Britannica Student Encyclopedia - 2010

#More to explore

Algonquian • French and IndianWar

• Native Americans

Ali, Muhammad

U.S. boxer Muhammad Ali was a gifted

athlete with a personality that brought

him fans and fame. He was known for

such phrases as “I am the greatest!” and

“float like a butterfly, sting like a bee.”

Muhammad Ali was born on January

17, 1942, in Louisville, Kentucky. His

original name was Cassius Marcellus

Clay. At the age of 18 Clay won a gold

medal at the Olympic Games in Rome.

He became the world heavyweight

champion in 1964.

In 1964 Clay joined the Nation of Islam

and changed his name to Muhammad

Ali. At the time the United States was

fighting the VietnamWar. In 1967 Ali

refused to join the armed forces because

of his religion. He was convicted of

breaking the law. His title was taken

from him and he was not allowed to box

again until 1970. In 1971 the U.S.

Supreme Court cleared Ali of all criminal

charges.

In a match against George Foreman in

1974, Ali regained the world heavyweight

title. In 1979 Ali announced that

he would retire. He came out of retirement

for matches in 1980 and 1981,

but he was defeated both times. In later

years Ali suffered from Parkinson’s disease,

which affects the brain and the

muscles.

Allegheny

Mountains

The Allegheny Mountains, or the

Alleghenies, extend from Pennsylvania

to Virginia in the eastern United States.

They are noted for their scenic beauty.

At one time these mountains were an

obstacle to settlers who wished to move

westward.

Muhammad Ali fights Ernie Terrell

in 1967.

82 Ali, Muhammad BRITANNICA STUDENT ENCYCLOPEDIA

The Alleghenies are part of the Appalachian

Mountains. They stretch more

than 500 miles (800 kilometers) and

consist of two nearly parallel ridges.

At Mount Davis near the Maryland border,

the Alleghenies rise to 3,213 feet

(979 meters), the highest point in Pennsylvania.

The highest point inWest Virginia

is 4,863 feet (1,482 meters), at

Spruce Knob.

A large amount of coal is mined from

the Allegheny range. Heavy forest cover

makes the Alleghenies a rich source of

timber, too.

#More to explore

Appalachian Mountains

Allen, Ethan

Ethan Allen was a patriot and a soldier.

He won an important early victory in

the American Revolution. Allen led a

band of fighters called the Green Mountain

Boys against the British at Fort

Ticonderoga, in what is now New York.

Ethan Allen was born on January 21,

1738, in Litchfield, Connecticut. In

1757 he fought in the French and

IndianWar. In 1762 Allen became an

ironworker. Several years later he moved

to what is now Vermont.

Vermont was not a separate colony at the

time. NewHampshire and New York

both claimed the territory.To aid the

NewHampshire side in the dispute,

Allen organized the GreenMountain

Boys. (The name of Vermont comes from

the French words for “green mountain.”)

After the start of the American

Revolution, the group fought the British.

On May 10, 1775, the Green Mountain

Boys captured Fort Ticonderoga. Later

that year Allen was captured by the British

during an unsuccessful attack on

Montreal, Canada. He was released in

1778. The Army then made him a colonel,

but he fought no more in the war.

The Allegheny Mountains become very colorful

in the fall as the leaves on the trees

begin to change.

A picture from the 1800s shows Ethan Allen

capturing Fort Ticonderoga.

BRITANNICA STUDENT ENCYCLOPEDIA Allen, Ethan 83

Allen spent his later years trying to make

Vermont a state. New York still wanted

the territory for itself and interfered with

his efforts. After the war Allen even

talked with the British about making

Vermont part of Canada. This hurt his

reputation as an American patriot. He

died on February 12, 1789, in Burlington,

Vermont.

#More to explore

American Revolution • French and

IndianWar • Vermont

Allergy

An allergy is the human body’s negative

reaction to certain foreign substances.

Some allergies are commonplace. Many

people suffer from hay fever when pollen

is in the air. Some develop skin

rashes when they touch certain substances.

Others experience stomach

cramps after eating particular foods.

When a person reacts in these ways to

any outside substance, that individual is

said to be allergic to it.

Allergies and the Immune

System

Several things happen to cause an allergic

reaction. First, a person is exposed to

a substance such as pollen. The bodies of

most people would simply ignore pollen.

Some people’s bodies, however, treat it

as a harmful invader. When this happens,

the person’s immune system produces

substances called antibodies to

fight the pollen’s effects.

The antibodies produced in the body

tend to stay in the blood. Because of

this, the immune system remembers and

recognizes the specific substance that

attacked the body. The next time the

body comes in contact with the substance,

the antibodies react to it again.

Signs of an Allergic Reaction

The antibodies react by releasing a

chemical called histamine. Histamine

causes fluid to build up in the body and

cell tissues to swell. That is why the eyelids

of a person with hay fever become

red and puffy. Histamine also affects

muscles. This can cause breathing difficulties

or stomach cramping and pain.

One severe type of allergic reaction is

known as anaphylactic shock, or anaphylaxis.

Some people have this reaction

if they take certain drugs, eat foods such

as nuts and shellfish, or get stung by

certain insects. Anaphylaxis has very

severe symptoms and sometimes leads to

death.

Treatment

Most people quickly learn which allergies

they have. When possible, they try

Sneezing is a common sign of some allergies,

such as hay fever.

Pets are a

common cause

of allergies.

Skin cells and

saliva of cats,

in particular,

can cause

sneezing, itching,

and

watery eyes.

84 Allergy BRITANNICA STUDENT ENCYCLOPEDIA

to avoid contact with the substance that

causes the allergy. Unfortunately, substances

such as dust and pollen are

everywhere. Taking drugs known as antihistamines

can decrease the allergic reactions.

Antihistamines prevent histamine

from reaching the cell tissues.

#More to explore

Asthma • Immune System

Alligator

Alligators are large lizardlike animals

with long, rounded snouts and powerful

tails. They spend most of their time in

the water, but they also travel on land.

Alligators belong to the group of animals

called reptiles. They are related to

crocodiles.

Where Alligators Live

Alligators live along the edges of

swamps, lakes, and slow-moving rivers.

There are two species, or types, of alligator.

The American alligator lives in the

southeastern United States. The Chinese

alligator lives in the Yangtze River region

in China. It is very rare.

Physical Features

Male American alligators measure about

11 feet (3.4 meters) in length on average.

The females are slightly smaller.

Young American alligators are black

with yellow stripes on the tail. The

adults are brownish.

The Chinese alligator normally grows to

a length of about 5 feet (1.5 meters). It is

blackish with faint yellowish markings.

Alligators have many features in common

with crocodiles. They have thick

skin composed of many scales and

plates. They each have a long body and

four short legs. The eyes, ears, and nostrils

are located on top of the head.

These show above the water when the

animal floats.

However, there are easy ways to tell alligators

and crocodiles apart. One of the

most obvious is that alligators have

broad, rounded snouts, while most

crocodiles have narrow, pointed snouts.

Behavior

Alligators eat mainly fish, small mammals,

and birds. But they sometimes kill

American alligator prey as large as deer or cattle.

A view from above shows the different

snouts of an alligator and a crocodile.

BRITANNICA STUDENT ENCYCLOPEDIA Alligator 85

Alligators usually mate during the

spring. The female builds a nest of mud

and grass. She lays 20 to 60 white eggs

in the nest. The eggs hatch after about

65 days. The young alligators live with

their mother for as long as a year.

#More to explore

Crocodile • Reptile

Allosaurus

Allosaurus was a fierce dinosaur that

roamed Earth before the similar but

more well-known Tyrannosaurus rex

appeared. The name Allosaurus means

“other lizard.” Allosaurus is a member of

the group of dinosaurs known as theropods.

The theropods were meat-eating

dinosaurs that walked on their two back

legs.

When and Where Allosaurus

Lived

Allosaurus lived about 163 to 144 million

years ago. Most Allosaurus fossils, or

remains, have been found in North

America, in Colorado, Utah, New

Mexico, Montana, South Dakota, and

Wyoming.

Physical Features

Allosaurus reached up to 39 feet (12

meters) in length, stood about 15 feet

(4.5 meters) tall, and weighed up to 2

tons. The massive head of Allosaurus

measured about 3 feet (1 meter) long

and was supported by a short, thick

neck. The sharp teeth of Allosaurus were

curved and had sawlike edges. Allosaurus

had sharp claws on the three toes of each

hind foot. It also had long, grasping

claws on the three toes of each front foot.

The long, heavy tail of Allosaurus may

have helped the animal balance itself.

Behavior

Allosaurus was a meat-eating dinosaur

that preyed on plant-eating dinosaurs.

When it hunted alone, Allosaurus would

hide among thick plants and then jump

out on its prey. Some scientists believe

that Allosaurus also hunted in packs.

Together, a pack of Allosaurus could

bring down very large dinosaurs, such as

Apatosaurus and Diplodocus. Scientists

believe that Allosaurus reproduced by

laying eggs.

#More to explore

Dinosaur • Tyrannosaurus rex

Allosaurus

86 Allosaurus BRITANNICA STUDENT ENCYCLOPEDIA

Alloy

An alloy is a substance made of two or

more metals or of a metal and nonmetallic

materials. To make an alloy, the

ingredients are melted and mixed

together. When the mixture cools, it

hardens.

Alloys are generally more useful than

pure metals. Pure metals may rust or

wear away easily. They may also be too

soft to hold a shape. But mixing other

substances with a pure metal often

results in a hard and strong substance.

People first learned to make alloys more

than 5,000 years ago. Ancient peoples

used a combination of copper and tin,

called bronze, to make tools and weapons.

Today such things as church bells

and statues are made of bronze. Brass, a

combination of copper and zinc, is

another ancient alloy. People today use

brass to make such things as doorknobs

and musical instruments.

Steel is one of the most important modern

alloys. Steel is a mixture of iron,

carbon, and other substances. Steel is

useful in building construction and

many other industries. Another important

modern alloy contains aluminum

and small amounts of copper or other

substances. Aircraft and other vehicles

are often made of aluminum alloys.

#More to explore

Brass • Bronze • Metals • Steel

Almond

Almonds are commonly called nuts, but

they are actually seeds. They come from

a tree that is closely related to the peach

tree. People eat almonds as a snack and

also use them in cooking and baking.

Almonds can also be pressed to obtain a

fragrant oil.

The United States, Spain, Greece, Iran,

and Turkey are major almond producers.

Most almonds produced in the United

States come from California.

There are two types of almonds: sweet

and bitter. Sweet almonds are the kind

people eat. Bitter almonds contain a

poison, but their oil can be used for

food after the poison is removed.

Almond trees do not grow much taller

than 30 feet (9 meters). They bloom in

early spring. Bitter almond blossoms are

white, and sweet almond blossoms are

pink. The fruits look like peaches, but

they are smaller and flatter. Inside each

fruit is a pit, or nut. The nut has a hard

A South American mask is made of a gold

and silver alloy. Its ears and eyes are made

of copper.

Stainless steel

is an alloy that

contains iron,

chromium,

and other metals.

Stainless

steel is useful

because it

does not rust

easily.

BRITANNICA STUDENT ENCYCLOPEDIA Almond 87

shell surrounding a seed. The seed is the

part that people eat.

As the fruit ripens, it splits open to

reveal the nut.Workers use machines to

shake the trees and make the nuts fall to

the ground. The nuts may be left to dry

on the ground, or they may be dried in

an oven.Workers then use machines to

shell, sort, and pack the nuts for shipment.

#More to explore

Nuts • Peach

Alphabet

An alphabet is a system used to represent

language in written form. Each letter

stands for a single spoken sound. Many

languages use alphabets. But some languages

use other systems to represent

words in writing. For instance, in Japanese

and Cherokee each symbol represents

a group of sounds rather than a

single sound. The Chinese writing system

uses symbols to represent the meaning

of words, not their sounds.

The Latin alphabet is the alphabet of

English and most European languages.

It has 26 letters. Other alphabets might

have fewer or more letters. Like other

alphabets, the Latin alphabet developed

from earlier forms.

EarlyWriting Systems

People in early societies drew pictures to

communicate ideas. In ancient times

people in the Middle East developed the

world’s first writing system. It used symbols

to stand for the meanings of words.

Later it also used some symbols to represent

the sounds of words.

More than 3,000 years ago people in

what is now Syria used a simpler writing

system. This system is called North

Semitic. Most modern alphabets trace

their history back to that system. North

Semitic used only 22 symbols. It did not

have any signs representing whole

words. Instead each letter represented a

consonant. There were no symbols for

vowels. People known as the Phoenicians

later slightly changed this system.

The fruits of the almond tree open to reveal

the nuts. The almond seeds are inside the

hard shells.

A computer keyboard has Latin and

Japanese letters. It sits on top of a document

written in Chinese characters.

88 Alphabet BRITANNICA STUDENT ENCYCLOPEDIA

Greek and Latin Alphabets

The ancient Greeks changed the Phoenician

writing system to create their own

alphabet. Some people consider the

Greek alphabet to be the first true alphabet.

This is because it has symbols for

vowels and consonants. The Greek

alphabet is the ancestor of all modern

European alphabets, including Latin.

The ancient Romans, who spoke Latin,

developed the Latin alphabet. As the

Roman Empire grew, the Latin alphabet

spread throughout the empire’s vast

lands. It became the alphabet of many

other languages in addition to Latin.

The alphabet changed over time. New

letters were needed to pronounce words

in other languages. Other letters were

combined.

Other Alphabets

The North Semitic writing system also

gave rise to other ancient alphabets,

including Aramaic. The modern Hebrew

and Arabic alphabets developed from the

Aramaic alphabet. Today people in Israel

and Jews around the world use the

Hebrew alphabet. People in large parts of

theMiddle East and North Africa use

the Arabic alphabet. In Hebrew and

Arabic a small group of consonants gives

the basic meaning of a word. Vowels

slightly change the meaning.

The ancient Aramaic alphabet probably

also influenced the earliest-known writing

system of India. This system, called

Brahmi, dates back more than 2,500

years. Nearly all the modern alphabets of

India trace their history to Brahmi.

The Cyrillic alphabet was created more

than 1,000 years ago. Members of the

Eastern Orthodox church in eastern

Europe used it for religious texts. The

Cyrillic alphabet was based on the Greek

alphabet of the time. Today people in

Russia, Ukraine, Bulgaria, Serbia, and

elsewhere use versions of the Cyrillic

alphabet.

#More to explore

Language •Writing

Alps, The

The Alps are the youngest, highest, and

most densely populated mountain range

in Europe. They were formed about 44

million years ago. The Alps fill most of

Switzerland and Liechtenstein and

extend into France, Germany, Austria,

Italy, and Slovenia. On the west, the

The word

alphabet was

created from a

combination

of “alpha and

beta.” These

are the Latin

names for the

first and second

letters of

the Greek

alphabet.

BRITANNICA STUDENT ENCYCLOPEDIA Alps, The 89

Alps run along the border between

France and Italy.

The highest peak in the Alps is Mont

Blanc in France, at 15,771 feet (4,807

meters). Several other high peaks are

located on or near the Swiss-Italian border.

They include the Matterhorn.

The Alps receive a great deal of snow

and rain. At high elevations, the snow

turns to ice and then flows down to the

valleys as glaciers. Sometimes masses of

snow rush uncontrolled down the

mountainsides. These events, called

avalanches, endanger Alpine

communities. The clear Alpine lakes are

noted for their beauty. Among the most

prominent are Lakes Geneva,

Constance, Como, and Zurich.

The Alps are nearly treeless near the top,

but forests grow below. The higher forests

have mostly spruce, pine, and larch

trees. Oak, beech, and chestnut trees

grow on the valley floors and lower

slopes. A few kinds of animals have

adapted well to living in the higher

mountains. These include the ibex, the

Alpine marmot, and the mountain hare.

Humans have lived in the Alps since

prehistoric times, 50,000 to 60,000

years ago. German cultures developed

in the eastern Alps, while Roman

culture influenced the west. Some areas

of the Alps were cleared of forests

during the Middle Ages (500 to 1500).

Farmers settled the land, planted crops,

and raised cattle. During the 1800s,

railroads were constructed, opening up

the area.

Many people began to travel to the Alps

during the 1900s. Air, auto, and rail

transportation to the Alps improved,

making it easier for people to get there.

Today entire villages lodge, feed, and

entertain tourists. Popular resorts

include Innsbruck, Austria; Grenoble,

France; and Saint Moritz, Switzerland.

#More to explore

Avalanche • Europe • Mountain

The Matterhorn is one of the tallest peaks in

the Alps.

90 Alps, The BRITANNICA STUDENT ENCYCLOPEDIA

Alzheimer’s

Disease

Alzheimer’s is one of the most destructive

diseases of old age. The disease

destroys nerve cells in the brain. As a

result, the brain stops working correctly

and the memory is affected. Most

people who have Alzheimer’s disease are

more than 60 years old. Some people,

however, get it before that age.

The symptoms, or signs, of Alzheimer’s

disease begin mildly and then become

more severe over time. At first, people

with Alzheimer’s seem forgetful. Gradually,

they lose their entire memory.

People with Alzheimer’s also have a hard

time speaking and understanding other

people. They may not even recognize

close friends and family, such as their

own children. Eventually, they lose control

of body and mind.

Scientists are not sure what causes the

death of nerve cells in the brains of

people with Alzheimer’s disease. They

think the cause might be a genetic

defect. This means there might be a

problem with one of the genes that is

passed from parent to child. Because the

cause is unknown, there is no way to

prevent or cure Alzheimer’s disease.

Medications help to slow the disease in

some patients.

Amazon River

The Amazon is the mightiest river in

South America. It carries more water

than any other river. It is about 4,000

miles (6,400 kilometers) long. Only the

Nile River in Africa is longer.

The Amazon begins in the Andes

Mountains in Peru. From there it flows

north and then east through Brazil. It

empties into the Atlantic Ocean. The

Amazon drains about one third of South

America. This area includes most of

Brazil and Peru and parts of Bolivia,

Ecuador, Colombia, and Venezuela.

Plants and Animals

The Amazon region is the site of the

world’s largest rain forest. Its plant and

animal life is remarkably rich. Almost

three fourths of all the types of plants in

the world grow there. The animals

include monkeys, anteaters, anacondas,

toucans, and huge rodents called capybaras.

The flesh-eating piranha is among

the river’s many fish.

People

Millions of Brazilians live in cities in the

Amazon region. Belem, Manaus, and

Santarem are large, growing cities.

The Amazon

River carries

about 10 times

as much water

as the Mississippi

River.

BRITANNICA STUDENT ENCYCLOPEDIA Amazon River 91

At one time almost 7 million Indians

lived in the Amazon region. Europeans

arrived in the 1500s. They took many

Indians into slavery and removed them

from Brazil.Other Indians died from

diseases carried by the Europeans. In the

1990s there were about 600,000 Indians

in the Amazon.Most live in remote areas.

Economy

The countries of the Amazon region

have encouraged businesses to use the

resources found there. Mahogany, Amazonian

cedar, and other trees are cut

down for their wood. Rubber is another

valuable plant product. Diamonds, gold,

and oil are mined.

Many people have become concerned

about the effects of economic development

in the Amazon. Scientists warn

that destroying parts of the forest threatens

the plants and animals that live there.

#More to explore

Brazil • Rain Forest

Amber

Amber is a hard, yellowish, and often

see-through substance that formed from

tree resin. Resin is a thick fluid that

oozes from pine and fir trees when their

bark is injured.

The resin that formed amber came from

trees that grew millions of years ago.

Over time these trees and their resin

became buried beneath Earth’s surface.

The trees eventually decayed and disappeared.

But the resin hardened further,

until it became amber.

Many pieces of amber contain the

remains of insects or plants in the form

of fossils. These living things were

trapped in the resin before it hardened

into amber. Scientists study these creatures

to learn how living things have

changed over millions of years.

People have found amber throughout

the world. However, most of it comes

from the shores of the Baltic Sea in

northern Europe. This amber is buried

in sands that are 40 million to 60 million

years old.

Ancient people valued amber for its

beauty. They used it to make beads and

carvings. The ancient Greeks and

Romans also believed that amber had

magical and healing properties. Artists

today turn pieces of clear amber into

jewelry and other objects.

#More to explore

Fossil • Jewelry and Gems

Millions of years ago, insects were trapped

in resin. The resin eventually hardened into

amber.

92 Amber BRITANNICA STUDENT ENCYCLOPEDIA

Ambulance

An ambulance is a vehicle used to transport

people who are sick or injured.

Most ambulances are either trucks with

space for patients or cargo vans with

raised roofs. Ambulances usually take

patients to a hospital.

Specially trained people called emergency

medical technicians, or EMTs,

ride in ambulances. They give sick or

injured people emergency medical care

before they reach the hospital.

Ambulances have many types of

equipment that are used to move and to

treat patients. Equipment for moving

patients includes stretchers and cots with

wheels. An ambulance’s medical

equipment helps to treat breathing

problems, heart attacks, broken bones,

and burns right away.

Large cities have hundreds of ambulances.

They are owned by public and

private hospitals, fire departments, and

private emergency medical services.

Some places use airplanes or helicopters

as ambulances. These air ambulances

have the same equipment as ground

ambulances. Air ambulances reach

people in out-of-the-way areas. They

also transport patients more quickly

than ground vehicles.

Most ambulance developments took

place during wartime. In the early 1800s

the French army used two-wheeled,

horse-drawn wagons to bring soldiers to

battlefield hospitals. In the 1860s public

hospitals began keeping their own horsedrawn

ambulances. The first motorized

ambulance was built in 1899. Airplanes

were used as ambulances for the first

time duringWorldWar I (1914–18).

Helicopters first served as ambulances

during the KoreanWar (1950–53).

#More to explore

Hospital • Medicine

Amendment

A change or addition to a law is called

an amendment. The word usually refers

to a change to the constitution of a government.

In the United States there have

been 27 amendments to the Constitution.

The most famous of these are the

first 10. They are known as the Bill of

Rights.

Emergency medical technicians treat a

patient in an ambulance.

BRITANNICA STUDENT ENCYCLOPEDIA Amendment 93

Passing an amendment to the U.S. Constitution

is a two-step process. The first

step is for two thirds of the members of

the Senate and two thirds of the members

of the House of Representatives to

vote for the amendment. The second

step is for the amendment to be ratified,

or approved, by the legislatures of three

quarters of the states.

Every U.S. state has its own constitution,

and almost all of them have been

amended more times than the U.S.

Constitution. The constitution of Alabama

has more than 700 amendments.

In many states voters must approve

amendments.

#More to explore

Bill of Rights • Constitution • United

States Constitution

American

CivilWar

In the 1860s the northern and southern

parts of the United States fought the

American CivilWar. The war started

after 11 Southern states separated themselves

from the United States and

formed their own government. Their

army fought the forces of the U.S. government.

The CivilWar threatened to

break up the United States. It is also

called theWar Between the States.

Buildup toWar

The North and the South had been

divided for many years over the issue of

slavery. The Southern economy was

based largely on cotton, which was

grown on large farms called plantations.

African slaves did most of the work on

the plantations. The North had small

farms that used paid workers. The

Northern economy also relied more on

manufacturing.

Neither side wanted the other’s ideas to

spread to new states being created in the

West. Northerners wanted to stop the

spread of slavery. But Southerners

believed that the U.S. government did

not have the right to decide whether or

not slavery should be allowed in a state.

They feared that the government’s next

step would be to stop slavery altogether.

Missouri Compromise

In 1819 the U.S. Congress had to decide

whether to allow Missouri to become a

state. Missouri wanted to join as a state

that would allow slavery. Some North-

The only way

to repeal, or

cancel, an

amendment to

the U.S. Constitution

is to

pass another

amendment.

Only one

amendment to

the U.S. Constitution

has

ever been

repealed.

The 19th Amendment to the U.S. Constitution

gave women the right to vote.

94 American Civil War BRITANNICA STUDENT ENCYCLOPEDIA

erners in Congress were not happy with

this. Congress therefore could not agree

about what to do. Finally, Maine asked

to join the country as a free state, or a

state that would not allow slavery. Congress

then agreed to let Missouri join as

a slave state and Maine join as a free

state. This became known as the Missouri

Compromise of 1820. The Compromise

also banned slavery north of

Missouri’s southern border.

Kansas-Nebraska Act

The Missouri Compromise lasted until

Congress passed the Kansas-Nebraska

Act in 1854. The act created Kansas and

Nebraska as new territories in the area

where slavery was supposed to be forbidden.

Yet the act allowed the people of

the territories to choose whether or not

to allow slavery. In Kansas the act led to

armed conflict. On one side were Southerners

who supported slavery. On the

other side were Northern abolitionists,

who wanted to end slavery.

The Confederacy and the Union

Southerners became more upset when

Abraham Lincoln was elected U.S. president

in 1860. Lincoln belonged to the

Republican Party, which opposed slavery.

Southern states decided to secede

(withdraw) from the United States to

protect their right to keep slaves. South

A map shows where the major battles of the American Civil War took place.

BRITANNICA STUDENT ENCYCLOPEDIA American Civil War 95

Carolina, Mississippi, Florida, Alabama,

Georgia, Louisiana, Texas, Virginia,

Arkansas, North Carolina, and Tennessee

seceded. They formed a government

called the Confederate States of

America, or the Confederacy. Jefferson

Davis was the Confederate president.

The states that stayed loyal to the

United States were called the Union.

Four states—Kentucky, Missouri, Maryland,

and Delaware—stayed in the

Union even though they allowed slavery.

They were called border states. In addition,

the western counties of Virginia

refused to join the Confederacy. They

later joined the Union as the state of

West Virginia.

Going into the war the Union had several

advantages over the Confederacy. It

had more people, more industries, and

more railroads. But the Confederacy had

better military leaders.

Events of theWar

Fighting broke out in 1861 and lasted

until 1865. By the end of 1861 two

major battlefronts had developed. One

was in the East, where Virginia, Maryland,

and Pennsylvania suffered most of

the fighting. The other front was in the

West. That front started along the Mississippi

River and then spread.

1861

The American CivilWar began on April

12, 1861, in Charleston, South Carolina.

Confederate troops captured Fort

Sumter from the Union Army. Afterward

both sides quickly raised armies.

The first major battle of the war was

fought on July 21. About 30,000 Union

troops marched toward the Confederate

capital of Richmond, Virginia. The

Confederates stopped them at a stream

named Bull Run, near the town of

Manassas. The Union troops were forced

back toWashington, D.C. The defeat

shocked the Union.

1862

Union forces had some success in the

West in 1862. In February Union troops

under General Ulysses S. Grant captured

Confederate forts in western Tennessee.

These included Fort Henry and Fort

Donelson. In April Grant led the Union

to victory in the battle of Shiloh, near

Pittsburg Landing, Tennessee. Then the

Union navy took the city of New

Orleans.

The war’s most notable battle at sea was

fought in Virginia in March 1862. It

was the first battle ever fought between

ships that were covered with iron. Nei-

There were 21

million Northerners

and

only 9 million

Southerners at

the time of the

American Civil

War. More

than one third

of the Southerners

were

slaves.

Many African Americans fought in the

Union Army. Members of the 107th U.S.

Colored Infantry pose for a photograph in

Virginia in 1865.

96 American Civil War BRITANNICA STUDENT ENCYCLOPEDIA

ther the Confederacy’s Merrimack nor

the Union’s Monitor could win a clear

victory.

General Robert E. Lee led the Confederacy

to important victories in the East.

In August 1862 his forces won a second

battle at Bull Run. Then Lee invaded

the North. Union troops stopped the

Confederates at Antietam Creek, Maryland,

in September. But in December

Lee’s troops defeated Union troops at

Fredericksburg, Virginia.

1863

At the start of the war President Lincoln

wanted mainly to keep the United States

together. Ending slavery was not his

main goal. This changed after the battle

of Antietam. The Union victory encouraged

Lincoln to issue a statement called

the Emancipation Proclamation. The

proclamation freed all slaves in Confederate

states. As a result of the proclamation,

many blacks joined the Union

Army.

In May 1863 Lee defeated Union forces

near Chancellorsville, Virginia. Then he

again invaded the North. Lee suffered

his first big defeat in July at Gettysburg,

Pennsylvania.

The battle of Gettysburg turned the war

in favor of the Union. A day later Grant

captured the city of Vicksburg, Mississippi,

for the Union. Then the Union

controlled the entire Mississippi River.

In November 1863 Grant and General

William Tecumseh Sherman drove the

Confederates out of Chattanooga, Tennessee.

1864–65

In March 1864 Lincoln rewarded Grant

by giving him command of all the

Union armies. While Grant fought in

Virginia, Sherman went to Georgia. He

captured Atlanta in September. Then he

led his troops on a march to Savannah, a

port on the Atlantic Ocean. Along the

way they destroyed railroads and sup-

Confederate Generals Stonewall Jackson

(left) and Robert E. Lee are pictured

together in 1863. Jackson died after being

wounded in the battle of Chancellorsville in

that year.

Union Army officers are photographed in

Virginia in August 1865.

BRITANNICA STUDENT ENCYCLOPEDIA American Civil War 97

plies. Sherman captured Savannah in

December.

By March 1865 Lee was very short of

men and supplies. On April 3 Grant

captured Richmond, the Confederate

capital. He accepted Lee’s surrender in

Appomattox, Virginia, on April 9. By

the end of May all Confederate armies

had surrendered.

Reconstruction

After the war the defeated states were

gradually allowed back into the United

States. The South rebuilt damaged property

and changed its economy so it no

longer depended on slaves. This period

was known as Reconstruction. It lasted

until the last U.S. troops left the South

in April 1877.

#More to explore

AbolitionistMovement • Confederate

States of America • Davis, Jefferson

• Emancipation Proclamation • Grant,

Ulysses S. • Kansas-Nebraska Act • Lee,

Robert E. • Lincoln, Abraham •Missouri

Compromise • Reconstruction • Slavery

American

Indians

#see Native Americans.

American

Revolution

The American Revolution was the war

in which Great Britain’s 13 American

colonies won their independence. The

colonies became a new country, the

United States. The revolution began in

1775 and ended in 1783.

Background

Before the 1760s the colonies had a lot

of freedom even though they were under

British rule. The British government was

across the Atlantic Ocean, more than

3,000 miles (5,000 kilometers) away.

The colonies had their own leaders and

learned to solve their own problems.

Plus, because Britain was often at war, it

On April 9, 1865, General Robert E. Lee

(right) surrendered to General Ulysses S.

Grant at Appomattox, Virginia.

The first shots of the American Revolution

were fired in Lexington, Massachusetts, on

April 19, 1775.

98 American Indians BRITANNICA STUDENT ENCYCLOPEDIA

did not always pay close attention to the

colonies.

In the 1760s, however, the British government

tried to take more control over

the colonies. One major reason for this

change was the French and IndianWar.

Britain defeated France in the war in

1763. But the war had been very costly.

Afterward, Britain decided that its

American colonies should help to pay its

debts.

Taxes

To raise money, Britain forced the colonies

to pay new taxes. In 1765 the British

lawmakers, called Parliament, passed

a law called the Stamp Act. The act put

a tax on legal papers, newspapers, and

other printed items. The colonists protested

against the tax. They were especially

angry because Parliament was

taxing them even though they had no

representatives in Parliament. Because of

the protests, the British government

ended the tax in 1766.

In 1767, however, a British official

named Charles Townshend got Parliament

to pass several new tax laws. The

Townshend Acts taxed tea, lead, paint,

paper, and glass coming into colonial

ports. These taxes made the colonists

even angrier.

Boston Massacre and the Tea

Party

To keep order, the British government

sent soldiers to Boston, Massachusetts.

On March 5, 1770, British soldiers fired

shots into a crowd of colonists. Crispus

Attucks and several other Americans

were killed. This event became known as

the Boston Massacre.

On the same day as the Boston Massacre,

Parliament did away with most of

the Townshend Acts. They kept a tax on

tea, however. Then, in 1773, Britain

passed a law that allowed a British company

to sell tea more cheaply than colonial

merchants. On December 16, 1773,

colonists boarded British ships in Boston

Harbor and threw their cargo of tea into

the water. This event became known as

the Boston Tea Party.

Intolerable Acts

The British government then passed

laws that were even harsher. The colonists

called them the Intolerable Acts.

The strongest of these acts closed the

port of Boston until the colonists paid

for the tea they had ruined. Massachusetts

was put under military rule.

The colonists realized that the colonies

had to act together. In 1774 representatives

from every colony except Georgia

met in Philadelphia, Pennsylvania. The

meeting was called the Continental

Congress. The representatives called on

Britain to cancel the Intolerable Acts.

The British government answered by

sending in even more troops.

Early Battles

By this time many colonists believed

that their problems with Britain could

not be worked out peacefully. They prepared

to fight. They formed groups of

soldiers called minutemen. The minute-

Patriots in different

colonies

kept in touch

with each

other through

groups called

Committees of

Correspondence.

Samuel

Adams of

Massachusetts

started the first

one in 1772.

BRITANNICA STUDENT ENCYCLOPEDIA American Revolution 99

men were to be ready to fight “at a

minute’s warning.”

In April 1775 Britain sent a force to seize

the colonists’ military supplies in

Concord,Massachusetts. Paul Revere

andWilliam Dawes rode through the

countryside to warn the colonists that

the British soldiers were coming. On

April 19 a group of minutemen met the

British in Lexington, a town on the way

to Concord. After a short fight, the

British moved on to Concord. Another

group of American soldiers forced them

to turn back. The battles of Lexington

and Concord began the American

Revolution.

The Second Continental Congress met

in Philadelphia in May 1775. It brought

together the military forces of the colonies

to form the Continental Army. It

put GeorgeWashington in charge of the

army.Washington spent months preparing

his troops for battle.

Meanwhile the first major battle of the

war took place at Bunker Hill, near

Boston. The British captured Bunker

Hill on June 17, 1775. But they lost so

100 American Revolution BRITANNICA STUDENT ENCYCLOPEDIA

many soldiers that the colonists claimed

victory. The battle encouraged the

colonists.

Fighting for Independence

Before 1776, most colonists did not

want to break free from Britain. They

only wanted to get Britain to do something

about their complaints. But as the

fighting spread, more colonists became

convinced that they had to separate

from Britain. On July 4, 1776, the Continental

Congress approved the Declaration

of Independence.With this

document, the 13 colonies became the

United States of America.

The Americans struggled against the

larger and better-equipped British Army.

In the summer and autumn of 1776 the

British forced GeorgeWashington’s

troops out of New York. The Americans

were driven across New Jersey into

Pennsylvania. But thenWashington

defeated the British in Trenton and

Princeton, New Jersey. These victories

kept the struggle for independence alive.

The turning point of the war was the

battle of Saratoga, in New York. On

October 17, 1777, General Horatio

Gates led the Continental Army to a

great victory over the British. The victory

helped to bring France into the war

on the side of the new United States.

France sent ships and soldiers.

The winter of 1777–78 was a very hard

one for the Americans.Washington and

his troops camped at Valley Forge, near

Philadelphia. They suffered terribly from

hunger and illness. But they emerged in

the spring as a stronger fighting force.

They defeated the British in Monmouth,

New Jersey, on June 28, 1778.

Final Battles

In the last years of the war most of the

fighting took place in the South. In

British General John Burgoyne (center, in

red coat) surrenders in Saratoga, New

York, on October 17, 1777.

General George Washington

(right) walks through his army’s

camp at Valley Forge, Pennsylvania,

in 1778. With him is

Baron von Steuben, a German

officer who helped to train the

troops.

BRITANNICA STUDENT ENCYCLOPEDIA American Revolution 101

1780 the British, led by General Charles

Cornwallis, won battles in South Carolina.

But in 1781 American and French

forces trapped Cornwallis in Yorktown,

Virginia. He surrendered on October

19, 1781. The fighting was over.

The peace treaty was signed on September

3, 1783, in Paris, France. It was

called the Treaty of Paris. By signing the

treaty, Britain agreed that the United

States was an independent country.

#More to explore

Adams, Samuel • Attucks, Crispus

• Boston • Continental Congress

• Declaration of Independence

• Franklin, Benjamin • George III

• Jones, John Paul • Massachusetts

• Minuteman • Paine, Thomas • Revere,

Paul • United States •Washington,

George

American Sign

Language

#see Sign Language.

Americas,

Exploration and

Settlement of the

When Christopher Columbus crossed

the Atlantic Ocean in 1492, he thought

he had reached eastern Asia. In fact he

had opened up to Europeans a new

world with two continents—North

America and South America—and many

islands. Many more Europeans followed

Columbus to the Americas. Most were

from Spain, Portugal, France, and

England.

The Americas were named not for

Columbus but for Amerigo Vespucci.

He was an Italian merchant and explorer

who took part in at least two voyages to

the Americas in the late 1400s and early

1500s. Vespucci was one of the first

people to realize that the land Columbus

found was not a part of Asia.

Exploring by Ship

Vikings

Columbus was probably not the first

European to reach America. Vikings

from northern Europe traveled to the

coast of what is now Canada in about

AD 1000. The Vikings did not stay long,

however.

According to tradition, Molly Pitcher served

bravely in the battle of Monmouth, New

Jersey, on June 28, 1778.

102 American Sign Language BRITANNICA STUDENT ENCYCLOPEDIA

Columbus

By the time of Columbus, Europeans

had traveled to the East and explored

many parts of Asia. Many other Europeans

admired the cloths, spices, and

medicines that the explorers brought

back with them. They wanted more of

these goods. But the voyage to Asia was

long and expensive. Educated Europeans

knew that the world was round. They

thought that by sailing west, they could

find a shorter route to Asia.

Between 1492 and 1504, Christopher

Columbus made four voyages across the

Atlantic Ocean. Columbus reached

Central and South America as well as

the islands that are now called the West

Indies. He never reached Asia, but his

trips inspired many others to follow.

Magellan

Ferdinand Magellan of Portugal did

what Columbus had set out to do: he

found a western sea route to Asia. He

followed the South American coast

southward from Brazil. In 1520 he

passed around the tip of South America

into the Pacific Ocean. Magellan died,

but his crew kept sailing west. They

went past the southern tip of Africa back

to Spain. This was the first voyage

around the world.

Later Voyages

In 1497 John Cabot, an Italian working

for England, reached Newfoundland, in

what is now Canada. In 1535 Jacques

Cartier of France sailed from the Atlantic

Ocean into Canada on the Saint

Lawrence River.

In 1610 the Englishman Henry Hudson

sailed into the large bay in Canada that

is now called Hudson Bay. Hudson was

trying to find a water route through

North America to the Pacific Ocean.

People called this unknown route the

Northwest Passage. The first explorer to

find this passage was the Norwegian

Roald Amundsen—in 1906.

John Cabot landed in what is now Newfoundland

in 1497. He was one of the first

Europeans to land in North America.

Hudson Bay in Canada and the Hudson

River in the United States were named for

the explorer Henry Hudson.

BRITANNICA STUDENT ENCYCLOPEDIA Americas, Exploration and Settlement of the 103

Settling the Land

The riches of the Americas attracted

many early settlers, or colonists. Some

worked on their own, while others

worked for European trading companies.

Both groups wanted to make money

selling valuable things back to Europe.

Gold and silver were the most valuable

products of South America andMexico.

Further to the north, the furs of animals

were the most valuable products.

As Europeans began settling the land,

they met many Native Americans. Their

relations were often friendly. But Native

Americans grew angry as Europeans

took over more land.Wars between settlers

and Native Americans killed thousands.

Many more Native Americans

died from smallpox and other European

diseases.

Meanwhile, European settlers began to

grow the crops that Native Americans

grew, including corn, potatoes, pumpkins,

squash, peanuts, and tobacco.

Europeans also brought plants like sugarcane

and coffee to the Americas and

found that they grew well there. Some

Europeans set up large farms and sold

their crops back to Europe.

Some of the first European farmers captured

Native Americans and forced them

to work as slaves. African slaves eventually

replaced them. The Portuguese

brought in Africans to work as slaves

starting in 1502. The English were

active slave traders also. The slave trade

did not end until the 1800s.

Spanish Colonies

The earliest Spanish settlements were in

theWest Indies. The Spanish set up

Santo Domingo on the island of Hispaniola

in 1496. It was the first capital

of Spain’s colonial empire, called New

Spain.

In 1513 Vasco de Balboa traveled across

Central America. He became the first

European to view the Pacific Ocean

from the Americas. Six years later

Hernan Cortes made his first attack on

the Aztec Empire in Mexico. In 1533

Francisco Pizarro took Peru away from

the Inca people. The Spanish stole gold

and silver from the native empires and

shipped it back to Spain.

Spain’s colonial empire became the

biggest in the Americas. At its peak it

included the largest Caribbean islands,

all ofMexico and most of Central

America, large sections of South

The Roman

Catholic

church sent

many missionaries

into

Spanish, Portuguese,

and

French colonies.

Their task

was to convert

the Native

Americans to

Catholic

Christianity.

Francisco Pizarro conquered

what is now Peru and founded

the city of Lima there.

104 Americas, Exploration and Settlement of the BRITANNICA STUDENT ENCYCLOPEDIA

America, Florida, and the southwestern

quarter of what is now the United States.

English Colonies

The important English colonies were on

the Atlantic coast of North America. In

1607 merchants from the Virginia

Company founded Jamestown. This was

the first permanent English settlement

in North America.

Other English settlers soon founded

Plymouth Colony andMassachusetts

Bay Colony in New England. These

colonies were unusual. The people who

started them had reasons besides making

money. They wanted freedom to practice

their own forms of Christianity. They

could not find this freedom in Europe.

The English settled other parts of the

Americas, too. Starting in 1670, the

English traders of the Hudson’s Bay

Company set up trading posts in

Canada. In the Caribbean Sea, England

had settlements on several islands. The

largest was Jamaica, which England

seized from Spain in 1655. The English

settled Belize in Central America in

1638. Scattered settlements in South

America united to form British Guiana

in 1831.

French Colonies

France’s settlements in North America

were known as New France.Most of

these settlements were in what is now

Canada. The French explored widely,

made friends with Native Americans,

and built forts and trading posts. The fur

trade became the basis of New France’s

economy. In the late 1600s and early

1700s the French captured many trading

posts from the Hudson’s Bay Company.

In 1608 Samuel de Champlain founded

Quebec as the first permanent French

settlement. One French explorer, the

Sieur de La Salle, floated down the Mississippi

River in 1682 and claimed all

the land it drained.

France also claimed islands in the Caribbean

Sea, including what is now Haiti.

Queen Elizabeth I is pictured asking English

explorer Sir Walter Raleigh to start a colony

in Virginia for England.

Massasoit, chief of the Wampanoag Native

Americans, visits with the English settlers

called Pilgrims.

BRITANNICA STUDENT ENCYCLOPEDIA Americas, Exploration and Settlement of the 105

In the mid-1600s France founded

French Guiana on the northeastern coast

of South America.

France and England (which united with

Scotland to form Great Britain in 1707)

often fought over land in North America.

106 Americas, Exploration and Settlement of the BRITANNICA STUDENT ENCYCLOPEDIA

One such fight became known as the

French and IndianWar. At the end of

that war, in 1763, Great Britain won

control of French Canada. It also won all

other French territory east of the

Mississippi River. France sold its

territories farther west to the United

States in 1803.

Other Colonies

The Portuguese were among the earliest

explorers in the Americas. However, the

only colony they set up was Brazil, in

South America.

In about 1626 the Dutch built a settlement

in North America called New

Amsterdam. The English took over New

Amsterdam in 1664 and renamed it

New York. The Dutch also set up colonies

in the Caribbean. They are now

known as the Netherlands Antilles.

Russia came to North America from the

west. The Russians set up their first permanent

settlement in Alaska in 1784.

The Russians traded for furs as far south

as California. In 1867 Russia sold Alaska

to the United States.

End of Colonialism

Most colonies in North, Central, and

South America became independent

between 1776 and 1826. Many islands,

however, remained colonies.

In 1823 President James Monroe of the

United States issued a statement called

the Monroe Doctrine. It declared that

European countries were no longer welcome

to set up colonies in the Americas.

#More to explore

Balboa, Vasco Nunez de • Cabot, John

• Cartier, Jacques • Columbus,

Christopher • Cortes, Hernan • Fur

Trade • La Salle, Sieur de • Magellan,

Ferdinand • Massachusetts Bay Colony

• Native Americans • Plymouth Colony

• Slavery • Vespucci, Amerigo

In 1562 French explorer Jean Ribaut

brought colonists from France to North

America. They landed near Saint John’s

River in what is now Florida.

The first colonies

in the

Americas to

win their independence

were the 13

colonies that

became the

United States.

An illustration from 1698 depicts the last

expedition of the French explorer Sieur de

La Salle

BRITANNICA STUDENT ENCYCLOPEDIA Americas, Exploration and Settlement of the 107

Amman

Population

(2004 estimate)

1,036,330

Amman is the capital of the Middle

Eastern country of Jordan. The city

spreads over a series of rolling hills.

Amman is Jordan’s largest city. It is also

Jordan’s main center of business,

finance, and international trade.

People have lived in the area for thousands

of years. In ancient times the city

was the capital of the Ammonites, a

people often mentioned in the Bible.

Egypt conquered the city more than

2,000 years ago. Many other powers

controlled the city over the years. But

for reasons that are still unknown,

Amman disappeared by AD 1300.

In 1878 some people fleeing Russia created

a small village in the area. Amman’s

revival began in 1921. That year it

became the capital of a territory called

Transjordan. Transjordan (now Jordan)

became an independent country in

1946. After that, Amman grew rapidly.

..More to explore

Jordan

Amoeba

An amoeba is a one-celled creature that

is among the simplest of all living organisms.

Most amoebas are so small that

they can only be seen though a microscope.

There they look like tiny blobs of

colorless jelly.

Amoebas are found in fresh and salt

water. They also live in the moist body

parts of other animals and in moist soil.

At least six types of amoeba are found in

human beings.

An amoeba has few parts. It has a thin

covering called a membrane. Inside is a

nucleus, food vacuoles, and a contractile

vacuole. The food vacuoles digest food.

The contractile vacuole gets rid of extra

water.

Amoebas move by changing their shape.

First, an amoeba extends a part of its

jellylike body outward, like a stubby

finger projecting out of a closed fist. This

projection is called a pseudopod, or false

foot. The amoeba then pours the main

Amman has many remains of

buildings from ancient times. A

theater built by the Romans

almost 2,000 years ago is just

one example.

108 Amman BRITANNICA STUDENT ENCYCLOPEDIA

part of its body into the pseudopod,

which makes the pseudopod grow

bigger. Eventually the pseudopod gets so

big that it becomes the whole body. New

pseudopods form as old ones disappear.

For food, amoebas depend mainly on

plants and other one-celled animals.

Amoebas use their pseudopods as

mouths. The pseudopods reach out to

surround the food and flow over it.

To reproduce, the nucleus of the amoeba

simply splits into two pieces. The two

halves pull apart, and each half takes

part of the cytoplasm. In this way, a

single amoeba becomes two.

Amphibian

Most of the animals known as amphibians

can live on land or in water.

Amphibians are vertebrates, or animals

with backbones. Amphibians were the

first vertebrates to appear on land. The

early amphibians were the ancestors of

all reptiles, birds, and mammals.

There are three basic groups of amphibians.

The first group consists of frogs

and toads. The second group consists of

salamanders, including newts and mud

puppies. The third group is made up of

wormlike creatures called caecilians.

Altogether there are more than 4,000

species, or types, of amphibian.

Where Amphibians Live

Amphibians are found nearly all over the

world. They are most common in hot,

humid areas such as the tropics. Some

adult amphibians live only on land.

Other types live only in water. However,

most amphibians spend part of the time

on land and part of the time in water.

Physical Features

Most amphibians are relatively small.

However, they vary greatly in length,

from less than 0.4 inch (1 centimeter) to

more than 60 inches (150 centimeters).

Amphibians do not have hair or feathers.

Their skin takes in oxygen. In other

words, amphibians breathe through

their skin. Most kinds also breathe

through lungs or organs called gills.

Amphibian skin takes in water, too.

Most amphibians have moist skin. In

most species, if the skin dries up, the

animal soon dies. The skin often contains

glands that make a slimy fluid

called mucus. Mucus helps protect the

skin from drying out.

Many amphibians also have glands in

the skin that make poison. This helps

protect an amphibian from other animals

that want to eat it. For example,

poison may make the amphibian taste

bad or hurt the predator’s mouth.

Some

amphibians

change their

skin color to

blend in with

their surroundings.

This

makes them

harder for

enemies to

see.

BRITANNICA STUDENT ENCYCLOPEDIA Amphibian 109

Frogs and Toads

Adult frogs and toads are tailless. Their

eyes are large and well developed. They

have short, thick bodies and four legs.

Frogs use their long, powerful back legs

for leaping and swimming. Toads have

shorter back legs than frogs do. They

walk or hop about. Unlike other

amphibians, toads have skin that is often

dry, with bumps that look like warts.

Salamanders

Salamanders have long tails. Most

salamanders have a small head, a short

body, and four legs. If a salamander

loses its tail or a leg, it can usually grow

a new one.

Caecilians

Caecilians look like worms or snakes.

They have long, slender bodies with no

arms or legs. Skin or bone covers their

eyes, so the animals are blind or nearly

blind. Most kinds live underground,

where they tunnel about.

Behavior

Amphibians are cold-blooded. This

means that their body temperature is

always about the same as the temperature

of their surroundings. If their environment

gets too hot or cold,

amphibians move to another place to

become more comfortable. For instance,

a frog may move from the shade into the

sunshine to warm its body.

During cold winters some amphibians

become very inactive for months. They

enter a resting state called hibernation.

They become active again when it gets

warmer. Some amphibians also become

inactive during hot, dry summers.

Adult amphibians eat a wide variety of

foods. Frogs, toads, and salamanders eat

mainly small boneless animals such as

Tree frogs, such as the green tree frog, have

special sticky feet that help them climb trees.

Salamanders (top) have smooth, wet skin,

like frogs’ skin. Caecilians (bottom) are

amphibians that look like worms.

110 Amphibian BRITANNICA STUDENT ENCYCLOPEDIA

insects, worms, and spiders. Some large

salamanders and frogs eat small birds

and mammals. Most caecilians eat

worms.

Life Cycle

Most amphibians lay eggs, but some

species give birth to live young. In most

egg-laying species, the female deposits a

large number of eggs in the water.

The life cycle of most amphibians is

divided into two phases. In the first

phase the amphibian lives in the water

in an immature form called the larva. In

frogs and toads the larva is also called a

tadpole. The larva begins life with gills,

which allow it to breathe underwater

like a fish. The larva stage may last from

several weeks to five years, depending on

the species.

In the second phase the larva develops

into the adult form. In most species, the

animal loses its gills and develops lungs.

It is then capable of living on land at

least part of the time. The animal’s body

structure may change in many other

ways, too. For example, a tadpole grows

legs and loses its tail. The change from

larva to adult is called metamorphosis.

However, some species do not have separate

larva and adult forms. They are

born in the same form as adults, only

smaller.

..More to explore

Animal • Frog • Hibernation

• Metamorphosis • Poison • Salamander

• Toad

Amsterdam

Population

(2008

estimate), urban

area,

1,482,287

Amsterdam is the largest city in The

Netherlands, a country in northwestern

Europe. It is the official capital of The

Netherlands. However, the government

offices are in the city of The Hague.

Amsterdam is a historical city as well as

the country’s major economic center. It

is also famous as a place of freedom and

tolerance. Tourists go to Amsterdam to

see its scenic canals and collections of

great art. Museums in the city display

the works of important artists from The

Netherlands, including Rembrandt and

Vincent van Gogh.

The Amstel River flows through Amsterdam.

The city also lies on a body of

A boat travels down a canal in Amsterdam.

BRITANNICA STUDENT ENCYCLOPEDIA Amsterdam 111

water called the IJ (pronounced “eye”).

A canal connects the IJ with the North

Sea. Amsterdam is a major port.

Part of Amsterdam’s land used to be

underwater, but people drained the

land. A system of pumps, barriers, and

canals keeps the water from rushing in

again. Boats travel through the city

along a cobweb pattern of canals. More

than 1,000 bridges provide land connections

over the canals.

Economy

For seven centuries Amsterdam has been

a center of international trade and transportation.

Other important industries

include banking, insurance, and tourism.

Industries that provide services to

businesses also bring money to the city.

History

Amsterdam began as a fishing village in

the 1200s. By the 1400s it was an

important port.

During the 1500s many Jews and Protestants

fled religious wars in other parts

of Europe. Many settled in Amsterdam

because it was known for its religious

freedom.

The 1600s were Amsterdam’s golden

age. The city grew wealthy as a center of

trade and banking. Amsterdam declined

somewhat in the 1700s.

Nazi troops from Germany controlled

Amsterdam in the 1940s, duringWorld

War II. The Nazis murdered most of

Amsterdam’s Jews.

After the war Amsterdam began to

thrive again. Its economy grew greatly in

the late 20th century.

#More to explore

Canal • Hague, The • Netherlands, The

• Rembrandt • Van Gogh, Vincent

Amundsen,

Roald

The Norwegian explorer Roald Amundsen

was one of the most important

people in the history of polar exploration.

He traveled to both the Arctic and

the Antarctic, and he was the first person

to reach the South Pole.

Roald Engelbregt Gravning Amundsen

was born in Borge, Norway, on July 16,

1872. His father, a shipowner, died

when Roald was 14. Young Amundsen

always wanted to be a polar explorer, but

to please his mother he studied medi-

A young Jewish

girl named

Anne Frank

and her family

hid from the

Nazis in

Amsterdam for

two years. The

building

where they hid

is now a

museum.

Roald Amundsen

112 Amundsen, Roald BRITANNICA STUDENT ENCYCLOPEDIA

cine. When his mother died, Amundsen

left school and went to sea.

At age 25 Amundsen made his first

voyage to the Antarctic, as part of a

Belgian expedition. Then in 1903 he

set out with his own ship and crew to

explore the Arctic. By the end of this

expedition, in 1906, Amundsen had

become the first navigator to find his

way through the Northwest Passage

from the Atlantic to the Pacific Ocean.

This had been a dream of explorers for

400 years.

In 1909 the explorers Robert Peary and

Matthew Henson became the first

people to reach the North Pole. Amundsen

then decided to try to be the first to

reach the South Pole. He set out with

four men, 52 dogs, and four sleds and

reached the pole on December 14,

1911.

In 1918 Amundsen tried to drift across

the North Pole in a boat, but the ice was

too thick. In 1926, with two companions,

Amundsen flew over the North

Pole in a dirigible, a lighter-than-air

craft. Amundsen died near the Arctic

island of Spitsbergen on June 18, 1928.

#More to explore

Henson, Matthew • Northwest Passage

• Peary, Robert E. • Polar Exploration

Anaconda

Anacondas are huge, nonpoisonous

snakes. They live in or near water in

warm parts of South America. Anacondas

are constrictors. This means that

they usually kill their prey by coiling

their body around it and squeezing until

the animal can no longer breathe. Anacondas

are one of the two largest types

of snakes in the world. Certain pythons

grow longer, but anacondas are much

heavier.

Anacondas are members of the boa family.

There are two species, or types, of

anaconda: the giant, or green, anaconda

and the yellow, or southern, anaconda.

The giant anaconda is the larger species.

It is usually brown or olive green with

oval-shaped black spots. The yellow anaconda

is tan or greenish yellow with

overlapping black spots.

The largest anacondas reach about 30

feet (9 meters) in length, but most grow

only to about 16 feet (5 meters). Some

anacondas weigh as much as 550

pounds (249 kilograms). Their thick,

bulky bodies may measure 12 inches (30

centimeters) or more around.

Anacondas usually hunt at night for

mammals, reptiles, and birds. Although

The giant anaconda is one of the largest

snakes in the world.

BRITANNICA STUDENT ENCYCLOPEDIA Anaconda 113

anacondas constrict larger prey, they

may kill turtles, birds, or other small

animals by using their mouth and sharp

teeth alone. Sometimes they may pull

their prey underwater to drown it. After

killing their prey, anacondas swallow it

whole.

Nine months after mating, female anacondas

give birth to large litters of live

young. A litter has 14 to 82 young. Each

young measures more than 2 feet (0.6

meter) long.

#More to explore

Boa Constrictor • Python • Snake

Anasazi

The Anasazi were a Native American

people whose civilization developed

beginning in about AD 100. They are

also known as the Cliff Dwellers because

of the great buildings they constructed

along the sides of cliffs. They lived in the

area where the present-day states of Arizona,

New Mexico, Colorado, and Utah

meet.

Early Anasazi houses were underground

pits lined with stone walls. In time,

these pit houses developed into kivas,

or structures where religious ceremonies

were performed. Then the Anasazi

began to live aboveground in simple,

one-story houses made from mud and

wood or stone.

Probably by about the mid-800s, the

Anasazi began constructing multistoried

structures that resembled modern apartment

buildings. The Anasazi built some

of these buildings into the sides of cliffs,

where they were difficult for their

enemies to attack.

The earliest Anasazi survived by hunting

and gathering wild plants. By about

700, however, they had learned to grow

corn, beans, squash, and other crops. As

their farming methods improved, their

food supply grew. Their population

grew, too, and they built large permanent

settlements.

No one knows why, but by about 1300

the Anasazi had mostly abandoned their

multistoried buildings. They broke into

smaller groups and moved south and

east where they built new villages.

The Anasazi’s descendants are the

Pueblo Indians. They established smaller

villages, mostly clustered in the Rio

Grande Valley of New Mexico and Arizona.

At the end of the 20th century

there were about 60,000 Pueblo Indians

living in the United States.

#More to explore

Native Americans • Pueblo Indians

Cliff Palace is an ancient Anasazi building

at Mesa Verde National Park in Colorado.

114 Anasazi BRITANNICA STUDENT ENCYCLOPEDIA

Anatomy

Anatomy is the study of the structures

that make up the bodies of living

things. It is a branch of the science of

biology.

Scientists learn about body structures

mainly by dissecting, or cutting apart,

bodies. They may dissect human or animal

bodies, plants, or other life-forms

such as bacteria. Scientists identify the

structures inside the life-form and how

they are put together.

Importance of Anatomy

Scientists study anatomy to learn about

the size, shape, and position of different

body parts—for example, the skin,

muscles, bones, and organs of humans.

The study of human anatomy is

important in medicine. Medical

students learn how the parts of a

healthy human body fit together and

how they function. This helps them

treat bodies that are not functioning

properly.

Scientists also compare the anatomies of

different types of living things. They

observe the similarities and differences

of their structures. This helps them

determine how different types of living

things are related to one another and

how they developed over time.

History

An ancient Greek doctor named Herophilus

is often called the Father of

Anatomy. He performed dissections of

human bodies, sometimes in public, in

about the 300s BC. The ancient Greek

doctor Galen later wrote many books

about human anatomy. They were a

major source of anatomy information in

Europe for centuries. However, they

contained many errors. Many of his

ideas were not based on direct observations

of the human body.

The modern science of anatomy began

to develop in the 1500s. In 1543 a

doctor named Andreas Vesalius wrote

the first detailed and illustrated

anatomy textbook based on observed

facts. He performed careful dissections

of human bodies in order to study

them.

The first powerful microscopes were

developed in the late 1600s. These

instruments allow scientists to study tiny

structures in the body such as cells and

their parts. As technology has improved

Students study a model of a human body.

Anatomy models can help students understand

how the human body is made up and

how its different parts work together.

The most

famous book

about human

anatomy is

called Gray’s

Anatomy.

Henry Gray

wrote the first

edition in

1858. Other

scientists have

kept it up to

date.

BRITANNICA STUDENT ENCYCLOPEDIA Anatomy 115

over the years, scientists have been able

to learn more and more about anatomy.

#More to explore

Biology • Medicine • Microscope

Andersen,

Hans Christian

The fairy tales of Hans Christian Andersen

are popular today, just as they were

when first published in Denmark in the

mid-1800s. His stories include such

favorites as “The Ugly Duckling” and

“The Emperor’s New Clothes.”

Hans Christian Andersen was born on

April 2, 1805, in a Danish fishing village

called Odense. Andersen’s family was

very poor. As a boy, he attended school

only occasionally. He visited the theater

and found that he loved performing.

When Andersen was 11 years old, his

father died. Shortly after that, Andersen

began working in various trades.

At age 14 Andersen moved to Copenhagen,

the capital of Denmark, to try to

become an actor or dancer. But he did

not have much success. Andersen later

studied at the University of Copenhagen.

Andersen’s first collection of tales for

young people was published in 1835. It

included the story “The Princess and the

Pea.” Andersen wrote his tales as if they

were being told out loud, often using

expressions that people heard every day.

He also drew on his own experiences to

create characters who were poor or even

outcasts.During his long writing career,

he wrote more than 200 stories. Andersen

also spent much time traveling

throughout Europe, Asia, and Africa, and

he wrote several travel books.He wrote

plays, poems, and novels, too. Andersen

died on August 4, 1875, in Copenhagen.

Anderson,

Marian

The singer Marian Anderson had a pure,

rich voice and could sing a great range

of parts. An African American, she is

also remembered for breaking down

barriers between blacks and whites in

the United States.

Anderson was born on February 27,

1897, in Philadelphia, Pennsylvania. At

age 6 she began singing in her church

choir. At age 19 she studied singing

with a famous teacher who was so

A girl feeds the ducklings in an

illustration for the story “The

Ugly Duckling.”

116 Andersen, Hans Christian BRITANNICA STUDENT ENCYCLOPEDIA

impressed by her talent that he gave her

free lessons.

In 1925 Anderson gave a recital with the

New York Philharmonic Orchestra. But

because of her skin color, many opportunities

were closed to her in the United

States, where at the time blacks and

whites were often kept apart. Audiences

in other countries embraced Anderson,

however. In the 1930s she made successful

singing tours of Europe.

In 1939 Anderson was prevented from

arranging a concert inWashington, D.C.,

because blacks were not allowed in the

concert hall.Many Americans, including

First Lady Eleanor Roosevelt, were

outraged. They arranged for her to sing

outside the LincolnMemorial instead,

and 75,000 people came to hear her.

In 1955 Anderson became the first African

American to perform with the

renowned Metropolitan Opera in New

York City. Two years later she published

My Lord, What a Morning, the story of

her life. Anderson died on April 8,

1993, in Portland, Oregon.

#More to explore

African Americans • Opera

Andes

The Andes Mountains of South America

are the longest mountain chain in the

world. The chain also contains the highest

mountains in the Americas. The

Andes were settled long ago by American

Indian peoples. They continue to

attract interest today because of their

mineral wealth.

Features

The AndesMountains stretch from north

to south along the entire western side of

South America. They separate a narrow

strip of land along the PacificOcean from

the rest of the continent. The Andes are

Marian Anderson sings at the Lincoln

Memorial in Washington, D.C.

BRITANNICA STUDENT ENCYCLOPEDIA Andes 117

about 5,500 miles (8,900 kilometers)

long and in most places are no wider than

200 miles (320 kilometers).

Many Andean peaks are higher than any

mountains in North America. At 22,831

feet (6,959 meters), Argentina’s Mount

Aconcagua is the highest mountain anywhere

in the world outside Asia.

Plants and Animals

Plant and animal life in the Andes varies

based on height and climate. The highest

peaks and some very dry places have

very few plants. But rainy parts of the

eastern Andes have lush tropical forests.

Animals of the Andes include pumas,

chinchillas, and several relatives of the

camel, including llamas, guanacos, and

alpacas. The Andean condor is a vulture

that is one of the world’s largest flying

birds.

People

Humans first settled in the Andes more

than 10,000 years ago. Indian peoples

such as the Inca established cities in high

valleys and built roads through mountain

passes. Most people in the Andean

region even today have at least some

Indian ancestors.

Most of the people of the mountains are

involved in farming. Most crops are

grown for use within the region, but

some are exported. Increasing numbers

of people have also become involved in

mining. The Andean region is one of the

world’s richest sources of minerals. Copper,

iron ore, tin, lead, zinc, silver, gold,

platinum, and emeralds are all produced

in the Andes, especially in the south.

#More to explore

Inca • Mountain • South America

Mount Fitzroy, or El Chalten, is part of the southern Andes Mountains. It rises above a

plain in the Patagonia region of Argentina.

118 Andes BRITANNICA STUDENT ENCYCLOPEDIA

Andorra

The European country of Andorra is

one of the smallest in the world. The

capital is Andorra la Vella.

Geography

Andorra lies in the southern Pyrenees

Mountains between Spain and France.

The Valira River runs through its valleys.

Andorra has a number of natural

sources of hot water called thermal

springs.

The climate of Andorra is generally dry.

It has cold, snowy winters and warm

summers.

Plants and Animals

Pines and firs grow in Andorra’s mountains,

where chamois (goatlike animals)

and birds of prey also live. Andorra has

reintroduced several threatened animals,

including species of trout and deer, to

their former habitats.Wild boars and

weasels are other native animals.

People

Most Andorrans are of Spanish origin

and Roman Catholic. Catalan, a language

of eastern Spain, is the official

language. Andorrans also speak Spanish

and French. Only about one third of the

people are Andorran citizens. The rest

are mostly citizens of Spain, France, or

Portugal.

Economy

Tourism, banking, trade, and construction

are the most important parts of

Andorra’s economy. Some tourists visit

the medieval churches, castles, and

bridges. Others come for skiing and

other winter sports.

Manufacturers in Andorra make electrical

equipment, cars and car parts, newspapers,

and clothes. A few farmers raise

tobacco, hay, potatoes, and sheep.

History

The emperor Charlemagne captured

Andorra from the Muslims in AD 803. It

later passed to the Spanish bishops of

the town of Urgel. In the late 1200s

Andorra became a coprincipality, a land

governed by two princes: the bishop of

Urgel and the leader of France. In 1993

Andorrans voted for a new constitution

that gave more power to their legislature,

the General Council.

..More to explore

Andorra la Vella • Charlemagne • France

• Pyrenees • Spain

Facts About

ANDORRA

Population

(2008 estimate)

84,100

Area

179 sq mi (464

sq km)

Capital

Andorra la Vella

Form of

government

Parliamentary

coprincipality

Major urban

areas

Andorra la Vella,

Les Escaldes-

Engordany,

Encamp

BRITANNICA STUDENT ENCYCLOPEDIA Andorra 119

Andorra la Vella

Population

(2008 estimate)

24,574

Andorra la Vella is the capital of the tiny

western European country of Andorra.

The town lies in a valley of the Pyrenees

Mountains.

Andorra la Vella is popular with tourists

because of its scenic beauty and winter

sports areas. It is also a retail shopping

center for goods from Asia and other

parts of Europe.

Andorra la Vella was long isolated from

the outside world. Roads built in the

1930s helped make it more modern. In

the second half of the 1900s the town’s

population grew along with its industries.

AngkorWat

A temple dating back to the 1100s,

AngkorWat is located in Cambodia. It

is the world’s largest religious structure.

Physical Features

AngkorWat is about 5,100 feet (1,554

meters) long and 4,498 feet (1,371

meters) wide. It is surrounded by a wall

and a moat. Of its original nine towers,

five still stand.

The temple was originally dedicated to

the Hindu god Vishnu. Carvings illustrate

Hindu legends and glorify the king

who ordered the temple built. Sculptures

portray him as Vishnu or show

him performing kingly functions. Many

Hindu images were later replaced by

Buddhist art.

History

From the 800s to the 1400s the city of

Angkor was the capital of a powerful

Cambodian kingdom called the Khmer

Empire. AngkorWat is the most famous

of the city’s temples. The Khmer started

building the temple during the reign of

King Suryavarman II, which lasted from

about 1113 to 1150. It was not finished

until after his death. In 1177 Angkor

was looted by invaders. The next king

decided that the Hindu gods had failed.

He made AngkorWat a Buddhist

shrine.

The city of Angkor was abandoned in

the 1400s. However, AngkorWat itself

was maintained by Buddhist monks as a

Andorra la Vella sits in a mountain valley.

One of the main tourist sites in the city is the

Casa de la Vall. It is where Andorra’s legislature

meets.

120 Andorra la Vella BRITANNICA STUDENT ENCYCLOPEDIA

pilgrimage site. Even so, parts of it were

damaged by plant roots or worn away by

water.

#More to explore

Buddhism • Cambodia • Hinduism

• Monk • Pilgrimage

Anglo-Saxon

Hundreds of years ago people known as

the Anglo-Saxons lived in and ruled

England. They were descendants of

three different peoples. The Angles and

Saxons came from different parts of

what is now Germany, and the Jutes

came from Jutland, a part of Denmark.

In the 400s the Celtic Britons who were

living in England asked the Angles, Saxons,

and Jutes to protect them from

fierce tribes in the north. In return for

their services the Angles, Saxons, and

Jutes were given land. Gradually they

became more powerful and pushed the

Britons aside. They became the rulers of

the land.

Eventually the name Anglo-Saxon came

to be used for all people living in

England, as the Angles, Saxons, and

Jutes mixed with other invaders and the

original Britons. The Anglo-Saxons

spoke an early form of English that is

now called Old English. They lived in

houses made of wood, thatch (straw),

and twigs woven together and covered

with mud or clay. When the mud or clay

hardened it made a solid roof or wall.

Anglo-Saxons fed themselves by farming.

They harvested grains, fruits, and

vegetables and raised livestock.

Anglo-Saxon rule ended in 1066. In that

year England was conquered by the

French forces ofWilliam, duke of Normandy,

during what is known as the

Norman Conquest.

#More to explore

England • Norman Conquest

Buddhist monks walk toward the main

temple building at Angkor Wat.

A rare gold coin shows an

Anglo-Saxon king.

BRITANNICA STUDENT ENCYCLOPEDIA Anglo-Saxon 121

Angola

The country of Angola lies on the southwestern

coast of Africa. After about 500

years as a colony of Portugal, Angola

suffered decades of civil war beginning

in 1975. The capital and largest city is

Luanda.

Geography

Angola is bordered by Congo, the

Democratic Republic of the Congo,

Zambia, and Namibia. The Atlantic

Ocean lies to the west. The small oilrich

area of Cabinda is separated from

the rest of Angola by a strip of the

Democratic Republic of the Congo.

A plateau, or raised land, covers the eastern

two thirds of Angola. Mountains

separate the plateau from the coast.

Lowlands lie along the coast and near

the Congo River.

Angola has a warm, tropical climate,

with a rainy season that lasts from October

to mid-May. The southwest is dry,

while the northeast is humid.

Plants and Animals

Rain forests once covered Angola, but

loggers and farmers cut down many of

the trees. Angola now has many savannas,

or grasslands with scattered trees.

Civil war and hunting have endangered

many animals, including African

elephants, black rhinoceroses, giant sable

antelopes, and Angolan giraffes. Angola

also has leopards, lions, hyenas,

elephants, hippopotamuses, zebras, and

buffalo. Many birds and a wide variety

of reptiles, including crocodiles, live

there, too.

People

Bantu peoples make up most of Angola’s

population. The two largest groups are

the Ovimbundu and the Mbundu.

Groups of San live in the southeast. Portuguese

is the official language. How-

Houses with thatched roofs line a hillside in

Angola.

122 Angola BRITANNICA STUDENT ENCYCLOPEDIA

ever, the people speak such local Bantu

languages as Umbundu, Kimbundu, and

others. Traditional religions have largely

given way to Christianity. A majority of

the Christians are Roman Catholics.

Economy

Angola’s economy is based on its natural

resources of petroleum (oil), natural gas,

and diamonds. Agriculture, fishing, and

manufacturing play smaller roles in the

economy. Farmers raise cassava, corn,

sugarcane, sweet potatoes, bananas,

cattle, and goats. Manufacturers make

food products, beer, shoes, and fabric.

History

Ancient peoples in what is now Angola

practiced ironworking and agriculture.

Eventually Bantu peoples set up a number

of kingdoms. The most powerful of

these was the Kongo kingdom around

the Congo River. It was founded in the

1300s.

Portuguese explorers arrived in 1483.

The Kongo kingdom traded ivory, hides,

and slaves for European firearms. By the

early 1600s Portugal was exporting

5,000 to 10,000 slaves from Luanda

every year, especially to Brazil. Portugal

slowly expanded its control of Angola.

Some Angolan leaders fought the Portuguese,

but others worked with them.

Portugal continued the slave trade in

Angola until the mid-1800s.

In 1961 Angolans took up arms against

Portugal, and violent fighting lasted for

14 years. The two main independence

groups were the Popular Movement for

the Liberation of Angola (MPLA) and

the National Union for the Total

Independence of Angola (UNITA).

Cuban troops and Soviet arms

supported the MPLA, while South

Africa and the United States provided

aid to UNITA.

Angola won independence in 1975. The

MPLA gained control of the government.

UNITA challenged its power,

however, and fighting broke out. A devastating

civil war lasted until the leader

of UNITA died in 2002. After that, the

MPLA had firm control of Angola. The

country slowly rebuilt from the war.

..More to explore

Africa • Luanda • Portugal • Slavery

Masks from Angola are on display at a

museum. Facts About

ANGOLA

Population

(2008 estimate)

12,531,000

Area

481,354 sq mi

(1,246,700 sq

km)

Capital

Luanda

Form of

government

Republic

Major cities

Luanda, Huambo,

Lobito, Benguela,

Namibe

BRITANNICA STUDENT ENCYCLOPEDIA Angola 123

Animal

Animals are living things. Like plants,

animals need food and water to live.

Unlike plants, which make their own

food, animals feed themselves by eating

plants or other animals. Animals can

also sense what goes on around them.

Their bodies allow them to move in

reaction to their surroundings. They use

their senses and movement to find food,

mates, and safety.

Millions of different kinds of animals

live on Earth. Animals are found

throughout the world, from the freezing

polar zones to the hottest deserts. They

live on land and in the water. They

come in a huge variety of shapes and

sizes.

Scientists divide animals into two main

groups. Animals that have a backbone

are called vertebrates. Animals that do

not have a backbone are called invertebrates.

About 95 percent of all animals

are invertebrates.

Invertebrates

Some invertebrates have a soft, unprotected

body—for example, sponges,

jellyfish, and worms. Most soft-bodied

invertebrates have no legs. Many live in

water, but some worms live on land.

Other invertebrates have a covering to

protect their body. Animals called

echinoderms—for example, starfish and

sea urchins—have tough skin covered in

stiff points. These animals all live in

oceans. Many mollusks, including oysters

and snails, have a hard shell around

124 Animal BRITANNICA STUDENT ENCYCLOPEDIA

their soft body. Some mollusks live on

land, but many live in water.

Invertebrates with jointed legs are called

arthropods. They have a hard covering

called an exoskeleton. Insects, spiders,

crustaceans, and centipedes are all

arthropods. Arthropods live on land and

in water all over the world.

Vertebrates

Fish are the oldest known vertebrates.

They live in water and are often covered

in scales. Most fish have a bony skeleton.

However, sharks and rays have a

skeleton made of cartilage, a strong and

flexible tissue.

Animals that live part of their life on

land and part of their life in water are

called amphibians. Frogs and salamanders

are examples of amphibians.

Most young amphibians live in water

and breathe with gills. As they grow they

form lungs and legs and move onto

land.

The first vertebrates to live completely

on land were reptiles—for example, lizards,

snakes, and crocodiles. Reptiles

have dry, scaly skin. Some reptiles, such

as turtles, spend a lot of time in water,

but they breathe air.

Vertebrates that have wings and feathers

are called birds. Most, but not all, birds

can fly.

Vertebrates that feed their babies with

milk from the mother are called mammals.

Mammals include mice, deer,

seals, whales, monkeys, and humans.

BRITANNICA STUDENT ENCYCLOPEDIA Animal 125

Mammals live on land in all parts of the

world. A few types, such as whales, live

in the ocean but still must breathe air.

#More to explore

Amphibian • Bird • Fish • Insect

• Living Things • Mammal • Mollusk

• Plant • Reptile •Worm

Animal Disease

#see Disease, Animal.

AnimalMigration

#see Migration, Animal.

Animals, Extinct

When an entire species, or type, of animal

dies out, that species is extinct.

Once a species becomes extinct, it is

gone forever.

Causes of Extinction

The most common cause of extinction is

a sudden, serious change in a species’

habitat. A habitat is the surroundings in

which an animal lives. Animals can

rarely survive such sudden change. Their

food supply may be wiped out. They

may also lose shelter or other things that

they need to survive.

Many things can change a species’ habitat.

Floods, fires, droughts, volcanoes,

and other natural events may be causes.

People also change the environment in

ways that drastically affect animals.

People clear forests and drain wetlands.

They build dams that disrupt the flow of

rivers. They build cities on land that

animals need to survive. They also create

harmful pollution.

Some changes that cause extinction

affect only a small area. Others are large

enough to affect the entire world. A fire

or other local event may cause the

extinction of animals that live only in

that region. A sudden change in the

global climate might wipe out an animal

species that lives in many parts of the

world.

People can cause extinctions more

directly as well. Some species have been

hunted to extinction. The passenger

pigeon is one example. Humans killed

millions of the birds over many years.

The last one died in the early 1900s.

Mass Extinctions

Sometimes many different species

become extinct in a short time. This is

A bird called the dodo once lived on an

island in the Indian Ocean. Europeans took

control of the island in the 1500s and

began to hunt the bird. By 1681 the dodo

was extinct.

126 Animal Disease BRITANNICA STUDENT ENCYCLOPEDIA

called a mass extinction. Several major

mass extinctions have occurred in the

past. Each time many animal species

were wiped out. Some survived, however,

and over millions of years new species

developed.

The worst mass extinction happened

about 248 million years ago. This

extinction included mainly animals

without backbones that lived in water.

Another mass extinction occurred about

65 million years ago. It wiped out many

of the planet’s land animals, including

the dinosaurs.

Dinosaur Extinction

Dinosaurs first appeared on Earth about

215 million years ago. They were the

most important land animals for more

than 150 million years. By 65 million

years ago, however, the dinosaurs had

died out.

Many scientists believe that a large asteroid,

or rock from space, caused this mass

extinction. When the asteroid hit Earth,

the impact caused drastic changes. Thick

dust and other materials blocked the

sun. Temperatures dropped, and plants

could not grow. The dinosaurs could not

survive the cold temperatures and lack

of food. But early species of birds and

mammals did survive.

Large Mammal Extinction

About 10,000 years ago another mysterious

animal extinction occurred. This

extinction was especially dramatic in

North America, where many large mammals

disappeared. Among them were

woolly mammoths and saber-toothed

cats.

Scientists do not know what caused this

extinction. Some believe that growing

numbers of human beings hunted and

killed too many of the animals or their

prey. Another theory is that the climate

changed and affected the availability of

food.

Endangered Species Today

In the past 200 years the world has lost

many animal species. Hundreds of others

are on the verge of extinction. Animals

at risk of dying out are called

endangered species.

Governments today are working to protect

the world’s endangered species.

Laws protect some animals’ habitats

from being polluted or destroyed. Other

laws make it illegal to hunt endangered

animals. Some species respond well to

these protective measures and increase in

number. Others are not as successful.

#More to explore

Animal • Dinosaur • Endangered

Species • Mastodon and Mammoth

The Carolina

parakeet and

the passenger

pigeon were

birds once

found in the

United States.

People killed

so many of

them that both

types became

extinct in

1914.

The Tasmanian wolf is an extinct animal.

The last members of the species died out in

the 1930s.

BRITANNICA STUDENT ENCYCLOPEDIA Animals, Extinct 127

Animals,

Legendary

Stories about unusual animals were

commonplace in earlier times. Such

animals are called legendary because

they exist only in these stories, or

legends. The stories were often based on

travelers’ reports of animals that were

unfamiliar to them. Some famous

legendary animals include the dragon,

various sea serpents, the unicorn, and

the phoenix. Even today some people

speak of having seen animals such as

the yeti, Bigfoot, and the Loch Ness

monster.

The Dragon

The dragon was usually thought of as a

huge scaly lizard or snake that breathed

fire and had wings like a bat. In the

Middle Eastern world, the serpent or

dragon symbolized evil. In Christian art

the dragon came to stand for sin. In

China, however, the dragon is known as

a kind creature.

Sea Creatures

Sea serpents were supposed to be

enormous snakes, or huge creatures that

inhabited the deep sea. Sailors

throughout the ancient world reported

having seen such creatures. In

Norwegian sea folklore, the kraken was

a huge creature, part octopus and part

crab. Accounts of these creatures might

have been based on sightings of giant

squid, which can reach a length of 60

feet (18 meters).

Mermaids were also mythical sea creatures.

They were thought to have the

head and upper body of a woman and

the tail of a fish. Stories of mermaids

may have come from people who saw

water-dwelling mammals, such as the

dugong and manatee. These animals

feed their young in human fashion

A sculpture of a dragon decorates a tiled

wall in Beijing, China.

Mermaids have appeared in many stories,

including “The Little Mermaid” by Hans

Christian Andersen.

128 Animals, Legendary BRITANNICA STUDENT ENCYCLOPEDIA

above water and from afar may have

looked like a person.

The Unicorn

The unicorn was a mythological animal

with a single horn on its forehead. Its

body shape resembled a horse or a

young goat. The unicorn was referred to

in the ancient myths of India and

China. It appears in artwork from the

ancient civilization of Mesopotamia.

During the Middle Ages (about AD 500–

1500) artists from Europe, the Islamic

world, and China included the unicorn

in their artwork as well.

The Phoenix

Mythological creatures also have taken

the form of birds. A fabulous bird

known as the phoenix was associated

with the worship of the sun in ancient

Egypt. It was said to be as large as an

eagle, with brilliant scarlet and gold

feathers. Legend had it that only one

phoenix existed at any one time and

that it lived at least 500 years. As its

death approached, the phoenix made a

nest. It then set the nest on fire and

was consumed in the flames. A new

phoenix miraculously emerged from the

ashes.

Modern Creatures

Some people have claimed to have seen a

“monster” in Loch Ness, a lake in northern

Scotland. No one has ever proved

the monster’s existence, however.

More recent legendary creatures are the

Abominable Snowman and Bigfoot. The

Abominable Snowman, or yeti, is a

monster thought to live in the Himalayan

mountain range. Reports of the

monster are based mostly on mysterious

markings in the snow. Many people

think that the markings come from

bears. Bigfoot, or Sasquatch, has been

described as a large, hairy creature

resembling a human. It is believed by

some to exist in the northwestern

United States and western Canada.

Animation

Animation is the art and science of making

pictures, or images, appear to move.

Animated movies and television shows

are popular forms of entertainment.

There are two basic types of animation:

traditional animation and computer animation.

The mermaid

is not the only

legendary

creature with

a human head

and an animal

body. The centaur

has the

body of a

horse, and the

sphinx has the

body of a lion.

A tapestry made in the 1400s

shows a unicorn with a large

horn.

BRITANNICA STUDENT ENCYCLOPEDIA Animation 129

Traditional Animation

Movies and television shows made with

traditional animation are also called

cartoons. Teams of artists create them

one picture at a time.

Thousands of drawings are needed for

only a few minutes of animation. Each

drawing is a bit different from the one

before it. For example, to show a character

walking, the first drawing might

show the character with both feet on the

ground. The next drawing might show

the knee with a tiny bend and the foot

slightly off the ground. In the third

drawing, the knee might be bent more

and the foot might be a little farther off

the ground, and so on.

To save work and time, artists paint or

draw the moving parts of a scene on

sheets of clear plastic film. They place a

drawing of the parts of the scene that do

not move under the clear film. In this

way they do not need to redraw the

background in every picture.

Then filmmakers use a special camera to

take a picture of each drawing on its

background. Each of these pictures is

called a frame. The camera records the

frames one after another on long strips

of film. To make the images move

smoothly, 24 frames are needed for every

second of film.

Filmmakers can also create animation

with figures made of clay or other materials.

Instead of drawing thousands of

images, they take many photographs of

figures set up in a scene. They move the

figures slightly between each photograph.

This technique is called stopmotion

animation.

Computer Animation

Computers have made animation a

faster process. They can produce the

To create an animation an artist draws the

same character many times. In each drawing

the character has changed position

slightly.

Artists used computers to make

the animated movie Toy Story in

1995.

130 Animation BRITANNICA STUDENT ENCYCLOPEDIA

thousands of pictures needed for an animated

film more quickly than human

artists. Artists can also use computers to

create characters, objects, and backgrounds

that look more real than drawings

do. Today computers are used in

almost all animation.

Computer animation can be used to

make a whole movie or to create special

effects in live-action films. Many spacecraft,

robots, and monsters in movies are

actually computer images.

Computer animation can be used for

more than just entertainment. Scientists

use computer animation to show things

that people cannot easily see in real life.

Such things include the movement of

the solar system, weather patterns, and

the inside of the human body.

History

In the 1800s people invented spinning

machines that made a series of drawings

appear to move. The first animated films

appeared in the early 1900s. Walt Disney

made the first animated film with

sound, SteamboatWillie, in 1928. In

1937 Disney made Snow White and the

Seven Dwarfs. It was the first full-length

animated film to be released as a major

motion picture in the United States.

Animated television shows appeared in

the United States in the 1950s. Toy

Story, from 1995, was the first long film

made completely with computer animation.

..More to explore

Cartoon • Disney,Walt • Movie

• Television

Ankara

Population

(2007 census)

3,763,591

Ankara is the capital of the country of

Turkey. The city is located in the part of

Turkey that lies in southwestern Asia,

called Asia Minor. Ankara is Turkey’s

second largest city, after Istanbul.

Ankara is one of Turkey’s main industrial

centers. Its factories produce wine

and beer, processed foods, decorative

flooring, construction materials, and

tractors. Tourism and other service

industries have expanded rapidly in the

city.

People have lived in the Ankara area for

many thousands of years. In 334 BC

Alexander the Great conquered Ankara.

The city later became part of the Roman

Empire and then the Byzantine Empire.

Mustafa Kemal is buried in a mausoleum,

or tomb, in Ankara.

BRITANNICA STUDENT ENCYCLOPEDIA Ankara 131

Ankara was part of the Ottoman Empire

from the 1400s to the early 1900s. In

1919 the Turkish leader Mustafa Kemal

set up a rival government in Ankara. He

wanted Turkey to become its own country.

Turkey became an independent

republic in 1923, and Ankara became its

capital.

..More to explore

Asia Minor • Istanbul • Turkey

Annapolis

Population

(2000 census)

35,838; (2007

estimate)

36,603

Annapolis is the capital of the state of

Maryland. The city lies along the Severn

River at its mouth on Chesapeake Bay.

Annapolis has a port on the bay, which

leads to the Atlantic Ocean.

Many people in Annapolis work for the

state government. The United States

Naval Academy in Annapolis trains

officers for the Navy and Marine Corps.

The city’s leading industries are crab and

oyster fishing, seafood processing, and

boatbuilding.

The city was founded in 1649. It was

originally called Providence. The city

became the capital of Maryland in 1694.

The following year the city was renamed

Annapolis.

In the 1700s Annapolis was an important

center of social and political life in

the American Colonies. It served as the

capital of the United States from 1783

to 1784. Many historic buildings from

the 1700s can still be seen in Annapolis

today.

Saint Mary’s Church was built between 1858 and 1860. It is located on Spa Creek in

Annapolis’ historic district.

132 Annapolis BRITANNICA STUDENT ENCYCLOPEDIA

Ant

Ants are social insects. This means that

they live together in organized communities

called colonies. There are more

than 10,000 different species, or kinds,

of ant. Ants are found almost everywhere

in the world, but they are most

common in hot areas.

Ants range in size from 0.08 inch to 1

inch (2 to 25 millimeters). They are

usually yellow, brown, red, or black. The

body of an ant is divided into three sections:

the head, the thorax (midsection),

and the abdomen. The head is large, and

the abdomen is slender and oval. The

thorax is connected to the abdomen by a

small waist. Two antennas are located on

the top of the head. Ants use their

antennas for guidance, smell, and communication.

Most types of ant live in nests that they

make from many different materials,

including soil, sand, wood, and leaves.

Some ants build anthills.Within each

nest there is usually a queen, workers,

and soldiers. The queen spends her life

laying eggs. The workers are females

who do the work of the nest—for

example, collecting food, cleaning the

nest, and caring for eggs. Soldiers are

larger females who defend the colony.

They also raid other colonies and often

capture slaves.

At certain times of the year, many species

produce winged males and queens.

The males’ only purpose is to mate with

the queens. The males and the queens

fly into the air to mate. The males die

soon afterward. Each queen then lays

her eggs and sets up a new nest. It takes

several weeks for the eggs to develop

into adults. Most ants live for 6 to 10

weeks, though some live up to 15 years.

#More to explore

Insect

Harvester ants work to store grass, seeds,

and berries in their nest.

Carpenter ants like wood of all kinds. They

make their nests in live or dead trees or in

wooden structures such as telephone poles

and porches.

BRITANNICA STUDENT ENCYCLOPEDIA Ant 133

Antananarivo

Population

(2001 estimate)

1,403,449

Antananarivo is the capital of Madagascar,

an island country off the southeastern

coast of Africa. Antananarivo stands

on a high hill in the country’s central

highlands. It is the largest city in Madagascar

by far.

Antananarivo’s historic sites include

royal palaces from the 1800s. The city

also has Anglican and Roman Catholic

cathedrals and the National Library. The

University of Madagascar was opened in

the city in 1961.

Antananarivo has been a government

center for hundreds of years. Many of

the city’s residents work for the government

of Madagascar. Banking and business

services are also important to the

economy. The city’s factories process

tobacco and make foods, leather, and

clothing.

Antananarivo began as a fortress town

in the 1600s. It became the capital of

the Merina kingdom in the 1700s. In

1895 French troops took control of the

town. Within 10 years the French

controlled most of the island. They

made the town the capital of their

colony. In 1960 the colony became an

independent country with its capital at

Antananarivo. The city grew quickly in

the late 20th century.

#More to explore

Madagascar

The sun sets on the hilly city of Antananarivo.

134 Antananarivo BRITANNICA STUDENT ENCYCLOPEDIA

Antarctica

The southernmost continent in the

world, Antarctica surrounds the South

Pole. Its name means “opposite to the

Arctic” (the Arctic is the region around

the North Pole). Antarctica is larger than

both Europe and Australia. But it has no

permanent human population.

Land

An ice sheet covers nearly all of Antarctica.

It contains 90 percent of the

world’s ice and 70 percent of the world’s

freshwater. At its thickest point the ice

sheet is 15,670 feet (4,776 meters) deep.

Around the coast, glaciers continually

break off icebergs into the sea.

The continent has two unequal parts.

The larger is generally known as East

Antarctica, while the smaller is West

Antarctica.West Antarctica includes the

Antarctic Peninsula, an 800-mile

(1,300-kilometer) extension of the continent

that juts northward toward the

southern tip of South America. The

Transantarctic Mountains separate East

andWest Antarctica. Mountains with

only their peaks showing through the

ice, known as nunataks, are found in

some areas. Antarctica has several active

volcanoes.

About 2 percent of Antarctica is ice-free.

These unusual land areas, called oases,

are mostly found near the coast. They

include the dry valleys of southern Victoria

Land and the Bunger Oasis in

Wilkes Land.

Penguins are among the few animals that can survive the very cold temperatures of

Antarctica.

BRITANNICA STUDENT ENCYCLOPEDIA Antarctica 135

136 Antarctica BRITANNICA STUDENT ENCYCLOPEDIA

Antarctica does not have 24-hour periods

divided into days and nights. At the

South Pole the sun rises on about September

21 and moves in a circular path

until it sets on about March 22. This

“day,” or summer, is six months long.

From March 22 until September 21 the

South Pole is dark, and Antarctica has its

“night,” or winter.

Antarctica is the coldest continent. The

average annual temperature in the

interior is .70° F (.57° C). But the

coast is warmer. Along the Antarctic

Peninsula temperatures can rise up to

59° F (15° C).

Plants and Animals

The extreme cold has kept the

continent almost empty of life. Some

mosses and liverworts grow in ice-free

areas along the coast, and two types of

flowering plants grow on the peninsula.

Native land animals are limited to

certain kinds of arthropods, or

insectlike animals.

About 45 kinds of birds live in Antarctica.

The emperor and the Adelie penguins

are found in large numbers around

the entire coastline. Gentoo and chinstrap

penguins occupy the Antarctic

Peninsula coasts and some islands. Several

kinds of seals and whales inhabit the

waters around Antarctica. Fishes limited

to the Antarctic include the Antarctic

cod and the icefish.

History

The first recorded landing on Antarctica

was on Cape Adare in 1895. The first

people to spend a winter on the continent

did so in a ship that was caught in

ice at Cape Adare during the period

from March 1898 to March 1899.

Englishmen Robert F. Scott and Ernest

Henry Shackleton led three expeditions

to the Antarctic between 1901 and

1913. They pioneered routes into the

interior of the continent, and the

research they conducted provided a base

for present-day scientific programs. On

December 14, 1911, Roald Amundsen

of Norway became the first person to

reach the South Pole. Many other expeditions

followed.

Every year hundreds of researchers travel

to Antarctica to conduct experiments.

Widespread scientific investigation of

Antarctica began during the International

Geophysical Year in 1957–58. In

1959, 12 countries signed the Antarctic

Treaty to reserve the continent for

peaceful, scientific purposes. By 2000,

44 countries had signed the treaty.

#More to explore

Amundsen, Roald • Continent • Glacier

• Iceberg • Penguin • Polar Exploration

Facts About

ANTARCTICA

Area

5,400,000 sq mi (14,200,000 sq km)

Population

No permanent population

Coldest Recorded Temperature

July 21, 1983, Vostock Station: .129° F

(.89° C)

Hottest Recorded Temperature

January 5, 1974, Lake Vanda: 59° F (15° C)

BRITANNICA STUDENT ENCYCLOPEDIA Antarctica 137

Anteater

Anteaters are curious-looking animals.

Their long heads and snouts look like

tubes, and they have no teeth at all. Anteaters

use their strong front legs and

heavy claws to break open nests of ants

and termites. When the insects rush out,

the anteaters eat them with their long,

sticky tongues.

Anteaters live in the swamps and forests

of Central and South America. They are

related to sloths and armadillos, which

also live in Latin America.

True Anteaters

There are four species, or types, of anteater.

They make up a scientific group

called Vermilingua, which means

“worm-tongue.”

The largest species is the giant anteater.

From the tip of its snout to the end of

its tail, the giant anteater is about 6 feet

(1.8 meters) long. Its coat is mostly gray,

and its long tail is bushy. It feeds on the

ground by day and by night.

There are two different species of lesser

anteater, or tamandua, but they look

very similar. Lesser anteaters are only

about half the length of giant anteaters.

They also have shorter muzzles. Lesser

anteaters have tan, black, or tan-andblack

coats. They live in trees and feed at

night. They use their long, nearly hairless

tails to climb on tree branches.

The silky, or two-toed, anteater is the

smallest of the group. It is the size of a

squirrel. It has a silky, yellowish coat and

a long, furry tail. Like lesser anteaters,

the silky anteater lives in trees and feeds

at night.

Other Animals Called

Anteaters

People sometimes call other insecteating

animals anteaters, but these animals

are not related to true anteaters.

They include the numbat (or banded

anteater), the aardvark (or ant bear), the

echidna (or spiny anteater), and the

pangolin (or scaly anteater).

#More to explore

Armadillo • Sloth

Antelope

Antelopes are a group of plant-eating

mammals that belong to the same family

as sheep, goats, and cattle. The impala,

the addax, gazelles, gnus, and kudus are

all antelopes. The pronghorn, or prongbuck,

is also known as an antelope, but

it belongs to a different family.

Antelopes live on the large, grassy plains

of Africa and in the central and southwestern

regions of Eurasia (the continents

of Europe and Asia). Only the

pronghorn is found in North America.

The giant

anteater’s

tongue can be

as long as 24

inches (60

centimeters).

giant anteater

138 Anteater BRITANNICA STUDENT ENCYCLOPEDIA

Antelopes are generally about the same

size as most goats and deer. They have

hooves on their feet. Their coats are generally

golden, reddish tan, or gray. The

face, belly, and rump tend to be white.

Most male antelopes have horns that

curve backward.

Antelopes have excellent senses of smell

and hearing. These help them to detect

danger and leap to safety. The impala

can make leaps as long as 30 feet (9

meters). Antelopes can also run very

fast. One type of gazelle can run 50

miles (80 kilometers) per hour.

Antelopes generally travel in herds of

several hundred animals. During the

mating season, male antelopes mark

their territory by rubbing their scent

glands against plants and trees. A male

will fight other male antelopes to defend

his territory. The male then attracts a

female, or doe, and they mate. The doe

gives birth to one young about four to

eight months later, depending on the

type of antelope.

#More to explore

Hoof • Horn • Mammal

Anthem,

National

#see National Anthem.

Anthony,

Susan B.

In the 1900s women in the United

States fought to gain equal rights with

men. One of the leaders of that movement

was Susan B. Anthony.

There are many different kinds of antelope. They include the blackbuck, which is found in

India; the saiga from elsewhere in Asia; and the gerenuk, Thomson’s gazelle, common

eland, impala, and suni from Africa. In most of these animals only the males have horns.

BRITANNICA STUDENT ENCYCLOPEDIA Anthony, Susan B. 139

Susan Brownell Anthony was born on

February 15, 1820, in Adams,

Massachusetts. When she was 6 years

old her family moved to Battenville,

New York. As a young woman she

taught school.

In the 1850s Anthony became involved

in both the temperance movement,

which fought alcohol abuse, and the

abolitionist movement, which sought to

end slavery. She traveled widely, spoke at

public meetings, and began to take an

interest in women’s issues.

At the time, women in the United States

did not have the right to vote. To fight

this injustice, Anthony and her friend

Elizabeth Cady Stanton formed the

NationalWoman Suffrage Association

(NWSA) in 1869. “Suffrage” means the

right to vote.

To draw attention to the struggle,

Anthony tried to vote in the 1872 presidential

election. She was arrested, but

she refused to pay her fine. In 1890 the

NWSA merged with another group to

form the National AmericanWoman

Suffrage Association. Anthony was president

from 1892 to 1900.

Susan B. Anthony died on March 13,

1906, in Rochester, New York. In 1920

the 19th Amendment to the U.S. Constitution

gave voting rights to women in

all states.

#More to explore

Abolitionist Movement • Stanton,

Elizabeth Cady •Women’s Rights

Anthropology

Anthropology is the study of human

beings and their cultures, from

prehistoric times to today. The people

who practice anthropology are called

Susan B. Anthony

Some anthropologists study how certain

groups of people live. They may travel to

remote places, such as the Ituri Forest in

central Africa, to observe these groups.

140 Anthropology BRITANNICA STUDENT ENCYCLOPEDIA

anthropologists. Anthropologists often

compare different human communities.

They try to determine their similarities

and differences. By doing this,

anthropologists hope to increase their

knowledge about humanity as a whole,

as well as about specific groups of

people.

Anthropology has two main divisions:

physical and cultural. Physical anthropologists

study the physical features of

humans. Cultural anthropologists examine

human cultures. Both these kinds of

anthropology may include the study of

prehistoric, ancient, and modern

humans.

Physical Anthropology

Physical anthropology is related to the

science called biology. Physical anthropologists

examine differences in human

physical features. They often study

human genes. These are the things that

pass along traits from parents to their

children. They may also measure the

shape, size, and structure of body parts

or properties such as blood types.

Some physical anthropologists compare

the physical features among people from

different geographic areas. Others may

examine what makes humans physically

different from other animals, such as

apes. Some physical anthropologists

study the remains of prehistoric humans

to learn about human origins. They try

to determine how and when modern

humans developed from early forms of

humans and from nonhuman ancestors.

In other words, they study human evolution.

In the past, some physical

anthropologists divided people into

races. They ranked the races based on

such features as skull size and skin

color. They thought that some races

were better than others. However, that

idea came from prejudices, not from

true science. In the late 20th century

anthropologists found that modern

humans are all very similar in their

genes. In fact, there is no scientific basis

for dividing people into races.

Cultural Anthropology

Cultural anthropology is a social science,

or a field of study concerned with

human societies. Cultural anthropologists

study many aspects of human cultures,

in different places and times.

These may include art, language, religion,

clothing, customs, and social

structure. Anthropologists try not to

judge a culture’s practices as good or

bad. Instead, they try to find out what

the practices mean to the people of that

culture. They also compare the practices

of various societies.

Some anthropologists study the bones and

other remains of humans.

Margaret

Mead of the

United States

was a famous

anthropologist.

She studied

the

peoples of

Oceania during

the mid-

1900s.

BRITANNICA STUDENT ENCYCLOPEDIA Anthropology 141

Archaeology is one type of cultural

anthropology. Archaeologists uncover

and study pottery, tools, and other

objects left by prehistoric and ancient

peoples. They try to learn how such

peoples lived.

In the 1800s and early 1900s most cultural

anthropologists were from western

Europe or the United States. They usually

traveled to another part of the

world, such as Africa or Asia, to study

different cultures. Today cultural anthropologists

from all around the world

study a wide variety of human groups.

For instance, they may study small fishing

villages, gangs in big cities, religious

groups, or large companies.

#More to explore

Archaeology • Biology • Culture

• Evolution • Genetics • Human Origins

• Social Science

Antibiotic

Doctors sometimes treat patients with a

type of medicine called an antibiotic.

Antibiotics treat illnesses and infections

caused by bacteria, or tiny organisms.

Antibiotics can come in the form of a

pill, a liquid, a cream, or a shot. One of

the first widely used antibiotics was

penicillin. It was discovered in 1928.

Doctors use antibiotics to cure serious

diseases such as pneumonia, tuberculosis,

and meningitis. Antibiotics can also

fight common problems such as acne

and strep throat. Antibiotics do not

work against common colds or other

illnesses caused by a virus.

Antibiotics work by killing bacteria or

by preventing them from multiplying.

Sometimes, however, not all the bacteria

die. The bacteria that survive are said to

have a resistance to the antibiotic. As

those bacteria multiply, they pass on the

resistance to new bacteria. The next time

those bacteria are exposed to the same

antibiotic, even fewer of them die. Eventually

the antibiotic does not kill enough

of the bacteria to make the illness go

away.

When enough types of bacteria become

resistant to an antibiotic, doctors no

longer use that antibiotic as medicine.

The number of resistant bacteria continues

to grow. Scientists are working to

find new antibiotics to replace the old

ones.

#More to explore

Bacteria • Disease, Human • Penicillin

• Virus

A special test shows whether or not antibiotics

can stop the growth of certain bacteria.

Tablets that contain antibiotics are placed

on a surface with bacteria on it. The clear

areas around the tablets show that the antibiotics

have stopped the bacteria from growing.

Antibiotics

should always

be used carefully.

Some

people have

bad reactions

to certain antibiotics.

142 Antibiotic BRITANNICA STUDENT ENCYCLOPEDIA

Antigua and Barbuda

The Caribbean island country of Antigua

and Barbuda is known for its powdery

beaches. The capital is Saint John’s.

Geography

The country consists of three islands:

Antigua, Barbuda, and Redonda. Antigua

has rolling hills and volcanic rocks.

Near the coast are coral reefs. Barbuda is

a flat island 25 miles (40 kilometers)

north of Antigua. No one lives on

Redonda, a large rock southwest of

Antigua.

The country has a warm, tropical climate.

Droughts often occur on Antigua.

Plants and Animals

Barbuda has rain forests and lush vegetation.

With its drier climate, Antigua has

no forests but many kinds of cactus.

Barbuda is home to many large seabirds

called frigate birds.

People

Most of the country’s people are descendants

of African slaves. Small populations

of whites, Asians, and American

Indians also live there. Most people are

Christian. The official language is

English.

Economy

Tourism is very important to Antigua

and Barbuda’s economy. Transportation,

communications, financial services, real

estate, and construction are also important.

There is little manufacturing,

mainly of beer and T-shirts. Agriculture

and fishing play a small role in the

economy. The main crops are tropical

fruits.

History

The first inhabitants of Antigua and

Barbuda were the Ciboney people and,

later, the Arawak people. The explorer

Christopher Columbus landed on Antigua

in 1493.

The English took over the islands in

1632. They brought in Africans to work

as slaves on large sugar plantations. The

slaves won freedom in 1834.

The islands were part of the British Leeward

Islands colony until 1956. Great

Britain then managed their foreign

affairs until 1981, when Antigua and

Barbuda gained independence.

..More to explore

Arawak • Caribbean Sea • Columbus,

Christopher • Coral

Facts About

ANTIGUA AND

BARBUDA

Population

(2008 estimate)

87,500

Area

171 sq mi (442

sq km)

Capital

Saint John’s

Form of

government

Constitutional

monarchy

Major city

Saint John’s

BRITANNICA STUDENT ENCYCLOPEDIA Antigua and Barbuda 143

Apache

The people known as the Apache

include several related Native American

groups. The Apache are familiar to many

people because of the WildWest stories

about Cochise and Geronimo. Both

men were famous Apache warriors who

fought to keep Apache lands free from

Mexico and the United States.

Historians believe that the ancestors of

the Apache lived in Canada. The Apache

probably migrated to the American

Southwest in about AD 1000. The traditional

Apache homelands are located in

what are now Arizona, Colorado, New

Mexico, Texas, and the Mexican states of

Chihuahua and Sonora.

The Apache were nomads who moved

from camp to camp depending on the

season and the food supply. They got

their food by hunting, gathering wild

plants, and farming. They also carried

out raids on other people to obtain

horses and supplies. The Apache made

dome-shaped shelters, known as wickiups,

by covering a wooden frame with

grass or branches.

Spanish explorers were the first non-

Indians to enter Apache lands. Mexicans

and Americans came later. American

settlement in Apache territory led to

fierce fighting between the Apache and

the U.S. military in the second half of

the 1800s. The last of the Apache wars

ended with Geronimo’s surrender in

1886. Some of the Apache settled in

Oklahoma; others moved to a reservation

in New Mexico. At the end of the

20th century there were about 57,000

Apache. Many lived on reservations in

the Southwest.

#More to explore

Geronimo • Native Americans

Apartheid

Apartheid was a system for keeping

white people and nonwhites separated in

South Africa. It lasted from about 1950

to the early 1990s. The word apartheid

means “apartness” in Afrikaans, a language

spoken in South Africa.

The population of the country is mostly

nonwhite. But for many years the white

people of South Africa controlled the

country’s government. They established

laws that kept the races separate and

discriminated against the nonwhite

majority.

Apartheid divided South Africans into

four groups: white, Bantu (black), Col-

An Apache woman holds a child in a

cradleboard. Many Native American

women used cradleboards to carry small

children on their back.

144 Apache BRITANNICA STUDENT ENCYCLOPEDIA

ored (of mixed descent), and Asian. The

policy created separate areas in cities for

each group. Members of a group were

not allowed to live, operate businesses,

or own land outside of their area. Under

“pass” laws, nonwhites had to carry

passes while in white areas. Other laws

set up separate schools and restricted

each race to different types of jobs. The

government also created 10 territories

called “homelands” and forced all blacks

to move to them.

With the support of some whites, many

blacks in South Africa protested against

apartheid. The African National Congress

(ANC) led the fight. The protests

sometimes turned violent. A district

called Soweto rioted in 1976 against a

requirement that blacks learn Afrikaans.

Other countries also condemned apartheid.

In 1985 Great Britain and the

United States restricted trade with South

Africa.

In response to the protests, the South

African government granted nonwhites

some rights in the late 1980s. In

1990–91 the government led by President

F.W. de Klerk ended most of the

apartheid laws. In 1994 all races were

allowed to vote in a national election.

Nelson Mandela, leader of the ANC,

was elected president. Apartheid was

over, but its effects remained. Racial

discrimination continued in South

Africa.

#More to explore

African National Congress

• Discrimination • Mandela, Nelson

• South Africa

Apatosaurus

A massive dinosaur, the Apatosaurus

weighed as much as five elephants. The

name Apatosaurus means “deceptive lizard.”

It used to be called Brontosaurus,

which means “thunder lizard.” Apatosaurus

belongs to the group of dinosaurs

known as sauropods, which also includes

Brachiosaurus. The sauropods were large,

plant-eating dinosaurs with a long neck,

a massive body, and four pillarlike legs.

When and Where Apatosaurus

Lived

Apatosaurus lived about 147 to 137 million

years ago. Most Apatosaurus remains

have been found in North America,

Scientists once

thought that

Apatosaurus

needed to live

in water to

support the

weight of its

heavy body.

Modern scientists

now

agree that the

dinosaur was

mainly a land

animal.

During the period of apartheid

blacks and whites were kept

apart in many ways. A sign from

that time says that a beach is for

whites only.

BRITANNICA STUDENT ENCYCLOPEDIA Apatosaurus 145

particularly inWyoming, Utah, Oklahoma,

and Colorado.

Physical Features

Apatosaurus was one of the largest land

animals of all time. It reached a length

of 70 feet (21 meters), weighed 30 to 36

tons, and stood 15 feet (4.6 meters) tall

at the hips. This dinosaur also had a very

long neck and tail. Apatosaurus stood

and walked on all four legs. It had claws

on its large feet. Its head was small and

horselike, with long, peg-shaped teeth.

Behavior

Apatosaurus fed on the leaves and

needles of trees and plants. Its long neck

may have let it reach trees as high as 35

feet (10.6 meters). It swallowed small

stones to help grind up the plants in its

stomach. Apatosaurus probably lived and

traveled in herds. Like other dinosaurs,

it reproduced by laying eggs.

#More to explore

Brachiosaurus • Dinosaur

Ape

Apes are the animals that are most

closely related to humans. Both apes and

humans are members of the scientific

group of animals called primates. Monkeys

are primates, too. However, apes

differ from monkeys in several ways. For

instance, apes have more complex brains

than monkeys do. Also, monkeys have

tails but apes do not.

The apes are divided into two categories:

great apes and lesser apes. Gorillas, orangutans,

chimpanzees, and bonobos are

great apes. They are larger and more

intelligent than the lesser apes. The gibbons

are lesser apes.

Where Apes Live

Apes live in warm or hot rain forests.

Gibbons and orangutans are found in

southeastern Asia. Gorillas and chimpanzees

are found in western and central

Africa. Bonobos have the smallest range.

They are found only in part of the

Apatosaurus

146 Ape BRITANNICA STUDENT ENCYCLOPEDIA

Democratic Republic of the Congo, a

country in central Africa.

Gibbons and orangutans live mainly in

trees. On the other hand, gorillas spend

most of their time on the ground.

Chimpanzees and bonobos tend to eat

and sleep in trees, but they travel mostly

on the ground.

Physical Features

The smallest apes are the gibbons. Most

gibbons are about 16 to 26 inches (40 to

65 centimeters) long. Gorillas are the

largest apes. They may grow to about 66

inches (170 centimeters) in length and

weigh 300 to 600 pounds (135 to 275

kilograms).

All apes have a coat of hair, which is

usually tan, brown, black, gray, or reddish.

They have long arms and shorter

legs. Gorillas, orangutans, and chimpanzees

generally have powerful arms and

broad chests. Bonobos and gibbons are

more slender. Like humans, all apes have

thumbs that can bend to meet the other

fingers.

Behavior

Most apes are active during the day.

They usually sleep in trees at night. All

Apes include orangutans, gorillas, bonobos, and gibbons. They vary in size, but some of

them can be as big as an adult human.

BRITANNICA STUDENT ENCYCLOPEDIA Ape 147

apes except gibbons build nests for

sleeping.

Most apes live in groups. Chimpanzees

and bonobos are the most social, sometimes

living in groups of more than 100

animals. However, male adult orangutans

live mostly alone.

Apes eat mainly plants, including fruits,

leaves, stalks, and seeds. Sometimes they

eat insects or other small animals.

Chimpanzees also hunt and kill monkeys

and other mammals for food.

Great apes are very intelligent. Some

chimpanzees and orangutans in the wild

use sticks or other objects as tools. For

instance, some chimpanzees poke sticks

into ant or termite nests. The chimps

pull the sticks out and eat the insects

clinging to them. Scientists study the

learning abilities of apes in laboratories

and zoos. They have taught some great

apes to communicate using sign language

or pictures of symbols. However,

not all scientists agree that these apes

have truly learned to use language.

Reproduction

Reproduction in apes is similar to reproduction

in humans. A female ape usually

gives birth after a pregnancy of seven to

nine months. Normally a single baby is

born. Twins are rare. Baby apes are

nearly helpless for the first few months

after birth. Adult apes may provide care

for the young for several years.

Under Threat

Most types of ape are endangered, or at

risk of dying out completely in the wild.

Humans have cut down the trees in forests

where some apes live, destroying

their habitats. People also kill apes for

their meat. However, people have also

begun trying to save these animals.

Some countries have national parks to

protect apes and their habitats. Laws

also make it illegal to hunt or capture

endangered apes.

#More to explore

Chimpanzee • Gibbon • Gorilla

• Orangutan • Primate

Aphrodite

In ancient Greek mythology Aphrodite

was the goddess of love and beauty. She

was one of the 12 chief gods believed to

live on Mount Olympus. Aphrodite is

associated with the Roman goddess

Venus because they shared many of the

same characteristics. The symbols of

Aphrodite are the dove, rose, myrtle

tree, and swan.

In one story Aphrodite was the daughter

of Zeus, the ruler of all the gods. Her

mother was a Titan named Dione.

Some apes spend part of their time in trees

and part on the ground. Orangutans, like

gibbons, spend most of their time in trees.

148 Aphrodite BRITANNICA STUDENT ENCYCLOPEDIA

Titans were giants who once ruled the

world. Other stories tell that Aphrodite

sprang fully grown from the foam of the

sea. The wind carried her on a shell to

the island of Cyprus, which became her

home. Sailors prayed to her to calm the

wind and waves.

According to legend, gods and humans

alike desired Aphrodite because of her

beauty. But she was proud and rejected

her admirers. To punish her, Zeus had

her marry the ugly god of fire, named

Hephaestus. Aphrodite soon left him

for Ares, the handsome god of war.

One of their children was Eros, the

winged god of love. Zeus later arranged

for Aphrodite to fall in love with a

handsome shepherd named Anchises.

From that union Aeneas was born. He

was said to be an ancestor of the

Roman people.

#More to explore

Ares • Greece, Ancient • Hephaestus

• Mythology • Zeus

Apia

Apia is the capital of Samoa, an island

country in the southern Pacific Ocean.

It lies on the northern coast of Upolu

Island. Apia is Samoa’s main port. It

ships dried coconut meat, bananas,

cocoa, and coffee to other countries.

Manufacturing and tourism also bring

money to the city.

Apia developed into a port after European

missionaries and traders arrived in

the mid-1800s. In the 1940s, during

WorldWar II, U.S. Marines used Apia

as a base.

The former home of Scottish writer

Robert Louis Stevenson sits on a hill

overlooking Apia. Today Samoa’s head

of state lives there.

#More to explore

Samoa

BRITANNICA STUDENT ENCYCLOPEDIA Apia 149

Apollo

In ancient Greek mythology Apollo was

the god of music, healing, light, and

prophecy (predicting the future). He

was one of the 12 main gods believed to

live on Mount Olympus. He also came

to be considered a sun god. Because of

Apollo’s many important roles, the

Greeks loved him greatly. The Romans

later worshipped him too. The laurel

tree, dolphin, and crow were sacred to

Apollo.

Apollo was the son of Zeus, the chief

god, and Leto. Leto was a Titan, or one

of the giants that once ruled the world.

Apollo was also the twin brother of

Artemis, the goddess of hunting.

According to tradition, one of Apollo’s

earliest deeds was to slay a giant snake,

called Python. No human dared

approach the monster. Apollo came

down from Mount Olympus and, after a

hard fight, killed Python using his silver

bow and golden arrows.

The famous Temple of Apollo stood at a

site called Delphi. This was near the

place where Apollo had killed Python.

People traveled great distances to visit

the shrine. There they would speak to

one of Apollo’s priestesses. She would

give them an oracle, or prediction of the

future, said to come from Apollo.

According to legend, the god Hermes

gave Apollo a lyre (a kind of stringed

instrument). Apollo loved the gift and

became skilled at playing it.With his

music, Apollo charmed the other gods at

feasts on Mount Olympus.

#More to explore

Artemis • Greece, Ancient • Hermes

• Mythology • Zeus

150 Apollo BRITANNICA STUDENT ENCYCLOPEDIA

Appalachian

Mountains

The Appalachian Mountains of eastern

North America are lower but much

older than the Rocky Mountains in the

West. For early settlers who wanted to

move from the territory of the original

13 American Colonies to the west, the

Appalachians were a natural barrier.

The Appalachians extend almost 2,000

miles (3,200 kilometers), from the

Canadian province of Newfoundland

and Labrador in the north to the U.S.

state of Alabama in the south. The

mountains are more than 250 million

years old and have been worn down over

the years.

Because they extend so far north and

south, the Appalachians have a wide

range of temperatures. In Canada and in

the White Mountains of New Hampshire,

Arctic conditions often prevail,

especially at high elevations. The south

has milder weather, but heavy clouds

and haze are common.

Before settlers arrived from Europe, the

Appalachian area from Maine to Georgia

was completely covered by forests.

The forested area is now smaller but still

impressive. Hawks, wild turkeys, and

many kinds of songbirds make the

Appalachians their home. The region

also has black bears, white-tailed deer,

wild boars, raccoons, and beavers.

Before the arrival of Europeans, the

northern part of the Appalachians was

occupied by Native Americans of various

EasternWoodland groups. In the southern

mountains, the Cherokee were the

main inhabitants. By the middle of the

1800s, most of the Native Americans

had been removed from the area. In the

south, they were replaced by settlers who

lived in isolated communities. Separated

from the outside world by the hills,

Screw Auger Falls are in a section

of the northern Appalachian

Mountains in Maine.

BRITANNICA STUDENT ENCYCLOPEDIA Appalachian Mountains 151

these people made their own distinctive

culture and music.

Eastern Appalachia has rich farmland.

Cotton is grown in the south, while

tobacco and fruit are the main crops

farther north. The Appalachian area is

also known for its minerals. Coal is the

most important mineral. It is mined in

large quantities in the Appalachian Plateau,

from Pennsylvania to Alabama.

Tourism is also a major industry. The

Appalachians offer splendid scenery and

many opportunities for outdoor activities.

The Appalachian National Scenic

Trail is a hiking path that winds through

14 states on its way from Mount Katahdin,

in Maine, to Springer Mountain in

Georgia.

#More to explore

Mountain • Rocky Mountains

Appendix

The appendix is a part of the human

digestive system. It is a finger-sized tube

attached to the large intestine. The

appendix does not seem to help with

digestion. However, if it becomes

blocked or infected, it can cause an illness

called appendicitis.

Human beings are one of the few animals

that have an appendix. The human

appendix is usually 3 to 4 inches (8 to

10 centimeters) long. It is less than half

an inch (1.3 centimeters) wide. It

extends outward from the first section of

the large intestine, in the right side of

the lower belly.

Appendicitis usually occurs in people

younger than 35 years of age. The illness

happens when something (such as digestive

waste) blocks the opening of the

appendix. The appendix then swells and

becomes infected. If swelling continues,

the appendix may burst.

An attack of appendicitis usually starts

with a dull pain in the belly.Within

hours the pain may worsen. The pain

may move downward, to the right side

of the lower belly. Nausea and vomiting

are also common.

Doctors treat appendicitis by removing

the appendix. The surgery to remove an

appendix is called an appendectomy.

#More to explore

Digestive System • Intestines

Apple

Apples are one of the world’s most

widely grown fruits. People have eaten

them since ancient times. There are

thousands of varieties of apple. They

grow on trees that belong to the same

scientific family as roses.

The highest

peak in the

Appalachian

Mountains is

Mount Mitchell

in North Carolina.

It reaches

a height of

6,684 feet

(2,037

meters).

152 Appendix BRITANNICA STUDENT ENCYCLOPEDIA

Where Apples Grow

People grow apples in North America,

Europe, and Asia. The leading producers

of apples include China, the United

States, Poland, Iran, Turkey, and France.

Apple trees grow best in areas where the

summers are mild and the winters are

somewhat cold.

Physical Features and Growth

Apple trees are small to medium in size.

In the spring they grow white flowers.

The fleshy fruits are usually ready to be

picked in autumn. Apples are red, yellow,

or greenish and fairly round. They

are about 2 to 4 inches (5 to 10 centimeters)

wide.

A new apple tree can grow from an apple

seed.However, it will not grow the same

variety of apple as the tree that made the

seed. Because of this, people normally

grow apple trees using another method.

They cut a twig or bud from the apple

tree to be reproduced. They attach this

twig or bud to a rootstock, or a young

apple tree grown for its strong roots. The

parts from the two trees soon grow

together into one tree. This new tree will

produce the same variety of apple as the

one from which the twig or bud came.

Uses

Apples contain fruit sugars, fiber, and

the vitamins A and C. Some varieties are

good for eating raw. Other types are best

cooked. In the United States apple pie is

a traditional dessert. In Europe people

often serve fried apples with sausage or

pork. Farmers grow some varieties of

apple for their juice. People drink the

juice fresh or make it into a drink called

cider.

#More to explore

Fruit • Tree

Apricot

Apricots are orange or reddish fruits

with smooth skin. The trees on which

they grow belong to the rose family.

Apricots are related to plums and

peaches.

Apricots originally grew only in China.

They were carried to other parts of the

Apples vary in size, color, and texture.

Apricots are golden ripe and ready to pick

in June and July, earlier than most other fruits.

BRITANNICA STUDENT ENCYCLOPEDIA Apricot 153

world, and today they grow in all of

central and southeastern Asia. They are

also found in parts of southern Europe,

North Africa, and North America. Turkey

is the world’s largest producer of

apricots. California produces almost all

the apricots in the United States.

Apricots are round or oval in shape.

They are usually less than 3 inches (8

centimeters) wide. Most apricots have

orange or yellow flesh. Some kinds have

nearly white flesh. Apricots have a large,

flat, smooth seed in the center. The seed

is also called a pit, or stone.

Apricots grow on large, spreading trees

with bright green, oval leaves. Apricot

trees produce small white or pink flowers

in spring. The fruits grow from these

flowers. The fruit develops slowly at

first. After the pit forms, the fruit grows

more quickly. Apricots are ready to pick

in early summer.

Fresh apricots taste sweet and mild.

Most apricots are dried, canned, or

made into jam. They are a good source

of vitamin A and iron.

#More to explore

Fruit • Peach • Plum

Aquarium

An aquarium can be a small container

for a few goldfish. It can also be a building

that displays a large collection of

water animals. Aquariums give people

the chance to observe an ecosystem very

different from their own.

Types of Aquariums

People who like fish often keep aquariums

as a hobby. Popular fish for home

aquariums include goldfish, guppies,

zebra danios, and bettas. Home aquariums

can be as small as a bowl or as large

as an entire wall. For their fish to sur-

Orca whales swim past visitors to a public aquarium.

154 Aquarium BRITANNICA STUDENT ENCYCLOPEDIA

vive, owners must make sure that their

aquariums stay clean and that the water

is at the right temperature. They also

must provide the right type and amount

of food.

Public aquariums are buildings with

large tanks of fish and other water animals.

Different tanks contain fish, animals,

and plants from cold, warm, fresh,

and salty waters. People come to see and

learn about fish and their habitats. Public

aquariums often care for sick or

injured water animals, too. Marine

biologists help the animals to get well

and then return them to the wild.

History

People have kept fish in artificial habitats

for at least 4,500 years. The ancient

Egyptians and Romans kept fish in

aquariums. The Chinese bred goldfish in

ponds and bowls. Artificial ponds filled

with fish later became popular in European

gardens. The trend spread to North

America in the 1800s. In 1853 the Zoological

Society of London, England,

opened the first public aquarium. Public

aquariums soon opened in many other

major cities.

#More to explore

Ecology • Fish • Goldfish

Aqueduct

An aqueduct is a system for carrying

water. Aqueducts can supply water to

cities or to farms for irrigation. The

water is carried from a lake, river, or

reservoir through a conduit, or channel.

The channel may be an underground

Early aqueducts had to rely on the force of gravity to move water over long distances. This

meant that the water could only move from a high point to a lower point. Modern aqueducts

use electric pumps to move the water along.

BRITANNICA STUDENT ENCYCLOPEDIA Aqueduct 155

tunnel or pipe, a canal at ground level,

or a bridge.

People built aqueducts in ancient

Greece, Babylonia, Persia (now Iran),

and India. Many of these aqueducts

were tunnels dug into hillsides. Early

aqueducts depended on gravity to create

the flow of water. The water source had

to be higher than the destination so the

water could flow downhill all the way

there. Variations in the height of the

land, such as mountains and valleys,

caused problems.

To move water across valleys people

sometimes built aqueducts in the form

of arched bridges with two or three layers

of arches on top of each other. The

water flowed through a channel in the

top of the uppermost layer. The ancient

Assyrians used 2 million stone blocks to

build an aqueduct to carry water across a

valley to their capital, Nineveh.

Ancient Rome had a complex system of

11 aqueducts built from 312 BC to AD

226. The system used both bridges and

underground pipes. Some of the aqueducts

are still used today. The Romans

also built aqueducts in other parts of

their empire.

Most engineers today use powerful

pumps to force water upward when necessary.

This allows modern engineers to

design aqueducts in ways that ancient

engineers could not. Instead of building

a bridge over a valley, for example, modern

engineers can simply run pipes

down one side of the valley and up the

other. Pumps powered by steam were

first used in the late 1700s. Later pumps

were powered by electricity.

#More to explore

Bridge • Canal • Rome, Ancient

Arabian

Peninsula

The Arabian Peninsula, or Arabia, is a

piece of land in southwestern Asia. It is

the original homeland of the Arab

people. It is also the birthplace of the

religion of Islam. The country of Saudi

Arabia takes up about four fifths of the

peninsula. The peninsula also includes

Kuwait, Oman, Qatar, the United Arab

Emirates, Yemen, Bahrain, and parts of

Jordan and Iraq.

Geography

The Arabian Desert covers almost all of

the peninsula. Some parts of the desert

get enough rain for grass and shrubs to

grow. In general, however, the climate is

very dry and hot. At least one third of

the desert is sandy. Other parts are cov-

The Inca

people of

South America

built a system

of aqueducts

to carry water

down from the

Andes Mountains.

One

Inca aqueduct

was 360 miles

(579 kilometers)

long.

156 Arabian Peninsula BRITANNICA STUDENT ENCYCLOPEDIA

ered by bare rock. There are some hills

and mountains.

The Arabian Peninsula has almost half

of the world’s supplies of petroleum

(oil). Most of the oil is in or near the

Persian Gulf, the body of water east of

the peninsula. The countries of the

region sell the oil to other countries.

People

Arabs make up most of the population

of the peninsula. Nearly all Arabs speak

the Arabic language. Most Arabs are

Muslims, or followers of Islam. Muhammad,

the founder of Islam, was born in

what is now Saudi Arabia.

History

In ancient times the Sabaeans, the

Minaeans, and the Himyarites built up

powerful kingdoms in southwestern

Arabia. These Arab peoples traded with

Egypt, China, and India.

In the 600s Muhammad started Islam.

Soon all of Arabia was united under the

religion. Then the Arabs spread Islam

beyond the peninsula by conquering

other lands. The Muslim leaders who

followed Muhammad ruled a large

Islamic empire. At first they ruled from

Arabia. Later, however, they ruled from

other parts of the empire.

In the 1500s the Ottoman Turks made

Arabia part of their empire. However,

they never gained firm control of the

peninsula. The Arabs revolted

repeatedly against the Ottomans. The

Sa!ud family controlled the middle part

of Arabia.

Meanwhile, the British took control of

most of the southern and eastern coasts

of Arabia. The local Arabian rulers

united with the British against the Ottomans.

They defeated the Ottomans in

the early 1900s. Then the peninsula

gradually became free from British rule.

By 1971 the peninsula was made up

entirely of independent countries. In

1990 the countries of North Yemen and

South Yemen were united to form the

Republic of Yemen.

#More to explore

Arabs • Islam • Petroleum • Saudi

Arabia

Arab-IsraeliWars

Since the creation of Israel in 1948, the

Jewish state has gone to war with its

Arab neighbors on several occasions.

The differences between the groups continued

into the 21st century.

The Arabian Desert features large areas of

mountains and raised flat areas called

plateaus.

BRITANNICA STUDENT ENCYCLOPEDIA Arab-Israeli Wars 157

Background

The Middle Eastern region known as

Palestine was the ancient home of the

Jewish people. It became part of the

Islamic world in the AD 600s. From

1923 to 1948 the British ruled the

region. During this time, many Jewish

immigrants from Europe settled there.

Arabs also lived in Palestine, and both

groups wanted to control the land.

When Britain gave up Palestine, the

United Nations (UN) divided the land.

Each group got the same amount, but

the Arabs were unhappy because the

Jews were given some land that was

owned by Arab Palestinians.

The War of 1948–49

On May 14, 1948, as soon as Israel

came into existence, Arab Palestinians

and neighboring Arab countries declared

war on Israel. Arab forces occupied parts

of Palestine, but by the time the war

ended Israel ended up with more land

than it had before the war.

In 1949 Israel and the Arab states signed

border agreements. There was no peace

treaty, however. The many Palestinians

who had left their homes ended up in

refugee camps in Arab countries.

The Six-DayWar

In the spring of 1967, fighting between

Syria and Israel led to the Six-DayWar.

Israel saw that Egypt was preparing for

war in order to aid Syria. On June 5

Israel struck quickly and wiped out

nearly the whole Egyptian air force on

the ground. In six days’ time Israel

seized the Old City of Jerusalem, the

Sinai Peninsula, the Gaza Strip, the Jordanian

territory west of the Jordan River

(known as the West Bank), and the

Golan Heights, on the Israeli-Syrian

border.

The Yom KippurWar

On October 6, 1973, on the Jewish holy

day of Yom Kippur, Egypt and Syria

both attacked Israel. In the Yom Kippur

A map shows the territories that Israel

and its neighbors fought over during the

Arab-Israeli wars. At the end of the Yom

Kippur War in 1974 Israel controlled the

area marked in orange.

158 Arab-Israeli Wars BRITANNICA STUDENT ENCYCLOPEDIA

War, Israel pushed both armies back into

their own territory but in turn suffered

heavy losses. After fighting ceased early

in 1974, the UN established neutral

zones between those countries and

Israel.

Ongoing Tensions

On March 26, 1979, Israel and Egypt

signed a peace treaty. Tensions continued,

however, between Israel and other

Arab communities. The Palestine Liberation

Organization (PLO) attacked

Israel from camps in Lebanon in 1982.

On June 5, 1982, Israel invaded the

country. The PLO eventually left, but

some Israeli troops remained in the

country until 2000.

In the late 1970s Israelis began to build

settlements on the land that it occupied

on the Gaza Strip andWest Bank. In

1987 the growth of these settlements

caused Palestinians to protest. Demonstrations

and riots—known as the intifada

(uprising)—broke out and

continued until the early 1990s. In 1993

Israel agreed to start turning over control

of some of the occupied territories

to the Palestinians. In 2000, however, a

new intifada erupted. It stalled peace

talks between Israel and the Palestinians.

#More to explore

Arabs • Egypt • Israel • Jerusalem

• Middle East • Palestine • Palestine

Liberation Organization • Syria

Arabs

An Arab is someone whose native language

is Arabic. The term was first used

to describe people who lived in a part of

southwestern Asia called the Arabian

Peninsula. Today the word Arab also

refers to Arabic-speaking people who

live in the Middle East, North Africa,

and other places. In the early 21st century

there were more than 100 million

Arabs throughout the world.

Early Arabian society was made up of

families that came together to form

tribes. Tribes traced their heritage back

many centuries. According to tradition,

some Arabs are descended from a man

named Qahtan, who lived in southern

Arabia. Others are descended from a

man named !Adnan, of northern Arabia.

The religion of Islam brought Arabs

together beginning in the early AD

600s. Because Islam’s holy book (the

Koran) is written in Arabic, that

language soon was used by all who

practiced the religion.

Arabs shop at a street market in

Cairo, Egypt.

BRITANNICA STUDENT ENCYCLOPEDIA Arabs 159

More than 90 percent of modern Arabs

practice Islam. Religion is an important

part of everyday life for many Arabs. It

influences how people behave and dress.

Arabs, especially women, tend to dress

modestly. In many areas women are

expected to wear dark robes and to cover

their face with a veil in public.

Arabs who live in cities tend to have less

traditional attitudes than those who live

in small villages. Both men and women

have more educational and employment

opportunities in cities.

#More to explore

Arabian Peninsula • Islam

Aral Sea

The Aral Sea is a saltwater body in central

Asia. The sea’s name comes from the

Kyrgyz word Aral-denghiz, meaning “Sea

of Islands,” because of the many islands

in its waters.

Also called Lake Aral, the Aral Sea is

situated more than 250 miles (400 kilometers)

east of the Caspian Sea. It is

bordered by Kazakhstan on the north

and Uzbekistan on the south. The Amu

Darya and Syr Darya rivers are the sea’s

two main sources of inflowing water.

The Aral Sea area has cold winters and

hot summers. The area gets very little

rainfall.

In 1960 the Aral Sea covered an area of

26,300 square miles (68,000 square

kilometers). However, during the

second half of the 1900s, most of the

inflowing river water was used for

irrigation before it reached the sea. The

sea also loses water through

evaporation. Because there is not much

rainfall this water is not replaced fast

enough to maintain the water level.

The Aral has therefore shrunk

drastically in its area and volume. By

the end of the 1900s the Aral Sea had

lost so much water that the exposed

land divided the sea into three separate

parts.

Scientists view the changes to the Aral

Sea as a serious threat to the local

environment and human health. As the

water has evaporated, the salt and

mineral content has risen dramatically.

This has made the water unfit for

drinking and killed the once-abundant

supplies of freshwater fish. The fishing

industry along the Aral Sea was

virtually destroyed. Many groups tried

to address these issues, but the

problems continued into the 21st

century.

#More to explore

Kazakhstan • Uzbekistan

160 Aral Sea BRITANNICA STUDENT ENCYCLOPEDIA

Arapaho

The Arapaho are Native Americans who

originally lived in the Great Lakes

region. They gradually moved westward

and became great buffalo hunters and

warriors of the western Great Plains.

The Arapaho traditionally were farmers,

but as they moved west they began

hunting instead. Bison (buffalo) meat

became their main source of food. They

used bison hides to make clothing and

covers for their tepees.

The Arapaho were very religious people.

They believed that sacred objects had

supernatural power. Their most sacred

object was the Flat Pipe, a tobacco pipe

with a very long stem. They used this

pipe only during special religious

ceremonies.

By the mid-1800s the Arapaho had

separated into two groups. The Southern

Arapaho lived in what is now Colorado,

and the Northern Arapaho lived in

what is nowWyoming.

The Arapaho were pressured by the U.S.

government to move to a reservation. In

1869 the Southern Arapaho moved to

land in Indian Territory, which is now

part of Oklahoma. In 1878 the Northern

Arapaho moved to the Shoshone

Reservation (now called theWind River

Reservation) in what is nowWyoming.

Later in the 1800s both Arapaho groups

lost much of their reservation lands to

white settlers. At the end of the 20th

century more than 6,000 Arapaho lived

in the United States.

#More to explore

Native Americans

Arawak

The Arawak Indians once lived in South

America and on islands in the Caribbean

An Arapaho man wears the traditional

clothing of his people.

The Arawak people were forced to leave

the islands of the Lesser Antilles long ago.

They left behind stone carvings and pottery.

BRITANNICA STUDENT ENCYCLOPEDIA Arawak 161

Sea. The island Arawak, or Taino, were

the Indians the explorer Christopher

Columbus met on his first journey to

the Americas.

The Arawak lived in large villages. They

built their houses from logs, poles, and

the leaves of palm trees. They got most

of their food by farming. They also

fished, caught shellfish, and hunted

birds, lizards, and other small animals.

The Arawak first lived in northern

South America. Then they spread to the

Caribbean islands. Shortly before Europeans

arrived, the warlike Carib people

pushed the Arawak off the islands called

the Lesser Antilles. Columbus met the

Arawak in 1492. At that time the

Arawak lived only on the Greater Antilles

(Cuba, Jamaica, Hispaniola, and

Puerto Rico).

Columbus’ men and the Spaniards who

followed them treated the Arawak

harshly. They forced the Arawak to

work in fields and in mines. Some

Arawak died of starvation. Many others

died of diseases brought by the

Europeans.

By 1550 the island Arawak population

had been reduced from 1 million or

more to almost nothing. Their traditional

way of life largely disappeared as

well. Small groups of Arawak managed

to survive. Their descendants now live in

Cuba, Puerto Rico, and Florida.

#More to explore

Carib • Columbus, Christopher

Arbor Day

A day set aside for the planting of trees,

Arbor Day began in Nebraska in 1872.

Today people across the United States

celebrate Arbor Day.

How Arbor Day Is Celebrated

Many states observe Arbor Day on the

last Friday in April, though the date may

vary depending on the climate. On

Arbor Day people plant trees throughout

their neighborhood. They plant trees

as memorials to loved ones, to restore

damaged landscapes, or just to add natural

beauty to the surroundings.

History

J. SterlingMorton, a newspaper editor

and politician, founded ArborDay. In

1854 he moved fromMichigan to

Nebraska, which was then a territory. The

NebraskaTerritory was a land of rolling

plains with few trees.Morton missed the

trees he had known in the East.

After Nebraska became a state, Morton

asked the state to create a holiday for

The largest

Arawak villages

had as

many as

3,000 people

living in them.

Girl Scouts plant a tree on Arbor Day.

162 Arbor Day BRITANNICA STUDENT ENCYCLOPEDIA

tree planting. Nebraskans celebrated the

first Arbor Day in 1872. Arbor Day

became a legal state holiday in 1885.

The holiday later spread across the

United States as well as to other

countries.

Archaeology

Archaeology is the study of things that

people made, used, and left behind. The

goal of archaeology is to understand

what people of the past were like and

how they lived. Scientists who study

archaeology are called archaeologists.

An archaeologist’s works begins with

finding a site to study. Some sites, such

as ancient cities, are visible on the surface.

Other sites are buried. Special

devices can be used to sense structures

that are underground or underwater.

After finding a site, an archaeologist digs

slowly and carefully. This work is called

excavation, or a “dig.” Archaeologists use

spoons, knives, picks, brushes, and other

tools in their work. They try to uncover

buildings, tools, weapons, art, and anything

else that people made. These items

are called artifacts.

Then archaeologists study the objects.

They want to know when an artifact was

made, what it was made from, and what

it was used for. Archaeologists have several

methods for figuring out an artifact’s

age. One method is called

carbon-14 dating. Carbon-14 is a

chemical found in all organisms, or living

things. After an organism dies, the

amount of carbon-14 decreases at a certain

rate. An archaeologist measures this

decrease to find out how long ago the

organism died.

Archaeologists uncovered life-size figures of soldiers in an ancient tomb in China.

BRITANNICA STUDENT ENCYCLOPEDIA Archaeology 163

Archaeologists also try to understand the

culture from which artifacts came. For

example, tools such as arrow tips, knives,

and grinding stones can tell an archaeologist

how people got and prepared

their food.

An archaeologist sometimes works with

experts from other fields of study. Botanists,

zoologists, and geologists can help

to identify plants, animals, soils, and

rocks found along with artifacts.

#More to explore

Botany • Geology • Zoology

Archaeopteryx

A prehistoric bird, Archaeopteryx is best

described as a feathered dinosaur with

wings. Archaeopteryx is considered proof

that birds developed from dinosaurs,

because it had the traits of both.

When and Where

Archaeopteryx Lived

Archaeopteryx lived about 159 to 144

million years ago. All known Archaeopteryx

remains have been found in southern

Germany.

Physical Features

Archaeopteryx reached 2 feet (60 centimeters)

in length and had a wingspan of

2 feet (60 centimeters). It had wing

feathers like those of modern pigeons.

Archaeopteryx also shared several features

with a group of small, meat-eating dinosaurs,

however. It had well-developed

teeth and a long, slender and flexible

neck. It had long leg and foot bones,

and it had claws on its hands.

Behavior

Some scientists believe that Archaeopteryx

took off by running along the

ground and leaping into the air, flapping

its wings. However, other experts believe

that Archaeopteryx most likely spent a lot

of time perched in low-growing trees.

The animal could simply launch itself

from atop the branches and glide out on

short flights. When it was not in the

A team of archaeologists works

on a “dig,” or excavation, in

Peru.

Archaeopteryx

164 Archaeopteryx BRITANNICA STUDENT ENCYCLOPEDIA

trees it is possible that Archaeopteryx

swam and fished in the lagoons surrounding

the islands on which it lived.

Archaeopteryx, like both dinosaurs and

modern birds, reproduced by laying

eggs.

..More to explore

Bird • Dinosaur

Archery

The sport of shooting arrows with a bow

at a target is called archery. But archery

is not just a sport. For thousands of

years people used the skills of archery

mostly for war and for hunting. Even

today bow hunting is a popular activity.

Bows and Arrows

Bows allow people to shoot arrows farther

and with greater force than is possible

by simply throwing them. At its

most basic, a bow is a long, thin piece of

wood with a string stretched tightly

from one end to the other. The string

holds the wood in a curved position.

People competing in archery contests

today often use more complex bows

made of wood, plastic, or fiberglass.

An arrow is a long, thin piece of wood,

metal, or other material. It ends in a

pointed tip. Near the other end of the

arrow is a tail of feathers or plastic fins.

The tail helps the arrow fly straight.

The tail end of the arrow fits onto the

string of the bow. To shoot the arrow, an

archer pulls the string back and lets it

go. A lot of energy is stored up by the

string being stretched. When the string

is released, this energy is also released.

This sends the arrow flying with great

force.

Archery Competitions

There are many kinds of archery events.

In most kinds the archers shoot arrows

at round targets. Each target is marked

with a circle surrounded by several rings.

Archers earn a set number of points for

hitting the various areas on the target

with their arrows. They earn the most

points for hitting the circle in the center

and the least points for hitting the outer

ring.

The most common types of archery

used in contests are target archery and

field archery. In target archery archers

shoot a set number of arrows at targets

at set distances. For example, an archer

Modern archers shoot at targets up to 295

feet (90 meters) away.

BRITANNICA STUDENT ENCYCLOPEDIA Archery 165

may have to shoot 18 arrows at a target

that is 230 feet (70 meters) away. In

field archery the archer shoots arrows at

several targets on a course set up to imitate

hunting conditions.

World championships are held regularly

in target, field, and other kinds of

archery. The Summer Olympic Games

feature target archery events for men

and women, individually and in teams.

History

In prehistoric and ancient times many

peoples in Europe, Asia, Africa, and the

Americas made bows and arrows. The

bow was one of the main weapons of

war and hunting. The ancient Egyptians,

Greeks, and Chinese also practiced

archery as a sport.

The Huns, the Turks, the Mongols, and

other groups used the bow and arrow for

warfare while riding on horseback. Their

skills as archers helped them conquer

large parts of Asia.

English soldiers began using a large bow

called the longbow in the 1300s. It

helped them win great military victories

against France. The leading bow in other

parts of Europe at the time was the

crossbow. It was a small, powerful bow

attached crosswise to a piece of wood. It

had a groove to guide the arrow across

the wood and a lever to pull and release

the string.

In Europe guns replaced the bow and

arrow as the major military weapon in

the 1500s. Today soldiers in most parts

of the world use firearms. However,

many people still use a bow and arrow

to hunt. Archery has also grown popular

as a sport. In the 1900s archery became

an Olympic event.

#More to explore

Olympic Games •War •Weapon

Hundreds of years ago warriors used bows and arrows to fight battles.

166 Archery BRITANNICA STUDENT ENCYCLOPEDIA

Architecture

The science and art of designing buildings

is known as architecture. People

who practice architecture are called

architects. Architects express an artistic

vision through the size, shape, color,

materials, and style of a building’s elements.

But unlike painters or sculptors,

who can create a work of art for its own

sake, architects must design a building

for a specific purpose. The architect can

produce a work of art, but it must also

be functional.

Elements of Design

The architect must consider how a

structure will be used and by whom. An

apartment building, a palace, a hospital,

a museum, an airport, and a sports arena

all have different building requirements.

Another factor in the design is the ideas

the structure should communicate. For

example, some buildings are designed to

impress people with a display of power

and wealth. Others are intended to

make everyone feel welcome.

Other factors are the location and surrounding

environment, including

weather, and the cost of materials. And

above all the architect must create a

stable structure.Walls and roofs can

buckle, crack, or collapse if they are not

properly designed. Over the centuries, as

people discovered building techniques

that worked, those features became standard

elements of design.

The arch was one of the first elements of

this kind. It is a curved structure used to

span an opening and support loads from

above. It allowed builders to create larger

doorways and other openings in walls.

The vault is a continuous arrangement

of arches, usually forming a ceiling or

roof. Another common support element

is the truss, or frame composed of triangular

sections.

BRITANNICA STUDENT ENCYCLOPEDIA Architecture 167

Materials

Building materials are chosen based on

many factors, including their appearance,

strength, availability, and cost.

Stone, brick, wood, and concrete have

been used for thousands of years. Stone

has often been used for large monuments

because it lasts a long time and is

easy to carve. But it is difficult to cut

and transport, and it is too weak for

certain support functions. Brick resists

fire and is easy to produce, transport,

and lay. Wood is very easy to acquire,

transport, and work. But it burns easily,

can develop mold, and may be eaten by

termites. Concrete is made by mixing

cement, water, and small pieces of sand

and stones. It can be poured into molds

to create various shapes, and it hardens

into a solid, fire-resistant material.

A major advance came in the 1800s with

the use of cast iron and then steel for

support elements. These materials are

fire-resistant, can be formed into many

shapes, and can produce very strong, tall

structures. Builders also began embedding

steel rods in concrete to make the

concrete stronger.

History

The earliest buildings were simple structures

made of materials that were easy to

find. Eventually people began to live in

large groups and form communities. As

they did so their buildings became more

elaborate. The Great Pyramids of the

ancient Egyptians were enormous stone

A pyramid in Saqqarah, Egypt, was built

for an ancient Egyptian king.

168 Architecture BRITANNICA STUDENT ENCYCLOPEDIA

tombs for their leaders. In ancient times

people in what is now Iraq built huge

brick temple towers, called ziggurats,

that were shaped like pyramids with

several levels rising in steps.

The traditional architecture of China

also developed in ancient times. It reflects

a deep feeling for the harmony and order

in nature.Traditional temples and houses

are built chiefly of wood and decorated

with tiles. The pagoda, a tower stretching

toward heaven, developed from the stupa

of ancient India. The stupa was a

dome-shaped monument, usually built

over the remains of a holy person.

Ancient Greece and Rome

The ancient Greeks and Romans established

what became known as the classical

style inWestern architecture. The

Greeks built simple structures of marble

and stone. They developed three

styles—called Doric, Ionic, and

Corinthian—identified by the type of

columns they use as a basic unit. Each

type of column had a special design,

called a capital, at the top. These styles

have been used inWestern architecture

ever since. A Greek temple was rectangular

and had a porch, called a portico,

at each end. Lines of columns supported

the roof. An outstanding example is the

Parthenon on the Acropolis in Athens.

The ancient Romans used round arches

and other structural methods that

allowed them to build enormous public

buildings. An amphitheater was a large

round or oval arena surrounded by several