to the economy of the Czech Republic.
Most people in the city work in industries
that provide services, such as tourism,
banking, and trade. Manufacturing
also brings money to Prague. Factories
in the city make machinery, chemicals,
food products, and electronics.
History
Prague dates back to at least the 800s.
The rulers of the country called Bohemia
made it their capital in the 900s.
The city became one of Europe’s major
centers of trade and culture.
In 1918 an independent country called
Czechoslovakia was created in central
Europe. Prague was its capital.
German troops controlled Prague from
1939 to 1945, during World War II. A
few years later Czechoslovakia became a
Communist country. The Soviet Union
invaded Prague in 1968 to make sure
that the country stayed Communist. In
1989 Prague’s citizens held large
protests against Communism. Soon
afterward Communism ended in
Czechoslovakia.
In 1993 Czechoslovakia broke into two
separate countries, the Czech Republic
and Slovakia. Prague became the capital
of the Czech Republic.
..More to explore
Czech Republic
Praia
Population
(2005 estimate)
111,500
Praia is the capital of Cape Verde, an
island country off the northwest coast of
Africa. It is the largest city in Cape
Verde. It lies on Sao Tiago, the country’s
largest island.
Praia has a port on the Atlantic Ocean.
Ships load up there with foods, shoes,
clothing, and other products for sale
overseas. Factories in the city process
fish.
Arched bridges span the Vltava River in
Prague, Czech Republic.
142 Praia BRITANNICA STUDENT ENCYCLOPEDIA
No one lived on the islands of Cape
Verde in ancient times. The Portuguese
began settling the islands in the 1460s.
They first settled the town of Ribeira
Grande, which became the first capital.
They later moved the capital to Praia.
This was partly because Praia’s harbor
was safer for ships involved in the slave
trade. The slave trade became a major
part of the city’s economy. Slavery
ended on the islands in 1876.
Cape Verde became an independent
country in 1975. Praia remained its
capital.
#More to explore
Cape Verde
Prairie Dog
Prairie dogs are rodents that bark like
dogs. They belong to the squirrel family.
Prairie dogs are known for their large
underground colonies. Sometimes called
towns, these colonies have many rooms
and tunnels.
There are five species, or types, of prairie
dog. The best known are the black-tailed
prairie dog and the white-tailed prairie
dog. Prairie dogs live on prairies in western
North America.
Prairie dogs have plump bodies and
short legs. Their claws are long and powerful.
Not including their tails, prairie
dogs are about 11 to 13 inches (28 to 33
centimeters) long. They can weigh
almost 4 pounds (2 kilograms). Most
prairie dogs have yellowish brown fur.
Prairie dogs are active in the daytime.
During winter, three of the species
hibernate. This means that they stay
inactive until spring.
A female prairie dog gives birth to a
litter of up to 10 young. After about two
years the male young are driven away.
They move to new colonies. Females
usually stay.
Prairie dogs eat grass. Sometimes they
leave little grass for cattle. For this reason
some people consider prairie dogs a
pest.
Other people think prairie dogs are very
important. They say that many animals
depend on the prairie dog. Foxes, coyotes,
badgers, and hawks eat prairie
dogs. Rabbits and snakes live in holes
dug by prairie dogs.
#More to explore
Rodent • Squirrel
The largest
prairie dog
colony ever
seen was in
Texas. It contained
about
400 million
prairie dogs.
A black-tailed prairie dog can look out over
prairie grass when it stands upright.
BRITANNICA STUDENT ENCYCLOPEDIA Prairie Dog 143
Pregnancy
#see Gestation.
Prehistoric Life
Long before people appeared on Earth,
other forms of life existed. Many of
these living things are now extinct,
meaning they have died out completely.
The period when they lived is called
prehistory, or prehistoric times.
Everything that people today know
about prehistoric plants and animals
comes from fossils. Fossils are the
remains or traces of early life-forms.
They are often found in rocks.
Precambrian Life
The earliest life-forms developed during
the earliest period of Earth’s history,
called Precambrian time. Precambrian
time began with the formation of
Earth’s crust, about 4 billion years ago.
It ended about 543 million years ago.
Scientists do not know exactly when
life-forms first appeared, but the oldest
known fossils are more than 3 billion
years old.
The first life-forms had only one cell.
They included early types of bacteria,
algae, and protozoans. Living things
with more than one cell began to appear
late in the Precambrian. All life at this
time lived in Earth’s oceans.
Paleozoic Life
The next period of Earth’s history is
called the Paleozoic era. It lasted from
about 543 million years ago to about
248 million years ago. At first, all living
things were in the oceans. By the end of
the era, plants and animals also lived on
land.
Over hundreds of millions of years, life spread through the seas and over Earth’s surface.
144 Pregnancy BRITANNICA STUDENT ENCYCLOPEDIA
Ocean Life
