Sharks powerpoint
- 2. Class Chondrichthyes • Includes sharks, skates and rays
- 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. Characteristics • Cartilage instead of bone (chondros = cartilage) • Lighter, more flexible • Jaws and paired fins (unlike Class Agnatha)
- 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
- 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. 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. Senses • Excellent sense of smell – nostrils only for smell, not breathing • Simple, internal ear to hear low-frequency vibrations
- 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. 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. 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 can work independently and in opposition to each other
- 14. Feeding • Many are predators – Eat fish, marine mammals – Speed
- 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. Shark Attacks • Rare • Average of 6 per year worldwide • Very few species attack humans • Usually mistake humans for seals
- 17. Shark Attacks • Great whites most dangerous – up to 23 feet and 3,000 pounds • Other dangerous species: mako, tiger, hammerhead
- 18. Symbiosis • Remora - suckerfish • Mutualistic symbiotic relationship with shark – Picks up scraps and feeds on external parasites
- 19. Human Uses • Food – Steaks – Shark fin soup • Vitamin A in livers • Skin – leather = shagreen • Overfished
- 20. Rays and Skates • Flattened bodies • Broad, wing-like pectoral fins • Glide or “fly” through water • Both eyes on top of head
- 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