GEOSC 040 Lecture Notes - Lecture 15: Agnatha, Osteichthyes, Chondrichthyes
Document Summary
Streamlined body that allows them to swim rapidly. Gill- efficient transfer: extraction of dissolved oxygen from water, remove carbon dioxide from bloodstream, water and blood circulate in opposite direction, diffusion of molecules by gill membranes. Why do they die out of water: gills dry out and are ineffective, they cant keep gills moist on their own. Need to keep salt and fluid content constant. Salt-water fishes- drink lots of seawater, excrete salt through gills, don"t pee a lot. Fresh-water fishes- don"t drink, absorb salt through gills, large amount of urine. Maintaining buoyancy: most fish are denser than the water they live in, must swim constantly to provide lift. Gas content is adjustable on a low scale. Cartilaginous fish have no bladder and must swim constantly to provide lift. Pacific salmon shrink and resorb their intestinal system when they are about to spawn- die shortly after. Spawn then larvae migrate to fresh water.
