This trait changes seasonally in captive polar bear populations due to Chlorella (“klor-eh-lla”) and Scenedesmus (“SEEN-ee-des-muss”) growth within enclosure swimming pools. In a case study of natural selection by Hopi Hoekstra, this trait diverged in two rock pocket mouse populations in New Mexico following a volcanic eruption. Input from U-shaped pupils and dermal opsins allow one class of animals to determine how this trait should be modified. After exposure to UV, (10[1])certain mammalian cells express tyrosinase to release the “eu-” and “pheo-” forms of a molecule that controls this trait. Melanocytes control this trait in mammals, whereas other animal species alter this trait through the activity of chromophores. For 10 points, name this trait that can be changed by cuttlefish and chameleons for adaptive camouflage. ■END■