Sharks are classified as cartilaginous fish and range greatly in size, from the smallest deepwater dogfish that reaches 8 inches to the largest whale shark. Sharks have specialized bodies such as placoid scales, a fatty liver for buoyancy, and a conveyor belt-like system for replacing lost teeth. Reproduction varies between oviparous, ovoviviparous, and viviparous depending on the species. Camouflage techniques include countershading which makes the shark difficult to see from above or below. Many shark species are threatened by overfishing for their skin, oil, and fins.

1. Sharks Read pages 155-159 & 174-177 See also: http://www.flmnh.ufl.edu/fish/education/questions/basics.html

2. Types of Fishes – Where Do Sharks Fit In? Three types: Jawless, Cartilaginous, & Bony Sharks fall into the Cartilaginous category Primitive fishes No true bones, only cartilage Related to skates and rays Most are harmless See the model in C114

3. Shark Diversity The smallest shark is a deepwater dogfish (adults are about 8 inches long)  The largest shark is the whale shark (a planktivore)  The fastest shark is the shortfin mako (swims up to 20 mph) (Note: Average person swims about 3 mph) http://dsc.discovery.com/videos/ultimate-guide-to-sharks-the-many-species-of-sharks.html

4. Shark Bodies Notice that sharks are fish and obtain oxygen from the water through their gills-usually 5 – 7 gills

5. Shark Bodies Cont. Lost teeth are replaced in a “conveyor belt” system, with back teeth moving forward to replace lost ones

6. Shark Bodies Cont. Placoid Scales – sharp-edged scales can injure prey; gives shark skin a sandpaper-like feel Liver – very fatty; helps shark maintain buoyancy Tail-upper lobe is usually longer for better power & thrust Usually two dorsal fins, paired pectoral fins

7. Shark Reproduction Fertilization is internal Males use claspers to insert sperm into female’s cloaca

8. Shark Reproduction Cont. Some sharks are Oviparous (lay an egg-mermaids’ purse) Some sharks are Ovoviviparous (have an egg that develops inside female-sometimes eating siblings!) Rarely, sharks can be Viviparous (Live-bearers-like mammals) http://dsc.discovery.com/videos/ultimate-guide-to-sharks-how-are-sharks-born-take-a-look.html

9. Shark Camouflage Countershading – darker on dorsal surface to blend with the deeper water or the sea bottom & lighter on ventral surface to blend with lighter colored surface waters, making it difficult for both predators & prey to see a shark

10. Shark Trouble Most sharks need to force water over gills to breathe, and can “drown” when trapped in nets Skin, oil, and fins are overharvested to the point of near extinction for some species PSA aimed at stopping these practices: http:// www.youtube.com/watch?v =fkxoRPv4ugE&playnext=1&list=PLB4E6B7A755C66293

11. Additional Shark Links More on the importance of sharks in healthy oceans: http://www.youtube.com/watch?v=xVKrwsXvC0A&feature=autoplay&list=PLB4E6B7A755C66293&index=5&playnext=2 Clearinghouse of all known Shark links: http://www.postmodern.com/~fi/sharklinks/links.htm More general shark information: http:// www.youtube.com/watch?v =xVKrwsXvC0A&feature= autoplay&list =PLB4E6B7A755C66293&index=5&playnext=2