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 one animal's lifetime, but over several generations or longer. A trait or characteristic that has evolved to help a living thing survive in changing environmental conditions is called an adaptation. In this lesson you’ll learn about adaptations—especially, how an adaptation's structure (how it looks) is related to its function (how it's used).

Goals
Here are the big ideas you will learn about in this lesson:

• An adaptation is a physical feature or behavior that helps a living thing survive in its environment
• Adaptations develop as living things make changes to better fit in their environment
• Structure (how something looks) and function (what it's used for) of the adaptations are closely related

Strategies
You will be using many reading and writing strategies to complete this lesson. The key strategies that you will focus on are:

• Comparing and contrasting ideas
• Identifying and using text features
• Determining important information

• digestion
• survival

Sometimes we can tell what a body part does—how it helps an animal survive—just by looking at it. For animals, food is one of the most important components, or parts, of their environment. It should come as no surprise then that animals have different adaptations that make it easier for them to get the food they need for survival.

Choose one of the animals pictured on the left. For this animal, identify

1. its unique structure for getting food,
2. the kind of food you think it eats, and
3. how this structure is good for getting that kind of food.

Adaptations improve an animal's chances for survival by making it better suited to its environmental conditions. Snakes and humans each have adaptations that help them eat. These structures are located in and around the jaws, which are the bones or bony parts that hold the teeth in place and give shape to the mouth.

In this video, you will see how each structure is specialized, or serves a specific purpose. For example, humans are omnivorous, which means they eat both plants and animals. We have several kinds of teeth to help us eat. Snakes are carnivorous, which means they eat only meat or flesh. When a snake eats, certain ligaments (tissue that connects two bones) allow its jaw to swing wide open—or "unhinge." Click "View" on the left to watch the video.

Then write down what the structure of a snake's mouth and jaw can tell you about its diet.

Think about what you have learned about the jaw structures of snakes and humans and how they function to get food into the body. In this activity, you will decide which adaptations belong to snakes and which belong to humans. You may want to watch the video again before doing the activity (see below).

Click "View" on the left to begin the activity. Your teacher will review the answers with you.

Unhinged!

Video
Length: 3m 45s

View

You have just learned that the way a jaw is shaped relates to its function in eating. Here are some examples of how structural adaptations in other animals are related to certain functions.

• To avoid being spotted by other animals that might eat them—or by ones they might be trying to eat—some insects use different colors or patterns to blend in with their environment. This adaptation is called camouflage.
• To better survive in the dark, animals that are active at night have evolved various adaptations. Owls have excellent night vision. Bats send out high-pitched sounds to find insects. And foxes and rabbits have large ears that improve their sense of hearing.
• To remain active in winter, many animals such as foxes and snowshoe hares have large furry feet that keep them from sinking into deep snow.

You've learned that animal species evolve different adaptations that help them survive in the environment in which they live. In this passage, you will have a chance to read more about structural and behavioral adaptations and how these help improve a species' chances of survival.

Click "View" on the left to read the passage.

Then write down your ideas about how two of the species pictured on the left use the adaptation in the image to survive.

Now you will show what you have learned so far by choosing the correct answer to each of these three questions. Be sure to save all your answers before you go to the next screen.

You will now check your understanding of the vocabulary words for this lesson by placing them in sentences. Click "View" on the left to begin the activity.

Before moving to the next screen, choose two words from the vocabulary list and write a new sentence for each word.

Vocabulary words: feature, evolve, adaptation, digestion, survival

In this lesson, you have learned about adaptations—both structural and behavioral—that evolve over time to help living things survive. You will now write an essay that shares what you have learned and what you think about it.

Begin by reviewing your notes. Click "review my work" above and view or print out the screen that pops up.

Final Assignment Instructions

• Click Snake Jaws: Connecting Structure and Function—Final Assignment (PDF).
• Choose one of the topics in the PDF and write an essay.
• Organize your response so that it includes at least three supporting details that you have learned from the reading passage, video(s), and other materials in this lesson.
• Use at least three vocabulary words (or form of the words) as part of your supporting details.