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INDEX

Introduction 3

Objectives 4

Content

Biomes 5

Tropical Rain Forest 6

Taiga 7

Tundra 7

Biomes established by altitude 8

Biomes established by rainfall 9Temperate rain forests 9

Grasslands 9

Desserts 10

Chaparral 11

Conclusions 12

Annexes 13

Bibliography 14

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INTRODUCTION

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OBJECTIVES

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BIOMES

They are climatically and geographically defined as similar climatic

conditions on the Earth, such as communities of plants, animals, and soil

organisms. They are often referred to as ecosystems.

Some parts of the earth have more or less the same kind of abiotic and

biotic factors spread over a large area, creating a typical ecosystem

over that area.

Such major ecosystems are termed as biomes. Biomes are defined by

factors such as plant structures (such as trees, shrubs, and grasses), leaf

types (such as broadleaf and needleleaf), plant spacing (forest,

woodland, savanna), and climate.

There exist 8 different types of biomes around the world:

Tundra

Taiga

Temperate deciduous forest

Scrub forest (called chaparral in California)

Grassland

Desert

Tropical rain forest

Temperate rain forest

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If there is ample rainfall, we find 4 characteristic biomes as we proceed

from the tropics (high temperatures) to the extreme latitudes (low

temperatures). In order, they are:

Tropical rain forest or jungle Temperate deciduos forest Taiga Tundra

Tropical Rain Forest

In the Western Hemisphere, the tropical rain forest

reaches its fullest development in the jungles of

Central and South America.

The trees are very tall and of a great variety ofspecies.

One rarely finds two trees of the same speciesgrowing close to one another.

The vegetation is so dense that little lightreaches the forest floor.

Most of the plants are evergreen, notdeciduous.

The branches of the trees are festooned withvines and epiphytes (see the photo taken in

the Luquillo National Forest of Puerto Rico).

Epiphytes are plants that live perched on sturdier plants. They do not

take nourishment from their host as parasitic plants do. Because their

roots do not reach the ground, they depend on the air to bring them

moisture and inorganic nutrients. Many orchids and many bromeliads

(members of the pineapple family like "Spanish moss") are epiphytes.

The lushness of the tropical rain forest suggests a high net productivity,

but this is illusory. Many of the frequent attempts to use the tropical rain

forest for conventional crops have been disappointing. Two problems:

The high rainfall leaches soil minerals below the reach of plantroots.

The warmth and moisture cause rapid decay so little humus isadded to the soil.

The tropical rain forest exceeds all the other biomes in the diversity of its

animals as well as plants. Most of the animals mammals and reptiles,

as well as birds and insectslive in the trees.

The closest thing to a tropical rain forest in the continental United Statesare the little wooded "islands" found scattered through the Everglades in

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the southern tip of Florida. Their existence depends on the fact that it

never freezes, and they often escape the fires that periodically sweep

the Everglades.

Temperate Deciduous Forest

This biome occupies the eastern half of the

United States and a large portion of Europe. It ischaracterized by:

hardwood trees (e.g., beech, maple, oak,hickory) which

are deciduous; that is, shed their leaves inthe autumn.

The number of different species is far morelimited than in the jungle.

Large stands dominated by a single speciesare common.

Deer, raccoons, and salamanders arecharacteristic inhabitants.

During the growing season, this biome canbe quite productive in both natural and

agricultural ecosystems.

Taiga

It is a land dominated by conifers,especially spruces and firs.

It is dotted with lakes, bogs, andmarshes.

It is populated by an even more limitedvariety of plants and animals than is the

temperate deciduous forest.

In North America, the moose is such atypical member that it has led to the

name: "spruce-moose" biome.

Before the long, snowy winter sets in,many of the mammals hibernate, andmany of the birds migrate south.

Although the long days of summerpermit plants to grow luxuriantly, net

productivity is low.

Tundra

At extreme latitudes, the trees of the taiga become stunted by the

harshness of the subarctic climate. Finally, they disappear leaving a land

of bogs and lakes.

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The climate is so cold in winter that even the long days of summerare unable to thaw the permafrost beneath the surface layers of

soil.

Sphagnum moss, a wide variety of lichens, and some grasses andfast-growing annuals dominate the landscape during the short

growing season. Caribou feed on this growth as do vast numbers of insects. Swarms of migrating birds, especially waterfowl, invade the tundra

in the summer to raise their young, feeding them on a large variety

of aquatic invertebrates and vertebrates.

As the brief arctic summer draws to a close, the birds fly south, and all but a few of the permanent residents, in one way or another,

prepare themselves to spend the winter in a dormant state.

Biomes established by altitude

Temperature is the major influence on the biomes discussed above.

Because temperatures decline with altitude as well as latitude, similar

biomes exist on mountains even when they are at low latitudes. As a rule

of thumb, a climb of 1000 feet (about 300 m) is equivalent in changed

flora and fauna to a trip northward of some 600 miles (966 km).

Field studies in various parts of the Northern Hemisphere have shown

that in recent decades many species of animals and plants have:

Shifted their ranges farther north (averagiing 16.9 kilometers perdecade);

Shifted their ranges higher in the mountains (averaging 11.0 metersper decade).

These observations add to the growing body of evidence that global

warming is affecting a broad assortment of living things.

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Biomes established by rainfall

The other major biomes are controlled not so much by temperature but

by the amount and seasonal distribution of rainfall.

The prevailing winds in the western half of North America blow in fromthe Pacific laden with moisture. Each time this air rises up from the

western slopes of, successively, the Coast Ranges, the Sierras and

Cascades, and finally the Rockies, it expands and cools. Its moisture

condenses to rain or snow, which drenches the mountain slopes

beneath. When the air reaches the eastern slopes, it is relatively dry, and

much less precipitation falls. How much falls and when determine

whether the biome will be:

Temperate rain forest Grassland Desert or Chaparral

Temperate Rain Forest

The temperate rain forest combines high annual rainfall with a

temperate climate. The Olympic Peninsular in North America is a good

example. An annual rainfall of as much as 150 inches (381 cm) produces

a lush forest of conifers.

Grasslands

Grasslands are also known

as prairie or plains. The annual

precipitation in the grasslands

averages 20 inches (~51 cm)

per year. A large proportion of

this falls as rain early in the

growing season. This promotes

a vigorous growth of perennialgrasses and herbs, but

except along river valleys is

barely adequate for the

growth of forests.

Fire is probably the factor that tips the balance from forest to grasslands.

Fires set by lightning and by humans regularly swept the plains in

earlier times. Thanks to their underground stems and buds, perennial

grasses and herbs are not harmed by fires that destroy most shrubs and

trees.

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The abundance of grass for food, coupled with the lack of shelter from

predators, produces similar animal populations in grasslands throughout

the world. The dominant vertebrates are swiftly-moving,

herbivorous ungulates. In North America, bison and antelope were

conspicuous members of the grassland fauna before the coming of

white settlers.

Now the level grasslands supply corn, wheat, and other grains, and the

hillier areas support domesticated ungulates: cattle and sheep.

When cultivated carefully, the grassland biome is capable of high net

productivity. A major reason: rainfall in this biome never leaches soil

minerals below the reach of the roots of crop plants.

Desert

Annual rainfall in the desert is lessthan 10 inches (25 cm) and, in

some years, may be zero.

Because of the extreme dryness

of the desert, its colonization is

limited to:

Plants such as cacti,sagebrush, and mesquite that

have a number of

adaptations that conservewater over long periods;

Fast-growing annuals whose seeds can germinate, develop tomaturity, flower, and produce a new crop of seeds all within a few

weeks following a rare, soaking rain.

Many of the animals in the desert (mammals, lizards

and snakes, insects, and even some birds) are

adapted for burrowing to escape the scorching

heat of the desert sun. Many of them limit their

forays for food to the night.The net productivity of the desert is low. High

productivity can sometimes be achieved

with irrigation, but these gains are often only

temporary. The high rates of evaporation cause

minerals to accumulate near the surface and soon

their concentration may reach levels toxic to plants.

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Chaparral

The annual rainfall in the chaparral biome may reach 2030 inches (64

76 cm), but in contrast to the grasslands, almost all of this falls in winter.

Summers are very dry and all the plants trees, shrubs, and grasses

are more or less dormant then.

The chaparral is found in California. Similar biomes (with other names,

such as scrub forest), are found around much of the Mediterranean Sea

and along the southern coast of Australia.

The trees in the chaparral are mostly oaks, both deciduous and

evergreen. Scrub oaks and shrubs like manzanita and the California lilac

form dense, evergreen thickets. All of these plants are adapted to

drought by such mechanisms as waxy, waterproof coatings on their

leaves.

The chaparral has many plants brought to it from similar biomes

elsewhere. Vineyards, olives, and figs flourish just as they do in their native

Mediterranean biome. So, too, do eucalyptus trees transplanted from

the equivalent biome in Australia.

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CONCLUSIONS

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ANNEXES (GLOSSARRY)

Woodland: Land with a lot of trees.

Grassland: an area, as a prairie, in which the natural vegetation consists

largely of perennial grasses, characteristic of subhumid and semiaridclimates.

Deciduous: Shedding the leaves annually, as certain trees and shrubs.

Conifer: Any of numerous, chiefly evergreen trees or shrubs of the class

Coniferinae, including the pine, fir, spruce, and other cone-bearing trees

and shrubs, and also the yews and their allies that bear drupelike seeds.

Spruces: any evergreen, coniferous tree of the genus Picea, of the pine

family, having short, angular, needle-shaped leaves attached singlyaround twigs and bearing hanging cones with persistent scales.

Sagebrush: any of several sagelike, bushy composite plants of the genus

Artemisia, especially A. tridentata, having silvery, wedge-shaped

leaves, with three teeth at the tip, common on the dry plains of the

western U.S.

Dryness: From moisture or excess moisture; not moist; not wet.

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BIBLIOGRAPHY

http://diccionario.reverso.net/ingles-cobuild/woodland http://www.bio.miami.edu/ecosummer/lectures/lec_biomes.html http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/Biomes.html http://dictionary.reference.com

http://diccionario.reverso.net/ingles-cobuild/woodlandhttp://www.bio.miami.edu/ecosummer/lectures/lec_biomes.htmlhttp://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/Biomes.htmlhttp://dictionary.reference.com/http://dictionary.reference.com/http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/Biomes.htmlhttp://www.bio.miami.edu/ecosummer/lectures/lec_biomes.htmlhttp://diccionario.reverso.net/ingles-cobuild/woodland