Final answer:
The heat conservation mechanism where warm and cold blood flows in opposite directions in seagulls is called countercurrent exchange. It is an adaption used by various animals to maintain body temperature.
Step-by-step explanation:
The process by which cold blood returning to the body from extremities in seagulls flows in the opposite direction of warm blood entering the extremities to conserve heat is known as countercurrent exchange. This heat conservation strategy is common in many animals living in cold regions and allows them to capture some of the heat from blood flowing out from the body core and return it, reducing heat loss. In seagulls and other animals like dolphins, sharks, and even bees, this adaption is crucial for maintaining body temperature in cold environments.