Final answer:
Birds and mammals exhibit convergent evolution in the form of a (C) four-chambered heart that supports high metabolisms and warm-bloodedness, independently evolved from the three-chambered hearts seen in other vertebrates.
Step-by-step explanation:
The convergent evolution of birds and mammals is exemplified by the development of a four-chambered heart, which allows for a more efficient circulatory system that supports a high metabolism and endothermy (warm-bloodedness). Fish have a two-chambered heart, while amphibians and reptiles typically have a three-chambered heart, often with a partial separation of ventricles.
However, both birds and mammals have independently evolved a four-chambered heart, which ensures the complete separation of oxygenated and deoxygenated blood, thus contributing to their ability to maintain high levels of activity and a stable body temperature. This adaptation was critical for their respective lifestyles, with birds utilizing it for the rigors of flight and mammals using it to support their varying degrees of activity and endothermy.