yellow and hang in clusters. The fruit is
about 0.5 to 3 inches (1.3 to 7.6
centimeters) across. It can be round or
oval or shaped like a pear. When ripe,
the fruit is soft, juicy, and usually red or
yellow. Tomatoes contain many small
seeds surrounded by jellylike pulp. This
pulp contains most of the tomato’s
vitamin C.
Tomato plants first grew wild in the
Andes Mountains of South America.
The Spanish brought tomatoes to
Europe after finding them growing in
the Americas. At first Europeans grew
tomatoes only for decoration. They
thought that tomatoes were poisonous
because they are related to the deadly
nightshade plants. Tomatoes did not
become popular in the United States
until the early 1900s.
#More to explore
Fruit • Nightshade
The Toltec are
known for the
art objects
they made
from stone
and metal.
Tomatoes come in different sizes and
shapes. Some small varieties are called
cherry tomatoes or grape tomatoes.
78 Tomato BRITANNICA STUDENT ENCYCLOPEDIA
Tonga
The country of Tonga is made up of
about 170 islands in the southern Pacific
Ocean. The largest island is Tongatapu.
It is where the capital, Nuku’alofa, is
located.
Tonga is a part of the Pacific region
called Oceania. People live on only
about 40 of Tonga’s islands. Some
islands are the peaks of underwater volcanoes.
Others are atolls, or coral reefs
that surround a pool of water. Tonga’s
climate is warm and rainy.
Rain forests grow on the volcanic
islands. Mangrove trees grow in swampy
areas. Tonga’s birds include doves, kingfishers,
cuckoos, and shrikes. Large fruit
bats, called flying foxes, live on Tongatapu.
Almost all the people of Tonga are
Polynesians, the native people of eastern
Oceania. The main languages are Tongan
and English. Nearly all Tongans are
Christians. About two thirds of the
people live on Tongatapu. Fewer than
half of the people live in cities.
The economy of Tonga is based on
farming and fishing. Farmers grow
squash, coconuts, cassava, yams,
bananas, and vanilla beans. They also
raise pigs, goats, and cattle. Tourism is
another important part of the economy.
People have lived on the islands for at
least 3,000 years. Kings and queens have
ruled Tonga since the AD 900s.
Dutch and British explorers visited the
islands in the 1600s and 1700s. Christian
missionaries arrived in the 1800s. In
1900 Tonga gave control of its foreign
affairs to Great Britain.
Tonga became independent of Britain in
1970. In the 1990s some Tongans began
asking the king to make the country a
democracy.
..More to explore
Nuku’alofa • Oceania
Schoolchildren in Tonga raise their hands to
answer the teacher’s question.
Facts About
TONGA
Population
(2008 estimate)
103,000
Area
290 sq mi (750
sq km)
Capital
Nuku’alofa
Form of
government
Constitutional
monarchy
Major towns
Nuku’alofa,
Neiafu,
Haveluloto
BRITANNICA STUDENT ENCYCLOPEDIA Tonga 79
Tongue
The tongue is an organ, or body part, in
the mouth. It is made up of a group of
muscles. Most vertebrates, or animals
with a backbone, have a tongue.
The tongue is firmly attached to the
bottom of the mouth. This attachment
keeps the tongue from being swallowed.
The underside of a mammal’s tongue is
smooth. The top of the tongue is rough
and bumpy. These bumps are called
papillae. The papillae contain taste buds.
They also produce some of the fluid in
saliva, a sticky liquid that keeps the
mouth moist.
Eating and Tasting
In many animals the tongue helps in
chewing and swallowing food. Papillae
help to grip and hold food. The front
muscles of the tongue move food
around and over the teeth during chewing.
The back muscles of the tongue
help in swallowing. They push chewed
food to the back of the mouth and
down the throat.
The tongue is also responsible for the
sense of taste. The taste buds contain
special cells that send information about
foods to the brain. These special cells
each respond to a particular kind of
taste. Humans can sense five basic tastes:
salty, sweet, sour (acid), bitter, and
umami. Umami represents the taste of
certain chemicals called amino acids.
People are born with about 10,000 taste
buds, and there may be 50 to 150 cells
in each bud. As people age, the number
of taste buds may drop to 5,000. This
may explain why some foods taste stronger
to young people.
Other Uses
Tongues have many other uses. The
human tongue plays an important part
in speaking. It forms and shapes the
sounds that make up language. Dogs
and cats use their tongues to clean themselves.
Frogs use their tongues to catch
insects and other small animals for food.
Snakes and other reptiles flick out their
tongues to collect scents in the air.
..More to explore
Mouth • Muscle
The drawing on the top shows papillae
on the tongue. The drawing on the bottom
shows how the tongue fits into the mouth.
80 Tongue BRITANNICA STUDENT ENCYCLOPEDIA
Tonsillitis
Tonsillitis is an infection of the tonsils.
The tonsils are oval-shaped lumps of
tissue in the throat. Usually they help
protect the body against disease. But
sometimes they become infected themselves.
An infection is an attack by tiny
germs that cause disease. Children get
tonsillitis more often than adults.
The germs that cause tonsillitis are
