Unit 4 Unit 4

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					          Unit
           4

            BEFORE READING

            Preview the Selection
            by looking at the photographs,
            illustrations, captions, and
            graphics to predict what the
            selection will be about.

            DURING READING

            Make Connections
            by comparing my experiences
            with what I’m reading.

             AFTER READING

            Recall
            by using the
            headings to
            question myself
            about what
            I read.




                                             LEARN
                                             the strategies
                                             in the selection
                                             Going, Going, Gone
                                             page 141


[ 138 ]
                     Endangered or Extinct?




PRACTICE                  APPLY
the strategies            the strategies
in the selection          in the selection
Valuing “Varmints”        DDT and the Peregrine Falcon
page 157                  page 169


                                                         [ 139 ]
          Think About
            the
                                 BEFORE READING

              Preview the Selection
              by looking at the photographs, illustrations,
              captions, and graphics to predict what the
              selection will be about.

                  My Thinking
                  The strategy says to preview the selection to
                  predict what the selection will be about. The
                  photographs, captions, and graphics are about
                  animals from around the world. Several graphics
                  and captions mention the words “endangered” and
                  “extinct.” I predict the selection will discuss animals
                  that are endangered or extinct. Now I’m ready to
                  read and find out if my prediction is right.

                                 DURING READING

              Make Connections
              by comparing my experiences with what I’m
              reading.

                  My Thinking
                  The strategy says to make connections by compar-
                  ing my experiences with what I’m reading. I will stop
                  and think about this strategy every time I come to a
                  red button like this   .




[ 140 ]
                                                 Going,
                                                        Going,
                                                                 Gone

Hua Mei, the first surviving                                 A model of the extinct dodo
giant panda born in a
North American zoo




Introduction
    In the 1500s sailors found a huge, clumsy, flightless bird
on the Mauritius [maw•rish•uhs] Islands in the Indian
Ocean. The dodo couldn’t move very fast and it couldn’t fly.
Animals that the sailors brought with them hunted and
                                                                    Vo • cab • u • lar • y
killed the dodos. Whenever the sailors wanted food, they            extinct (ik•stingkt)—
clubbed the birds. By 1680 the dodos became extinct.                no longer living


                                                                                            [ 141 ]
                                       In August of 1999, the birth of Hua Mei [hwah may] at
                                    the San Diego Zoo was reason for celebration around the
                                    world. Why all the excitement? Scientists believe there are
       Make Connections             just 1,000 giant pandas left in the wild and about 120 in
    by comparing my                 captivity. Bamboo, the sole food of giant pandas in the
    experiences with what           wild, is scarce. The destruction of the bamboo forests in
    I’m reading.
                                    China has caused the near-extinction of the giant panda.
   My Thinking                      Without intervention, the only giant pandas left will be
   My dog has really                those born in zoos.
   long, thick fur.
   My dad says it is
   because the region where the
                                    What Is Extinction?
   dog breed comes from is              Plants and animals on our planet have become extinct
   cold. The dogs use the fur to    since the earth began. Some scientists believe that extinc-
   keep warm. I understand          tion is a natural process. As one species disappears,
   what it means to adapt.          another replaces it. This development takes place over
                                    millions of years. It creates a natural biological variety of
                                    living things. For all the species that we know today, there
                                    are thousands of others that lived millions of years ago.
                                    These extinct species are all gone. Paleontologists know
                                    this because they study the fossil record of plants and
   Vo • cab • u • lar • y           animals. When a fossil no longer appears, the scientists
                                    assume this species became extinct. No extinct animal or
   intervention                     plant has ever reappeared. During the history of the earth,
   (in•tuhr•ven•shuhn)—the act      masses of animals and plants have become extinct within
   of coming in to help
                                    a short period of time. These mass extinctions have hap-
   species (spee•sheez)—            pened five times. Today we are in the sixth period of mass
   a group of living things that
   are alike in certain ways
                                    extinction. What caused this to happen in the past? Why is
                                    it happening today?
   paleontologists
   (pay•lee•uhn•tol•uh•jists)—
   scientists who study ancient     Ecosystems
   forms of life, such as fossils
                                        All living things, plants or animals, depend on other
   fossil (fos•uhl)—the hard-       living things to stay alive. Every living thing from one-
   ened remains of a plant or
   animal                           celled amoebae to giant dinosaurs is part of an ecosystem
                                    (a group of living things in an environment). Over mil-
   amoebae (uh•mee•bee)—
   tiny organisms that change       lions of years, living things adapt to their environment and
   form                             become part of ecosystems. When something disrupts the
   environment                      ecosystem, the living thing does one of two things: It
   (en•vy•ruhn•muhnt)—the           adapts or becomes extinct. When one animal or plant dies,
   conditions and surroundings in   other animals that depend on it for food can die, too.
   which something lives            When the ecosystem is disrupted, this leads to the extinc-
                                    tion of some species within it.

[ 142 ]
Keystone Species
   Creatures with the greatest impact on others in an
ecosystem are called keystone species. The alligator, once
an endangered species in the United States, is a keystone
species in its swamp ecosystem. Alligators dig holes to rest
and to stay cool. These fill with water and become small
ponds. Plants and marine animals begin to inhabit the
ponds. The alligator makes a nest of sticks and mud,
which soon becomes an island where plants and trees
grow. Birds nest in the trees. When the alligator was hunt-
ed to near extinction, its ecosystem was almost destroyed.
Without the alligators, there were no ponds and islands.
No ponds and islands meant loss of habitat for other
creatures.
                                                                         An alligator in
                                                                         its habitat on
                                                                         Cumberland Island,
                                                                         Georgia




Causes of Five Periods of Mass Extinction
   Throughout history the loss of keystone species and         Vo • cab • u • lar • y
ecosystems led to the gradual extinction of many species.      habitat—a place where an
But there were also periods of mass extinction when            animal or plant is normally
thousands of plants and animals disappeared quickly from       found
the earth. Until A.D. 1600, major changes in the geology       geology (jee•ol•uh•jee)—
and climate of the earth caused major changes in the           the structure of the earth’s
                                                               surface
environment.

                                                                                         [ 143 ]
                                   The earth is not a quiet planet. It is always changing.
                                Earthquakes show that the land is shifting. Glaciers
                                [glay•shuhrz] are constantly moving all around the world.
       Make Connections         Floods and storms wash away forests and grasslands.
    by comparing my             Violent changes in the land, sea, or climate can cause a
    experiences with what       loss of ecosystems. Loss of ecosystems in turn causes
    I’m reading.
                                habitats for plants and animals to vanish. As a result,
   My Thinking                  many plants and animals became extinct. Mass extinctions
   My grandparents              happened during dramatic changes in the earth.
   live on the East
   Coast, which has
                                   The Ordovician [or•duh•vish•uhn] extinction happened
   eroded because of the
   weather. So I understand
                                about 440 million years ago. Scientists think this was
   the idea of decreased        caused by a sudden cooling of the earth’s surface. This
   habitat for the animals      resulted in widespread glaciation. Lands that had been
   that live there.             tropical were covered with ice sheets and glaciers. This
                                caused between 20 and 50 percent of the species on Earth
                                to become extinct.
                                   During the late
                                Devonian period,
                                about 360 million
                                years ago, scientists
                                believe the same
                                thing happened.
                                As the seas cooled,
                                many fish and
                                marine invertebrates
                                died. About 1/4 of all
                                species became
                                extinct.
                                   Around 250
                                million years ago,
                                the Permian extinc-
                                tion occurred.
                                During that period,
                                half of all living
   Vo • cab • u • lar • y       things disappeared.
   glaciation                   Some scientists
   (glay•shee•ay•shuhn)—being   believe that the earth
   covered with sheets of ice   was hit by a large
   invertebrates                object from space.
   (in•vur•tuh•brits)—animals   Others believe the
   that have no backbone                                Part of this Alaskan glacier is breaking off
                                                        and falling into the ocean.

[ 144 ]
same climatic changes as the two previous periods were
responsible. However, this time there was a warming of
the earth’s surface.
    Volcanic eruptions and asteroid impacts seem to have
caused the Late Triassic [trye•as•ik] extinction. About 1/3
of all plants and animals on Earth disappeared. Dinosaurs
survived
the Triassic extinc-                       Some Endangered Animals Today
tion. But during the
late Cretaceous
[kri•tay•shuhs]                                                           Giant Panda
extinction, they too                                                        (China)
disappeared. There       California
                          Condor
is evidence that this
                                               Arctic Polar
was caused by a                                   Bear
huge impact.
Scientists think that
a comet hit the
earth in Central
America. Although
only 15 percent of
all the species
                                                                    African
disappeared during                                                  Cheetah
this event, the
dinosaurs were one
of them.

Causes of the Sixth Mass Extinction
   The earth is now in a period called the Holocene
[hol•uh•seen]. This period began 65 million years ago.
Gradual extinction has been taking place for all that time.
In the past 400 years, however, a mass extinction seems
to have been going on. Its cause is not a meteor, glacia-
tion, change in sea level, or global cooling. Its cause is
anthropogenic. That is, it has been caused by humans.
Humans deliberately or inadvertently are causing other              Vo • cab • u • lar • y
species to become extinct. People have destroyed habitats           asteroid (as•tuh•roid)—one
and polluted the globe. They have hunted and collected              of many small celestial bodies
plants and animals. People have introduced non-native               that orbit the sun
plants and animals to regions where they did not belong.            anthropogenic
All of these are contributing to the loss of ecosystems.            (an•thruh•puh•jen•ik)—
                                                                    caused by humans


                                                                                              [ 145 ]
                               Modern Causes
                                  In the past 50 years, people all over the world have
                               become aware of what extinction means. By placing ani-
       Make Connections        mals and plants on an endangered species list, people hope
    by comparing my            to save them from extinction. In the 1980s, species were
    experiences with what
    I’m reading.
                               becoming extinct at the rate of one a day, or 365 per year.
                               Today it is 2.7 a day. That’s about 1,000 per year! In the
   My Thinking                 previous 600 million years, the rate was 10 per year.
   There are a lot             Animals that are near extinction include every species of
   of deer in our              whale, the African cheetah, the Arctic polar bear, and oth-
   neighborhood.
   Maybe it is because we
                               ers. Plants, insects, and birds too numerous to list are
   have built our houses in    endangered. In some parts of the world, one small plant of
   their ecosystem, and they   a species is all that survives. Why has this happened?
   have lost their habitat.    There are many causes.

                               Expansion Causes Habitat Destruction
                                  As the human population of the earth has grown,
                               so has the need for farmland. More farms and people
                               have led to destruction of
                               many animals’ and plants’
                               natural habitats. As a
                               result, ecosystems—the
                               complex relationships of
                               plants, animals, and their
                               habitats—have also
                               been destroyed.

                                   One of the primary
                               habitats being destroyed
                               is the rain forest. In the
                               Amazon region alone,
                               more than one third of
                               the rain forests has been
                               destroyed. The habitat
                               of hundreds of songbirds
                               has gone with it.




                                   Illegal logging of the rain forest
                                   near La Amistad Biosphere
                                   Reserve in Costa Rica

[ 146 ]
Several large felines are endangered. Removing the forest
canopy and burning the land add to the pollution of the
atmosphere. In 1987 biologists counted 1,000 golden toads
in the rain forest of Central America. Today they cannot                      Make Connections
find any.                                                                  by comparing my
   Another habitat being destroyed is the wetland. People                  experiences with what
                                                                           I’m reading.
build houses and roads right through wetlands. With the
destruction of wetlands, habitats for small marine animals                My Thinking
that are part of much larger ecosystems are disappearing.                 I remember seeing
These include frogs, toads, salamanders, and many                         footage of an oil
microorganisms. Birds that live in wetlands need to seek                  tanker spill on
other places to nest. Animals that come to drink in marshy                television. Volunteers
areas are deprived of water. With no place to hide, eat, or               were trying to save birds
                                                                          that were covered by oil
drink, an animal can soon disappear.
                                                                          and were unable to fly.

Pollution—Another Cause
   As people build cities, houses, factories, and roads, the
air is filled with smoke that is poisonous to plants and ani-
mals. People dump toxic chemicals in rivers. The chemi-
cals are swallowed by fish and other marine creatures.
Birds eat the fish and die. DDT, a pesticide used in the
1940s and 1950s, almost made several species of birds
extinct. The bald eagle, whose eggshells were made too
thin by DDT, almost disappeared in the 1960s. Since this
bird was placed on the endangered species list, it has
renewed itself. In 1999, the bald eagle was removed from
the endangered species list.
                                  Ecological disasters such as
                              fires, oil spills, wars, and glob-
                              al warming—caused mostly by
                              humans—are also causing
                              many species to rapidly
                              diminish.
                                                                       Vo • cab • u • lar • y
                                                                       felines (fee•lynz)—
                                                                       members of the cat family
                                                                       canopy (kan•uh•pee)—the
                                                                       covering of trees overhead
                                                                       microorganisms
                                                                       (my•kroh•or•guh•niz•uhmz)
                                      The bald eagle is no longer on
                                                                       —tiniest living things
                                      the endangered species list.


                                                                                                 [ 147 ]
                                    The Effect of Hunting and Collecting
                                       As people hunted animals for food, their fur, or their
                                    exotic skins or feathers, they did not realize that these
                                    animals could disappear.
                                       For example, in the early 1800s, there were so many
                                    passenger pigeons that flocks of them would block out the
                                    sun for as long as 8 hours at a time. By 1914, these birds
                                    were extinct. One reason is that people hunted them
   Bison like these were            because they were delicious to eat. People killed many
   brought back from the            others because they thought the birds were pests.
   edge of extinction.                                                       Other animals have
                                                                         been overhunted, too.
                                                                         In 1800, there were
                                                                         more than 60 million
                                                                         bison in the United
                                                                         States. By 1889, there
                                                                         were about 800. The
                                                                         bison had provided
                                                                         food, clothing, and
                                                                         shelter for the settlers
                                                                         as they moved west.
                                                                         No one believed bison
                                                                         could disappear.
                                                                         No one understood
                                                                         that they couldn’t
                                                                         reproduce as fast as
                                                                         they were killed. When
                                                                         conservationists
                                                                         realized the danger
                                                                         of losing the last bison,
                                    people intervened. Today, there are about 260,000 bison
                                    in the United States.

                                    Another Cause: Introduced Species
   Vo • cab • u • lar • y              As people have traveled around the globe, they have
                                    brought animals and plants with them. Often these species
   conservationists                 are introduced to habitats that are not suitable for them.
   (kon•sur•vay•shuhn•ists)—
   people who work to protect
                                    Sometimes the result is a loss of ecosystems for the native
   wildlife and the environment     plants and animals.
   intervened (in•tuhr•veend)
                                       In New England, people planted a flower called
   —came in to change a situation   Purple Loosestrife. It grows quickly and looks very pretty,


[ 148 ]
                            Purple Loosestrife,
                            a New England pest

                                                                  Make Connections
                                                               by comparing my
                            but it takes over the ponds        experiences with what
                            and wetlands where it lives.       I’m reading.
                            Because it is killing off
                            other plants, many native         My Thinking
                            plant species are now             We own cats
                                                              that live outside.
                            disappearing.
                                                              They help keep
                                During World War II, a        mice out of our barn.
                            small snake whose native habi-    That is like introducing
                            tat was the Solomon Islands,      a species.
                            New Guinea [gi•nee], and
                            northern Australia was acci-
                            dentally brought to the island
                            of Guam. On Guam this tiny
                            brown tree snake has eliminat-
                            ed several species of native
                            lizards. It has destroyed most
                            of the songbirds on the island,
                            too. It is also threatening
                            native bats. So far, no known
                            means of destroying it have
been found. Although nothing was done intentionally,
this is a good example of what can happen when people
introduce species into a new habitat.
   Is there anything that can be done to stop the mass        The tiny brown tree snake
extinction happening today?                                   has eliminated several
                                                              species of lizards.

Can Laws Have an Effect?
   In the United States the
Endangered Species Act of 1973
makes it illegal to “kill, hunt, collect,
harass, harm, pursue, shoot, trap,
wound, or capture any endangered
species.” It prohibits buying and sell-
ing species that are endangered and
protects critical habitat. Large fines
and jail terms are given to those who
break the law.

                                                                                         [ 149 ]
                                           The Convention on International Trade in Endangered
                                       Species of Wild Fauna and Flora (CITES) is an interna-
                                       tional treaty that protects endangered species worldwide.
       Make Connections                It also bans buying and selling endangered species.
    by comparing my                    However, not all nations obey this law. Whales are still
    experiences with what              hunted in some nations. Tigers, rhinoceros, elephants, and
    I’m reading.
                                       other unusual animals are still killed by
   My Thinking                         poachers for their skins and ivory.
   I think most
   people follow anti-
   litter laws, so I’m
   sure antihunting and
   antipoaching laws work
   for the environment.




                                       These pilot whales have been hunted in the Faroe Islands.



                                       Restoration of Species
                                          Animals that are in danger of extinction are protected
                                       in the United States. In some instances they are restored
                                       in captivity and then released in the wild. In 1986 there
                                       were only 2 California condors left in the wild. These
                                       magnificent birds were victims of DDT. In the past 14
   Vo • cab • u • lar • y              years, these birds have been bred and raised in captivity.
   poachers (poh•chuhrz)—              Today they are being released in small numbers into the
   people who hunt or fish illegally   wild again. The entire world population has reached 198.


[ 150 ]
Education
   Much is being done throughout
the world to educate people about
the dangers of extinction. Efforts
are being made to slow pollution,
reduce logging, and limit or ban
hunting. A worldwide effort is
being made to save animals and
plants. National parks, preserves,
and conservation land are being
saved to protect habitats. It is
hoped that the tales of the dodo
bird, passenger pigeon, and gold-
en toad will not be repeated.
Instead, stories of animals that
have been saved—the California
condor, the bison, and the giant                                          The California condor
panda—will be more common.
   Humans have caused this latest mass extinction, and
only humans can stop it. They can change how they treat
the planet Earth and all its living things.




      Think About
            the

                                AFTER READING

               Recall
               by using the headings to question myself about
               what I read.

                  My Thinking
                  The strategy says to use the headings to question
                  myself about what I read. “What Is Extinction?” It is
                  the total elimination of a species. “Modern Causes”:
                  The modern causes for extinction are habitat destruc-
                  tion, pollution, hunting, and introduced species.


                                                                                          [ 151 ]
   Organizing Information


                               Graphic organizers help us organize information. I think this article
                               can be organized by using a cause-and-effect chart. Here is how I
                               organized the information. I listed initial causes of a few events.
                               Then I listed what the effects were.




                               Cause-and-Effect Chart
                                       Going, Going, Gone
                       Causes                                               Effects

          The Ordovician extinction was                       Widespread glaciation occurred;
          caused by a sudden cooling of                       20%–50% of all species became
          Earth.                                              extinct.
          Late Devonian extinction was                        Many fish and marine
          caused by cooling, especially in                    invertebrates died. About 1/4 of
          the seas.                                           all species became extinct.

          Permian extinction was caused by                    Half of all living things
          either rapid warming or by Earth                    disappeared.
          being struck by a large object.
          Late Triassic extinction was
                                                              One third of all plants and
          caused by volcanic eruptions and
                                                              animals disappeared.
          asteroid impacts.
          Late Cretaceous extinction was
                                                              Fifteen percent of all species
          caused by a comet hitting
                                                              (including dinosaurs) disappeared.
          Central America.
          Current Holocene extinction is                      Nearly 1,000 species are
          caused by people polluting and                      becoming extinct each year.
          destroying natural habitats.




[ 152 ]
                                                    Writing for Comprehension


I used my graphic organizer to write a summary of the article.
Can you find the information in my summary that came from
my cause-and-effect chart?


                            A Summary of
                     Going, Going, Gone
                                                                              Introduction
  It seems as if Earth is much the same every day, just changing with         Here is how I developed
the seasons. In fact, Earth has experienced sudden and shattering             my introductory para-
                                                                              graph. It gives readers
changes. These changes have shaped our lives today. Scientists have
                                                                              an idea of what they
identified 6 major extinctions and their results.                             are about to read.
  The first extinction that we know about happened during the
Ordovician Period. About 440 million years ago, Earth’s surface
suddenly cooled. This change caused widespread glaciers to form,
even over tropical land. As a result, 20 to 50 percent of all the             Body
                                                                              I used information from
species on Earth became extinct.
                                                                              the cause-and-effect
  The next extinction came during the Devonian Period, 360 million            chart for each para-
years ago. The same kind of cooling seems to have occurred again.             graph in the body of
This time, it killed about 1/4 of all species. That included many fish and    my paper.
marine vertebrates.
  The third major extinction happened during the Permian Period. It
was about 250 million years ago. Earth either experienced a rapid
warming, or it was struck by a large object. Half of all living things dis-
appeared.
  The fourth extinction occurred during the Late Triassic Period.
Volcanic eruptions and the impact of asteroids probably caused this
extinction. One third of all plants and animals were destroyed, but
not the dinosaurs.
    The fifth extinction dates to the Cretaceous Period. Scientists think
that a comet hit Central America. This impact set off changes that
killed 15 percent of all species. This time, the dinosaurs were victims,
too.
  You are living through the sixth extinction. We are now in the
Holocene Period. Unlike the other extinctions, this one is happening
slowly and quietly. It occurs daily as people pollute and destroy
                                                                              Conclusion
natural habitats. We are losing about 1,000 species every year.               I concluded my paper by
   At last, we have an extinction we can control, but will we?                asking the reader for a
                                                                              response.

                                                                                                [ 153 ]
 Developing



              Word Origins
              Scientific classification groups all known living things into a class,
              family, genus, and species. The names for all of these categories
              come from Greek and Latin words.
              For example, humans belong to the class of mammals. Mammal
              comes from the Latin word mamma, meaning “breast,” because
              mammals are fed from their mother’s breast.
              In “Going, Going, Gone,” you learned that several large felines, or
              cats, are endangered. Felis is the genus name for cats, both domes-
              ticated and wild. Cats are also mammals, but they are of the
              Felidae family.



                 Match the class, family, or genus name from the list with the
                 Greek and Latin words and meanings. Write your answers on
                 a separate sheet of paper.

                           a. Reptila    b. Amphibia      c. Arachnida

                                   d. Muridae        e. Canis

                     1. The family of rats and mice is derived from the Latin
                        word mus, meaning “mouse.”
                     2. The class that includes frogs is derived from the Greek
                        word amphi, meaning “both,” and bios, meaning
                        “life.”
                     3. The class of alligators is derived from the Latin word
                        reptilis, meaning “creeping.”
                     4. The genus of dogs is derived from the Latin word
                        caninus, meaning “conelike tooth.”
                     5. This class is derived from the Latin word arachnida,
                        meaning “spider.”




[ 154 ]
                                                                      Developing



  Poetry
  Practice reading this poem about the endangered chimpanzee
  with a partner. Alternate stanzas with your partner. When you
  are ready, perform the poem for your class.

      ency
      ➢ TIP
Flu




                    This poem encourages people to battle against
                    animal extinction. Read it as a radio announcer
                    might. Use your voice to convince people to
                    take action.


                       Won’t You Help, Please?
                The habitat of the chimpanzee
                Is disappearing too rapidly.
                Deforestation is the reason
                For increased vulnerability.

                Foreign hardwood logging companies
                Make it easy to cut down the trees—
                Leaving the chimp without a place
                To hide, to hunt, or to just run free.

                What about the innocent babies?
                Sold to the circus so that maybe
                We can see something entertaining.
                A laugh is not worth a life, you see.

                It’s disease, shock, and malnutrition
                That have put chimps in this position.
                The ones that survive are mistreated.
                Giving chimps help should be our mission.

                Jane Goodall insisted we protect
                The chimpanzee from callous neglect.
                She studied them so that you and I
                Would always care and never forget.



                                                                            [ 155 ]

				
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