TITLE OF LESSON PLAN:
Bears

LENGTH OF LESSON:
Two class periods

GRADE LEVEL:
6-8

SUBJECT AREA:
Animals

CREDIT:
Lisa Lyle Wu, science teacher, Thomas Jefferson High School for Science and Technology, Alexandria, Virginia.

OBJECTIVES:
Students will understand the following:

1. Polar bears inhabit areas near the North Pole, where the climate is cold.

2. Polar bears exhibit physical adaptive characteristics that keep them warm in their cold habitat.

3. Guard hairs, the hollow outer hairs in a bear's coat, absorb the radiation of the sun.

4. Blubber acts as an insulator.

5. A polar bear's black skin absorbs more heat than light-colored skin can absorb.

MATERIALS:
Groups will require different materials, depending on the designs of their projects. Advise students to create designs that will require only easily obtained materials.

PROCEDURE:

1. Review with students what a polar bear looks like and where its habitat is located. (You may need to clarify that polar bears live near the North Pole; there are no polar bears in areas surrounding the South Pole.) Students should be aware that polar bears inhabit a generally cold climate.

2. Encourage students to conjecture about how polar bears stay warm in their cold habitat.

3. Most students will agree that a polar bear's thick fur keeps the animal warm. Let them know that polar bears exhibit additional physical adaptations for surviving in a cold climate.

4. Tell the class that the outermost hairs on a polar bear's body are called guard hairs. Unlike the fur beneath, the guard hairs are hollow. They absorb radiation from the sun and store the heat inside.

5. Tell students that polar bears have blubber, or a thick layer of fat, beneath their skin. Challenge students to guess why blubber helps a polar bear stay warm. (The blubber acts as an effective insulator, preventing body heat from escaping.)

6. Tell students that, while polar bears have white fur, their skin is black. Challenge students to guess why black skin is an advantage to an animal living in a cold climate. (Dark colors absorb more heat from the sun than do light colors.)

7. Divide the class into small groups, and challenge each group to design a model that would demonstrate the effectiveness of two or three adaptive characteristics you have discussed.

8. Each group should list the materials needed for each model, sketch and label their prototypes, and write a procedure that outlines the steps of the demonstrations.

9. Have each group complete and present at least one of its demonstrations.

ADAPTATIONS:

Have older students do research to discover for themselves which adaptive characteristics help polar bears keep warm in a cold climate. They may come up with behavioral characteristics, such as winter sleep (partial hibernation), as well as physical ones.

DISCUSSION QUESTIONS:

1. Compare the different species of bears. Discuss the characteristics they have in common despite their differences in habitats and physical appearance.

2. Explain the type of data that is studied to trace the evolutionary path of bears. Consider anatomical, biochemical, genetic, and behavioral.

3. Explain how an animal with a stomach designed to digest meat has adapted to a herbivorous diet.

4. Discuss the physical adaptations necessary for different bears to satisfy their various diets (insects, fruit, nuts, honey, fish).

5. Discuss the evolutionary significance of the presence of a sixth digit (or thumb) in the giant panda. 

6. Discuss what physiological changes would need to take place when an animal hibernates for several months.

7. Discuss characteristics that distinguish the giant panda from the rest of the bear family.

EVALUATION:

You can evaluate your students on their models using the following three-point rubric:
  
Three points:design clearly demonstrates effectiveness of each adaptation; prototype carefully executed and labeled; materials list complete; description of procedure well written
  
Two points:design adequately demonstrates effectiveness of each adaptation; prototype executed and labeled with sufficient care; materials list incomplete; description of procedure difficult to follow
  
One point:design fails to demonstrate effectiveness of each adaptation; prototype carelessly executed and labeled; materials list lacking or incomplete; description of procedure disorganized and difficult to follow
  
You can ask your students to contribute to the assessment rubric by determining criteria for the effectiveness of a model.

EXTENSION:

Home Sweet Home (for Bears)
Bears are omnivorous, and most require large home ranges to survive. It doesn't take much to disrupt a natural habitat. A new highway, a shopping center, the development of homes, or even a new recreational park can unbalance the ecosystem. Bears have suffered the most from the destruction of wilderness areas, but they have also been the victims of trophy hunting, poaching, and human contact. Invite your students to contact a wildlife conservancy (Bear Watch, for example) and find out what measures are being taken to protect bears from these threats.

Bear in Mind
Have your students check out “Cybearspace.” See if your class can join an “expedition” to follow on the Internet or at least find out the kind of research that is being done to learn more about bears in the wild. Examples are tracking, home range, migration patterns, and hibernation studies. (See Links.)

Shaped by the Bear
From constellations, to children's fairy tales, to teddy bears, to European folklore, bears have served as a source of inspiration for political symbolism, art, and literature. Bears have also been a source of subsistence (hide, meat, and handicraft) for Inuit and Alaskan Natives. Divide the class into small groups to research and report on the cultural influence of bears.

SUGGESTED READINGS:

Amazing Bears
Theresa Greenway. New York: Knopf, 1992.
Introduces the physical characteristics and habits of bears and pandas.

Bears: Animals that Hibernate
Isidro Sanchez
Describes the physical characteristics, habitat, behavior, and life cycle of these powerful mammals, who live on all of Earth's continent.

The Panda's Thumb
Stephen J. Gould. New York: Penguin, 1983.
The panda appears to use a “thumb” when stripping bamboo. In reality, it has to make do with a modified wrist bone. The eminently readable Stephen J. Gould explains why evolution is in many ways a tale of imperfection. 

WEB LINKS:

The Bear Den
This site provides information about several species of bears and conservation efforts.
http://www.bearden.org/

The Cub Den
This site developed specifically for students provides information about bears.
http://www.nature-net.com/bears/cubden.html

American Black Bear
This is an informational site provided by the US Fish & Wildlife Service about the American Black Bear.
http://www.fws.gov/r9extaff/biologues/bio_bear.html

Maine Black Bear Research and Field Study Activity
This Access Excellence lesson plan intended for high school students to use academic research to learn about mammals and specifically black bears.
http://www.gene.com/ae/AE/AEC/AEF/1996/brandt_bear.html

Bear Watch Home Page
This site provides information about the threats to bears in Canada and efforts to save them.
http://www.bearwatch.org/index.html

VOCABULARY:

prehensile
Adapted for seizing or grasping, especially by wrapping around.
Context:
Most bear lips are prehensile.

land bridge
A natural bridge connecting two pieces of land above water.
Context:
Two million years ago, it crossed the Panamanian land bridge into South America.

extinct
No longer existing.
Context:
The cave bear became extinct.

hibernate
To be or become inactive or dormant.
Context:
She loses 40% of her body weight during a four-to-six month hibernation.

adaptation
Adjustment to environmental conditions.
Context:
Adaptation is the key to survival in a cold climate.

ACADEMIC STANDARDS:

Grade Level:
6-8
Subject Area:
life science

Standard:
Understands how species depend on one another and on the environment for survival.

Benchmarks:
Knows that behavior is one kind of response an organism may make to an internal or environmental stimulus, and may be determined by heredity or from past experience; a behavioral response requires coordination and communication at many levels including cells, organ systems, and whole organisms.

Grade Level:
9-12
Subject Area:
life science

Standard:
Understands the basic concept of the evolution of species.

Benchmarks:
Knows that biological evolution accounts for a diversity of species developed through gradual processes over many generations; species acquire many of their unique characteristics through biological adaptation, which involves the selection of naturally occurring variations in populations.

Grade Level:
6-8
Subject Area:
life science

Standard:
Knows about the diversity and unity that characterize life.

Benchmarks:
Knows that although different species look very different, the unity among organisms becomes apparent from an analysis of internal structures, observation of the similarity of their chemical processes, and the evidence of common ancestry.

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