1 Quiz 01 Results Name Quiz 01a Attempt Score 1.29139 Attempts 151 (Total of 151 attempts for this assessment) Graded Attempts 151 Question 1: Multiple Choice Average Score 0.4404 points Which one of the following mechanisms is least likely to generate heritable variation within a population? Correct Percent Answered epigenetic modifications of the genome 4.636% developmental plasticity 88.079% recombination 2.649% mutation 4.636% Unanswered 0% Question 2: Multiple Choice Average Score 0.46358 points Assuming that all other factors are equal, which one of the following diseases or conditions would you expect to be eliminated most rapidly over the course of human evolution? Correct Percent Answered Alzheimer’s disease 1.325% Atherosclerosis 3.974% Diabetes type 2 1.987% Hemophilia B 92.715% Unanswered 0% Question 3: Multiple Choice Average Score 0.38742 points Malocclusion refers to misalignment of the teeth or a mismatch between teeth of the upper and lower jaw. Analysis of skeletons during historical times and of fossils from prehistoric times indicates that malocclusion was rare over much of human existence. We, like others mammalian species, evolved to have a good match between teeth in the upper and lower jaws. In the last few hundred years, however, the incidence of malocclusion has increased dramatically in most parts of the world. This increased susceptibility to malocclusion is most likely due to … Correct Percent Answered mutation(s) in gene that determine jaw alignment. 1.325% an effect of malocclusion to increase evolutionary fitness. 6.623% rapid evolutionary change in tooth/jaw structure, driven by dietary changes. 14.57% a mismatch between the mechanisms of tooth/jaw development and the soft texture of modern, cooked food. 77.483% Unanswered 0%2 Question 4: Essay Average Score 0 points In many ways, the human body is an amazingly well “designed” machine, superbly suited to its functions. On the other hand, there are many flaws and quirks in the structure and function of the human body that seem useless, silly, stupid, or dangerous. The list below contains some of these obvious “design” flaws. Choose one of these, or propose another that is not in the list. Note: Do not use one of the examples discussed in lecture! This question will likely require you to do some research. In as few words as possible, provide the following information. Describe why the design is less than optimal. Does the flawed arrangement cause a problem, or is it just stupid? Speculate on how natural selection could have produced the flaw. Propose a better solution. Some flaws or quirks in human structure and function: 1. The retina has a blind spot, i.e., a central region with no photoreceptors. 2. Variation in eyeball shape commonly causes focusing errors, e.g., lengthening of the anterior-posterior axis causes myopia (nearsightedness). 3. The heart has only one pacemaker (the sinoatrial node), so there is no backup if disease affects the SA node. 4. Humans have muscles that wiggle their ears, with no known function. 5. Men have nipples but are incapable of nursing babies. 6. A large venous plexus in the walls of the rectum near the anal sphincter predisposes people to painful hemorrhoids. 7. Testes develop in the abdomen but must descend into the scrotum to be functional. 8. The left recurrent laryngeal nerve takes an extraordinarily long detour to reach its target muscles in the larynx. 9. If part of the heart is weakened by disease, that part may have difficulty expelling blood. This causes chronic over-inflation of the heart. Excessive stretching of the heart muscle weakens it further. If untreated, this positive feedback cycle causes rapid deterioration leading to death. Given Answers Although men have nipples, they cannot nurse babies. Why do they still have this body part if it is incapable of use? The design is less than optimal because in a typical parenting arrangement, the work of breastfeeding a baby could have been split between the mother and father, if the father's nipples could produce milk. However, though the arrangement is flawed, the fact that men have nipples does not actually cause any problems. Natural selection could have produced this flaw because there were no negative consequences inherently involved with the existence of male nipples, so there was no need to select against the trait. In fact, men have nipples because during fetal development, the embryo first follows the blueprint of female development, until weeks later when the testosterone of those with the Y-chromosome begins to affect development. Since the cause of male nipples emerges from early development and does not harm the human species, I would say that there is not a better solution, and that it is fine if men continue to have nipples. 3. The sinoatrial node, or the hearts "natural pacemaker," regulates the electrical impulses sent out that are responsible for the beating of the heart. When the SA node is performing abnormally (e.g. in Sick Sinus Syndrome), the heart lacks the ability to control the rate at which it beats (resulting in tachycardia or bradycardia among other things). The heart cannot respond regularly to activities such as exercise or sleeping, which can be detrimental to human health. It would make more sense to have a "back up" node that can process these electrical impulses in a nearby area of the heart. The structure of the heart is extremely complicated, so maybe natural selection simplified the design by only having one SA node. Optimally, there would be a way in which the heart could incorporate a back up system to the SA node3 function, or somehow make the heart less dependent on the SA node by sending the incoming signals from the brain to other more specific parts of the heart. Topic: Testes develop in the abdomen but must descend into the scrotum to be functional. a. This developmental 'design' in human males in problematic for a number of reasons. During embronic development of the male fetus, testicles are located in the abdomen near the kidneys. During the last stages of development, however, the testes gradualy migrate down the abdomen into the scrotum. This evolutionary 'design' is less than optimal becasue it has the potential to cause more than one problem. As a result of the descent of testicles prior to birth, men are more suscepticble to inguinal herniation because