Final answer:
Crocodiles are the most efficient at transporting oxygen among frogs, turtles, and themselves, owing to their four-chambered heart and unique circulatory adaptations such as the foramen of Panizza.
Step-by-step explanation:
In considering which is more efficient at transporting oxygen - frogs, turtles, or crocodiles, we must look at their respiratory systems and heart structure. All of these animals use hemoglobin in their red blood cells for the transportation of oxygen. However, crocodiles are particularly specialized amongst these animals due to their four-chambered heart and unique circulatory adaptations.
Crocodiles' four-chambered heart, similar to those of mammals and birds, allows for more efficient separation of oxygenated and deoxygenated blood than the three-chambered heart found in other reptiles and amphibians. This aids in preventing the mixing of these two blood types and ensures a more efficient delivery of oxygen throughout the body. Additionally, crocodiles have evolved certain mechanisms, such as the foramen of Panizza and specialised connective tissues, which further optimise their oxygen transport, especially during extended periods under water.
In contrast, frogs being amphibians, rely more heavily on their skin for gas exchange and have a less effective, two-chambered heart. While turtles, which fall under reptiles, have a more efficient lung structure than amphibians and a three-chambered heart with a partial septum, they are still not as specialized as crocodiles in transporting oxygen.