Fishes 1

Question 1

First vertebrates

Answer 1

Agnathans in Cambrian (500mya)

Evolved from ostracoderms

Question 2

Ostracoderms

Answer 2

Look like fish but had carbon armour covering and no bones or jaws
Pits and pores in head region (sensory organs for prey)

Question 3

Jawless fishes

Answer 3

Complex sensory organs

Cartilage skeletons without ribs

Question 4

Jawed fishes

Answer 4

Early Cambrian > Ordovician
Jaws developed for respiratory purposes
Had vertebrae as well as ribs
Had sensory organs that agnathans did not

Question 5

Gnathostome orders

Answer 5

2 extinct:
Placoderms
Acanthodians
2 extant:
Chondrichthyes
Osteichthyes

Question 6

Functions of jaw

Answer 6

New feeding methods like grasping prey and different types of prey
Cutting
Digging
Manipulate objects
Grasping mate during copulation

Question 7

Evolution of jaw

Answer 7

Appeared in early Silurian period (440mya)
Organisms became more active and needed more oxygen
Jaws evolved for respiration
Brachial arch and mandibular arch covered gills
Enlargement of mandibular arch paralleled with muscle development
-muscles made it more robust and allowed fish to suck water in
-lead to formation of proto-jaw and later jaw

Question 8

Fins and jaws

Answer 8

Fins evolved with jaws
-pelvic and pectoral fins
Agnathans had tail fins for balance

Question 9

Fin functions

Answer 9

Apply pressure on water and the opposing force creates propulsion
They prevent:
Pitching (up/down)
Rolling (about body axis)
Yawing (swinging from left to right)