Chordates
Author: Bruce Neville
Phylum: Chordata |
Description:
The phylum Chordata includes three subphyla: the Urochordata or
tunicates, the Cephalochordata or lancelets, and the Vertebrata or vertebrates. All Species of the
subphyla Urochordata and Cephalochordata are marine, so they do not occur in New Mexico. Members of 5 of
the 7 living classes of Vertebrata occur in New Mexico.
The phylum Chordata is characterized by the presence at some stage of life of a notochord, a dorsal hollow
nerve cord, and gill slits. The notochord is a stiff dorsal rod of cartilage that provides rigidity and
protection for the dorsal nerve cord. It is present in adults of the subphylum Cephalochordata and the fish
classes Agnatha and Chondrichthyes, but is replaced by a bony vertebral column in the other classes of the
subphylum Vertebrata. The dorsal hollow nerve cord is present in adults of all classes of vertebrates. All
fishes and some amphibians have gill slits as adults, but they are present only in the larvae of the other
classes of vertebrates. The vertebrates are characterized by the presence of a skull that protects the
brain and, in most classes, a cartilaginous or bony vertebral column that protects the spinal cord.
Vertebrates are tremendously varied in body form and include fishes, amphibians, reptiles, birds, and
mammals. They range in size from some fishes only an inch long as adults to the blue whale.
Geographic range:
Vertebrates are found worldwide, except at the very centers of the
polar ice caps.
Habitat:
Vertebrates occur in essentially every habitat on Earth, including the open
ocean, the deepest sea bottoms, the air, and the edges of the polar ice caps. They may be marine,
freshwater, terrestrial, aerial, or subterranean.
Food Web:
Vertebrates feed on essentially every available source of food. They may
be herbivores, carnivores, or omnivores.
Reproduction and Development:
Vertebrates display an amazing range of reproductive
adaptations. Some Species lay eggs, while others bear live young. The live young may be nourished by the
mother (as in mammals) or simply develop as eggs within the mother's body (as in rattlesnakes). Vertebrates
may build a nest and care for the young to varying degrees, or they may simply release their gametes into
the environment to develop without help from the parents. Most Species of vertebrate participate in sexual
reproduction, but some Species of fishes and reptiles are all female and do not undergo sexual
reproduction.
Behavior:
Vertebrates exhibit a wide variety of behaviors.
Ecosystem roles:
Vertebrates and arthropods are the two most important groups of
animals in nearly every habitat on earth.
Conservation:
Many vertebrate Species have huge populations and are not endangered.
Others, however, have limited ranges or have been reduced to such small populations that they are severely
endangered.
Taxonomy:
Kingdom: Animalia
Phylum: Chordata
Subphylum: Urochordata, tunicates (marine; not in New Mexico)
Subphylum: Cephalochordata, lancelets (marine; not in New Mexico)
Subphylum: Vertebrata
The 7 living classes of vertebrates are:
Agnatha: Lampreys and hagfishes; not found in New Mexico
Chondrichthyes: Cartilaginous fishes (sharks and rays); not found in New Mexico
Osteichthyes: Bony fishes; many Species in New Mexico
Amphibia: Frogs, salamanders, and caecilians; many Species in New Mexico
Reptilia: turtles, crocodilians, lizards, snakes, and tuatara; many Species in
New Mexico
Aves: birds; many Species in New Mexico
Mammalia: mammals; many Species in New Mexico
References:
The Audubon Society Encyclopedia of Animal Life. 1987. New York:
Portland House, 606 p.
Grzimek, Bernhard. 1974. Grzimek's Animal Life Encyclopedia. New York: Van Nostrand Reinhold, 13
vols.
Margulis, Lynn, and Karlene V. Schwartz. 1998. Five Kingdoms: an Illustratred Guide to the Phyla of Life
on Earth. New York: W.H. Freeman and Co., 520 p.
The New Larousse Encyclopedia of Animal Life. Rev. Ed. 1987. New York : Bonanza Books, 640 p.