[Campbell Biology P.924] Why do complex multicellular animals like whales require specialize... | Practice Question

Why do complex multicellular animals like whales require specialized internal exchange surfaces, unlike simple organisms such as amoebas or hydras?

  • A: Their cells are too far from the external environment for direct diffusion.
  • B: They need to protect delicate tissues from abrasion and dehydration.
  • C: They have a higher surface area to volume ratio, making direct exchange inefficient.
  • D: They lack a circulatory system to transport substances.

Explanation

Complex multicellular animals are large, and their cells are too far from the external environment for nutrients and oxygen to reach them, or for wastes to be removed efficiently, solely by direct diffusion across the body surface. Therefore, they have evolved specialized internal exchange surfaces like lungs, digestive tracts, and kidneys that are extensively branched or folded to vastly increase the surface area available for exchange. These surfaces are then connected to a circulatory system that transports substances to and from all body cells.