Origin of Chordates

Phylum Chordata

• Has the 5 key structures at least once in their certain lifetime

• Subphylums include

  • Subphylum Urochordata

  • Subphylum Cephalochordata

  • Subphylum Craniata

Phylum Hemichordata

Does not fulfill all 5 criteria

Protostomes

animals under this develops through spiral cleavage

coelom or cavity

What forms in the protostomes and deuterostomes?

Splitting of Mesoderm

Where does the coelom or cavity of protostomes orignate from?

Deuterostomes

animals development of this starts off with radial cleavage of embryonic cells

Out-pouching of the primitive gut

Where does the coelom or cavity of deuterostomes orignates from?

Chordates

Animals that have a NOTOCHORD in the embryo stage at least

Craniates

Chordates with a NEUROCRANIUM or BRAINCASE

False

TRUE OR FALSE

Craniates don’t need to have a CRANIUM

True

TRUE OR FALSE

Craniates’ cranium comes from the neural crest

True

TRUE OR FALSE

Craniates have a paired external sense organs (olfactory, optic, and otic) with a single semicircular canal, lateral line system with unicellular sense organs

• Head

• Trunk

• Postnatal Tail

What does a typical craniate body contain

Head

• Special sense organ to monitor external environment through senses

• Brain that is at least large enough (CEPHALIZATION) to receive and process essential information and to provide appropriate stimuli to the body musculatature

Jaws

What does a craniate use to acquiring, retaining, and macerating food?

Gills

What does a craniate use for respiration?

Cephalization

• centralization/localization of nervous structures and functions in the head with accompanying dominance of the head

• process of forming the craniate’s head

False

TRUE OR FALSE

A craniate’s head is formed through localization

Trunk

• Contains coelom that houses most of the visceral organs

• Body wall surrounds the coelom and consists chiefly of muscle, vertebral column, and the ribs

• Associated with paired pectoral and pelvic appendage

True

TRUE OR FALSE

The neck of a craniate is a narrow extension of the trunk that connects it to the head

False

TRUE OR FALSE

The neck of a craniate is part of the head instead of the trunk

Postnatal Tail

• Commences at the anus or vent

• Consists almost exclusively or a caudal continuation of body wall muscles, axial skeleton, nerves and blood vessels

• Present in ALL EMBRYOS though adult form may lose the tail along development

Vertebrates

• Chordates with vertebrae

• Vertebrae appear during embryonic development after the notochord has formed

• Vertebral column

• Two semicircular canals

• Electroreception

• Lateral line system with multicellular neuromasts

• Number of soft tissue specializations