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 worlds 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 worlds 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