The jacklabbit is a desert mammal. the jackrabbit's circulatory system increases blood flow to the ears during hot days. the blood flow to the ears decreases during cool or cold nights. this circulation pattern is most directly related to -

The correct answer is homeostasis.

Explanation:

A mechanism of the body to sustain a steady internal environment in spite of the modifications occurring in the external surrounding is known as the homeostasis. Maintaining the temperature of the body, controlling blood pH, and the concentration of glucose in the body are some of the ways followed by the body to sustain homeostasis. One of the prime examples of homeostasis is the internal body temperature of an organism.  

the answer to your question is sperm