- If we compare the cutaneous respiration in amphibian and pulmonary mammals we will find that gas exchange is due to
(1) Positive pressure in both amphibian and mammals
(2) Negative pressure in both amphibian and mammals
(3) Positive pressure in amphibian and negative in mammals
(4) Negative pressure in amphibian and Positive in mammals
Introduction
Respiration in animals involves the exchange of gases—oxygen and carbon dioxide—between the organism and its environment. Amphibians and mammals employ differing respiratory mechanisms that reflect their distinct evolutionary adaptations, particularly seen in the pressures driving air into the lungs or respiratory surfaces.
Amphibian vs Mammalian Respiration
-
Amphibians:
Amphibians rely partly on cutaneous respiration (gas exchange through the skin) and partly on pulmonary respiration (lung breathing). Their lungs typically utilize positive pressure breathing.
Positive pressure breathing means that the amphibian actively pushes air into its lungs by creating pressure in the buccal cavity (mouth cavity) using muscular movements. Essentially, they force air down into the lungs. This is often described as “gulping” air. -
Mammals:
In contrast, mammals use negative pressure breathing.
Negative pressure is created when the diaphragm and intercostal muscles contract, expanding the thoracic cavity and creating a vacuum that pulls air into the lungs. This passive suction mechanism enables mammals to breathe efficiently at a higher metabolic rate.
Cutting Edge Differences in Gas Exchange Pressure
Feature Amphibians Mammals Primary gas exchange method Cutaneous + lung respiration Pulmonary respiration Breathing pressure mechanism Positive pressure (active air push) Negative pressure (air pulled in) Respiratory muscle involvement Buccal muscles actively force air Diaphragm and intercostals expand thoracic cavity Evolutionary advantage Adapted for dual aquatic and terrestrial life High metabolic activity, efficient oxygen intake
Scientific Explanation
Amphibians’ reliance on positive pressure breathing is suited to their amphibious lifestyle, enabling air intake even in water or semi-aquatic conditions. Their skin facilitates additional oxygen uptake by diffusion—a process independent of airflow pressure dynamics but requiring a moist thin skin surface.
In mammals, negative pressure breathing allows for more efficient ventilation, supporting increased oxygen demands due to higher metabolic rates.
Why Other Options Are Incorrect
-
(1) Positive pressure in both amphibians and mammals: Incorrect; mammals use negative pressure.
-
(2) Negative pressure in both amphibians and mammals: Incorrect; amphibians use positive pressure.
-
(4) Negative pressure in amphibians and positive in mammals: Incorrect; reverse of the true physiology.
Thus, the correct answer is:
(3) Positive pressure in amphibians and negative in mammals
Summary Table
Option Description Correctness (1) Positive pressure in both Both species actively push air into lungs Incorrect (2) Negative pressure in both Both species passively draw air into lungs Incorrect (3) Positive pressure in amphibians and negative in mammals Amphibians use buccal pumping; mammals use diaphragm suction Correct (4) Negative pressure in amphibians and positive in mammals Reversed scenario compared to true physiology Incorrect
Conclusion
The mechanism of gas exchange pressure differs fundamentally between amphibians and mammals:
-
Amphibians breathe by positive pressure, actively pushing air into the lungs.
-
Mammals breathe by negative pressure, pulling air into lungs through thoracic expansion.
Answer: (3) Positive pressure in amphibians and negative in mammals
-
