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Sharks powerpoint


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Sharks powerpoint

  1. 1. The SharksClass Chondrichthyes
  2. 2. Class Chondrichthyes• Includes sharks, skates and rays
  3. 3. Class Chondrichthyes• Inhabited earth for 280 million years (twice as long as dinosaurs)• 350 species of sharks• 320 species of rays• Found worldwide at all depths – almost all marine
  4. 4. Characteristics• Cartilage instead of bone (chondros = cartilage)• Lighter, more flexible• Jaws and paired fins (unlike Class Agnatha)
  5. 5. Characteristics• Streamlined body – torpedo shape - fusiform• Placoid scales – denticles – small tooth-like plates – like sandpaper• Counter-shading – dark on top, light on bottom – form of camouflage
  6. 6. External Anatomy
  7. 7. Internal Anatomy
  8. 8. Respiration• 5 to 7 gill slits• No operculum covering gill slits• Water passes over gills, oxygen diffuses into blood, carbon dioxide out• Some pump water through mouths, some, take in water through spiracle, others keep swimming
  9. 9. Buoyancy liver• No swim bladder• Store oil in large liver• Heterocercal tail – asymmetrical – creates lift• Horizontal pectoral fins also provide lift• Cannot swim in reverse like bony fish
  10. 10. Senses• Excellent sense of smell – nostrils only for smell, not breathing• Simple, internal ear to hear low-frequency vibrations
  11. 11. Senses• Electroperception – ability to detect weak electric currents – Ampullae of Lorenzini – in skin pores – find prey and for migration• Lateral line – stretches from head to tail – fluid- filled sensory canals - sensitive to vibrations
  12. 12. Reproductio n claspers• Separate sexes• Usually internal fertilization – rare in fish• Claspers – male structures to transfer sperm to female• Some sharks give birth to live young• Some sharks lay few, large eggs - mermaid’s purse – Durable case – Large yolk - nutrition – Well-developed young hatch
  13. 13. Feeding• Ventral mouth• Teeth – specialized denticles• 6 – 20 rows deep• Easily lost and replaced – up to 50,000 in a lifetime• Hinged jaws – upper and lower canwork independently and in oppositionto each other
  14. 14. Feeding• Many are predators – Eat fish, marine mammals – Speed
  15. 15. Feeding• Some eat plankton – Whale shark – largest fish – up to 60 feet long – Filter plankton with open mouth – Low on food web• Some are scavengers
  16. 16. Shark Attacks• Rare• Average of 6 per year worldwide• Very few species attack humans• Usually mistake humans for seals
  17. 17. Shark Attacks• Great whites most dangerous – up to 23 feet and 3,000 pounds• Other dangerous species: mako,tiger, hammerhead
  18. 18. Symbiosis• Remora - suckerfish• Mutualistic symbiotic relationship with shark – Picks up scraps and feeds on external parasites
  19. 19. Human Uses• Food – Steaks – Shark fin soup• Vitamin A in livers• Skin – leather = shagreen• Overfished
  20. 20. Rays and Skates• Flattened bodies• Broad, wing-like pectoral fins• Glide or “fly” through water• Both eyes on top of head
  21. 21. Rays and Skates• Ventral mouth with “teeth” for scavenging and crushing invertebrates• Largest feed on plankton• Usually associated with ocean bottom• Most not harmful