Only some species—including the white
shark and the tiger shark—are considered
dangerous to humans. When these
sharks are hungry, disturbed, or defending
their territory, they may attack
humans. Even the movement and noises
of swimmers can cause some sharks to
attack. However, shark attacks are rare.
#More to explore
Fish • Ray
A hammerhead shark gets its name from its
wide, flat head.
BRITANNICA STUDENT ENCYCLOPEDIA Shark 77
Shawnee
The Shawnee are Native Americans who
traditionally lived over a large area in
what is now the eastern United States.
Their first known homeland was centered
in what is now Ohio.
During the summer the Shawnee lived
in wigwams.Wigwams were domeshaped
homes made from a frame of
wood poles covered with bark. The
women grew corn and other food crops.
The men hunted. During the winter the
Shawnee moved to hunting camps.
In the 1600s the Iroquois people drove
the Shawnee from their lands. The
Shawnee scattered. After 1725 many
Shawnee returned to Ohio.
The Shawnee fought repeatedly to
defend their lands against white settlers
who wanted to expand westward. In
1794 U.S. troops defeated the Shawnee
in the battle of Fallen Timbers. In 1795
Shawnee leaders signed a treaty in which
they gave up their Ohio lands.
Some Shawnee refused to leave the area.
Among them was Tecumseh, who organized
a confederacy (group) of tribes to
fight the Americans. Tecumseh died in
battle in 1813. His confederacy fell
apart soon afterward.
By the late 1800s most Shawnee had
settled in Indian Territory (now Oklahoma).
At the end of the 20th century
there were more than 6,000 Shawnee.
Most lived in Oklahoma.
#More to explore
Iroquois • Native Americans • Tecumseh
Sheep
Sheep are among the most valuable of all
domestic animals. Domestic animals are
ones that have been tamed for use by
humans. People eat sheep meat and
drink sheep milk. The animals’ wool is
used to make cloth. Male sheep are
called rams. Female sheep are called
ewes. Sheep are closely related to goats.
There are more than 200 breeds of
sheep. They are found on every continent
except Antarctica. Sheep can be
A Shawnee man wears a traditional headdress
and feathers.
A ewe watches over two lambs.
78 Shawnee BRITANNICA STUDENT ENCYCLOPEDIA
either wild or domestic. Most sheep like
to live in high and dry areas.
Adult sheep weigh 80 to 400 pounds
(35 to 180 kilograms). Some sheep have
horns. They curl in loops alongside the
head. Certain types of wild sheep have
very long horns. The horns of the bighorn
sheep can be more than 3.3 feet (1
meter) in length. Most domesticated
sheep grow a thick coat of fibers called
wool.Wild sheep grow both hair and
wool.
Sheep eat grass and plants. They often
graze in large groups, or flocks. Sheep
have four separate stomach compartments,
or sections. They regurgitate
their food (bring it back up from the
stomach) and chew it again. This helps
the stomach fully digest the food.
People raise sheep for their meat, milk,
and wool. The meat of an adult sheep is
called mutton. Meat from a younger
sheep is called lamb. Some people drink
sheep milk. It is also used to make
cheese. Certain types of sheep are raised
specifically for their wool. These include
Merino and Rambouillet sheep.
#More to explore
Goat
Shell
Every empty seashell on the beach once
contained an animal known as a mollusk.
Clams, oysters, scallops, conchs,
mussels, and snails are all types of mollusks.
The shells of these animals are
exoskeletons, or hard, outside skeletons
that protect their soft bodies.
Structure
All mollusk shells are made of a mineral
called calcium carbonate. To form a
shell, the mollusk’s body gives off substances
that contain calcium carbonate.
The substances harden into layers of
shell. As the animal grows, its shell also
gets bigger to make room for its body.
The Swaledale is an English
breed of sheep with curling horns.
Shells come in many shapes, colors, and
patterns.
BRITANNICA STUDENT ENCYCLOPEDIA Shell 79
Mollusk shells differ greatly in shape,
size, color, and texture. The way a shell
looks can help a mollusk avoid enemies.
Bright colors or patterns may scare away
enemies. Textures and colors that match
the surroundings help a mollusk to hide
from enemies.
Shells are also put together in various
ways. Snails and conchs have single
shells in the shape of a twisted cone.
These mollusks are called univalves.
Clams, oysters, scallops, and mussels
have shells with two halves joined on
one side. These mollusks are called
bivalves. Chitons have shells made of
eight overlapping plates.
Uses
The main purpose of a mollusk’s shell is
to protect its body. When in danger, a
mollusk can quickly pull its entire soft
body into the hard shell.
Shells have other purposes, too. Some
shells have ridges that keep the animal
anchored to the ocean floor. Other shells
are smooth, which allows the animal to
burrow easily into mud or sand. Shells
with long spines trap food.
Many people collect shells. They may
use them to make buttons and jewelry
and in other crafts. In the past, peoples
in Africa, North America, and the
Pacific islands used shells as money.
Other Types of Shells
