An earthworm absorbs oxygen directly through its skin. The worm has a circulatory system that brings oxygen to all its cells, which are evenly distributed throughout the worm’s volume. A typical specimen of the common earthworm (Lumbricus terrestris) has the following average dimensions: • Length – 12 cm • Radius – 0.32 cm The worm’s skin can absorb oxygen at a rate of A = 0.24 µmol per cm2 per hr (1 µmol = 10−6 moles). The worm’s body uses oxygen at a rate of B = 0.98 µmol per gram of worm per hr. Discuss whether the cylinder-without-endcaps model of a worm seems reasonable. Do you expect that your answers will change much if you include the endcaps? Why do you think the model was simplified to ignore the endcaps?

An earthworm absorbs oxygen directly through its skin. The worm has a circulatory system that brings oxygen to all its cells, which are evenly distributed throughout the worm’s volume. A typical specimen of the common earthworm (Lumbricus terrestris) has the following average dimensions: • Length – 12 cm • Radius – 0.32 cm The worm’s skin can absorb oxygen at a rate of A = 0.24 µmol per cm2 per hr (1 µmol = 10−6 moles). The worm’s body uses oxygen at a rate of B = 0.98 µmol per gram of worm per hr. Discuss whether the cylinder-without-endcaps model of a worm seems reasonable. Do you expect that your answers will change much if you include the endcaps? Why do you think the model was simplified to ignore the endcaps?

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