Part D The idea of molecular clock genes has been studied for decades, but the hypothesis remains a controversial topic in
evolutionary biology. Why do you think that is the case? What are three questions you still have about the use of
molecular clocks?

Drag each tile to the correct box. the body monitors the levels of oxygen in the blood to regulate breathing. isabel is running in a marathon and is near the finish line. she feels out of breath. how will her nervous system work to generate a reaction? arrange the tiles in chronological order. isabel's breathing rate increases. sensory receptors in the arteries detect low oxygen levels. the brain sends signals through motor neurons. sensory neurons generate an impulse. the central nervous system relays an impulse to certain brain regions.