Introduction:
Snake Jaws: A Lesson in Evolution

Each part of your body—your eyes, limbs, skin, and teeth—has a specific function to perform. Each of these specialized functions helps you, as a human being, survive. How might this be true in other living things, as well?

The purpose of this activity is to help you understand that an animal’s physical characteristics, such as the specialized jaw structures of snakes, play a particular role in how that animal interacts with its environment.

Next: Why Are Animals Different from Each Other?

As an environment changes, the animals that live there must respond to the changes in order to survive. Some responses need to be made quickly. For example, if disease strikes an animal's normal food source, it must find another source. Most other responses take place very gradually at the species level. This means they do not happen during an individual's lifetime, but over several generations or longer. This type of response is called an evolutionary adaptation.

For example, a mammal might evolve a white fur pelt to help it blend into a snowy environment, or a bird might evolve a long-pointed beak to reach nectar deep inside a flower.

Using what you already know, list three examples of body parts found on different animals. Next to the body parts, write any ideas you have for why that particular feature appears or functions the way it does for that animal in its environment. You may want to limit your thinking to mammals, birds, and reptiles.

Write your text in the box below, then click "save notes" before moving on to the next page.

Next: Creature Features

Sometimes we can tell what a body part does, and the survival advantages it provides, just by looking at it. For animals, food is one of the most important components of the environment. For each of the animals shown here, identify:

• its unique structure for getting food,
• the kind of food you think it eats, and
• how this structure is especially suited to the function of getting that kind of food.

Write your text in the box below, then click "save notes" before moving on to the next page.

Next: Human and Snake Jaws: Watch This!

The environment plays a dramatic role in shaping the evolutionary changes that species undergo. Evolutionary adaptations improve an animal's chances for survival by making it better suited to its environmental conditions.

Watch this video segment to learn some of the important adaptations that snakes and humans each possess that help them eat. As you watch, notice how each structure serves a distinct purpose. (For example, human teeth help us eat different kinds of food, and the snake's glottis helps it breathe as it fills its mouth with prey.)

Note: You will hear the following words in the video segment. Click on each word to see its definition.

• gullet
• constriction
• immobilize
• envenomation
• carnivorous diet

After you've finished watching, write down what the structure of a snake's mouth and jaw can tell you about its diet.

Write your text in the box below, then click "save notes" before moving on to the next page.

Next: Try This!

Think about what you have learned about the jaw structures of snakes and humans and how they function to deliver food into the body. In this activity, you'll be asked to identify which evolutionary adaptations relate to snakes and which relate to humans.

Click "View" on the left to begin the activity. Be sure to print your notes before you exit the activity. Your notes will not be saved.

If you want, you can also watch the video again.

Unhinged!

QuickTime Video
Length: 3m 46s

Next: Did You Know?

You've just learned that the way a jaw is shaped relates to its function in eating. Here is information about how certain structural adaptations are related to other functions.

• To better survive in the dark, nocturnal animals have evolved with various adaptations. Owls have excellent night vision, bats emit high-pitched sounds to locate insects, and foxes and rabbits have large ears that heighten their sense of hearing.
• To remain active in winter, many animals such as wolverines and snowshoe hares have large furry feet that keep them from sinking into deep snow.
• To avoid being detected by both would-be predators and prey, some insects have evolved various forms of camouflage to blend in with their environment. For example, the body shape and color of a praying mantis can resemble the leaves or even flowers of plants in its habitat.

Next: Read and Write About It!

Now you will have a chance to demonstrate what you've learned about evolutionary adaptations.

• Print out your notes. (After you print, your notes will be erased. Make sure you are done before printing.)
  
  
• Print out and read Evolutionary Adaptations (Version A) (PDF) or Evolutionary Adaptations (Version B) (PDF). Check with your teacher if you are not sure which version to use.
• After reading, take a look at your chart and make any changes or add new information.
• Then, select and complete a writing assignment on page 2 of the printout.

Note: The following words will appear in the readings. Click on each word to see its definition.

Version A

• climate

Version B

• climate
• common ancestor
• gene pool