Lecture 16- Chondrichthyes

Question 1

What are Gnathostomata’s (subphylum vertebrae)

Answer 1

Jaws Vertebrates

Question 2

What’s the importance and 2 facts of jaws

Answer 2

One of most important events in vertebrate evolution
1. Allows biting off chunks of larger organisms
2. Allows manipulation of objects

Question 3

What’s the steps of jaw evolution

Answer 3

• Modifactions of first two gill arches
• Musculature there for pumping
• developed ability to squeeze gill arches together
• 2nd arch attached to skull

Question 4

What did jaws appear in and evolve from

Answer 4

Appeared in extinct jawed fish
Evolved from gill arches

Question 5

What are the 2 subclass of Chondrichthyes and their species

Answer 5

1. Elasmobranchii- true sharks, rays
2. Holocephali- chimaeras

Question 6

3 Physical characteristics of Chindrichthyes

Answer 6

• Heterocercal caudal fin
• Placoid scales
• Cartilaginous skeleton

Question 7

Characteristics of Elasmobranchi

Answer 7

• marine and freshwater
• 1000 species (300 Australian waters)
• arose ~400 mya
• notochord replaced by vertebrae
• evolved from organisms with bony skeleton (Neoteny)

Question 8

Label the parts of the shark

Answer 8

Question 9

2 physical characteristics (chordate) of sharks

Answer 9

Tripartite brain
External gill slits

Question 10

3 New Characteristics compared to Agnathans

Answer 10

• Jaws
• Stomach
• Paired fins

Question 11

4 New characteristics compared to jawless fish

Answer 11

• stomach
• spiral valve
• spiracle, gill, gill slits
• 2 chambered heart

Question 12

How do sharks and rays ventilate there gills

Answer 12

Sharks have to swim
Rays use spiracles

Question 13

How many orders, species and families are in Elasmobranchii (sharks)

Answer 13

6 orders
400 species
1 family

Question 14

4 physical characteristics of sharks

Answer 14

• Fusiform shape (to swim in open water)
• Gill slits (5-7 each side)
• 1/2 dorsal fins
• larger caudal fin

Question 15

Characteristics of rays

Answer 15

• Dorsoventrally flattened
• Pectoral fins enlarged (locomotion)
• Respiration: water enters spiracle, exits gills
• Gill slits (5-6 on ventral surface)

Question 16

How do sharks locomotate

Answer 16

• Paired immobile fins provide lift
• Tail provides thrust and lift
• Head and fins flattened to provide lift
• Notch in modified tail and rough scales reduces drag

Question 17

3 ways sharks have buoyancy

Answer 17

• Cartilage skeleton- lighter
• Shape of Pectoral fins (lift)
• Oily liver

Question 18

3 characteristics of Elasmobranchi skin (and teeth)

Answer 18

• Thin outer epidermis
• Thick dermis
• Placoid scales

Question 19

What do sharks and rays feed on

Answer 19

Sharks: fish and mammals
Rays: Benthos

Question 20

Explain the shape and action of shark and rays teeth

Answer 20

Shark: trianglar/blade like- cutting, gripping
Rays small blunt- grinding or filter feeders

Question 21

Describe cartilagenous fishes hearing, sight and smell

Answer 21

Hearing: not well developed
Sight: Best at low light
Smell: excellent

Question 22

What are the 2 important sensory systems for cartilagenous fishes

Answer 22

Lateral line system: pressure changes
Ampullae of Lorenzini (electrical pulses)

Question 23

List 3 shark reproduction characteristics

Answer 23

• seperate sexes
• internal fertilisation
• Oviparous (egg bearing) or Viviparous (live bearing)