D. Number of protons in an atom's nucleus
        
                    
             
        
        
        
Nerve cells are functionally classified as sensory neurons, motor neurons, or interneurons. Sensory neurons (afferent neurons) are unipolar, bipolar, or multipolar shaped cells that conduct action potentials toward or into the central nervous system.
        
             
        
        
        
Answer: They compare the number of mutations to determine how long ago species separated and evolved.
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Answer:
Biomagnification stands for Biological Magnification, which means the increase of contaminated substances or toxic chemicals that take place in the food chains. These substances often arise from intoxicated or contaminated environments. The contaminants include heavy metals namely mercury, arsenic, pesticides, and polychlorinated biphenyls  compounds which are then taken up by organisms because of the food they consume or the intoxication of their environment.
Explanation:
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