn white in winter. White is protective colouration in a snowy environment and also minimizes heat loss by radiation. Musk oxen and caribou (wild reindeer) are large herbivores, which depend mainly on the abundant moss and lichens. Arctic hares and lemmings (small, rat-like rodents) are numerous and are preyed on by arctic foxes.

Polar bears are amphibious, frequenting coasts and ice flows but also wandering inland on the tundra. Insects, especially flies, are so numerous as to be one of the major drawbacks of the tundra from the human point of view. Their eggs and larvae are particularly cold resistant and the adults appear by the billions on warmer summer days.

Migratory birds, especially waterfowl, are conspicuous during the short summer. Well marked oscillations, or cycles, in population density of some animals are characteristic of tundra communities. For example, when lemmings abound, predatory birds, such as owls are abundant and breed. Whereas few predators breed at all during the years of prey scarcity.

However, the life does not end at the northern margin of the tundra but extends farther into the ice and bleak rock of the soilless polar region. Polar life is almost exclusively animal, and it is not really terrestrial in any way but is based on the sea {e.g. walrus, seals, penguins).

However, some authors also describe the so-called alpine tundra biome. This occurs above the tree line as in the Rocky Mountains of North America and on the Tibetan Plateau of Central Asia. The alpine and arctic tundra have some similarities as well as differences. Alpine tundra does not contain permafrost; it has warmer and longer growing seasons resulting in higher productivity, less severe winters, and higher species diversity than arctic tundra.