Exam 3 Ch 14 part 2

Question 1

Agnathans include what three classes?

Answer 1

ostracoderms, myxini, and petromyzontida

Question 2

What are the characteristics of Myxini, or hagfish?

Answer 2

1. scavengers and predators
2. Acute sense of smell and touch
3. osmotic equilibrium
4. No vertebrae

Question 3

Characteristics of Petromyzontida?

Answer 3

pore like gill openings and eel-like body
no jaws, scales, or paired fins
Fibrous and cartilaginous skeleton
notochord persistent
rudimentary vertebrae

Question 4

Describe the Petromyzontid life cycle.

Answer 4

both parasitic and vegetative forms
larval form…ammocoetes
Example: Sea Lamprey Petromyzon marinus

Question 5

What do we know about the movement from Agnathostome to Gnathostome?

Answer 5

Jaws revolutionized diet and feeding niches.
Hypothesis: jaws derived from gill arches of jawless fishes (Mallatt, 1996)

Evidence includes:
Neural crest involved in the formation of gioll arches and jaws
muscles of gill arches and jaws are homologous
similar genes expressed in mandibular segment of lamprey and jawed fishes

Question 6

Facts about Gnathostomata?

Answer 6

410 mya
eg. placoderms
jaw doesn’t necessarily mean teeth

Question 7

What are the two categories in Gnathostomata?

Answer 7

Chrondrichthyes

Osteichthyes

Question 8

Characteristics of Chrondrichthyes?

Answer 8

large oily liver
unique teeth
gill slits
spiracles
heterocercal tails

Question 9

Unique features of Chrondrichthyes?

Answer 9

tough leathery skin (Placoid scales/dermal denticles)
internal fertilization (claspers for reproduction)
Oviparous/oviviviparous

Question 10

Chrondichthyes and sensing prey?

Answer 10

powerful sense of smell
lateral line
sight
ampullae of lorenzini

Question 11

What are general traits of Osteichthyes?

Answer 11

1. operculum w 1 external gill slit
2. Swim bladder for buoyancy
3. Homocercal caudal fin
4. Thin, flat scales

Question 12

What are the two types of Osteichthyes?

Answer 12

Actinopterygii (ray finned)

Sarcopterygii (lobe finned)

Question 13

What is the function of the swim bladder in Actinopterygians?

Answer 13

Depth controlled by adjusting volume of gas in swim bladder
Descending increased density (compresses bladder)
Ascending lowers density (bladder is larger)

Question 14

What controls respiration in Actinopterygians?

Answer 14

Gills that are thin filaments w/ membranes folded into plate-like lamellae
Operculum (moveable flap over gills) serves to protect delicate gills and streamline body
Water flow is opposite to blood flow which optimizes gas exchange

Question 15

What do we know about osmoregulation in Actinopterygians?

Answer 15

Fresh water is hypotonic to fish blood
Water enters body and salt is lost by diffusion
Opisthonephric kidney pumps excess water out
Salt-absorbing cells in gill epithelium actively move salt ions from water into fishes blood.

Question 16

What do we know about marine water and osmoregulation in Actinopterygians?

Answer 16

Marine water is hypertonic
Tend to lose water and gain salt
To compensate for water loss, marine fish drink sea water, bringing in more salt
Salt removed from body by salt-secretory cells in gills and feces.

Question 17

What do we know about Actinopterygians and reproduction?

Answer 17

Most dioecious with external fertilization
Variations include:
ovivipourous: guppies
Oviparous: pelagic fish form lots of eggs
Some bury eggs, some attached to vegetation, incubation in mouth, egg guarding, etc.

Question 18

What do we know about freshwater Actinopterygians and reproduction?

Answer 18

Egg takes up water, outer layer hardens and cleavage occurs.
Blastoderm develops and yolk consumed
Fish hatches carrying a semi transparent yolk-sac to supple food until it can forage.

Question 19

What three kinds of scales do Actinopterygians have?

Answer 19

ganoid, cylcoid, or Ctenoid

Question 20

What is specialized about the jaw of Actinopterygians?

Answer 20

increased suction

better prey handling

Question 21

Do Actinopterygians have a lateral line and a homocercal caudal fin?

Answer 21

yes.