Sharks skates and rays

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!

Oviparity(most primitive)

Ovoviviparity Viviparity (most advanced)

• Eggs laid outside body• Protective case attaches to sea floor• Smaller bc limited nutrients

• Eggs hatch in mothers uterus • Nutrients stored in egg• Single pup

• Babies get milk directly from mother • Live young

• Whale Sharks• Basking Sharks

• Horn shark • Great White

• Hammerhead • bull sharks

Types of Reproduction

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– Small fins on tail– Swim by creating a wave

and starts at head then ripples down rest of body

– oviparous

• Rays– Venomous barb or

spines– Swim by moving fins up

and down (like a bird)– Ovoviviparous