Editing Yellow (section)

=== Biology ===
Autumn [[leaves]], yellow flowers, bananas, oranges and other yellow fruits all contain [[carotenoid]]s, yellow and red organic pigments that are found in the [[chloroplast]]s and [[chromoplast]]s of plants and some other [[photosynthetic]] organisms like [[algae]], some bacteria and some fungi. They serve two key roles in plants and algae: they absorb light energy for use in [[photosynthesis]], and they protect the green [[chlorophyll]] from photodamage.<ref name="fasebj.org"/>

In late summer, as [[daylight]] hours shorten and temperatures cool, the [[vein]]s that carry fluids into and out of the leaf are gradually closed off. The water and mineral intake into the leaf is reduced, slowly at first, and then more rapidly. It is during this time that the chlorophyll begins to decrease. 
As the chlorophyll diminishes, the yellow and red carotenoids become more and more visible, creating the classic [[autumn leaf color]].

Carotenoids are common in many living things; they give the characteristic color to carrots, maize, [[daffodil]]s, [[rutabaga]]s, [[buttercup]]s and bananas. They are responsible for the red of cooked [[lobster]]s, the pink of [[flamingoes]] and [[salmon]] and the yellow of [[Domestic canary|canaries]] and [[egg yolk]]s.

[[Xanthophylls]] are the most common yellow [[pigment]]s that form one of two major divisions of the carotenoid group. The name is from Greek ''xanthos'' ({{lang|grc|ξανθος}}, "yellow") + ''phyllon'' ({{lang|grc|φύλλον}}, "leaf"). Xanthophylls are most commonly found in the leaves of green plants, but they also find their way into animals through the food they eat. For example, the yellow color of chicken egg yolks, fat, and skin comes from the feed the chickens consume. Chicken farmers understand this, and often add [[xanthophyll]]s, usually [[lutein]], to make the egg yolks more yellow.

Bananas are green when they are picked because of the chlorophyll their skin contains. Once picked, they begin to ripen; [[hormones]] in the bananas convert amino acids into ethylene gas, which stimulates the production of several [[enzymes]]. These enzymes start to change the color, texture and flavor of the banana. The green chlorophyll supply is stopped and the yellow color of the carotenoids replaces it; eventually, as the enzymes continue their work, the cell walls break down and the bananas turn brown.

<gallery mode="packed" heights="140px">
File:Fall colors near the Eagle Lake trailhead.jpg|Autumn colors along the [[Eagle River (Cook Inlet)|Eagle River]] near [[Anchorage]], [[Alaska]]
File:Cornwall Daffodils.jpg|[[Daffodils]] in Cornwall
File:Bananas.jpg|[[Banana]]s, like autumn [[leaves]], [[Domestic canary|canaries]] and [[egg yolks]], get their yellow color from natural pigments called [[carotenoids]].
File:Raw egg.jpg|The yolk of a raw egg. The color comes from the [[xanthophyll]] carotenoids [[lutein]] and [[zeaxanthin]]
File:Duckling chicks (Unsplash).jpg|Duckling chicks
</gallery>

==== Fish ====
* [[Yellowtail (fish)|Yellowtail]] is the common name for dozens of different fish species that have yellow tails or a yellow body. Most of the time, yellowtail (fish) actually refers to Japanese amberjack, a fish that lives between Japan and Hawaii.
* [[Yellowfin tuna]] (''Thunnus albacares'') is a species of tuna, having bright yellow [[Anal fin|anal]] and second [[dorsal fin]]s. Found in tropical and subtropical seas and weighing up to {{convert|200|kg|lb|abbr=on}}, it is caught as a replacement for depleted stocks of [[bluefin tuna]].
* [[Smallmouth yellowfish]] (Labeobarbus aeneus) is a species of [[ray-finned fish]] in the genus [[Labeobarbus]]. It has become an invasive species in rivers of the Eastern Cape, South Africa, such as the Mbhashe River.

==== Insects ====
[[File:European wasp white bg.jpg|thumb|A [[yellow jacket]] [[wasp]]]]
* The [[yellow-fever mosquito]] (''Aedes aegypti'') is a mosquito so named because it transmits [[dengue fever]] and [[yellow fever]], the mosquito-borne viruses.
* [[Yellowjacket]]s are black-and-yellow [[wasp]]s of the genus ''Vespula'' or ''Dolichovespula'' (though some can be black-and-white, the most notable of these being the [[bald-faced hornet]], ''Dolichovespula maculata''). They can be identified by their distinctive black-and-yellow color, small size (slightly larger than a [[bee]]), and entirely black [[Antenna (biology)|antennae]].

==== Trees ====
[[File:Snowbowlaspens.jpg|thumb|left|American aspens, ''[[Populus tremuloides]]'']]
* [[Populus tremuloides]] is a [[deciduous]] tree native to cooler areas of North America, one of several species referred to by the common name [[aspen]].  ''Populus tremuloides'' is the most widely distributed tree in North America, being found from Canada to central Mexico.
* The [[yellow birch]] (''Betula alleghaniensis'') is a [[birch]] species native to eastern North America, from [[Nova Scotia]], [[New Brunswick]], and southern [[Quebec]] west to [[Minnesota]], and south in the Appalachian Mountains to northern Georgia. They are medium-sized [[deciduous]] trees and can reach about {{convert|20|m|abbr=on}} tall, trunks up to {{convert|80|cm|abbr=on}} in diameter. The bark is smooth and yellow-bronze,<ref>{{cite web|url=http://landscaping.about.com/cs/fallfoliagetrees/a/fall_foliage4.htm|archive-url=https://web.archive.org/web/20040105225057/http://landscaping.about.com/cs/fallfoliagetrees/a/fall_foliage4.htm|url-status=dead|archive-date=5 January 2004|title=Fall Foliage of 4 Types of Birch Trees|first=David|last=Beaulieu|website=About.com Home}}</ref> and the wood is extensively used for flooring, cabinetry, and toothpicks.
* The [[Thorny Yellowwood]] is an Australian rainforest tree which are valued for their deep yellow-white wood.
* [[Liriodendron|Yellow poplar]] is a common name for ''[[Liriodendron]]'', the [[tuliptree]]. The common name is inaccurate as this genus is not related to poplars.
* The ''[[Handroanthus albus]]'' is an urban tree with yellow flowers native to the [[Cerrado]] of Brazil.