OVERVIEW BIODIVERSITY BACKGROUND Biological Diversity by jianghongl


   Students will look at the three differnt levels where biodiveristy exists and
   how the interdependence of plants and animals becomes crucial to their

BACKGROUND                                          There is concern about the mainte-
Biological Diversity                           nance of natural biodiversity worldwide       GRADE LEVELS:
                                               because of the realization that species are   Grades 6–9
    Biodiversity is the variety and the
                                               being lost today at an unprecedented          OBJECTIVES: Students will (1) ex-
    abundance of species, their genetic
                                               rate. “An annual rate of extinction of        plain the importance of biodiversity, (2)
    diversity, the communities, ecosys-                                                      describe the interdependence of living
                                               20,000 to 50,000 species of flora and
    tems, and landscapes in which these                                                      things, and (3) describe how changes to
                                               fauna (assuming a conservative 10 mil-        one species can affect another.
    species occur. In addition, biodiversi-
                                               lion total species) or 55 to 150 species
    ty refers to the ecological structures,                                                  PENNSYLVANIA PROPOSED
                                               per day” is predicted by the year 2000
    functions, and processes at each of                                                      ENVIRONMENT & ECOLOGY
                                               (Yahner, 1995, p. 1280). In Pennsylvania,     STANDARDS ADDRESSED:
    these four levels. (Yahner, 1995,
                                               there are numerous reasons for the loss       4.3.7
    p. 125)                                                                                  C. Explain biological diversity.
                                               of species. Some of these reasons include
    As was noted in the previous section                                                     D. Explain biological diversity and the
                                               habitat loss and fragmentation, pollu-           interdependence of living things on
on “Benefits of Pennsylvania Forests,”         tion, and competition from exotic                earth.
more than 3,500 species of plants and          species.                                      4.3.10
animals have been documented in the                 How much biodiversity is enough?         C. Explain biological diversity as an indi-
various habitats throughout                                                                     cator of a healthy environment.
                                               This is a difficult question to answer.       D. Analyze the need for a healthy envi-
Pennsylvania. The forests of the               The loss of even one species could have          ronment.
Commonwealth contain more than 90              damaging effects on an ecosystem and
species of trees and two-thirds of                                                           ESTIMATED DURATION: one or
                                               its organisms in ways that are not yet        two 30 to 60 minute periods
Pennsylvania’s native plants, creating         understood. This can be especially true if
the primary habitat for 120 species of         the species is a key link between other       MATERIALS NEEDED: copies of
birds and 50 species of mammals. The           organisms in the ecosystem.                   student pages.
variety of forest ecosystems within the             Ecologists and foresters have recog-
eastern deciduous forest provides habitat      nized the advantages of a diverse stand
for an incredible variety of plant and an-     of tree for some time. Diverse stands
imal species — but in many cases that          provide habitat for a wider array of
diversity is being negatively affected by      plants and animals, and are less likely to
human activity.                                be destroyed by an epidemic of disease
    Pennsylvania has lost as many as           or insect attack.
    156 species of native vascular plants           Plants and animals have a variety of
    and vertebrates in the past 300 years.     values and benefits, some not yet known
    An additional 351 species have be-         or recognized by humans. Not only do
    come endangered or threatened.             many provide major sources of food, but
    Moreover, 56 percent of                    some are also important for the preven-
    Pennsylvania’s wetlands have been          tion and cure of human illnesses.
    lost since 1780. Currently, habitat        Maintaining or restoring biodiversity is
    destruction and fragmentation,             essential to sustain all the many benefits
    along with degradation from pollu-         of the eastern deciduous forest.
    tion, are the greatest threats to biodi-        Wetlands include areas like freshwa-
    versity. (Penn’s Woods, p.9)               ter and saltwater marshes, wet meadows,
    Wetlands in Pennsylvania and else-         swamps, lagoons, bogs and prairie pot-
where are being lost at an alarming rate.      holes. All wetlands, whether coastal or
Close to 45 percent of Pennsylvania’s          inland, provide special habitats that
wetlands are forestland wetlands, such as      serve areas far beyond their boundaries.
riparian (streamside) forests, temporary       Wetlands are uniquely important to
ponds and spring seeps. These forested         plants, animals, humans and the total
wetlands are particularly important for        environment.
watershed protection and as wildlife                Biodiversity exists at three different
habitat.                                       levels: ecosystem diversity, species diver-
Section II — Activity 8                                                                                            Biodiversity 77
sity, and genetic diversity. Learning about   PROCEDURES
these different levels will help you under-   1. Hand out copies of “Student Pages,”
stand the full importance of biodiversity.       briefly lead a class discussion to an-
    Ecosystem diversity: an ecosystem is         swer the “pre-activity questions.”
a community of living organisms in a             x What is biodiversity? (Answer: bio-
particular environment and the nonliv-              diversity refers to the variety of liv-
ing things with which it interacts. A               ing things on earth.)
desert, for instance, is an ecosystem that       x Why is biodiversity important?
includes organisms such as cacti, lizards,          (Answer: biodiversity helps to en-
and birds and nonliving parts such as               sure the health of the planet by
sandy soil, rocks, and sunlight.                    maintaining the balance of living
Ecosystem diversity is used to refer to             things and providing building
the various large categories of ecosys-             blocks of evolution.) Encourage
tems called biomes, such as a desert or             students to give examples of why
rain forest, as well as smaller ecosystems,         they think biodiversity is impor-
such as riverbank or the north side of a            tant.
mountain. The organisms in an ecosys-         2. Have students read the passage under
tem depend on each other and on the              “Activity A” and discuss how habitat
non-living parts for survival.                   changes can affect biodiversity in
    Species diversity: species diversity is      positive and negative ways. Use the
often what is meant when the term bio-           background information above to
diversity is used. Species diversity is the      help facilitate the discussion. Then
remarkable variety of species of living          have students study the graph that
things – plants, animals, fungi, and mi-         shows species loss during this century
croorganisms. It is not known how                and answer the questions. Students
many different species there are on              should recognize that the rate of ex-
earth. Over 1.4 million have been identi-        tinction has sharply increased in the
fied, and millions have yet to be deter-         last decade. The reason for the in-
mined. In the 1980’s, scientists                 crease is habitat destruction. Answers
estimated there were about 5 million             to questions:
species in total. But as they have done          x What do living things need in
more studies, especially in tropical                order to survive? (Answer: respons-
forests where species diversity is enor-            es include clean water, food, clean
mous, their estimates have gone up and              air, each other.)
up — to over 30 million. In fact, some           x How do living things depend on
research suggests there may be 30 mil-              each other? (Answer: responses in-
lion species of insects alone.                      clude providing food sources, pro-
    Genetic diversity: each individual or-          tection, balance of predators and
ganism has thousands of genes that de-              prey.)
termine its characteristics — its color,         x What is an extreme result of habi-
height, weight, shape, resistance to dis-           tat loss? (Answer: students should
ease, and so forth. A common group of               realize that extinction is the ex-
genes, called the gene pool, exists for             treme result of habitat loss.)
each species. Individual members of a         3. Have students complete “Activity B.”
species develop with different genes             Encourage them to identify the inter-
drawn from the gene pool, which results          dependence of living things in the
in genetic diversity. Because of this ge-        landscape depicted in the activity.
netic diversity, organisms can evolve and        Answers to questions:
adapt to changes in their environment,           x What features of this habitat can
including developing the ability to sur-            you identify? (Answer: meadow,
vive diseases.                                      field, trees, agriculture, plants and
    Wild plants and animals have more               wildlife.)
varied characteristics — that is, more ge-       x What could happen to the biodi-
netic diversity — than cultivated ones.             versity in this habitat if a flood
Individual plants of a cultivated crop, for         wiped out the corn crop? (Answer:
example, all have the same genes, and               there would be fewer mice, which
none may have the characteristic to                 would affect the snake, owl and
fight a particular disease.                         hawk populations.)

78 Biodiversity                                                                               Section II — Activity 8
   x Mice are an important source of       4. Activity C: have students share their
     food for owls. How could the owls        responses to the questions in
     be affected by the loss of the corn      “Activity B.” Once students have
     crop? (Answer: they would not            identified evidence of interdepen-
     have mice to eat.)                       dence on the student sheet, have
   x How would the owls be affected by        them brainstorm a list of plants and
     the loss of the hawks? (Answer: the      animals and then make their own
     owls might have more food to eat         connections.
     because they wouldn’t be compet-
     ing with hawks.)                      EXTENSIONS
   x What other examples of interde-       s Think about how you depend on
     pendence can you identify?              other species of plants and animals.
     (Answer: hawks eat snakes, snakes       During the next 24 hours, have your
     eat mice, mice eat corn; the bird       students keep track of all the things
     nest in the trees and snags; the        their families use that are connected
     snakes and mice nest in the             to another species. For example, furni-
     meadow.)                                ture comes from trees, clothing comes
   x What could you do to increase the       from plants and animals, food comes
     biodiversity in this habitat?           from plants and animals. Have them
     (Answer: possible answers include       list their connections on a piece of
     plant more trees and shrubs.)           paper. During the next class you may
   x What could happen if this habitat       wish to discuss these connections.
     were developed into a shopping
     mall? (Answer: all of the animals     ASSESSMENT
     would need to find other places to    (See Rubric for Biodiversity in General
     live.)                                Information Section)

Section II — Activity 8                                                                Biodiversity 79

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