23. chordates
DESCRIPTION
Zoology class at Ava High School over Chordates, chapter 23TRANSCRIPT
Chordates
Chapter 23
Phylum Chordata
Phylum Chordata
Phylum Chordata
Chordates have:Bilateral symmetryA coelom Deuterostome development
Radial, indeterminate cleavageEnterocoelous coelom development
MetamerismCephalization.
Phylum Chordata
Five distinctive characteristics define the chordates:NotochordDorsal tubular nerve cordPharyngeal pouches (gill slits)EndostylePostanal tail
Notochord
The notochord is a flexible, rod-like structure derived from mesoderm.
Dorsal Tubular Nerve Cord
In chordates, the nerve cord is dorsal to the alimentary canal and is a tube.
Pharyngeal Pouches and Slits
Pharyngeal slits are openings that lead from the pharyngeal cavity to the outside.
Endostyle or Thyroid Gland
The endostyle in the pharyngeal floor, secretes mucus that traps food particles.
Postanal Tail
The postanal tail provides motility in larval tunicates and amphioxus.
Phylum Chordata
Two protochordate subphylaSubphylum UrochordataSubphylum Cephalochordata
Subphylum Urochordata
Tunicates
Subphylum Urochordata
Life Cycle of ascidian
Subphylum Urochordata
Adult of Ciona
Subphylum Urochordata
Subphylum Urochordata
Subphylum Cephalochordata
Subphylum Cephalochordata
Subphylum Vertebrata
Subphylum Vertebrata
Subphylum Vertebrata = Craniata
Neural Crest Cells
Notochord
(a) The neural crest consists of bilateral bands of cells near the margins of the embryonic folds that form the neural tube.
(b) Neural crest cells migrate todistant sites in the embryo.
Migrating neuralcrest cells
Ectoderm
Ectoderm
Dorsal edgesof neural plate
Neuralcrest
Neuraltube
The Origin of Vertebrates
The Earliest Vertebrates
Ammocoete Larva of Lampreys
Closely resembles the amphioxus lancelet
The Earliest Vertebrates
The Earliest Vertebrates
The Earliest Vertebrates
Agnathans.
Gnathostomes