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Overview:
In this lesson, students will consider the significance of the hammerhead shark's "hammer." They will watch two videos and compare the way hammerhead sharks and white sharks swim. Students will click through an interactive shark diagram to learn about sharks' senses, and hypothesize about how hammerheads' head shape might enable them to use their senses differently from other types of shark. They will conclude by writing paragraphs answering the question: "What good is the 'hammer' for a hammerhead shark?"
Connections to the Curriculum:
Geography, life science
Connections to the National Geography Standards:
Standard 8: "The characteristics and spatial distribution of ecosystems on Earth's surface"
Time:
One to two hours
Materials Required:
- Computer with Internet access
Objectives:
Students will
- list and discuss animals that have strange or unique physical features;
- compare and contrast two videos of sharks swimming (one of a hammerhead and the other of a white shark);
- click on an interactive shark diagram to see how sharks use their six senses and take notes on what they learn;
- hypothesize how hammerheads' oddly shaped heads enable them to use their senses differently or better than other sharks; and
- write paragraphs explaining the possible advantages of the "hammer."
Geographic Skills:
Asking Geographic Questions
Acquiring Geographic Information
Organizing Geographic Information
Answering Geographic Questions
Analyzing Geographic Information
S u g g e s t e d P r o c e d u r e
Opening:
Ask the class to name animals that are particularly strange-looking or that look different from most other animals. Their answers will vary, but they might mention giraffes, camels, spiders, flamingoes, etc. List their ideas on the board.
Ask students why they think some types of animals are so different from others. What can some of the animals on their list do that other animals can't? Do these animals have special features that allow them to survive in places where they might otherwise not be able to live? Discuss students' ideas and examples.
Development:
Have students look at this picture of hammerhead sharks. Ask them why they think an animal would have such a strange-shaped head, and discuss their ideas.
Have students watch two videos:
- First, show this video of hammerhead sharks swimming (click on the first video at the top of the page). Ask them to describe the things they notice about the way hammerheads swim. How do they move through the water?
- Next, watch a National Geographic video of a great white shark swimming (click on "Video"). Ask students to compare the white shark's swimming style to that of the hammerhead. Do they think the "hammer" provides an advantage or a disadvantage, or do both sharks appear to swim with equal ease through the water?
[Note: There is no right or wrong answer to the above question; both sharks have adapted to their "head style" and seem to swim with ease. This question is intended to get students to observe the sharks swimming and to think about how the "hammer" affects motion.]
Ask students to make charts with two columns. They should label the first column "Sharks' Six Senses" and the second column "Hammerheads."
Have students look at this Web page about sharks' six senses. Ask them to try to locate each of the six senses. As they explore, have students list each sense in the first column and write one or two sentences describing how sharks use it.
After they have found all six senses, ask students to look at this picture of hammerheads again. Ask them to think about how a hammerhead's body structure (primarily its head shape) might allow it to use its senses differently or perhaps better than a non-hammerhead shark. Have them write their ideas in the second column of their charts. They will get some clues by reading the text under the picture.
Closing:
Discuss as a class what students have written in the "Hammerhead" column. Why do they think the hammerhead's head is shaped as it is? Can they see any advantages for it to have this shape? If so, do they think these advantages are related to its ability to sense or to swim, or both?
Suggested Student Assessment:
Inform students that for a long time scientists have been trying to figure out why hammerheads have hammer-shaped heads. They have different ideas about why these sharks may have developed this unusual head shape while other sharks did not. Ask students to write paragraphs explaining their ideas about the question: "What good is the 'hammer' for a hammerhead shark?"
Extending the Lesson:
- Have students look at the Great White Shark coloring page. Ask them to create new coloring pages for hammerheads. They should include sketches from at least two different angles and a text caption.
- Have students imagine that they are living near the sea a thousand years ago and have not been exposed to scientific information about sharks (or about anything else). Have them write a myth explaining their idea of how the hammerhead got its "hammer."
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