On land, water is continuously lost by evaporation from the body surface, during breathing and through excretion, and water is not always available. So the main physiological challenge for a terrestrial animal is to conserve water. Adaptations include an impermeable body covering (skin with keratin, exoskeleton with wax), internal lungs, excretion of uric acid in birds, reptiles and insects, and production of concentrated urine by the loop of Henle in mammals. Pumping salts out through the skin or excreting large amounts of water is typical of aquatic animals, not land animals. So a terrestrial animal must be able to conserve water.
ConceptWater conservation on land
Excretory Products and their Elimination in past papers
60 questions from this chapter have appeared across 24 exam years.
