Temporary Covering Protects From Dirt and Impact

a gray and white striped tabby cat sticks its tongue out while its inner eye lid comes out on a wooden surface

Biological Strategy

Mammals

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Protect From Dirt/solids

When dirt and other small solids adhere to living systems, they can slow them down, create blockages, reduce their ability to carry out vital functions, or cause surface wear and tear. Due to electrostatic forces, it’s easy for dirt and other solids to adhere to surfaces, so living systems must overcome those forces. An earthworm, for example, uses a small electric current to keep soil particles from adhering to its body as it moves through the soil. This enables it to move more efficiently by reducing drag.

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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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The eyes of mammals are protected from dirt and impacts by eyelids.

“Being a particularly delicate instrument, the eye needs protection — usually, an eyelid. Most mammals have two eyelids, one above and one below, but some – such as horses and deer – have a third, inner eyelid, the nictitating membrane, which may move upwards or sideways across the eyeball. Both types of eyelid can be closed to protect the eye from a blow, or from dirt; in closing – blinking – they wipe the eyeball clean and lubricate it with teardrops.” (Foy and Oxford Scientific Films 1982:124)

Foy S, Oxford Scientific Films. The Grand Design: Form and Colour in Animals. Lingfield, Surrey, U.K.: BLA Publishing Limited for J. M. Dent & Sons Ltd, London; 1982. 238 p.

Last Updated August 18, 2016

References

Book

The grand design: Form and colour in animals

BLA Publishing Limited for J.M.Dent & Sons Ltd, Aldine House, London | 26/02/1983 | Sally Foy

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