BIOL 1002 Chapter : Biol 1002 Chapter 24
Document Summary
A notochord: a stiff flexible rod extending the length of the body. A dorsal, hollow nerve cord: lies above the digestive tract and expands anteriorly to form the brain. Pharyngeal gill slits: located in the pharynx that may form respiratory organs or may appear as grooves. A post-anal tail: the chordate tail extends past the anus. Humans are members of the phylum chordata. In humans, the chordate features are best seen during embryonic development, but later, we lose our notochord, gill slits, and tails. Only the dorsal nerve cord is retained in post embryonic human development. This group includes frogs, toads, salamanders, and caecilians. Amphibians begin life adapted to an aquatic environment (e. g. , tadpoles have gills) They later mature into semi-terrestrial adults with lungs. Most adults respire through lungs and moist skin. Most amphibians are confined to moist habitats. Their skin must be kept moist to avoid desiccation when out of water.
