Why sa node called pacemaker of heart

How is ribosomal rna useful as a molecular clock? a. a large portion of the dna ring is not vital to structure or function, allowing it to accumulate neutral mutations. b. its rate of mutation increases over time as organisms continue to evolve and differentiate from each other. c. a slow mutation rate makes it useful for determining evolutionary relationships between ancient species. d. it is only found in select organisms, making it easier to compare relationships between species that have it.

Ascience research group is testing a new type of plant food. one trial is conducted in a controlled experiment. the data from the trial show that the plant that received the new food grew faster than the control plant. the group announces that the new plant food makes plants grow faster. what is the main weakness in this scientific claim?

Hurry i need your (100 points) 1) what are the responsibilities of the region of the brain highlighted below? (picture located below) the highlighted portion is at the rear base of the brain, behind the brain stem. regulating homeostasis, hunger and eating, thirst and drinking, and many other functions of basic survival. coordinating movement and balance by using information from sensory nerves, including hand-eye coordination. controlling voluntary body movements, processing information from sense organs, thoughts, and learning abilities. regulating important involuntary bodily functions such as blood pressure, heart rate, breathing, and swallowing. 2)which of the following systems or structures is correctly paired with its function? neurons - brain cells that control thoughts, calculations, and memory cerebral cortex - portion of the brain that controls involuntary body movement peripheral nervous system - carries impulses to and from the central nervous system central nervous system - carries information from the nerves to the muscles and glands