Britannica Student Encyclopedia - 2010

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.

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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.

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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.

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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