Zoology 10th Edition by Stephen Miller,John Harley

Exercise 10

Amphibian body systems show adaptations for their double life in the water and on land. An amphibian's skin is thin and glandular. It must remain moist as it functions in defense, gas exchange, temperature regulation, and water regulation. The amphibian skeleton is modified to provide flexibility and support on land. Adult amphibians are carnivores. The amphibian heart, with its undivided ventricle, pumps blood into carotid, pulmonary, and systemic arteries. Separation of pulmonary and systemic circuits is unnecessary as gas exchange occurs across lung capillaries, the skin, and moist surfaces of the mouth and pharynx. Visual and auditory senses are important in feeding, reproduction, and many other functions. Amphibians excrete ammonia, uric acid, and urea. In freshwater, osmoregulation rids the body of excess water and conserves ions. On land, behavioral and physiological processes conserve water. Reproduction involves external or internal fertilization, larval development in moist environments, and metamorphosis to the adult. Vocalization and other courtship behaviors are often used in attracting mates in anurans where fertilization is external. In salamanders, males use visual and chemical signals to attract females to spermatophores.
What evidence is there in the circulatory systems of amphibians and lungfish (see figure 18.15) of the sarcopterygian ancestry of amphibians?
FIGURE 18.15 Circulatory System of Fishes. Diagrammatic representation of the circulatory systems of ( a ) bony fishes and ( b ) lungfishes. Hearts are drawn from a ventral view. Major branches of arteries carrying blood to and from the gills are called branchial arteries (or embryologically, aortic arches) and are numbered with Roman numerals. They begin with II because aortic arch I is lost during embryonic development.