"...an organism's characteristics are not wholly determined by genetics. There are environmental factors...that influence the makeup of an organism. With all the talk of Punnett squares and the emphasis on phenotypes that are completely determined by genetics, it is important to remind ourselves that genetics is not the only thing at play. We can observe the effect that the environment has on a genotype to make its phenotype change." -Jay Wile, Exploring Creation with Biology
We planted 60 radish seeds in two egg cartons, wetting the soil. We covered one egg carton with a box to keep out light and let one have sunlight. When half of the seeds sprouted, we examined them daily. The cotyledons (the two leaves in the sprout) were either yellow or green.
We discovered that those seeds in the light had some yellow cotyledons to begin with but turned green over time. Those left in the dark continued to stay yellow, and in fact, even the ones that were green to start with, turned yellow over time. By the end of a week of observation, all of the cotyledons in the egg carton in the dark were yellow and all of the cotyledons in the egg carton in the light were green.