Yolanthe Nguyen November 15, 2019 Fruit
Animals produce color in both direct and indirect ways. Direct production occurs through the presence of visible colored cells known as pigment which are particles of colored material such as freckles. Indirect production occurs by virtue of cells known as chromatophores which are pigment-containing cells such as hair follicles. The distribution of the pigment particles in the chromatophores can change under hormonal or neuronal control. For fishes it has been demonstrated that chromatophores may respond directly to environmental stimuli like visible light, UV-radiation, temperature, pH, chemicals, etc. Color change helps individuals in becoming more or less visible and is important in agonistic displays and in camouflage. Some animals, including many butterflies and birds, have microscopic structures in scales, bristles or feathers which give them brilliant iridescent colors. Other animals including squid and some deep-sea fish can produce light, sometimes of different colors. Animals often use two or more of these mechanisms together to produce the colors and effects they need.
While many animals are unable to synthesize carotene pigments to create red and yellow surfaces, the green and blue colors of bird feathers and insect carapaces are usually not produced by pigments at all, but by structural coloration. Structural coloration means the production of color by microscopically-structured surfaces fine enough to interfere with visible light, sometimes in combination with pigments: for example, peacock tail feathers are pigmented brown, but their structure makes them appear blue, turquoise and green. Structural coloration can produce the most brilliant colors, often iridescent. For example, the blue green gloss on the plumage of birds such as ducks, and the purple blue green red colors of many beetles and butterflies are created by structural coloration. Animals use several methods to produce structural color, as described in the table.
Countershading was first described by the American artist Abbott Handerson Thayer, a pioneer in the theory of animal coloration. Thayer observed that whereas a painter takes a flat canvas and uses colored paint to create the illusion of solidity by painting in shadows, animals such as deer are often darkest on their backs, becoming lighter towards the belly, creating (as zoologist Hugh Cott observed) the illusion of flatness, and against a matching background, of invisibility. Thayer’s observation ”Animals are painted by Nature, darkest on those parts which tend to be most lighted by the sky’s light, and vice versa” is called Thayer’s Law.
Winston Churchill once said “We shape our buildings, thereafter they shape us”. (Grangaard, 1993) Environmental factors play an essential role in the nutrition, growth, development and education of children. Each and every characteristic of their physical environment contributes to their education and development. Although residential location, design, order, plan, colors as well as the areas of play may contribute to a child’s learning, these same factors may also hinder the revelation of their potential.
Abbott Handerson Thayer’s 1909 book Concealing-Coloration in the Animal Kingdom, completed by his son Gerald H. Thayer, argued correctly for the widespread use of crypts among animals, and in particular described and explained countershading for the first time. However, the Thayers spoilt their case by arguing that camouflage was the sole purpose of animal coloration, which led them to claim that even the brilliant pink plumage of the flamingo or the roseate spoonbill was cryptic—against the momentarily pink sky at dawn or dusk. As a result, the book was mocked by critics including Theodore Roosevelt as having ”pushed [the ”doctrine” of concealing coloration] to such a fantastic extreme and to include such wild absurdities as to call for the application of common sense thereto.
Edward Bagnall Poulton’s strongly Darwinian 1890 book The Colours of Animals, their meaning and use, especially considered in the case of insects argued the case for three aspects of animal coloration that are broadly accepted today but were controversial or wholly new at the time. It strongly supported Darwin’s theory of sexual selection, arguing that the obvious differences between male and female birds such as the Argus pheasant were selected by the females, pointing out that bright male plumage was found only in species ”which court by day” The book introduced the concept of frequency-dependent selection, as when edible mimics are less frequent than the distasteful models whose colors and patterns they copy. In the book, Poulton also coined the term antisemitism for warning coloration, which he identified in widely differing animal groups including mammals (such as the skunk), bees and wasps, beetles, and butterflies.
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