Explain how the pulmonary circuit shows vertebrate adaptations to life on land. 2. Which vertebrate classes are fully adapted to a terrestrial lifestyle? 3. What anatomical feature is present only in mammals (the pig) but not in the other vertebrates? 4. How do the frog and pigeon (both air breathers) overcome the lack of this structure? 5. What anatomical feature(s) is/are present in pig and pigeon, but missing in the frog and perch
The Correct Answer and Explanation is:
Pulmonary Circuit and Vertebrate Adaptations to Life on Land
The pulmonary circuit in vertebrates is essential for transporting oxygenated blood from the lungs to the heart and then to the rest of the body. This system is a key adaptation to terrestrial life because it enables vertebrates to maintain the oxygen supply in an environment where the oxygen concentration in water is lower than in the air. The pulmonary circuit also allows the heart to pump blood to the lungs for oxygenation before distributing it throughout the body, ensuring efficient respiration, which is critical for sustaining high metabolic rates needed for active life on land.
Vertebrate Classes Fully Adapted to Terrestrial Lifestyle
The vertebrate classes that are fully adapted to a terrestrial lifestyle are the Amphibia (frogs, toads, salamanders), Reptilia (snakes, lizards, turtles), Aves (birds), and Mammalia (mammals). While amphibians require a moist environment for reproduction and early life stages, they are capable of living on land as adults. Reptiles, birds, and mammals have fully evolved adaptations such as waterproof skin (in reptiles), feathers (in birds), and fur (in mammals), which minimize water loss and allow them to thrive in terrestrial environments.
Anatomical Feature Present Only in Mammals (Pig)
An anatomical feature that is present only in mammals, including the pig, but not in other vertebrates is mammary glands. These specialized glands are responsible for producing milk to nourish their young. This feature is unique to mammals and supports the characteristic reproductive strategy of this class, where live birth and parental care are common.
How Frogs and Pigeons Overcome the Lack of Mammary Glands
Frogs and pigeons lack mammary glands, as they are not mammals. Instead, they use alternative strategies for feeding and nurturing their young. Frogs typically lay eggs that develop outside of the body, where the larvae (tadpoles) undergo metamorphosis. Pigeons, on the other hand, produce a secretion known as “pigeon milk” or crop milk, which they feed to their chicks. This secretion, although not the same as milk in mammals, provides necessary nutrients for the growing bird.
Anatomical Feature(s) Present in Pig and Pigeon, but Missing in Frog and Perch
The anatomical features present in pigs and pigeons but missing in frogs and perch include lungs for breathing air and three-chambered or four-chambered hearts. Pigs and pigeons both have highly developed lungs and efficient circulatory systems for fully terrestrial life. Frogs and perch, being amphibians and fish respectively, rely on gills (in their larval or aquatic life stages) and more primitive forms of breathing, and their circulatory systems are less complex, generally with fewer chambers in the heart.
