Lungs Efficiently Expel Air

close up photograph of a whale blowhole seen above water

Biological Strategy

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Image: NOAA / Wikimedia Commons / Public Domain - No restrictions

Distribute Gases

Gases of particular importance to living systems are oxygen, carbon dioxide, and nitrogen. Oxygen and carbon dioxide are involved in respiration, so distributing these gases efficiently and effectively is important for a living system’s survival. However, gases are difficult to contain because they disperse easily. To accommodate this, living systems have strategies for confining gases and using gases’ properties to their advantage. For example, prairie dogs and mound-building termites build systems of tunnels and mounds that take advantage of wind to ventilate their underground homes.

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Expel Gases

The most familiar forms of discharging gases are through respiration when many living systems release carbon dioxide, and when plants release oxygen as the end product of plant photosynthesis. Because gases cannot be effectively moved through pushing, a different kind of force is needed to expel them. Creating that force requires energy, even at the cellular level, so living systems must have efficient strategies worth the energy investment or use an external force. This typically entails strategies that build up pressure or use other forces to propel gases. For example, a human exhales about 15% of its spent air per breath. In contrast, when a whale surfaces, it exhales 90% of its spent air in just one spouting.

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Mammals

Class Mammalia (“breast”): Bats, cats, whales, horses, humans

Mammals make up less than 1% of all animals on earth, but they include some of the most well-known species. We know first-hand some of the characteristics that make mammals unique, like having hair, being able to sweat, and producing milk through mammary glands. Another critical shared feature is a set of highly-specialized teeth. Unlike sharks or alligators, for example, whose teeth are generally all the same size and shape, mammals have differently shaped teeth in different areas of the jaws to target specific foods or foraging strategies.

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Lungs of whales efficiently expel air via powerful exhalations.

“The mammals’ dependency on air for breathing must be considered a real handicap in water, but the whale has minimised the problem by breathing even more efficiently than most mammals. Man only clears about 15% of the air in his lungs with a normal breath. The whale, in one of its roaring, spouting exhalations, gets rid of about 90% of its spent air. As a result it only has to take a breath at very long intervals. It also has in its muscles a particularly high concentration of a substance called myoglobin, that enables it to store oxygen. It is this constituent that gives whale meat its characteristic dark colour. With the help of these techniques, the fin-back whale, for example, can dive to depth of 500 metres and swim for forty minutes without drawing breath.” (Attenborough 1979: 242)

Last Updated August 18, 2016

References

Book

Life on Earth: A Natural History

Little, Brown and Company | 01/01/1970 | David Attenborough

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