ranges from fish, birds, or snakes to rabbits,
foxes, monkeys, and even deer.
Female eagles are generally larger than
males. A female bald eagle may be as
long as 43 inches (1.1 meters). A male
bald eagle is about 36 inches (0.9 meter)
long. Golden eagles are similar in size.
The main groups of eagles are sea eagles,
booted eagles, forest eagles, and serpent
eagles. Sea eagles snatch fish out of rivers,
lakes, or seas. The bald eagle is a
type of sea eagle that lives in North
America. It is not actually bald. It has
brown body feathers with white feathers
on its head and neck.
The golden eagle is found in North
America, Europe, Asia, and northern
Africa. It is a type of booted eagle, which
has feathers on its legs. The golden eagle
is dark brown with golden feathers on its
head and neck.
Forest eagles are huge birds that live in
rain forests. Serpent eagles are snakeeating
birds of Asia and Africa.
#More to explore
Bird • Bird of Prey • Falcon • Hawk
• Vulture
Ear
Ears are the organs, or body parts, in
humans and many other animals that
allow them to hear. Ears work by picking
up vibrations (tiny back-and-forth
movements), usually in the air or water.
Then they change the vibrations into
signals that the brain understands as
sound. Ears also help an animal to keep
its body in balance.
The Human Ear
Humans have two ears, one on each side
of the head. Each ear has three sections:
the outer ear, the middle ear, and the
inner ear.
The bald eagle was once endangered, or at
risk of dying out. Laws protecting the bird
helped to raise the number of bald eagles
in the wild.
86 Eagle BRITANNICA STUDENT ENCYCLOPEDIA
The outer ear is divided into two main
parts: the auricle and the ear canal. The
auricle is the part of the ear that is visible
on the sides of the head. It is made of a
tough material called cartilage. It collects
sound waves and sends them into a
curved passageway called the ear canal.
The ear canal leads to the eardrum,
which separates the outer ear from the
middle ear. The eardrum vibrates when
sound hits it. It then passes the vibrations
to the middle ear.
The middle ear is an air-filled space. It is
about 0.75 inch (1.9 centimeters) high
and 0.20 inch (0.5 centimeter) wide.
Inside this space are three small bones.
These bones work together to send
vibrations along to the inner ear.
The inner ear is filled with fluid. It contains
the main organ of hearing, a coiled
tube called the cochlea. The vibrations
make waves in the fluid of the cochlea.
These waves produce the sound signals
that are sent to the brain. The inner ear
also has structures called the semicircular
canals, which help to keep the body in
balance.
Problems with the Ear
When people fly, drive in the mountains,
or swim deep underwater, their
ears may “pop.” This painful or stuffy
feeling usually goes away on its own.
Infections of the middle ear are a common
problem in children. They often
develop after a cold. Ear infections can
be quite painful, but they are usually not
serious. Serious problems with the inner
ear can lead to deafness.
Ears of Other Animals
Ears are much more important to mammals
than to other groups of animals.
Only mammals have the outside ear
parts called auricles. The ears of different
mammals work basically the same way
that human ears do. However, many
The three main parts of the human ear are
the outer, the middle, and the inner ear.
The huge auricles (outside ear parts) of a
bat help it to tell from which direction a
sound is coming.
BRITANNICA STUDENT ENCYCLOPEDIA Ear 87
mammals can move their auricles to
pick up sound coming from any direction.
Other groups of animals have only
some ear parts. Birds have an ear canal,
a middle ear, and an inner ear. Their
hearing is similar to that of humans.
Most amphibians and reptiles have
middle ears and inner ears with one
bone. The eardrums of frogs and some
reptiles are visible on the sides of the
head. Snakes lack outer and middle
ears. The snake’s skull bones pass
vibrations to the inner ear. Some fish
have a simple inner ear buried deep in
the head. Insects and spiders also lack
ears, but they can sense vibrations in
other ways.
#More to explore
Deafness • Sound
Earhart, Amelia
Amelia Earhart was a pioneer of aviation.
She was the first woman to fly
alone across the Atlantic Ocean. She
disappeared during a flight in 1937 and
was never found.
Amelia Mary Earhart was born on July
24, 1897, in Atchison, Kansas. Her family
did not want her to be a pilot, but
she learned anyway.
In 1928 Earhart became the first woman
to fly across the Atlantic. She was a passenger
in an airplane that someone else
piloted. Four years later she became the
first woman—and only the second
person—to fly across the Atlantic alone.
She flew from the island of Newfoundland
to Ireland. Her flight lasted 14
hours and 56 minutes.
Earhart next made a series of flights
across the United States. She wanted to
get more women involved in aviation.
She also wanted to make flying more
popular as a way to travel. For a time
Earhart worked for one of the first regular
passenger services to fly between
New York City andWashington, D.C.
