Chapter 24: Fishes, Class: Chondrichthyes-> Cartilaginous fishes

Question 1

List some very general characteristics of this class!

Answer 1

• well developed sense organs, powerful jaws and predacious habits
• true bone is completely absent
• nearly all are marine (28 live in freshwater primarily)
• after whales sharks are the largest living vertebrates

Question 2

What is the subclass that contains Sharks, Skates and rays?

Answer 2

• Elasmobranchii

Question 3

What type of body do sharks possess?

Answer 3

• fusiform ( spindle-like shape…the middle is wide and tapers at both ends of the body)

Question 4

What are thrust and lift provided by for sharks?

Answer 4

• asymmetrical heterocercal tail , vertebral column turns upward and extends into dorsal lobe of caudal fin.

Question 5

List the fins included on a shark! (4)

Answer 5

• paired pectoral and pelvic fins
• one or two median dorsal fins
• one median caudal fin
• sometimes a median anal fin

Question 6

In males what is the medial part of the pelvic fin modified for?

Answer 6

• copulation, it forms a clasper

Question 7

Paired nostrils are ___ to the mouth

Answer 7

anterior

Question 8

Lateral eyes are ___.

Answer 8

lidless

Question 9

Behind each eye there is a ___. Which is a remnant of what?

Answer 9

• spiracle, remnant of the first gill slit

Question 10

How do they detect prey at great distances?

Answer 10

• large olfactory organs sensitive to one part blood per 10 billion water

Question 11

What kind of scales do they have? Function?

Answer 11

• tough leathery placoid scales reduce water turbulence

Question 12

Nostrils to each side of the hammerhead shark may improve what?

Answer 12

• stereo-olfaction

Question 13

Prey can also be located from long distances by sensing low frequency vibrations in the ___.

Answer 13

• lateral line

L> consists of neuromasts in interconnected tubes and pores on the side of the body.

Question 14

At close range when located prey they switch to what detection method?

Answer 14

• vision

L> most sharks have excellent vision even in dimly lit water

Question 15

Up close sharks are guided by what?

Answer 15

• bioelectric fields that surround all animals

Question 16

What are ampullae of Lorenzini?

Answer 16

• electroreceptors located on the sharks head

Question 17

The upper and lower jaws are equipped with sharp, ____ shaped teeth that are constantly being ___.

Answer 17

• triangular

- replaced

Question 18

The mouth of sharks opens into a large ___, containing openings to ___ and ___.

Answer 18

• pharynx
• gill slits
• spiracles

Question 19

Sharks have a short ___ which runs to the stomach.

Answer 19

esophagus

Question 20

The liver and pancreas open up into what?

Answer 20

• straight and short intestine

Question 21

What in the sharks intestine slows passage of food and increases absorptive area?

Answer 21

• spiral valve

Question 22

Rectal glands secretes ___ and assists in what?

Answer 22

-NaCl
- assists the opisthonephric kidney
L> Origin of tissues two parts from embryological development

Question 23

The heart chambers provide what??

Answer 23

• standard circulatory flow through gills and body

Question 24

Elasmobranchs retain what?

Answer 24

• nitrogenous compounds in the blood
• They raise blood solute concentrations and eliminates the osmotic inequality between blood and seawater….TMAO and Urea

Question 25

Is fertilization internal or external?

Answer 25

- internal

Question 26

Maternal support of embryo is variable | What three types of "giving birth"?

Answer 26

- Oviparous- lay eggs - Ovoviviparous- eggs hatch within females without obtaining nourishment from it. - Viviparous-giving birth to live young that developed within the mothers body.

Question 27

What is a mermaids purse?

Answer 27

- horny capsule encasing eggs laid by some oviparous species

Question 28

- More than half of elasmobranchs are what?

Answer 28

rays

Question 29

Rays are specialized for what lifestyle?

Answer 29

Benthic

Question 30

Rays are ____ flattened and have enlarged ___ fins used to propel themselves.

Answer 30

- dorsoventrally flattened, pectoral fins

Question 31

What are the large spiracles on top of the head of a ray for?

Answer 31

- respiratory water enters through large spiracles on top of the head.

Question 32

Rays teeth are adapted for what?

Answer 32

- crushing prey