Phylum Chordata Chapter 23

Question 1

Phylum Chordata
5 Synapomorphies

Answer 1

5 Synapomorphies:
– Notochord (flexible axial support rod)
– Dorsal hollow nerve cord
– Pharyngeal pouches and slits
– Endostyle or thyroid gland
– Muscular postanal tail

Question 2

Subphylum Cephalochordata
Synapomorphy

Answer 2

Notochord to tip of head

Question 3

Subphylum Urochordata
Synapomorphy

Answer 3

possess outer non-living tunic

Question 4

Subphylum Craniata
Synapomorphy
 These are derived from neural crest!

Answer 4

Cranium
- (distinct head houses brain & complex sensory organs)
-neural grest forms cranum
Ectodermal placodes
-thickening of ectoderm
– Form sense organs (inner ear, nose, eye);
parts of ganglia & cranial nerves

Question 5

23.1 What is a notochord?

Answer 5

-rodlike, body of fluid-filled cells enclosed by a fibrous sheath
-flexible axial support rod
-sends signaling cues to a developing embryo

Question 6

23.2 Describe the five synapomorphies of Phylum Chordata

Answer 6

5 Synapomorphies:
– Notochord (flexible axial support rod)
– Dorsal hollow nerve cord
– Pharyngeal pouches and slits
– Endostyle or thyroid gland
– Muscular postanal tail

Question 7

Function of Notochord in Phylum Chordata

Answer 7

Sends signals to the developing embryo

Question 8

Function of Dorsal hollow nerve cord in Phylum Chordata

Answer 8

develops into the central nervous system: the brain and spine

Question 9

Function of Pharyngeal pouches and slits in Phylum Chordata

Answer 9

filtering food particles from the water

Question 10

Function of Endostyle or thyroid gland in Phylum Chordata

Answer 10

produces and secretes thyroid hormones

Question 11

Function of Muscular postanal tail in Phylum Chordata

Answer 11

provide a source of locomotion

Question 12

What is the difference between a notochord and a dorsal hollow nerve chord?

Answer 12

Notochord is a part of skeleton system whereas nerve cord is a part of nervous system.

Question 13

23.3 Describe the features of adult members of the Subphylum Urochordata.

Answer 13

Tunicates,
* Possess all 5 chordate features only in larval stage
* Adults retain only the endostyle and pharyngeal slits
* Synapomorphy: possess outer non-living tunic
* Possess neural crest (special tissue type)

Question 14

Why are Subphylum urochordates in the Phylum Chordata?
Subphylum urochordata- tube with two holes looking thing

Answer 14

The neural crest is why but they do not form a cranium
-neural crest is a tissue type that forms when the dorsal hollow nerve chord forms.

Question 15

Are all vertebrates craniates and vise versus?

Answer 15

All vertebrates are craniates but not all craniates are vertebrates.

Question 16

23.4 What is the unique feature of Phylum Cephalochordata?

Answer 16

Larval features retained in adults

Question 17

23.5 What defines Subphylum Craniata?
Hagfish and all other vertebrates

Answer 17

Synapomorphies of CRANIATES:
– Cranium (distinct head houses brain & complex sensory organs)
– Ectodermal placodes
 These are derived from neural crest!
- includes the 5 synapomorphies of phylum Chordata

Question 18

23.6 What is neural crest and how does it form?
-under subphylum craniata

Answer 18

– Derived from ectoderm
– Neural crest cells migrate from top of neural
folds
– Form cranium, parts of sense organs, nerve
ganglia & sensory system in head and more

Question 19

23.7 Define paedomorphosis

Answer 19

retention of juvenile features in adult

Question 20

23.7 Define paedomorphosis and describe how it explains the evolution of early craniates.

Answer 20

• Craniates evolved via Paedomorphosis (retention of juvenile features in adult)
  – Ancestral craniate had free swimming larvae
  – Change timing of development (heterochrony) to delay metamorphosis
  – Mature to adult without metamorphosis = retain larval features in adults
  – Free swimming adult evolves
• Ancestral craniate was a free swimming filter feeder

Question 21

23.8 What feature is shared by urochordates and craniates?

Answer 21

both have a neural crest

Question 22

23.9 Why is the ammocoete larva of a lamprey a model for understanding the vertebrate body
plan?

Answer 22

Paedomorphosis- the features stay the same in adults and juveniles

Question 23

23.10 What are Ostracoderms?Name some types of ostracoderms.

Answer 23

They are most of the earliest fishes
-were partly covered in a bony, dermal armor. This armor is modified as scales in later fishes.
-Osteostracans, Heterostracans & Anaspids

Question 24

23.11 What organisms are agnathans? What feature do agnathans share?

Answer 24

-jawless fishes; not monophyletic- jaws are lacking in vertebrate ancestors.

Question 25

23.12 What does gnathostome mean?

Answer 25

jaw mouth

Question 26

How did jaws evolve?

Answer 26

Jaws Evolved from Gill Arches

A. Ancestral filter feeder had
many gill arches; anterior
arches incorporate into
cranium
B. First gill arch (mandibular)
functions as jaws
C. Jaws associate with cranium
and second gill arch (hyoid)
supports jaws
D. 5 Posterior arches serve as gill
arches
D.