The Argument- Camouflage and the Environment
David Shenk mentions on page 30 how "young yellow-skinned grasshoppers became permanently black skinned for camouflage if exposed to a blackened (burnt) environment at a certain age" (Shenk 30) describing how the external phenotype of the grasshopper changes when exposed to a different environment. Explain how the change in the grasshoppers color would be an evolutionary advantage using the ideas presented in chapter 54 section 1 of Campbell on the cryptic coloration of animals and how animals are adapted to their environment, while also incorporating ideas discussed in chapter 52 over the different types of terrestrial biomes and how one may have helped induce this adaptation in the yellow-skinned grasshoppers. You may also want to include the similarities seen in this behavior and in the behavior of imprinting, both having to do with specific time periods in an animals life where a trait or behavior may be developed.
-Kyle Nelson (kynels21@gmail.com)
The coloration of grasshoppers is definitely an evolutionary advantage for the species. These grasshoppers are an example of cryptic coloration, or camouflaging to the environment (Campbell 1201). At first glance, it may seem that these grasshoppers are not evolutionarily advanced, for if they develop in a darkened environment, then they will remain like that later in life and not be able to change back to the normal yellow-green grass color to avoid predators. However, these grasshoppers are actually very evolutionarily advanced. First of all, while most grasshoppers can be found in a biome that is classified as “grassland,” this type of biome is very diverse by itself and may be a variety of different colors depending on where in the world the grassland is located. In addition, according to the University of Michigan, grasshoppers have very short lifetimes, and almost all grasshoppers die and do not make it through each winter. So if there is a fire and a grassland has a blackened color, it makes sense that the grasshoppers born around that time should be black in color, because by next spring when the grassland returns to its normal color, the grasshoppers will be dead. Grasshoppers also have many predators according to a University in Fairfax VA, so they need to be able to camouflage to the current environment very quickly in order to survive. Grasshoppers clearly need the selective advantage of being able to camouflage to whatever environment they were exposed to at a young age.
ReplyDeleteThese young grasshoppers are a perfect example of the GxE interactions that Shenk talks about throughout the book. The grasshoppers do not have a gene that codes for the yellow-green color of most grasslands. Instead, the grasshoppers seem to exhibit gene regulation that is affected by the environment. So, instead of having a specific gene that codes for one color, the grasshoppers most likely have multiple genes that could be turned on or off at any point. All the different skin colors that could be made from the grasshopper’s genes are turned off, and through environment interaction the correct color is turned on. This behavior must also be imprinting because after the grasshoppers environment changes, they cannot then develop a different skin color, they must stick with the first one they made. The grasshoppers have a critical period, during which they develop a certain characteristics (in this case skin color). This critical period is the only time that certain characteristics can be developed, and after that time the characteristics become permanent (Campbell 1126). Because of the critical period and the matching of the skin coloring with the environment, these grasshoppers are a good example of GxE as well as imprinting.
Brad Tiller (brad.tiller@comcast.net)