GRADE LEVEL: 5-8

TOPIC/SUBJECT MATTER: Life Science

TIME ALLOTMENT: One to two 45-minute class periods

OVERVIEW:

During this video-enhanced lesson, students will watch video segments from the NATURE film “The Secret World of Sharks and Rays” and learn about adaptations that have helped sharks and rays survive. Students will explore similarities and differences between sharks, rays and other fish. They will watch segments that provide information about physical features and behaviors that have helped sharks and rays survive, with specific attention paid to the angel, wobbegong and saw sharks and the electric, sting and manta rays. Students will work in small groups to research a specific type of shark or ray and share their findings with the class. Students will discover that different types of sharks and rays have different temperaments and diets and that some of the largest sharks and rays are the most gentle.

MEDIA RESOURCES

Video

Clip 1

Fish, Sharks and Rays: A comparison of fish, sharks and rays.

Clip 2

A Close Look at Sharks: A close look at angel, wobbegong and saw sharks and their survival techniques.

Clip 3

A Close Look at Rays: A close look at electric, sting and manta rays and their survival techniques.

Access the streaming and downloadable video segments for this lesson at the Video Segments Page.

Web sites

Ichthyology at the Florida Museum of Natural History

This site features a rich variety of information, games and photographs of a variety of fish, including sharks and rays. The following sections are recommended for this lesson:

• Sharks- This section features information, games and photographs of sharks.
• Biological Profiles- This section provides photographs and detailed information about specific sharks and rays, as well as other fish.

Kidzone Fun Facts for Kids: Sharks

This Web site features a variety of photographs, activities and facts about sharks.

National Geographic: Sharks
This Web site features many photos and facts about sharks, which can be used in this lesson.

Seaworld: Sharks and Rays

This site contains a variety of facts, photographs and diagrams of sharks and rays.

STANDARDS:

National Science Education Standards, Grades 5-8

LIFE SCIENCE: Content Standard C

As a result of their activities in grades 5-8, all students should develop understanding of

• Regulation and behavior
  • Behavior is one kind of response an organism can make to an internal or environmental stimulus. A behavioral response requires coordination and communication at many levels, including cells, organ systems, and whole organisms. Behavioral response is a set of actions determined in part by heredity and in part from experience.
  • An organism’s behavior evolves through adaptation to its environment. How a species moves, obtains food, reproduces, and responds to danger are based in the species’ evolutionary history.
• Populations and ecosystems

• Populations of organisms can be categorized by the function they serve in an ecosystem. Plants and some microorganisms are producers-they make their own food. All animals, including humans, are consumers, which obtain food by eating other organisms. Decomposers, primarily bacteria and fungi, are consumers that use waste materials and dead organisms for food. Food webs identify the relationships among producers, consumers, and decomposers in an ecosystem.

• Diversity and adaptations of organisms
  • Millions of species of animals, plants, and microorganisms are alive today. Although different species might look dissimilar, the unity among organisms becomes apparent from an analysis of internal structures, the similarity of their chemical processes, and the evidence of common ancestry.

• Biological evolution accounts for the 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. Biological adaptations include changes in structures, behaviors, or physiology that enhance survival and reproductive success in a particular environment.

MATERIALS

For each group of 2-3 students:

• Books, reference materials and/or computers to conduct research on sharks and rays.

For the class:

• A large sheet of paper or board and something with which to write.
• A photograph of a bull shark and a photograph of a whale shark. (See “Prep for Teachers” section for details.)
• One computer for the teacher with a digital projection system (to play video clips either downloaded or streaming from the Web).

OBJECTIVES

Students will be able to:

• Discuss similarities and differences between sharks, rays and other fish;
• Describe physical features and characteristics that have helped sharks survive, with specifics about angel, wobbegong and saw sharks;
• Provide details of physical features and characteristics that have helped rays survive, with specifics about electric, sting and manta rays;
• Explain that there are many different types of sharks and rays, with varied skills, physical features, temperaments and diets;
• Explain that some sharks and rays are harmful to humans, while others are not and provide specific examples of harmful and gentle species;
• Discuss that sometimes the largest species can be the most gentle;
• Provide detailed information about one species of shark or ray.

PREP FOR TEACHERS

Prior to teaching this lesson, you will need to:

Preview all of the video segments and Web sites used in the lesson.

Download the video clips used in the lesson to your classroom computer, or prepare to watch them using your classroom’s Internet connection.

Bookmark the Web sites used in the lesson on each computer in your classroom. Using a social bookmarking tool such as del.icio.us or diigo (or an online bookmarking utility such as portaportal) will allow you to organize all the links in a central location.

Print out one photo of a whale shark and one photo of a bull shark to show the class. Make sure that the image of the whale shark is about 3 times larger than the bull shark. See the “Web sites” section above for a list of sites with shark photos.

Proceed to ACTIVITIES

Downloadable QuickTime versions of the video segments:
(Note: To download a video, right click on the video title and click “Save Link As…’ or “Save Target As…”. On a Mac, press the CTRL key and simultaneously click the mouse, then save the link.)

Clip 1

Fish, Sharks and Rays

Clip 2

A Close Look at Sharks

Clip 3

A Close Look at Rays

Careful, there’s a myth lurking in these waters. Can you separate fact from fiction in five shark-essential categories?

Myth #1: Shark Attacks

Shark attacks usually occur near feeding grounds — sandbars, river channels, or in shallow water. The great white usually stalks its target while cruising along the ocean bottom, then springs to the surface for a vertical attack. It prefers high-energy, fatty prey.

Attack methods vary: elephant seals are bled to death before being eaten; sea lions are dragged beneath the surface, then eaten at the bottom. Attacks on

humans are usually aimed at the legs. The attack can prompt a feeding frenzy since great whites prefer and seek out human flesh. Many biologists believe that white sharks attack surfers because their surfboards resemble seals.

Myth #2: Habitat

There is still a great deal about the territo

rial and migratory habits of the great white that is not fully understood. The sharks tend to prefer temperate waters, but have been found as far north as Alaska and as far south as Australia. Their greatest numbers are concentrated off South Africa.
One area where great whites can alway

s be found is near a beach in the tropics. They tend to stay in the upper part of the water, but can descend to depths of more than 775 feet. Great whites can spend months at a time in the open ocean. In order to maintain constant body temperature, the great white’s metabolism keeps its body about ten degrees

warmer than the surrounding water.

There are no worldwide population estimates available for great whites, but the World Conservation Union has listed the white shark’s status

as “vulnerable.”

Myth #3: Diet

Great whites are apex predators, located

at the top of the ocean’s food chain. Their flat, serrated teeth and massive jaws let them prey on fat-rich marine mammals like sea lions, seals, whales, and dolphins as well as turtles, crabs, and other sharks. Weighing up to a ton, white sharks are essentially the ocean’s gigantic trash compactors, consuming not only animals but boat debris.

The carnivorous great whites favor the daytime for eating, and will often attack prey at the same time and at the same place. They can survive for

as long as 45 days on 60 pounds of whale fat. Fatty foods are required to keep the shark’s body temperature warm and give it energy for attacks at speeds of up to 15 miles per hour. A tactic called “bite and spit” is often used on prey — like humans — that are deemed an unsuitable, low-fat food.

Myth #4: Senses

Great whites are highly sensitive to their environment. Electric receptors are one of their greatest assets. Located along the sides of their bodies and in their heads, lateral lines send a nerve impulse to the great white’s brain when the surrounding water moves. The lines’ hair-lined cells can sense distance and direction, and can detect low-frequency sounds as vibrations.

While on the prowl, the great white also uses cells called ampullae of Lorenzini. Located in the shark’s snout, these cells can decipher electrical signals given off by hidden prey or any organism at close range.

Great whites have unusually large eyes for a daytime predator. Their retinas, roughly similar in structure to that of a human, have about 10 times the sensitivity to light. Yet great whites have notoriously bad vision — as demonstrated by their tendency to mistake surfboards for seals.

Myth #5: Brain Power

Relative to its body weight, the great white has a medium-sized brain — it is about 2 feet long, and narrow. In proportion to its body weight, the average great white’s brain mass is about 238 times less than that of a human, according to shark researchers Leo Demski and R. Glenn Northcutt. The great white is entirely a creature of instinct.

Large portions of the great white’s body are focused on interpreting external cues. For example, roughly two-thirds of the great white’s brain is dedicated to processing olfactory signals. Also, the great white’s cranial nerves — which analyze vibrations, sounds, and electrical currents — and optical nerves, which process viual information, are quite thick.

Little research has been done on the great white’s ability to learn. But in tests, they display a greater curiosity in unknown, brightly colored items than in bait. They are also thought to have a memory of place: Sharks off the coast of California and Australia gather for hunts at the same time each year.