In this activity, you will compare certain physical characteristics of Grizzly and Polar bears. Use the images provided and the Flash animation for your investigation.

A. Observe and Record

Step 1: Skulls

Compare the profiles of the two bears, referring to the 3D Flash animation and skull photos. At the end of this step, note down your observations about profile, forehead, muzzle, etc.

Step 2: Teeth

Compare the teeth of the two bears using the photos. At the end of this step, note down your observations about their shape, size, number, etc.

Step 3: Paws

Compare the paws of the two bears using the photographs. At the end of this step, note down your observations about comparative size, presence of fur, shape, etc.

Step 4: Claws

Compare the claws of the two bears using the photographs. At the end of this step, note down your observations about comparative length, shape, comparative thickness, etc..

B. Questions

Now that you have studied the images and recorded your observations, answer the following questions. Read More

In this activity, you will compare certain physical characteristics of Grizzly and Polar bears. Use the images provided and the Flash animation for your investigation.

A. Observe and Record

Step 1: Skulls

Compare the profiles of the two bears, referring to the 3D Flash animation and skull photos. At the end of this step, note down your observations about profile, forehead, muzzle, etc.

Step 2: Teeth

Compare the teeth of the two bears using the photos. At the end of this step, note down your observations about their shape, size, number, etc.

Step 3: Paws

Compare the paws of the two bears using the photographs. At the end of this step, note down your observations about comparative size, presence of fur, shape, etc.

Step 4: Claws

Compare the claws of the two bears using the photographs. At the end of this step, note down your observations about comparative length, shape, comparative thickness, etc..

B. Questions

Now that you have studied the images and recorded your observations, answer the following questions.

1. What are the differences between the Grizzly and Polar bear skulls? State a hypothesis that could explain these differences.

2. What are the differences between the teeth of the two bears? State a hypothesis that could explain these differences.

3. What are the differences between the paws? State a hypothesis that could explain these differences.

4. What are the differences between the claws? State a hypothesis that could explain these differences.

5. What habitat-related factors could explain these differences?

C. Extrapolation

Make extrapolations from the results of the skull analyses, and prepare a short presentation explaining how the skull and teeth variations indicate the polar bear’s adaptation to its Arctic climate. How does climate change threaten the survival of polar bears in the Arctic?


© 2007, Canadian Museum of Nature. All Rights Reserved.

The underside of a Grizzly Bear paw

View of a Grizzly Bear paw. See how big the Grizzly Bear paw appears. It can measure over 30 cm. Notice the large toes, the claws that extend past the paw, and the padding underneath. The grizzly bear and the polar bear have about the same size of paw. The difference lies in the amount of fur beneath the paw and the length of their claws.

Andrew Derocher, Canadian Wildlife Service.

© 2007, Canadian Museum of Nature. All Rights Reserved.


The underside of a Polar Bear paw

View of a polar bear paw. See how big it appears. It can measure over 30 cm. Notice the big toes beneath the abundant fur, but no trace of claws. The grizzly bear and the polar bear have about the same size of paw. The difference lies in the amount of fur beneath the paw and the length of their claws.

Andrew Derocher, Canadian Wildlife Service.

© 2007, Canadian Museum of Nature. All Rights Reserved.


Grizzly Bear Claws

Notice the long, curved claws of the Grizzly Bear. They can be used to dig up roots. See how they differ from the polar bear’s claws. They can grow up to 13 cm in length on the fore paws. The hind paw claws are always shorter than the ones on the fore paws.

Andrew Derocher, Canadian Wildlife Service.

© 2007, Canadian Museum of Nature. All Rights Reserved.


Polar Bear claws

Notice the polar bear’s sharp, black claws. They can grow up to 7 cm. They are shorter than the grizzly’s claws, but pointier. They are sharper to provide traction on ice.

Andrew Derocher, Canadian Wildlife Service.

© 2007, Canadian Museum of Nature. All rights reserved.


Lateral view of a Grizzly Bear Skull

Left profile of the grizzly bear skull. Notice the shape of the head, the large canines and flat molars. The head is larger than the polar bear’s. Also take note of the more prominent forehead. This skull is 25 cm long. Imagine it covered with muscle and fur!

Paul Bloskie.
Alex Tirabasso, Annick Deblois.

© 2007, Canadian Museum of Nature. All Rights Reserved.


Lateral View of a Polar Bear Skull

Left profile of a polar bear skull. Notice the shape of the head, the pointy canines and the sharp premolars. The head is longer than the grizzly bear’s. This skull is 33 cm long. Imagine it covered with muscle and fur!

Paul Bloskie.
Alex Tirabasso, Annick Deblois.

© 2007, Canadian Museum of Nature. All Rights Reserved.


Ventral view of a Grizzly Bear Skull

View of a grizzly bear skull from below. Look for the zygomatic arches and you will see where the temporal muscle that powers the jaw runs. Also take note of the grizzly bear’s molars, which are larger but also appear flatter than the polar bear’s. This is probably due to the fact that the grizzly’s omnivorous diet is largely derived from plants.

Paul Bloskie.
Alex Tirabasso, Annick Deblois.

© 2007, Canadian Museum of Nature. All Rights Reserved.


Ventral view of a Polar Bear Skull

View of a polar bear skull from below. You have probably noticed that the zygomatic arches are incomplete. Nevertheless, you can see where the temporal muscle that powers the jaw runs. Also take note of the polar bear’s molars. They seem sharper than the grizzly’s, which is probably due to the polar bear’s carnivorous diet.

Paul Bloskie.
Alex Tirabasso, Annick Deblois.

© 2007, Canadian Museum of Nature. All Rights Reserved.


3D Rotation of Grizzly bear skull

3D rotation of Grizzly Bear skull

Alex Tirabasso

© 2007, Canadian Museum of Nature. All Rights Reserved.


3D Rotation of Polar bear skull

3D rotation of Polar Bear skull

Alex Tirabasso

© 2007, Canadian Museum of Nature. All Rights Reserved.


Learning Objectives

• Examine the factors (natural and external) that affect the survival and equilibrium of populations in an ecosystem.

• Show that species evolve and survive because of their ability to adapt.

• State a prediction and a hypothesis based on available evidence and background information

• Explain why different ecosystems respond differently to short-term stresses and long-term changes

• Formulate hypotheses regarding the effects of modifying the interactions that occur within a given ecosystem.


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