Vivid Colors In Nature
The plant and animal kingdoms abound with bright colors, from the lush green of photosynthesizing plants to the bold black and orange stripes of tigers. Color plays a multitude of roles in the natural world, used to entice, to camouflage, or to warn other creatures. Colors signal harvest time, breeding conditions, and the change of seasons, from the first greens of spring to the brilliant reds and browns of the fall.
Pigments are chemical compounds responsible for color in a range of living substances and in the inorganic world. Pigments absorb some of the light they receive, and so reflect only certain wavelengths of visible light. This makes them appear “colorful.” Cave paintings by early man show the early use of pigments, in a limited range from straw color to reddish brown and black. These colors occurred naturally in charcoals, and in mineral oxides such as chalk and ochre. The WebExhibit on Pigments has more information on these early painting palettes. Many early artists used natural pigments, but nowadays they have been replaced by cheaper and less toxic synthetic pigments.
Biological pigments are pigments produced by living organisms. They can be found in many plants, including flowers, and even in our skin. Bacteria are colored by pigments. All biological pigments selectively absorb certain wavelengths of light while reflecting others. Color arises from the way the pigments react with light.
Biological pigments in plants
Plant pigments exist in a wide variety of forms, some with highly complex and large structures. Over 600 naturally occurring carotenoid structures have been identified, as well as over 7,000 flavonoids, including over 500 anthocyanins. This is discussed in more detail on the Flowers section. Biological pigments such as chlorophyll are colored organic molecules which owe their color to the presence of unsaturated bonds (e.g. C=C-C=C).
Biological pigments in animals
Melanin is the main pigment found in mammals. It is responsible for the color of hair and fur. There are different types of melanin (eumelanin and pheomelanin), and they produce a huge color range, from black to sandy to red.