Bonus: What does "N. B." mean?

The meselson-stahl experiment demonstrated that dna replication is semiconservative. in the figure, semiconservative replication is illustrated by

Why are adults bigger than they were as children biology

The pharynx is the structure in the body that serves as a pathway of both air and food. how does the body make sure that food does not get into the lungs? the salivary glands secrete enzymes that pull food out of the air pathway. the small intestine pushes the air out of the digestive system. the pancreas breaks down food in the air pathway. the epiglottis closes the air pathway so that food will not enter it.