The document summarizes key characteristics of the phylum Chordata. It describes the four defining characteristics of chordates as having a notochord, pharyngeal gill slits, a postanal tail, and a hollow dorsal nerve cord. It provides examples of chordate animals like fish, birds, reptiles, amphibians, and mammals. The phylum is divided into the subphyla of Urochordata, Cephalochordata, and Vertebrata. Vertebrata is further divided into classes including mammals, birds, reptiles, and amphibians.

1. CHORDATAMichelle & Aldo

2. Chordata…Members of the Phylum Chordata include animals with which we are probably most likely familiar (including fish, birds, reptiles, amphibians and beasts like ourselves)As unlikely as it seems, based on embryological evidence, the echinoderms appear to be the most-likely ancestors to the early chordatesPrimitive stemmed echinoderms are thought to have shifted from arm-feeding to filter-feeding acquiring a body plan similar to urochordatesUnfortunately, the fossil record is poor and intermediates are lacking. The rest of the evolutionary picture is better documented.

3. CHARACTERISTICFour structural characteristics set chordates apart from all other phyla: a notochorda pharyngeal gill slitspostanal taila hollow dorsal nerve cordThese attributes are always found in the larval forms or early embryo (although they may be absent in the adult).

4. The NotochordThe notochord is mainly composed of fibrous connective tissueFor those animals in which it persists into the adult form, the notochord provides support (it acts like our backbone) and increases swimming efficiencyIn animals like ourselves, bony structures called vertebrae develop near the notochord and eventually replace it during embryogenesis

5. Pharyngeal Gill SlitsPharyngeal gill slits are cuts in the pharynx that connect to a cavity surrounding the pharynxFor organisms in which they remain in the adult, they are often elaborated into respiratory structures (and are sometimes involved in filtering food during feeding).The morphological equivalent of gill silts are seen briefly during our own development (weeks 4-5), but they usually close or develop into other structuresOccasionally, the slits do not close, resulting in the newborn having an opening in the neck area (a cervical fistula).

6. In all the phyla we have studied up to this point, the anus was terminal (at the tip of the tail)Chordates, on the other hand, follow the anus with a tail of variable length (again, an adaptation for locomotion).In us, the tail is short and fused (the coccyx at the base of your spine). The Postanal Tail

9. EXAMPLES• sea squirts, lancelets, lamprey eels • sharks, rays, trout, bass, tuna • lungfish, frogs, salamanders • snakes, lizards• turtles, crocodiles, dinosaurs, birds • mice, elephants, whales, dogs, people

10. Phylum Chordata is divided into three subphyla:Subphylum UrochordataSubphylum CephalochordataSubphylum Vertebrata

11. Subphylum Urochordata

12. Subphylum Cephalochordata

13. Subphylum Vertebrata

14. Subphylum VertebrataSubphylum Vertebrata has several divisions you need to be familiar with:SuperclassTetrapodaClass AmphibiaOrder Caudata – Tailed Amphibians; Salamanders; NewtsOrder Anura – Tailless Amphibians; Frogs; ToadsOrder Gymnophiona – CaecilliansClass ReptiliaSubclass Anapsida – Turtles; TortoisesSubclass Diapsida – Crocodiles; Snakes; LizardsClass AvesSubclass Archaeornithes – Archaeopteryx (Extinct)Subclass Neornithes – All Other BirdsClass MammailiaSubclass Prototheria – Monotremes – Platypus; EchindaSubclass Metatheria – Marsupials – Kangaroo; KoalaSubclass Eutheria – Placentals

15. SuperclassTetrapodaSuperclassTetrapoda has four major class divisions:Class AmphibiaClass ReptiliaClass AvesClass Mammailia

16. ClassReptiliaReptiles have acquired several advances over amphibians that have allowed them to move successfully into terrestrial habitats. Their skin, for example, is more heavily thickened and is protected with surface scales that are impervious to water. A reptile's scales are very different in structure from that of fish. The outer layer of skin is a thick layer of dead, keratin-filled cornified cells. These cells are organized into horny scales covering the entire outer surface. Since reptiles have internal fertilization, water isn't even needed for mating.

17. There are two major subclasses:Subclass Anapsida – Turtles; Tortoises; some dinosaursSubclass Diapsida – Crocodiles; Snakes; Lizards; most dinosaursThis is based on the presence or absence of certain temporal openings:

18. Class AvesThe long hollow and porous bones of birds are thin and slender to aid in flight. Many bones overtime have fused together to give support. Teeth have been lost and replaced by a light beak.Feathers are cornified epidermal appendages that are probably related to scales. They are used for thermoregulation, communication, and as a flight surface.There are two subclasses of Aves:Subclass Archaeornithes (Extinct Archaeopteryx)Subclass Neornithes(All other birds)

19. Class Mammalia There are three subclasses based on birthing systems:Subclass Prototheria (egg-laying monotremes)Subclass Metatheria (marsupials)Subclass Eutheria (placental)

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