Craniates

Question 1

Where are the craniates positioned, phylum wise ?

Answer 1

One of the 3 subdivisions of chordates, (cephalochordates, tunictaes, craniates)

Question 2

Describe Craniates evolutionary place.

Answer 2

Craniates evolved from invertebrate chordates.
Vertebrates evolved from Craniates.
‘Transition group’

Question 3

Give a species example of a craniate.

Answer 3

Hagfish

Shows the evolutionary development of the vertebrate head.

Question 4

Describe the blood and sex of the hagfish

Answer 4

iso-osmotic (equal conc) to sea water,

Dioecious species.

Question 5

Describe the feeding methods of the hagfish

Answer 5

Scavengers
Detect prey via 4 sensory tentacles
No jaws, rely on rows of retractable teeth.
Knot around animal. ripping off skin.
Nostril enables breathing whilst mouth engaged.

Question 6

Describe a hagfish defence mechanism.

Answer 6

Slime production

Question 7

How many hearts does a hagfish have ?

Answer 7

4,
3 are accessory pumps,
1 is the main pump

Question 8

Are they invertebrates or vertebrates ?

Answer 8

Have partial cranium (skull)
But no Vertebrae, so are not true vertebrates
Also lack jaws and have cartilaginous skeleton.