On page 30, David Shenk talks about certain traits changing when exposed to a different environment. For example, he used yellow grasshoppers and how if you put them into a blackened environment, like a burnt one, the grasshopper's skin may change to black permanently if it's at a young enough age. What does this have to do with imprinting (look in the textbook) because of the specific age restriction of this change? Also explain the evolutionary advantage of this adaption in relation to certain environments (like forests, fields, etc).
(Mindy Shaw, mindyshaw95@yahoo.com)
When David Shenk describes the examples of certain traits changing in organisms when exposed to a foreign environment, he mentions that most changes happen during an early age. For example, the “temperature surrounding turtle and crocodile eggs determined their gender…[and] young, yellow-skinned grasshoppers became permanently black skinned for camouflage if exposed to a burnt environment at a certain age” (Shenk 30). What these results demonstrate is that genes are obviously influenced by the environment, and most environmental factors contribute to genetics during a young, developmental age. One such example of environmental factors being taken into account during developmental stages at a young age is imprinting. Imprinting, which is a type of animal behavior, “includes both learned and innate components” (Campbell 1126). Furthermore, imprinting is different because traits can only be learned during a “sensitive period, also called a critical period” (Campbell 1126). Imprinting is done on an imprinting stimulus, which is what the young follow to mimic actions and learn new behavior. Genes do have an important part in outcome of traits in an individual, and some factors are strictly innate, such as “the tendency to respond [to the imprinting stimulus] [which] is innate in birds” (Campbell 1126). However, the recognition of an imprinting stimulus depends on the environment in some cases as well, such as Konrad Lorenz’s experiment with graylag geese.
ReplyDeleteIt is possible that some of the experiments Shenk refer to require a critical period like imprinting. In contrast, however, while humans do not have a certain imprinting period, “human babies are special…not [because] they are born so intelligent but that they are designed to change their minds when faced with the data,” says Andrew Meltzoff, co director of the Institute for Learning and Brain Sciences at the University of Washington (Shenk 131). Shenk repeatedly argues that intelligence and traits are, in fact, not fixed, but “awaiting to be developed”(Shenk 131). While there is no specific ‘imprinting’ stage for human babies, there are different developmental milestones a baby crosses, usually within the first three months or so, like motor skills, hearing, vision, and communication (http://www.mayoclinic.com/health/infant-development/PR00061). Furthermore, a study conducted at the University of Minnesota demonstrated that the relationship between mothers and their children contribute to how aggressive their child becomes (http://healthland.time.com/2011/10/26/kids-behaving-badly-blame-it-on-mom/). This was a sound experiment designed to test nature vs. nurture, and the results demonstrated the GxE model because the way the mother interacts with the child determines the traits of the child; moreover, this shows parallel results to imprinting and how animals learn behavior from their environments, the imprinting stimulus.
*new paragraph after graylag geese*
DeleteIn contrast to humans, traits such as the skin color in grasshoppers can change due to their environment. Many other animals are able to camouflage to thrive in the environment, even if the environment exhibits any changes. Such changes include cryptic coloration, aposematic coloration, and Batesian mimicry, and all of these changes are usually in response to predators (Campbell 1201). In cryptic coloration, which is exhibited in the canyon tree frog, prey is difficult to spot. Similarly, animals with mechanical and physical defenses are able to threaten predators with physical traits. For example, a poison dart frog, which is harmful, exhibits aposematic coloration, or warning coloration, which is seen in animals with chemical defenses (Campbell 1201). Another type of camouflage is Batesian mimicry, in which a harmless species mimics a harmful one, like the hawkmoth Hemeroplanes ornatus which “puffs up its head and thorax when disturbed, looking like the head of a small poisonous snake” (Campbell 1201). Furthermore, other animals are able to camouflage with their environment without changing physically, such as the lion in the tall grasses it lives in, and the boreal owl in the balsam fir tree (http://curiosity.discovery.com/topic/ecology-and-the-environment/animal-camouflage-pictures3.htm). The evolutionary advantages of such adaptations to environment help the animals escape predation, which keeps populations sustainable. If species are able to avoid frequent predation and population remains high, then there will be an increase in genetic diversity. Also, in some cases, like the lion in fields of tall grasses, it is actually concealed from the prey, so predation is easier, and food is abundant.
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