Download OVERVIEW BIODIVERSITY BACKGROUND Biological Diversity

BIODIVERSITY
8
OVERVIEW
Students will look at the three differnt levels where biodiveristy exists and
how the interdependence of plants and animals becomes crucial to their
survival.
BACKGROUND
Biological Diversity
Biodiversity is the variety and the
abundance of species, their genetic
diversity, the communities, ecosystems, and landscapes in which these
species occur. In addition, biodiversity refers to the ecological structures,
functions, and processes at each of
these four levels. (Yahner, 1995,
p. 125)
As was noted in the previous section
on “Benefits of Pennsylvania Forests,”
more than 3,500 species of plants and
animals have been documented in the
various habitats throughout
Pennsylvania. The forests of the
Commonwealth contain more than 90
species of trees and two-thirds of
Pennsylvania’s native plants, creating
the primary habitat for 120 species of
birds and 50 species of mammals. The
variety of forest ecosystems within the
eastern deciduous forest provides habitat
for an incredible variety of plant and animal species — but in many cases that
diversity is being negatively affected by
human activity.
Pennsylvania has lost as many as
156 species of native vascular plants
and vertebrates in the past 300 years.
An additional 351 species have become endangered or threatened.
Moreover, 56 percent of
Pennsylvania’s wetlands have been
lost since 1780. Currently, habitat
destruction and fragmentation,
along with degradation from pollution, are the greatest threats to biodiversity. (Penn’s Woods, p.9)
Wetlands in Pennsylvania and elsewhere are being lost at an alarming rate.
Close to 45 percent of Pennsylvania’s
wetlands are forestland wetlands, such as
riparian (streamside) forests, temporary
ponds and spring seeps. These forested
wetlands are particularly important for
watershed protection and as wildlife
habitat.
Section II — Activity 8
There is concern about the maintenance of natural biodiversity worldwide
because of the realization that species are
being lost today at an unprecedented
rate. “An annual rate of extinction of
20,000 to 50,000 species of flora and
fauna (assuming a conservative 10 million total species) or 55 to 150 species
per day” is predicted by the year 2000
(Yahner, 1995, p. 1280). In Pennsylvania,
there are numerous reasons for the loss
of species. Some of these reasons include
habitat loss and fragmentation, pollution, and competition from exotic
species.
How much biodiversity is enough?
This is a difficult question to answer.
The loss of even one species could have
damaging effects on an ecosystem and
its organisms in ways that are not yet
understood. This can be especially true if
the species is a key link between other
organisms in the ecosystem.
Ecologists and foresters have recognized the advantages of a diverse stand
of tree for some time. Diverse stands
provide habitat for a wider array of
plants and animals, and are less likely to
be destroyed by an epidemic of disease
or insect attack.
Plants and animals have a variety of
values and benefits, some not yet known
or recognized by humans. Not only do
many provide major sources of food, but
some are also important for the prevention and cure of human illnesses.
Maintaining or restoring biodiversity is
essential to sustain all the many benefits
of the eastern deciduous forest.
Wetlands include areas like freshwater and saltwater marshes, wet meadows,
swamps, lagoons, bogs and prairie potholes. All wetlands, whether coastal or
inland, provide special habitats that
serve areas far beyond their boundaries.
Wetlands are uniquely important to
plants, animals, humans and the total
environment.
Biodiversity exists at three different
levels: ecosystem diversity, species diver-
GRADE LEVELS:
Grades 6–9
OBJECTIVES: Students will (1) explain the importance of biodiversity, (2)
describe the interdependence of living
things, and (3) describe how changes to
one species can affect another.
PENNSYLVANIA PROPOSED
ENVIRONMENT & ECOLOGY
STANDARDS ADDRESSED:
4.3.7
C. Explain biological diversity.
D. Explain biological diversity and the
interdependence of living things on
earth.
4.3.10
C. Explain biological diversity as an indicator of a healthy environment.
D. Analyze the need for a healthy environment.
ESTIMATED DURATION: one or
two 30 to 60 minute periods
MATERIALS NEEDED: copies of
student pages.
Biodiversity 77
sity, and genetic diversity. Learning about
these different levels will help you understand the full importance of biodiversity.
Ecosystem diversity: an ecosystem is
a community of living organisms in a
particular environment and the nonliving things with which it interacts. A
desert, for instance, is an ecosystem that
includes organisms such as cacti, lizards,
and birds and nonliving parts such as
sandy soil, rocks, and sunlight.
Ecosystem diversity is used to refer to
the various large categories of ecosystems called biomes, such as a desert or
rain forest, as well as smaller ecosystems,
such as riverbank or the north side of a
mountain. The organisms in an ecosystem depend on each other and on the
non-living parts for survival.
Species diversity: species diversity is
often what is meant when the term biodiversity is used. Species diversity is the
remarkable variety of species of living
things – plants, animals, fungi, and microorganisms. It is not known how
many different species there are on
earth. Over 1.4 million have been identified, and millions have yet to be determined. In the 1980’s, scientists
estimated there were about 5 million
species in total. But as they have done
more studies, especially in tropical
forests where species diversity is enormous, their estimates have gone up and
up — to over 30 million. In fact, some
research suggests there may be 30 million species of insects alone.
Genetic diversity: each individual organism has thousands of genes that determine its characteristics — its color,
height, weight, shape, resistance to disease, and so forth. A common group of
genes, called the gene pool, exists for
each species. Individual members of a
species develop with different genes
drawn from the gene pool, which results
in genetic diversity. Because of this genetic diversity, organisms can evolve and
adapt to changes in their environment,
including developing the ability to survive diseases.
Wild plants and animals have more
varied characteristics — that is, more genetic diversity — than cultivated ones.
Individual plants of a cultivated crop, for
example, all have the same genes, and
none may have the characteristic to
fight a particular disease.
78 Biodiversity
PROCEDURES
1. Hand out copies of “Student Pages,”
briefly lead a class discussion to answer the “pre-activity questions.”
◆ What is biodiversity? (Answer: biodiversity refers to the variety of living things on earth.)
◆ Why is biodiversity important?
(Answer: biodiversity helps to ensure the health of the planet by
maintaining the balance of living
things and providing building
blocks of evolution.) Encourage
students to give examples of why
they think biodiversity is important.
2. Have students read the passage under
“Activity A” and discuss how habitat
changes can affect biodiversity in
positive and negative ways. Use the
background information above to
help facilitate the discussion. Then
have students study the graph that
shows species loss during this century
and answer the questions. Students
should recognize that the rate of extinction has sharply increased in the
last decade. The reason for the increase is habitat destruction. Answers
to questions:
◆ What do living things need in
order to survive? (Answer: responses include clean water, food, clean
air, each other.)
◆ How do living things depend on
each other? (Answer: responses include providing food sources, protection, balance of predators and
prey.)
◆ What is an extreme result of habitat loss? (Answer: students should
realize that extinction is the extreme result of habitat loss.)
3. Have students complete “Activity B.”
Encourage them to identify the interdependence of living things in the
landscape depicted in the activity.
Answers to questions:
◆ What features of this habitat can
you identify? (Answer: meadow,
field, trees, agriculture, plants and
wildlife.)
◆ What could happen to the biodiversity in this habitat if a flood
wiped out the corn crop? (Answer:
there would be fewer mice, which
would affect the snake, owl and
hawk populations.)
Section II — Activity 8
◆ Mice are an important source of
food for owls. How could the owls
be affected by the loss of the corn
crop? (Answer: they would not
have mice to eat.)
◆ How would the owls be affected by
the loss of the hawks? (Answer: the
owls might have more food to eat
because they wouldn’t be competing with hawks.)
◆ What other examples of interdependence can you identify?
(Answer: hawks eat snakes, snakes
eat mice, mice eat corn; the bird
nest in the trees and snags; the
snakes and mice nest in the
meadow.)
◆ What could you do to increase the
biodiversity in this habitat?
(Answer: possible answers include
plant more trees and shrubs.)
◆ What could happen if this habitat
were developed into a shopping
mall? (Answer: all of the animals
would need to find other places to
live.)
Section II — Activity 8
4. Activity C: have students share their
responses to the questions in
“Activity B.” Once students have
identified evidence of interdependence on the student sheet, have
them brainstorm a list of plants and
animals and then make their own
connections.
EXTENSIONS
■ Think about how you depend on
other species of plants and animals.
During the next 24 hours, have your
students keep track of all the things
their families use that are connected
to another species. For example, furniture comes from trees, clothing comes
from plants and animals, food comes
from plants and animals. Have them
list their connections on a piece of
paper. During the next class you may
wish to discuss these connections.
ASSESSMENT
(See Rubric for Biodiversity in General
Information Section)
Biodiversity 79