Final answer:
Blue whales use two blowholes to breathe air and hold their breath while diving since they have lungs not gills. In cold waters, their countercurrent heat exchanger and thick blubber layer help maintain body temperature, demonstrating their adaptation to their marine habitat compared to other aquatic and land animals.
Step-by-step explanation:
Blue whales, like all mammals, breathe air using their lungs. The presence of two blowholes on the top of their heads facilitates this process by allowing them to efficiently take in air when they surface. Being mammals, they do not possess gills and thus cannot extract oxygen from water like fish do. Instead, blue whales must hold their breath while diving and surface periodically to breathe. The ability to hold breath for an extended period is essential for these marine giants as they dive to great depths in search of food.
Living in cold water, whales have adapted to maintain their body temperature. They possess a mechanism known as a countercurrent heat exchanger, where the proximity of veins and arteries allows for efficient heat exchange to keep the blood warm. Additionally, blue whales are insulated by a thick layer of blubber, which provides thermal insulation and energy reserves. This adaptation is akin to how land animals living in cold climates have thick fur or may hibernate to conserve heat and energy.
In comparison to fish like coelacanths and lungfish, which use gills or lung-like organs to breathe and can live out of water for a time, blue whales have made different evolutionary choices that enable them to thrive in their marine habitat. While bony fishes have a swim bladder for buoyancy, which is homologous to lungs in land vertebrates and some fish, whales have evolved lungs for breathing air and distinct mechanisms for buoyancy and temperature regulation in the aquatic environment.