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Chordates

Chordates include the vertebrates, or animals with backbones. However, not all chordates are vertebrates. Some chordates, such as the cephalochordates (as described by Berkeley) lack a spinal cord, and hence are not vertebrates.

The term chordate does not refer to the spinal cord, but rather the notocord. This is a stiff but flexible rod that runs the length of an animal at some stage of its life, whether embryonic, or adult. Other essential chordate features include gills, tails, and a nerve cord.

Yes, humans are vertebrates, and hence chordates. No, humans do not have gills or tails. We do have a notocord, and a nerve bundle. Embryonic humans at certain stages of development have gill-like structures, and tails. We lose those as we develop.

To focus in on the most relevant chordates, the vertebrates, there are five classes of vertebrates. These are, in roughly the order of complexity, Fish, Amphibians, Reptiles, Birds, and Mammals. To learn more about each of these important classes of wildlife, follow the links below.

Fish

FIsh are cold-blooded, aquatic vertebrates covered with scales. They spend their entire lifecycle as water-dwelling creatures, and can not breathe air (with few exceptions). In Ohio, there are over 160 known species of fish in our streams, rivers, lakes and ponds. Like any other animal, fish species have certain habitat needs. You can guess the condition of a stream by examining fish caught there. For example, trout are only present in Ohio in certain streams where there is a low sediment load, cool to cold temperatures, gravelly bottom, and pools of adequate depth for over-wintering safely. If you catch a brook trout, or red-sided dace, for example, you know you have a healthy cold-water stream. Learn more about fish at the Ohio Department of Natural Resources web site.

Amphibians

Amphibians are cold-blooded creatures that spend part of their life cycle in water and the remainder on land. These creatures are exclusively freshwater organisms. While some amphibians may tolerate brackish (a mixture of fresh and salt water) water, none are adapted to life in salt water. Examples of amphibians include: frogs, toads, and salamanders. They are adapted to life in moist environments, such as wetlands, ponds, streams, or the forest floor.

Salamanders are lizard-like creatures with four stubby legs and fairly long tails. While looking a bit like a lizard, salamanders are not reptiles. They lack the scales of lizards, and also have the amazing ability to re-grow legs or toes that are lost. Learn more about salamanders by visiting the Ohio Salamander Monitoring Program's web page.

Frogs and toads start out life as fertilized eggs, but soon develop into tadpoles, while have gills and a tail, but no legs. They then metamorphosize into the adult stage, whick breathes through both lungs and skin, but lacks gils. The tail is reabsorbed by the body and legs are formed. Adult frogs are smooth and more or less spend their time in and around fresh water. Toads are dry and warty looking, and tend to spend their adult lives in drier environments than frogs. You can help scientists learn more about frogs by keeping a frog log. To learn more about frogs, check out the Ohio Frog and Toad Web Page.

Reptiles

Reptiles are cold-blooded terrestrial animals with lungs and scales. Included in the class reptilia are snakes, lizards, turtles and crocodilians (alligators and crocodiles). In Ohio lizards, snakes and turtles can be found in appropriate habitats, but it does not stay warm enough during the winter months for crocodilians.