Britannica Student Encyclopedia - 2010

travel by truck, railroad, ship, or

airplane.

People need transportation to get from

home to work, too. Many people drive

cars to work. Others take public transportation,

including buses and trains.

People also take cars, trains, ships, and

airplanes to get to vacation spots and to

visit family and friends. Some people

drive just for enjoyment.

History

Early Transportation

Walking was the main method of transportation

until humans domesticated, or

tamed, animals. Camels, horses, and

cattle then carried goods and people.

More than 5,000 years ago people

invented the wheel. This allowed animals

to pull carts. Ancient peoples also

traveled by water, at first with simple

dugout canoes and rafts.

The Persians built a system of roads in

the 500s BC. The ancient Egyptians,

Indians, and Chinese also built roads.

By the AD 200s the Romans had built

roads across Europe.

Transportation by water expanded in the

Middle Ages (AD 500–1500). New ships

were built with multiple sails. They were

able to travel farther and faster than

earlier ships that were powered by rowing.

Improvements in navigation made

it possible to sail farther from land. Voyages

of discovery in the 1400s and 1500s

opened up trade routes between distant

points.

Modern Transportation

The invention of the steam engine in

the 1700s was an important event in

transportation history. Steam-powered

boats could easily travel upriver. Steampowered

ships could cross oceans without

wind. On land, inventors used

steam engines to power locomotives.

This led to the growth of railroads. By

1869 a railroad ran across the United

States, and steamships regularly crossed

Some people transport themselves through

a city on foot. Others use trains or cars.

92 Transportation BRITANNICA STUDENT ENCYCLOPEDIA

 

the Atlantic Ocean. Trips that had taken

weeks now took days.

Builders of canals made some ocean

trips much shorter. The Suez Canal in

Egypt shortened the trip between

Europe and Asia by thousands of miles.

The Panama Canal in Panama shortened

the trip between the East andWest

coasts of North America.

The late 1800s saw the first successful

bicycles and automobiles. They made

quick and easy transportation available

to more people than ever before. People

who bought cars demanded more and

better roads.

In 1903 the U.S. inventorsWilbur and

OrvilleWright flew the world’s first

airplane. The invention of the jet engine

in the 1940s made air travel the fastest

transportation in history.

Transportation Problems

Advances in transportation have led to

problems, however. Cars and trucks

cause traffic jams, accidents, and air

pollution. These vehicles also use oil for

fuel. The supply of oil is limited and

controlled by a few countries. To ease

crowded roads, governments have

worked to improve public transportation.

To fight pollution, scientists are

developing vehicles that run on different

types of fuel.

#More to explore

Airplane • Automobile • Bicycle • Boat

• Canal • Navigation • Railroad • Road

• Ship

Tree

Trees are tall, woody plants. They usually

have a stem called a trunk. Trees are

the largest and oldest living things on

Earth. Some trees live for hundreds or

even thousands of years. There are more

than 80,000 species, or types, of tree.

Well-known trees include birches, firs,

maples, palms, and pines.

Groups of Trees

Scientists divide trees into groups based

on how they reproduce. Some trees

reproduce with spores, or particles that

grow into new plants. They are called tree

ferns.Most trees reproduce with seeds.

An ocean liner unloads war prisoners during

World War II (1939–45). Liners were

an important means of transportation during

the first half of the 1900s. In peacetime

they carried rich people to vacation spots

and poor immigrants to new homes.

BRITANNICA STUDENT ENCYCLOPEDIA Tree 93

 

Some seed-bearing trees grow their seeds

in cones. They are called conifers.Most

conifers have needle-shaped leaves.

Other seed-bearing trees grow their seeds

in fruits or pods. They are known as

broad-leaved or flowering trees. They

have broad, flat leaves.

Scientists also group trees based on

whether they lose their leaves. Trees that

keep their leaves year-round are called

evergreens. Trees that lose their leaves at

some point during the year are called

deciduous trees.

Physical Features

Trees are usually more than 10 feet (3

meters) tall. They have roots, a trunk,

branches, and leaves. The trunk and

branches are made of fibers called wood.

These fibers are protected by an outer

covering called bark. As the tree ages,

the trunk and branches thicken.

The Lawson cypress and the English elm look different because they are two different types

of tree. The Lawson cypress is a conifer and an evergreen. It produces seeds in cones and

has needlelike leaves that stay on all year. The English elm is broad-leaved and deciduous.

It produces seeds in fruits and has leaves that fall off in autumn.

People grow eucalyptus trees for their wood

and oil. The leaves of some kinds of eucalyptus

contain an oil used in medicines.

94 Tree BRITANNICA STUDENT ENCYCLOPEDIA

 

The leaves make food for the tree

through a process called photosynthesis.