Structural and Behavioral Adaptations
All organisms have adaptations
that help them survive and
thrive. Some adaptations are
structural. Structural
adaptations are physical
features of an organism like the bill on a bird or
the fur on a bear. Other adaptations
are behavioral. Behavioral adaptations are the
things organisms do to survive. For example, bird
calls and migration are behavioral adaptations.
Adaptations are the result of evolution. Evolution
is a change in a species over long periods of time.
Adaptations usually occur because a gene
mutates or changes by accident! Some
mutations can help an animal or plant survive
better than others in the species without the
mutation.
For example, imagine a bird
species. One day a bird is born
with a beak that is longer than
the beak of other birds in the
species. The longer beak helps
the bird catch more food.
Because the bird can catch
more food, it is healthier than the other birds,
lives longer and breeds more. The bird passes the
gene for a longer beak on to its offspring. They
also live longer and have more offspring and the
gene continues to be inherited generation after
generation.
Eventually the longer beak can be found in all of
the species. This doesn't happen overnight. It
takes thousands of years for a mutation to be
found in an entire species.
Over time, animals that are better adapted to
their environment survive and breed. Animals that
are not well adapted to an environment may not
survive.
The characteristics that help a species survive in
an environment are passed on to future
generations. Those characteristics that don't help
the species survive slowly disappear.
Did You Know?
... the largest rodent in
North America is the
beaver.
... beavers' front teeth grow
throughout their lives.
... beaver ponds can improve water quality and
provide a water source for other animals.
What Do You Think?
Click here to test your adaptation
knowledge.
NatureFiles
Learn more about the adaptations these
animals have that help them survive
and thrive in their habitats.
porcupine
eastern chipmunk
arctic fox
Virginia opossum
beaver
Teacher's Guide
Click here to access the teacher's guide
for this episode.
Evolution
Change is
Good!
Dive Into
the Gene Pool
Why does a duck
have a rounded bill
and a heron have a
long pointed
bill? All organisms
are uniquely
adapted for their
environments.
Scientists know that over long periods of time
organisms have changed or adapted to better
survive in their environments. They call this slow
process of change evolution.
All of the genes in a
population of
organisms is called
a gene pool. The
gene pool of a
population has all
the characteristics
that can be passed on to organisms in a particular
population. The gene pool contains all the traits or
genes in any one population that can be passed
on through generation after generation.
Sometimes the gene pool of a population lacks
diversity or becomes contaminated with genes
from a closely
related species.
Natural
Selection
Individuals within
an animal species
are not exactly the
same. Just like you
are not exactly like
your parents or
your friends or any
other human on
earth. Each
organism in a species has a slightly different
genetic makeup. Organisms within a species that
have characteristics that help them survive in
their environment tend to breed and pass on
those positive characteristics. Individuals that
have characteristics that make survival more
difficult may not survive to pass on their
characteristics. Basically, characteristics that help
an organism survive and thrive get passed on to
future generations characteristics that don't slowly
disappear.
The red wolf is in
danger of going
extinct because its
gene pool has been
impacted by mating
with coyotes. If
enough red wolves
mate with coyotes,
their gene pool will
eventually disappear. In some areas, a species
population is so small that there are few choices
when mating.
The Florida panther
population is limited
to a very small
area. The gene pool
of the species lacks
variety because
generation after
generation is
descended from the
same animals.
When a gene pool
gets too small,
negative characteristics can easily be passed from
one generation to the next, endangering the
survival of the entire species.
North American Porcupine - Erethizon dorsatum
Classification
Phylum: Chordata
Class: Mammalia
Characteristics
Range
Habitat
Diet
Life Cycle
Behavior
Order: Rodentia
Family: Erethizontidae
Genus: Erethizon
Characteristics
The porcupine is a
rodent. It has black
to brownish-yellow
fur and strong,
short legs. It has
hairless soles on its
feet that help it
climb trees. It has a
round body, small
ears and a small
head. The most
recognizable feature
of the porcupine is
its quills. A
porcupine may have
as many as 30,000
quills. The quills are
hairs with barbed
tips on the ends.
Quills are solid at
the tip and base and
hollow for most of
the shaft. The
porcupine has quills
on all parts of its
body, except for its
stomach. The
longest quills are on
its rump. The
shortest quills are
on its cheeks.
The porcupine uses
its quills for
defense. The
porcupine cannot
shoot its quills. When a predator approaches, the
porcupine will turn its back, raise the quills and
lash out at the threat with its tail. If the porcupine
hits an animal with its quills, the quills become
embedded in the animal. Body heat makes the
barbs expand and they become even more deeply
embedded in the animal's skin. If an animal is hit
in a vital place it may die. The porcupine is not an
Diet
The common
porcupine is
anherbivore. It eats
leaves, twigs and
green plants like
skunk cabbage and
clover. In the
winter, it may eat
bark. It often climbs
trees to find food. It is mostly nocturnal, but will
sometimes forage for food in the day.
Life Cycle
Porcupines mate in late summer and early fall.
Porcupines are very vocal during mating season.
Males often fight over females. The male performs
an elaborate dance and sprays urine over the
head of the female. Seven months after mating
the female gives birth to a single baby. When the
baby is born, its quills are soft. They harden about
an hour after birth. The baby is begins to forage
for food after only a couple of days. The baby will
stay with its mother for about six months.
Behavior
aggressive animal. It will only attack if it is
threatened. Some animals, like the fisher, are
experts at attacking porcupines.
Range
The common
porcupine can be
found in most of
Canada and the
western United
States south to
Mexico. In the
eastern United
States, it can be found in Wisconsin, Michigan,
Pennsylvania, New York and New England.
Habitat
The common porcupine lives in coniferous,
deciduous and mixed forests. In the west, it can
be found in scrubby areas.
The common
porcupine is a
solitary animal,
although it may den
with other
porcupines in the
winter. It makes its
den in caves,
decaying logs and
hollow trees. The
common porcupine
doesn't hibernate,
but it may stay in
its den during bad
weather. The
common porcupine
is a good swimmer,
its hollow quills help
keep it afloat. It is
also an excellent
tree-climber and spends much of its time in trees.
It is a very vocal animal and has a wide-variety of
calls including moans, grunts, coughs, wails,
whines, shrieks and tooth clicking.
Eastern Chipmunk - Tamias striatus
Classification
Phylum: Chordata
Characteristics
Range
Habitat
Diet
Life Cycle
Behavior
Class: Mammalia
Order: Rodentia
Family: Sciuridae
Genus: Tamias
Click on the images for a larger view.
Characteristics
Diet
The eastern
chipmunk has
reddish-brown fur
on its back and
sides and white fur
on its stomach. It
has two white
stripes bordered by
black on its sides and one black stripe on the
center of its back. The eastern chipmunk has light
stripes above and below its eyes and it has
pouched cheeks that it uses to store and carry
food.
Range
The eastern chipmunk can be found in
southeastern Canada and most of the
northeastern United States south to Mississippi
and Virginia and west to North Dakota and
Oklahoma.
Habitat
The eastern chipmunk lives in open deciduous
forests and at the edges of woodlands. It can also
be found in bushy areas and in rocky areas like
walls near houses and other buildings.
Most of the eastern chipmunk's diet is made up
of nuts, acorns, seeds, mushrooms, fruits,
berries and corn. It also eats insects, bird eggs,
snails and small mammals like young mice. In
winter, it stays in its den. The eastern chipmunk
doesn't truly hibernate, but it does spend a lot of
time sleeping. It may wake up every few weeks to
eat the food it has stored.
Life Cycle
Eastern chipmunks mate in early spring. The
female usually has one litter a year with between
three and five young. In some areas, a female
may have a second litter. The young will come
above ground when they are about six weeks old.
Behavior
The eastern chipmunk spends a large part of its
waking hours gathering and storing food for the
winter. Eastern chipmunks are also very vocal and
can be heard chattering as they gather food. In
fact, they get their name chipmunk from the
"chip-chip" sound that they make!
Beaver - Castor canadensis
Classification
Phylum:Chordata
Class: Mammalia
Order: Rodentia
Characteristics
Range
Habitat
Diet
Life Cycle
Behavior
Family: Castoridae
Genus: Castor
Click on the images for a larger view.
Characteristics
The beaver is North
America's largest
rodent and is built
for life in the water.
Adults can be up to
four feet long and
weigh over 60
pounds. The beaver has webbed hind feet and a
large, flat, nearly hairless tail. It uses its tail to
help maintain its balance when it is gnawing on
trees. It will also slap its tail against the water to
signal danger or to warn away predators. The
beaver has short front legs with heavy claws.
Their rear legs are longer, and their webbed feet
help propel them
through the water
when they are
swimming. When
the beaver is under
water, its nose and
ears close up, and a
special membrane
covers its eyes.
It has dark brown fur on its back and sides and
lighter brown fur on its chest and belly. The
beaver waterproofs its thick fur by coating it
with castoreum, an oily secretion from its scent
glands. The beaver has a thick layer of fat under
its skin that helps keep it warm underwater.
Beavers have long sharp upper and lower incisor
teeth that they use to cut into trees and woody
vegetation. These teeth grow throughout the
beaver's life.
Range
The beaver is found throughout North America
except for Florida, the desert Southwest, Mexico,
and the northern most parts of Canada.
Habitat
Life Cycle
Beavers mate for
life, but if one mate
dies, the other one
will find another
mate. Beavers mate
when they are about
three years old.
Mating season runs
from January and
March in cold regions and in late November or
December in the south. Gestation lasts about
three months, and females have one litter of kits
a year between April and June. Before birth, the
female makes a soft bed in the lodge. The babies'
eyes are open when they are born. They can swim
within 24 hours of birth and will be exploring
outside the lodge with their parents within a few
days. Young beavers are weaned in about two
weeks. Both the male and the female take care of
the young beavers. They stay with their parents
for two years. Beavers can live to be 20 years old.
Behavior
Beavers live in family groups orcolonies. A
colony is made up of a breeding male and female
beaver and their offspring. Beavers are very
territorial and will protect their lodges from other
beavers. They mark their territory by building
piles of mud and marking it with scent.
Beavers can have both a positive and a negative
impact on the environment. When beavers build
dams, they create new wetland environments for
other species. These wetlands can help slow
erosion, raise the water table, and help purify the
water. Beavers can play a major role
insuccession. When beavers abandon their
lodges and dams, aquatic plants take over the
pond. Eventually,
shrubs and other
plants will grow,
and the area will
become a meadow.
The shrubs in the
meadow will
provide enough
shade to allow tree
Beavers live near
rivers, streams,
ponds, small lakes,
and marshes. They
build lodges of
sticks and mud on
islands, on pond
banks, or on lake
shores. Beaver dams are domed-shaped and can
up to ten feet tall. Beaver lodges have one large
central chamber and one or two entrances. The
floor of the chamber is a little bit above the water
and is usually covered in woodchips to absorb
moisture. A vent in the lodge lets in fresh air. Not
all beavers build lodges, some beavers build
burrows in the banks of rivers.
Diet
Most of the
beaver's diet is
made up of tree
bark andcambium,
the soft tissue that
grows under the
bark of a tree. They
especially like the
bark of willow,
maple, birch,
aspen, cottonwood,
beech, poplar, and
alder trees.
Beavers also eat
other vegetation like roots and buds and other
water plants. The beaver has a specialized
digestive system that helps it digest tree bark.
seedlings to grow. Once the trees grow, they will
take over, and the land will turn into a woodland
area.
Beaver dams can also cause problems. Dams can
slow the flow of water in streams and cause silt to
build up, and some other species can loose
habitat. Dams can also cause flooding in low-lying
areas.
Arctic Fox - Alopex lagopus
Classification
Phylum: Chordata
Characteristics
Range
Habitat
Diet
Life Cycle
Behavior
Class: Mammalia
Order: Carnivora
Family: Canidae
Genus: Alopex
Click on the images for a larger view.
Characteristics
The arctic fox is
dark gray to bluish
brown in the
summer. In the
winter its fur is
white or creamy
white. It has a long
bushy tail, a short
nose and small
curled back ears. It
has short, stubby legs and thick fur. Its short legs
and nose, thick fur and small ears are adaptations
that help it survive in cold climates. Because its
legs are so short and its ears and nose are small,
they are less exposed to the cold. The arctic fox
also has thick fur and hair on its paw pads that
help keep it warm. The fur on its paws also gives
the fox traction so it doesn't slide on the ice.
When the arctic fox is sleeping, it protects its
nose from the cold by curling its bushy tail around
its body. The arctic fox is about three feet long
and weighs between five and fifteen pounds.
Males are larger than females.
Range
In North America the arctic fox can be found from
western Alaska east through northern Canada in
the Northwest Territories, Alberta, Manitoba and
Quebec. It is also found in the arctic regions of
Europe, Asia, Iceland and Greenland.
Habitat
In the summer the
arctic fox lives in
the tundra at the
edge of forest. In
the winter it can be
found on ice floes
where its white coat
serves as
camouflage. Its den
is usually a burrow in a hillside or a bank and it
has more than one entrance. In the winter the fox
Diet
The arctic fox is an
opportunistic eater.
It will eat just
about whatever it
comes across. It
eats small
mammals like
lemmings, voles,
and ground squirrels; birds; insects; eggs; berries
and carrion. In fact, in the winter it often follows
polar bears and wolves and eats their leftover kill.
If food is really scarce, it will eat the feces of
other animals. In the summer the arctic fox will
carry extra food to its den and store it under
rocks to eat later. The arctic fox sometimes even
makes its own freezer by digging a hole in the
permafrost and storing its food there. A major
source of food for the arctic fox is the lemming. In
fact, the arctic fox population often peaks every
four years in a cycle that follows lemming
population changes.
Life Cycle
The arctic fox
mates between
February and June.
The female builds a
new den and gives
birth to between six
to twelve dark
furred kits. Both the
female and the male will take care of the young
kits. The male will guard the den and bring food
to the den for the mother and the kits. The kits
are weaned when
they are between
two to four weeks
old and then they
will start to leave
the den.
Behavior
The arctic fox
often makes its den in a snowbank.
isnomadic, it moves from place to place looking
for food. In the summer they live in family groups
made up of a male, one or two females and the
kits. The second female is a leftover kit from the
year before, she doesn't breed. She helps care for
the young.