In the early 1900s, experiments were conducted on two caterpillar species. The members of the two species
were each divided into two groups. One group of each species was placed under red light, while the other
group of each species was kept in the dark. When the caterpillars developed into butterflies, their wings
showed extreme color differences. Exposure to red light resulted in intensely colored wings, while those
kept in the dark had paler wing colors. The color differences were most likely due to
(1) mutations in the color-producing genes
(2) the caterpillars in the red light producing more DNA
(3) gene expression being affected by the environment
(4) the caterpillars in the dark evolving less than those in the light
