Class Chondrichthyes:Skeleton made of cartilage
Vertebrates• Everything up till now has been Invertebrates – What does this mean?• From now on all Fishes, reptiles, birds and mammals are all Vertebrates – What does this mean?• Can you think of some functions of Vertebrae that are advantageous? – Support – Attachment of muscles= increased movement
Primitive Fish (SHARK ANCESTORS)• hagfish and lampreys – Lack jaws and paired appendages (fins in fish) – Lack scales and muscles (all cartilage) Only living representatives of primitive fish
Class Condrichthyes• Sharks, Skates, and Rays – Defining characteristics • Skeletons composed of cartilage • Jaws • Paired fins • Placoid scales
Sharks!!!!!• Streamlined body shape• Heterocercal tail• Two dorsal fins• Paired pectoral fins• Paired pelvic fins – Modified in males (claspers) to transfer sperm
Types of Fins• Draw the following diagram in your notes and label the fins.• THIS WILL BE IMPORTANT WHEN WE STUDY FISH!
TYPES OF TAIL FINS• Label the diagram and draw it into your notes.• It will be important when classifying fish! A: heterocercal fin B: Protocercal Fin C: Homocercal Fin D: Diphycercal Fin
Advantages to a Cartilage Skeleton• Skeletons made of cartilage & connective tissue – What is the difference between cartilage and bone?• Flexible, durable• Half the normal density of bone – Advantages and disadvantages?
Why do sharks have to “just keep swimming”?• Lack a gas-filled swim bladder for buoyancy like fish• Most sharks must swim in order to breathe – When sleeping: sharks pump water over their gills – Moving: take water in through the mouth and over the gills
Osmoregulation• Maintain homeostasis• Blood and tissue of sharks are usually isotonic to marine environments – By holding large amounts of urea in body • Found in their urine – If they did not have this adaptation they would lose body water. • Then what would happen to the shark – Dehydrate and cells would……… » Shrink -> remember osmosis chapter?????
Sensory in Sharks• Sight – Lack eyelids – Scientists predict that they can see color, but what sense is most dominant in shark?• Smell!!!! – 2/3 of cells in brain are used to process sense of smell – Can detect 1 drop of blood in 1 million parts of water• Very intelligent! – Exhibit curiosity and play
Other well adapted senses• Lateral Line System – Canals that run length of body and open up to surrounding H2O – Used to detect movements in water – Can sense vibrations of prey • Locate prey and predators • Fine tuned enough to feel a heartbeat!• Electroreception – Feel the gravitational pull of other bodies in the water
Digestion• Teeth – Several rows of teeth – Fall out and are continually replaced throughout life • Not like ours where we only get two sets – Shake head to bite b/c they cant move jaws up and down to chew – Food is swallowed whole – Mouth ->stomach-> small intestine
Reproduction• Sexual, separate sexes• Fertilization is internal – Males transfer sperm via claspers – Females have ovaries and oviduct (modified uterus)• Most sharks like fish lay eggs – Some pelagic sharks give birth to live young!
Types of ReproductionOviparity Ovoviviparity Viviparity(most primitive) (most advanced)• Eggs laid outside • Eggs hatch in • Babies get milkbody mothers uterus directly from mother• Protective case • Nutrients stored in • Live youngattaches to sea floor egg• Smaller bc limited • Single pupnutrients• Whale Sharks • Horn shark • Hammerhead• Basking Sharks • Great White • bull sharks
Skates and Rays characteristics• Flattened bodies shape – Suited for bottom living • Always exception = manta ray – Enlarged pectoral fins attached to head – Reduced dorsal and caudal fins – Eyes and spiracles on top of head – Lack of anal fin – Specialized teeth for crushing prey
Differences between skates and rays• Skates • Rays – Small fins on tail – Venomous barb or – Swim by creating a wave spines and starts at head then – Swim by moving fins up ripples down rest of and down (like a bird) body – Ovoviviparous – oviparous