Phylum Chordata

• Presence of a solid supporting structure on the dorsal side of the body called notochord.

• Presence of a dorsal hollow, tubular nerve cords.

• Presence of pharyngeal gill slits at least in the embryonic stages.

The phylum is divided into 4 sub phyla.

Hemichordata, Urochordata, Cephalochordata (together called as Protochordates) and Vertebrata.

Characteristics of Protochordates

	Hemichordata	Urochordata	Cephalochordata I
Non-chordate features	Terminal anus. Blood flows forward in dorsal blood vessel. Pelagic larva similar b holothurian echinoderm larva,	No trace of notochord n adult. No nerve cord in adult. dult a sessil filter eeder, structirally nothing like a chordate
Chordate features	Tripartite body plan of preoral proboscis, collar and trunk Pharyngeal slits may have arisen initially to dispose of excess water created by feeding mechanism. Laterly developed into food-collecting device, e.g. Seccoglossus	Gill slits in adult multiplied to form large filter-feeding pharynx. Larva in ascidian tadpole possesses the following features: notochord, pharyngeal slits, dorsal tubular nerve cord, segmental myotomes, post-anal tail. e.g,Ciona intest/ne/is	Fish-like animals showing all recognisable chordath features. Notochord extends length of body in larval and adult stages. Large pharynx with clefts forms feeding mechanism. Ciliated gill bars. Pharyngeal slits open into atrium. Segmental myotomes. No head or limbs. e.g..’vnphioxus /encec/etus

 

                      fig. 10.22 - Classification of Vertebrata

The phylum is divided into six classes.

Characteristics	Class Pisces	Class Amphibia	Class Reptilia	Class Ayes	Class Mammalia
Habitat	Aquatic	Amphibious	Terrestrial	Terrestrial	Terrestrial
Exoskeletion	Scales (dermal)	Usually absent	Scales (epidermal)	Feathers	Hair
Respiratory organs	Gills	Lungs	Lungs	Lungs	Lungs
Locomotor organs	Fins	Limbs	Limbs	Limbs	Limbs
Heart	Two chambers	Three chambers	Three chambers	Four chambers	Four chambers
Aortic arch	On both sides	On both the sides	On both the sides	Only on right side	Only on left side
Mode of reproduction	Oviparous	Oviparous	Oviparous	Oviparous	Mostly Viviparous
Fertilisation	External	Internal	External	Internal	Internal
Examples	Cartilagenous Rays sharks Bony Fishes Hemiramphus Hippocampus	Froas Toads Salamanders	Turtles Tortoises Crocodiles Lizards Snakes	Parrot Sparrow Myna Ostrich Rhea Penguin	Whale Bat, Rat, Rabbit Horse Cow, Lion Tiger, Cat, Dog, Shrew Apes, Monkeys, Humans

 

               fig. 10.23 - Examples of Pisces

fig. 10.24 - Examples of Amphibians

          fig. 10.25 - Examples of Reptilia

           fig. 10.26 - Examples of Aves

                    fig. 10.27 - Examples of Mammalia

Note

Mammals exhibit the following unique features also.

• Presence of mammary glands to nourish the young ones.

• Presence of muscular diaphragm that separates thorax from abdomen.

• Presence of external ear called pinna.

• Presence of seven vertebrae in the neck region.

fig. 10.28 - Fish Anatomy