M2: L1: Gnathostomes (Jawed Fishes)

what did jaws evolved from?

anterior gill arches

what is the func of pharyngeal slits?

gas exchange only

define gill arches.

bones or cartilage btwn gill slits

define lateral line system.

1) sensory organ for detecting water movement and vibration

2) made of canals, sensory hairs, and mucus-filled cupulae

what are the characteristics of the gnathostomes (jawed fishes)?

1) jaws

2) pharyngeal slits

3) lateral line sys

what is the evo history of the gnathostomes?

placoderms (armored jaw fishes) extincted by ~ 359 MYA

3 main extant lineages:

1) chondrichthyes (cartilaginous fishes: rays, skates, and sharks)

2) osteichthyes (bony fishes):

a) ray-finned

b) lobe-finned

What are the difference btwn the chondrichthyes and osteichthyes?

chondrichthyes:

1) larger liver for storage of oil — buoyancy

2) spiral valve in their intestine — nutrient absorption

3) cloaca — discarding everything (rectal, gonad, and kidney)

what are the differences in anatomy btwn the chondrichthyes (cartilaginous fishes) and osteichthyes (bony fishes)?

osteichthyes:

1) terminal mouth

2) operculum

3) pectoral fins on the side of the body

4) cycloid scales

5) lobes of caudal fin are equal in length 

6) swim bladder

How do the osteichthyes float in water?

swim bladder:

1) muscles relax — floats

2) muscles tighten — sinks

T/F - swim bladders gave rise to the lungs.

false

T/F - lungs gave rise to swim bladder.

true

What are the characteristics of the ray-finned fishes?

1) rays (bony spines) in the fins

2) diverse body forms

3) most of what we call fishes today

What are the characteristics of the lobe-finned fishes?

1) three extant lineages:

a) coelacanth

b) lungfish

c) tetrapods (sister taxa)

2) sturdy, rod-shaped bones in fins

What allowed the early amphibians evolve onto land?

coelacanth evolved into the ichthyostega — walking

What is an example of convergent evo in ray-finned fishes?

some ray-finned fishes developed fin-walking independently from amphibians