Many things in nature display the color yellow. From plants and flowers to animals, minerals, and even celestial bodies, yellow is a commonly occurring color in the natural world. In this article, we will explore some of the most notable naturally yellow items and examine what causes them to take on this bright, sunny hue.
Plants and Flowers
Several plant species produce yellow flowers, often to attract pollinators. Some examples include sunflowers, dandelions, daffodils, buttercups, and black-eyed Susans. The yellow color in the petals comes from carotenoids – organic pigments produced by plants. Two carotenoids responsible for yellow are lutein and zeaxanthin.
Aside from flowers, other plant parts like leaves, stems, and fruit can also be yellow. Banana peels turn yellow as chlorophyll breaks down, revealing carotenoids. Yellow leaves may indicate nutrient deficiencies in some plants. Sulfur compounds produce vivid yellow colors in species like lemons and grapefruits.
Animals
Various animal species display yellow as well. It may serve as a warning, like the yellow and black stripes of bees and wasps. Some butterflies and moths have yellow wings to stand out. Canaries and some finches owe their yellow plumage to carotenoid pigments obtained from food.
| Animal | Yellow Features |
|---|---|
| Bees | Black and yellow stripes |
| Butterflies | Wings |
| Canaries | Feathers |
| Frogs | Undersides |
Yellow skin and eyes in some frogs may warn predators of toxins. Yellow snaketails get both their common name and yellow-striped tails from their coloration. In the animal kingdom, yellow serves various functions from camouflage to communication.
Minerals
There are a number of naturally occurring yellow minerals. Sulfur, an abundant chemical element, forms bright yellow crystals. Pyrite, also known as fool’s gold, contains iron and sulfur, giving it a metallic yellow color. Orpiment is an arsenic sulfide mineral that ranges from lemon to orange-yellow.
| Mineral | Chemical Composition |
|---|---|
| Sulfur | Elemental sulfur |
| Pyrite | Iron sulfide |
| Orpiment | Arsenic sulfide |
| Molybdenite | Molybdenum sulfide |
Other yellow-colored minerals include molybdenite, realgar, marcasite, and cinnabar. Trace elements like sulfur and arsenic paired with metals produce these yellows when the minerals form.
Celestial Bodies
Our sun and many distant stars emit yellowish light. This is because their surface temperatures of 5,000-6,000 K produce peak wavelengths in the green-yellow part of the visible spectrum. The exact hue depends on the chemical composition and temperature of the celestial object.
Our moon also appears yellow during lunar eclipses as light passing through Earth’s atmosphere is filtered and reddened. This gives the moon a yellow to orange hue. Atmospheric effects on lighting also cause the yellow colors we observe in the daytime sky, sunsets, and sunrises.
Foods
Many foods and spices we consume get their yellow color from natural plant pigments. As mentioned before, carotenoids like beta-carotene give mangos, carrots, squash, and pumpkin their orange-yellow hues. Turmeric contains a chemical called curcumin that produces its distinctive yellow color and flavor.
| Food | Source of Yellow |
|---|---|
| Bananas | Carotenoids |
| Corn | Lutein |
| Turmeric | Curcumin |
| Saffron | Crocin |
Saffron gets its color from crocin, a carotenoid specific to the Crocus sativus flower. So in summary, yellow plant pigments that serve various biological functions are responsible for many yellow foods.
Tree Leaves and Foliage
During autumn in many areas, deciduous tree leaves turn shades of yellow, orange, and red as chlorophyll breaks down before falling. The visible carotenoids and anthocyanins provide this seasonal fall foliage. Some tree varieties noted for yellow leaves are ginkgo, honey locust, mulberry, ash, and hickory.
Evergreen conifers also produce yellow-green foliage all year round. Their needles contain carotenoids without as much chlorophyll as deciduous trees. Some yellow-leaved conifers are spruce, false cypress, and juniper.
Fungi
Many species of fungi and lichen display yellow colors. Pigments called pulvinic acid derivatives produce most yellow hues in fungi and lichen. One group known as yellow symbiotic fungi form complex relationships with plants and algae. The bright yellow coloration signals the symbiotic function to potential plant hosts.
Some examples of yellow fungi are golden chanterelles, yellow foot chanterelles, and chicken of the woods. Lichen like British soldiers and sunburst lichen have yellow in their coloration. Once again, yellow pigments play an important biological role for recognition.
Rocks and Minerals
In geology, certain rocks and minerals appear yellow because of their mineral content. As mentioned earlier, sulfur compounds are a common source of yellow color in rocks and minerals. For instance, iron pyrite contains iron and sulfide, which gives it a golden metallic sheen.
Other yellow minerals include orpiment, realgar, and marcasite. Yellow limestone may get its color from jarosite compounds. Fossilized egg shells of reptiles and birds sometimes retain their yellow hue as well.
| Rock/Mineral | Composition/Source of Yellow |
|---|---|
| Pyrite | Iron sulfide |
| Limestone | Jarosite compounds |
| Fossilized eggshells | Original pigments |
| Yellow calcite | Mineral impurities |
Trace minerals result in yellow varieties of quartz, calcite, and other crystalline rocks. The color ranges based on the type and amounts of these mineral impurities.
Manmade Items
While this article focuses on yellow things found in nature, there are important manmade items that get their yellow color artificially. Highway lines and barriers are coated in an industrial yellow paint made from toxic lead chromate. This helps visibility. Post-it notes contain a synthetic yellow dye for visual appeal.
Many cleaning products are yellow due to added dyes and bleaches. Food dyes like Tartrazine (FD&C Yellow 5) color candies, drinks, etc. The toxic pigment chrome yellow was historically used in painting. So in summary, modern synthetic yellow pigments have replaced older mineral and plant based ones.
Conclusion
Yellow is an abundant color in the natural world due to its high visibility. Plants, animals, fungi, rocks, and minerals contain specialized yellow pigments that serve functions like attracting pollinators, warning predators, filtering light, and more. Understanding the chemical composition and biological basis of yellow coloration provides insight into nature’s intricate designs. Next time you encounter something yellow, consider the complex chemistry and ecology behind its bright hue.
