FOCUS Book
E x tr e m e
E n v i r o n m e n ts
Animals and plants have adaptations that allow them
to survive in extreme environments. Construct an
imaginary environment that includes three of the
extreme elements mentioned in this book.
Use materials such as a cardboard box, paper, cotton
balls, craft sticks, aluminum foil, tape, and glue
to build a diorama of your fictional environment.
Be sure your environment demonstrates extreme
characteristics that make it challenging for plants and
animals to survive. Next, describe three organisms
(real or made up) that would be able to survive in such
an environment. What adaptations would allow them
to produce energy, keep warm or stay cool, or find
nutrients? Share your environment with your class.
Beyond the Book
Conduct research to find an extreme
environment near your school. What
makes it an extreme environment?
Beyond the Ordinary
Rainforests, grasslands, oceans, and deserts are
just some of Earth’s key ecosystems. Each one is
unique and is home to many kinds of organisms.
But some environments are so extreme that only
certain organisms can live there.
E x tr e m e
E n v i r o n m e n ts
What makes an environment
extreme? It may be
boiling hot or freezing
cold. It may be filled
with salt or be
completely dark.
It may be waterlogged
or arid. The plants
and animals that live
in these extreme
environments have
special adaptations
that help them
survive. These
Most caves exist in total darkness,
amazing creatures
making it impossible for the Sun
to provide the energy needed
are called
for life inside the cave. Yet some
extremophiles do live in caves.
extremophiles.
FOCUS Question
How do organisms survive in
extreme environments?
Structure and Function
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Southampton Oceanography Centre/Science Source; page 9: © Duncan Usher/ardea.com
Extreme Environments
© Learning A–Z
Written by Joe Levit
All rights reserved.
www.sciencea-z.com
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Severely Salty
Too Cold or Too Hot
The Dead Sea is located
on the border between
Jordan and Israel. The
water is too salty for
The Dead Sea has almost ten
most organisms to
times more salt than the ocean.
survive. A few kinds
Israel
Syria
Iraq
of bacteria are the
Asia
Dead
Sea
only organisms
Egypt Jordan Saudi
Africa
that can live there.
Arabia
Some creatures have to adapt to living in an extremely
cold or hot environment. The wood frog has adapted
to chilly conditions. When the temperature dips below
freezing, so does most of the water inside the frog’s
body. In this state, the frog doesn’t breathe. It doesn’t
even have a heartbeat!
When the weather warms
up, so does the frog.
At the other extreme,
fennec foxes live in the
scorching Sahara Desert
in North Africa. Their
oversized ears release
body heat and help
keep the foxes cool.
Earth’s oceans are salty (but not as salty as the Dead
Sea!). Marine iguanas live on the Galapagos Islands,
off the coast of Ecuador. They feed on algae growing
in the ocean. As these iguanas eat, they swallow salt.
Too much salt in their bodies would kill them. These
lizards have special glands that filter salt from their
blood. Then they sneeze the salty liquid out through
their nostrils!
Europe
North America
PACIFIC OCEAN
Ecuador
Galapagos
Islands Peru
wood frog
Asia
Sahara
Desert
South
America
Africa
The pale spots on this iguana’s
snout are salt that it sneezed out.
Habitats and Environment • Extreme Environments
fennec fox
3
4
Too Wet or Too Dry
Complete Darkness
Too much water can
be hard on plants and
animals. But mangrove
trees have adapted to
live in waterlogged soil.
Special roots grow in the
air and act like snorkels.
They get the oxygen
the tree needs, even
when the tide is high.
Most caves are completely dark. With no sunlight,
there is no need for animals to have vision or be
colorful. Over many generations, some creatures that
live in caves have lost their eyesight and body color.
Mexican cave fish have no color and no eyes. They
don’t need to see in order to catch their food. These
fish have a strong sense of smell. They can also sense
tiny pressure changes in the water. These abilities help
cave fish find food and survive in complete darkness.
This mangrove tree has special
above-water roots to help it
get oxygen in salty water.
Too little moisture can
also be a problem for
most living things.
However, the tiny
tardigrade can survive
with no water at all!
A tardigrade is only the size
During dry times, it curls
of a poppy seed and can
be found almost anywhere
up into a ball called a tun
on Earth.
(rhymes with “sun”). The
water in its body is replaced with a special sugar
that keeps it alive. When water is available again,
the tardigrade uncurls and swims away.
Habitats and Environment • Extreme Environments
In Mexican cave fish, scales cover the area where the
eyes are found in other fish.
It takes energy for an organism to produce
body color, or pigment. In total darkness,
animals save this energy because they don’t
need color for protection or camouflage.
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6
Deep, Cold Waters
Like caves, the deep ocean is completely dark. In most
ecosystems, producers at the base of a food chain
use sunlight to make food. Then consumers eat the
producers. But in the deep ocean, living things must
find another source of energy.
A COMPARISON OF
Away from hydrothermal
DIVING ABILITIES
vents, temperatures
in the deep ocean are
human
extremely cold. Yet
100 m
(328 ft.) dolphin
southern elephant
300 m
seals dive as deep as
(984 ft.)
1,525 meters (5,000 ft.)
to hunt for food. How do
they survive such icy water?
Cold ocean water seeps into deep natural cracks on
the ocean floor. There the water is heated by magma
under Earth’s surface. Then the heated water shoots
out of vents in the ocean floor. This hot water brings
minerals with it. Special bacteria grow and produce
food from these minerals.
Elephant seals have blubber—
a layer of fat underneath their
skin. This layer can be up to
15 centimeters (6 in.) thick.
Blubber helps keep seals
warm on deep dives.
Because the water is hot and nutrients are available,
many creatures can live near these hydrothermal
vents. Small shrimp eat the bacteria. Then octopuses
may eat the shrimp.
hydrothermal
vent
To stay down deep for long periods
of time, elephant seals store oxygen
in their blood and muscles. Also,
their heartbeat slows down while
beaked whale
2,992 m
they dive. These features allow
(9,816 ft.)
them to hold their breath
Deep-diving mammals can
descend up to thirty times
for up to two hours!
This octopus preys on small
crustaceans that feed on
bacteria near the vent.
Habitats and Environment • Extreme Environments
elephant
seal
1,524 m
(5,000 ft.)
deeper than humans.
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8
The Microbe Rainbow
The scalding water in hot springs would burn most
living things. But certain microbes have adapted to
these near-boiling environments.
Write your answers on separate paper. Use details
from the text as evidence.
1 According to the book, how have marine iguanas
adapted to the salty water they swallow when
eating algae?
A hot spring called Grand Prismatic is the largest
in Yellowstone National Park. It is named for the
colorful microbes that call the hot spring home.
Mats of cyanobacteria give
the spring its vibrant colors,
United
States
like light through a prism.
Extreme environments are
found all over the world. But
you can be sure that some
form of life has adapted to
live in nearly all of them!
2 Like fennec foxes, jackrabbits have large ears.
How might big ears help jackrabbits live in
hot deserts?
3 Describe how the lack of sunlight caused the
Mexican cave fish to adapt in order to survive.
Montana
4 What makes life at a hydrothermal vent possible?
Idaho
Yellowstone
National Park
Utah
5 Using information in the book, predict what
characteristics a mammal capable of diving
to a depth of 8,000 meters (26,200 ft.) would
share with a southern elephant seal.
Wyoming
Colorado
FOCUS Question
How do organisms survive in extreme environments?
Select two examples described in the book. For each
one, explain how its physical structures help it adapt
to an extreme environment. Discuss the
function of those structures.
The water of the Grand Prismatic hot spring can
reach 86°C (188°F). Water boils at 100°C (212°F).
Habitats and Environment • Extreme Environments
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