AD Cartilaginous fish

Question 1

What are Gnathostome jaws?

Answer 1

vertebrates that possess jaws

Question 2

How did Gnathostome jaws evolve?

Answer 2

They developed from gill arches

Previously these gill arches had only been used as support for gills

Question 3

What are the Derived Features of Gnathostomes?

Answer 3

1) Jaws and gill arches
Derived from anterior branchial arches
Benefits:
1) New feeding behaviors (e.g., grasping)
2) New food resources (e.g. herbivory)
3) Manipulation of environment (e.g., digging holes / carrying objects)
4) Improved gill ventilation (primary driving force?)

2) Paired appendages
Benefits:
1) Control of body position (primarily pitch) in water (active, predatory fish…)
2) Defense (spines); Behavior (e.g., reproductive)

3) Teeth
(modified dermal scales), sometimes attached to large dermal bones.

Question 4

Pectoral & Pelvic Fins have moved over evolutionary time

Describe the difference between primitive and modern fish fins

Answer 4

Primitive fish: fins provide lift and maneuverability

Modern: fins used only for maneuvering

Question 5

What are Chondrichthyes?

Answer 5

Sharks, rays, skates

True bone is completely absent throughout the class. Have relatively flexible endoskeletons of cartilage rather than bone

Jaw teeth in rows

Placoid scales (most)

Absence of swim bladder – large liver

Although a smaller and more ancient group, their well-developed sense organs

Question 6

Describe shark senses

Answer 6

Sharks track prey using sequence of sensitive senses

Prey detected at a distance by large olfactory organs

Prey may also be located from long distances sensing low frequency vibrations (pressure changes) in the lateral line

At close range, sharks switch to vision

Up close, sharks guided by bioelectric fields

Question 7

How do sharks reproduce?

Answer 7

Shark eggs are fertilized internally.

Males transfer sperm via claspers on their pelvic fins to the reproductive tract of the female.

Oviparous sharks encase their eggs in protective cases and lay them outside the mother’s body. These hatch months later as juveniles.

Ovoviviparous sharks retain fertilized eggs in the oviduct.

The embryo completes development in the uterus, nourished by the egg yolk.

A few sharks are viviparous, providing nutrients through a placenta to the developing offspring

Question 8

Describe life history qualities of sharks

Answer 8

Live birth;

Slow growth;

Late maturity;

Long gestation periods;

Low fecundity;

Long lived.