Blue Lining of the digestive tract Purple 16. A mutation may cause misplacement of body segments. Only the daughter cell with the gray crescent will develop normally. Both daughter cells will develop abnormally. Both daughter cells will die immediately.
Gas exchange takes place across moist membranes.
The gases move across the exchange membranes by diffusion. The total exchange surface area is relatively large. The lining of the alveoli is only one cell thick. The concentration of CO 2 is higher in the air than in the alveolar capillaries. Water contains much less O 2 than air per unit volume.