1 12:46Class: Chondrichthyes The shark’s skeleton is entirely composed of cartilage. The skin is covered with tiny scales called denticles. Feels like sandpaper. They are similar in structure to teeth and cause the skin to be very abrasive if rubbed in the wrong direction. Most have gray, brown, white or black coloring; are not camouflaged but may be counter-shaded.

2 Predation: Efficient, top carnivore of the sick, weak, old and injured. Sharks will not eat a fish called Moses Sole. Researchers think this information may lead to a better shark repellant. Jaw is lined with rows of teeth like a conveyor belt. Teeth can be replaced every 24 hours and are used to identify species. Jaw can be extended out of the mouth for extra reach.

3 Their large liver may help detoxify their diet. It is unusual that they are somewhat resistant to tumors and cancer. Mote Marine Laboratory in Sarasota, FL is a leading research center in shark immunology. However, shark cartilage does not prevent cancer in humans, and sharks with tumors have been observed.

4 Circulation: 2 chambered heart; cold-blooded Sharks lack swim bladders and must constantly swim upwards to balance their weight. They do sleep. Respiration: Gills are located in muscular slits behind the mouth. They exchange oxygen from the water into the blood.

5 Senses: Vision is good in clear water. Eyelids close from the bottom upwards to prevent injury during an attack. Their ability to smell is excellent. Olfactory lobes compose 2/3 of the brain. Sharks can detect a drop of blood 1/4 mile away in the water and can determine the direction of the source. Hearing is also excellent. Sound vibrations can be detected by the lateral line from 3,000 feet away. The electrical impulses of breathing from a prey can be picked up through pores in the face.

6 Reproduction: sexual, internal fertilization. Most sharks have live births. Dogfish have 4-10 pups, while tiger sharks may have at one time. A few species of sharks and skates lay eggs. Shark EggShark Egg

7 Shark attacks on humans are rare, but with more people in the water the odds are increased. Sharks may be looking for new food sources due to over fishing. Most attacks occur in less than 6 feet of water, at dawn or dusk, during summer months. Risks are also increased for surfers and swimmers in water with reduced visibility. A surfer in black wet-suit, paddling out on a board, may look enough like a seal to interest a shark.

8 Most attacks occur in Florida, California, Australia, and Africa. Florida has 4 times the number reported in California. Most attacks are not fatal. Sharks only kill about 10 people worldwide per year. Bees kill hundreds of people and crocodile/alligator - related deaths number nearly People have done far greater damage to the shark population, especially the illegal practice of cutting the fins off live sharks to sell for making soup.

9 The whale shark is over 50 feet long. It is a filter- feeder with baleen instead of teeth. Largest shark Great White sharks are found in the temperate and tropical oceans worldwide. Most dangerous

10 Skates and rays are related elasmobranchs and cartilaginous fish. Some are bottom dwellers that eat small invertebrates and some small fish. Others are nekton, like the Manta Ray, and eat plankton. Rays have live births (viviparous) while skates are egg laying (oviparous). Several species of rays have a poisonous spines – skates do not.

11 Largest ray Manta Rays may have a 25 foot wide wing span. Most dangerous Sting Rays have a venomous stinger in their tail. Shuffle your feet when wading to avoid stepping on it.

Remora Fish Grow to 30–90 centimeters long (1–3 ft) First dorsal fin takes the form of a modified oval sucker-like organ with slat-like structures that open and close to create suction and take a firm hold against the skin of larger marine animals. 12

13 Question: How Do Sharks Sleep? Sharks need to keep water moving over their gills so that they receive oxygen. So that means they need to keep moving all the time... or do they? Answer: Even though sharks need to keep water moving over their gills to receive oxygen, some sharks need to keep moving to do this, while others don't. Either way, sharks, like other marine animals, don't seem to fall in a deep sleep like we do. Some sharks have spiracles, a small opening behind their eyes, that force water across the shark’s gills so the shark can be still when it rests. Other sharks do need to swim constantly to keep water moving over their gills and their bodies. These sharks have active periods, and restful periods, rather than undergoing deep sleep like we do. They seem to be “sleep swimming,” with parts of their brain less active, or "resting," while the shark remains swimming.