All cells receive nutrients and oxygen via diffusion. As cell size increases, its surface area increases by an exponent of 2 (n2) while its volume increases by an exponent of 3 (n3). Thus as cells increase in size, surface area to volume ratio decreases. Since cell requirements are governed by its volume and its uptake ability depends on its surface area, the small surface area to volume ratio will lead to the cell being unable to sustain itself as its uptake is too little as compared to its requirements.Therefore, it is advantageous for cells to be small as this would lead to a large surface area to volume ratio and thus the cell being able to sustain itself. Therefore having many small cells will lead to a greater total surface area than a single large cell.
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