comparative notes 11_11_10 - a Evolution of Lungs in tetrapods i Differences between fish and tetrapod lungs 1 paired unless they are secondarily lost 2

a. Evolution of Lungs in tetrapods i. Differences between fish and tetrapod lungs 1. paired, unless they are secondarily lost 2. larger surface to volume ratio 3. join the ventral side of the gut via a trachea a. in fish, the pneumatic duct joins the gut dorsally 4. receive unoxygenated blood from vessels derived from the 6 th aortic arch 5. return oxygenated blood directly to the heart with no mixing of blood from other organs 6. increasing compartmentalization of the lungs a. adaptation to larger body size or higher metabolic rate from amphibians to birds and mammals ii. Amphibians 1. Frogs a. Well developed lungs b. The lungs are simple sacs with partitions in the walls c. There are two short bronchi d. They have a larynx which connects to the hyoid apparatus e. The trachea may or may not have cartilage rings 2. Apoda (legless amphibians found in tropical areas) a. Legless b. Fossorial (= lives underground) c. They retain only the right lung (they secondarily lose the left lung) i. The larvae have both lungs 3. Urodela (salamanders) a. The vast majority have secondarily lost their lungs b. When lungs are present, they are long sacs with smooth walls iii. Reptiles 1. large lungs with lots of variation 2. snakes have one lung (have secondarily lost the other) 3.