BIOL108 Lecture Notes - Lecture 28: Chondrichthyes, Ichthys, Craniate

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

Document Summary

Biol 108 - lecture #28 - bony fish. Originally class osteichthyes: osteo = bone, ichthys = fish, skeleton becomes ossified (bony) Now 3 classes: marine and freshwater. Includes any completely aquatic craniate that uses gills for respiration. Includes jawless fishes, cartilaginous fishes, bony fishes: excludes tetrapods. Would need to create a new group, or include the tetrapods. Evolution of lungs and swim bladders: gas-filled structures, descended from fresh or brackish water ancestors that had simple lungs and gills. Brackish: salty-freshwater, mostly low in oxygen levels: simple lung: ventral out-pocketing of foregut with gas. Fill it with air by breathing in. However, fish are able to gulp water as a backup system. Original lung was modified into swim bladder in most extant bony fish: swim bladder. Swim bladder is homologous (same evolutionary origin) to the lungs. Still gas filled chambers, but now used for buoyancy. Ingest air to float: both lungs and swim bladder arise developmentally from the same embryonic tissue.