BIOL108 Lecture 29: Nov.21

• School: University of Alberta
• Department: Biology (Biological Sciences)
• Course: BIOL108
• Professor: Lien Luong

Document Summary

They are marine and freshwater, and range from 1cm to 6m in length. Paraphyletic: is restricted to sh, it includes any completely aquatic cranial even that uses gills for respiration. Includes jawless shes, cartilaginous shes, and body shes, but excludes tetrapods. To make the taxon osteichthyes monophyletic, include all other bony vertebrates and use modern classi cation. Evolution of lungs and swim bladders: gas lled structures. Extant bony sh descended from fresh or brackish water ancestors that had simple lungs and gills. Simple lung= ventral out-pocketing of foregut with gas. Original lung modi ed into swim bladder in most extant bony sh. The lungs and swim bladders serve di erent functions. Both arise developmentally from the same embryonic tissue. Lungs and swim bladders developed form out-pocketing of the gut. Other bony sh kept both lungs and gills, such as lung sh. Others became fully terrestrial and completely dispensed the gills.