Question

26. Due to the hypertonic environment in which they live, marine fish are always in danger of losing water to their surroundings. Provide three adaptations/behaviors that these organisms use to minimize water loss. (3)

27. Bluefin tuna are considered endotherms, but not homeotherms, why? (2)

Answer 1

26•Marine fishes have aglomerular kidneys with less number of nephrons.Such kidneys minimize the loss of water through urine.

•To compensate water loss the marine fishes drink more water,and along with this water salts are added to the body fluids and disturb the internal equilibrium.

•To maintain salt balance in the body they have salt secreting chloride cells in their gills.

•Some cartilagenous fishes retain urea and trimethylamine oxide in their blood to keep the body fluids isotonic to the sea water and avoid dehydration of the body due to exosmosis.

27.

Blue finned tuna are endothermic organisms.Their lateral swim muscles have veins,which when come in contact with the arteries coming from gills,heat the arterial cold blood therby elevating their body temperature above the surrounding water temperature.