Lecture 19 - Early Vertebrates Fishes 1

Question 0

Name of bony fishes

Answer 0

Acanthodians

Question 1

Name of Armoured , jawless fish

Answer 1

Ostracoderms

Question 2

What’s the name of the 1st gnathostomes.

Answer 2

Placoderms

• heavily armoured (like ostracoderms)
• evolved many forms
• extinct with no descendants

Question 3

2 distinct lineages of bony fish

Answer 3

Ray - finned

Lobe -finned

Question 4

What is the 2 classes of living jawless fish?

Answer 4

Myxini (hagfish). & petromyzontida ( lampreys).

Question 5

Hagfish. Name the class and key traits.

Answer 5

Skull of cartilage but no jaws or vertebrae
- swim using segmented muscles against cartilage notochord
- keratinized teeth
- secrete water absorbing substance
- forms slime to repulse other scavengers or predators
Members : all marine. Mainly scavengers.

Question 6

Lampreys . Name class and key traits.

Answer 6

Notochord is main axial skeleton in adult ( like hagfish). But is surrounded by cartilaginous pipe with projections partially enclosing nerve cord.

• round jawless mouth with rasping tongue.
• inject anticoagulant

Members : parasitic on fish
Marine members spawn in freshwater and die , leaving eggs.

Question 7

What is a lateral line?

Answer 7

Consists of mechanoreceptors

Detect vibrations

Question 8

Ampullae of Lorenzini

Answer 8

Consist of electroreceptors

Detect bioelectric fields from prey

Question 9

Oviparity

Answer 9

Lay eggs that hatch outside mother’s body

Release eggs encased in protective coating

Question 10

Ovoviviparity

Answer 10

Eggs retained in oviduct.
Embryos nourished by egg yolk
Born after hatching within uterus

Question 11

Viviparity

Answer 11

Young develop within uterus

Nourished by yolk sac placenta , absorbing fluid, eating other eggs

Question 12

Ray finned is within what class?

Answer 12

Class actinopterygii