Phylum Chordata Chapter 23 Flashcards
Phylum Chordata
5 Synapomorphies
5 Synapomorphies:
– Notochord (flexible axial support rod)
– Dorsal hollow nerve cord
– Pharyngeal pouches and slits
– Endostyle or thyroid gland
– Muscular postanal tail
Subphylum Cephalochordata
Synapomorphy
Notochord to tip of head
Subphylum Urochordata
Synapomorphy
possess outer non-living tunic
Subphylum Craniata
Synapomorphy
These are derived from neural crest!
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
23.1 What is a notochord?
-rodlike, body of fluid-filled cells enclosed by a fibrous sheath
-flexible axial support rod
-sends signaling cues to a developing embryo
23.2 Describe the five synapomorphies of Phylum Chordata
5 Synapomorphies:
– Notochord (flexible axial support rod)
– Dorsal hollow nerve cord
– Pharyngeal pouches and slits
– Endostyle or thyroid gland
– Muscular postanal tail
Function of Notochord in Phylum Chordata
Sends signals to the developing embryo
Function of Dorsal hollow nerve cord in Phylum Chordata
develops into the central nervous system: the brain and spine
Function of Pharyngeal pouches and slits in Phylum Chordata
filtering food particles from the water
Function of Endostyle or thyroid gland in Phylum Chordata
produces and secretes thyroid hormones
Function of Muscular postanal tail in Phylum Chordata
provide a source of locomotion
What is the difference between a notochord and a dorsal hollow nerve chord?
Notochord is a part of skeleton system whereas nerve cord is a part of nervous system.
23.3 Describe the features of adult members of the Subphylum Urochordata.
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)
Why are Subphylum urochordates in the Phylum Chordata?
Subphylum urochordata- tube with two holes looking thing
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.
Are all vertebrates craniates and vise versus?
All vertebrates are craniates but not all craniates are vertebrates.
23.4 What is the unique feature of Phylum Cephalochordata?
Larval features retained in adults
23.5 What defines Subphylum Craniata?
Hagfish and all other vertebrates
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
23.6 What is neural crest and how does it form?
-under subphylum craniata
– 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
23.7 Define paedomorphosis
retention of juvenile features in adult
23.7 Define paedomorphosis and describe how it explains the evolution of early craniates.
- 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
23.8 What feature is shared by urochordates and craniates?
both have a neural crest
23.9 Why is the ammocoete larva of a lamprey a model for understanding the vertebrate body
plan?
Paedomorphosis- the features stay the same in adults and juveniles
23.10 What are Ostracoderms?Name some types of ostracoderms.
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
23.11 What organisms are agnathans? What feature do agnathans share?
-jawless fishes; not monophyletic- jaws are lacking in vertebrate ancestors.
