Medical Tests MCAT-TEST Online Practice Questions and Exam Preparation

Medical Tests MCAT-TEST Online Questions & Answers

• Question 61:

  The most active non-metal has:

  A. medium electronegativity.
  B. high electronegativity.
  C. low electronegativity.
  D. large atom radii.
  B. high electronegativity.

• Question 62:

  The amount of lactic acid in muscles rises when they start lacking:

  A. carbon dioxide.
  B. oxygen.
  C. glucose.
  D. hydrogen carbonate.
  B. oxygen.

• Question 63:

  Although we know more about so-called Neanderthal men than about any other early population, their exact relation to present-day human beings remains unclear. Long considered sub-human, Neanderthals are now known to have been fully human. They walked erect, used fire, and made a variety of tools. They lived partly in the open and partly in caves. The Neanderthals are even thought to have been the first humans to bury their dead, a practice which has been interpreted as demonstrating the capacity for religious and abstract thought. The first monograph on Neanderthal anatomy, published by Marcelling Boule in 1913, presented a somewhat misleading picture. Boule took the Neanderthals' lowvaulted cranium and prominent brow ridges, their heavy musculature, and the apparent overdevelopment of certain joints as evidence of a prehuman physical appearance. In postulating for the Neanderthal such "primitive" characteristics as a stooping, bent-kneed posture, a rolling gait, and a forward-hanging head, Boule was a victim of the rudimentary state of anatomical science. Modern anthropologists recognize the Neanderthal bone structure as that of a creature whose bodily orientation and capacities were very similar to those of present-day human beings. The differences in the size and shape of the limbs, shoulder blades, and other body parts are simply adaptations which were necessary to handle the Neanderthal's far more massive musculature. Current taxonomy considers the Neanderthals to have been fully human and thus designates them not as a separate species, Homo neanderthalensis, but as a subspecies of Homo sapiens: Homo sapiens neanderthalensis. The rise of the Neanderthals occurred over some 100,000 years -- a sufficient period to account for evolution of the specifically Neanderthal characteristics through free interbreeding over a broad geographical range. Fossil evidence suggests that the Neanderthals inhabited a vast area from Europe through the Middle East and into Central Asia from approximately 100,000 years ago until 35,000 years ago. Then, within a brief period of five to ten thousand years, they disappeared. Modern human, not found in Europe prior to about 33,000 years ago, thenceforth became the sole inhabitants of the region. Anthropologists do not believe that the Neanderthals evolved into modern human beings. Despite the similarities between Neanderthal and modern human anatomy, the differences are great enough that, among a population as broad-ranging as the Neanderthals, such an evolution could not have taken place in a period of only ten thousand years. Furthermore, no fossils of types intermediate between Neanderthals and moderns have been found. A major alternative hypothesis, advanced by E. Trinkaus and W.W. Howells, is that of localized evolution. Within a geographically concentrated population, free interbreeding could have produced far more pronounced genetic effects within a shorter time. Thus modern human could have evolved relatively quickly, either from Neanderthals or from some other ancestral type, in isolation from the main Neanderthal population. These humans may have migrated throughout the Neanderthal areas, where they displaced or absorbed the original inhabitants. One hypothesis suggests that these "modern" humans immigrated to Europe from the Middle East. No satisfactory explanation of why modern human beings replaced the Neanderthals has yet been found. Some have speculated that the modern humans wiped out the Neanderthals in warfare; however, there exists no archeological evidence of a hostile encounter. It has also been suggested that the Neanderthals failed to adapt to the onset of the last Ice Age; yet their thick bodies should have been heat-conserving and thus well-adapted to extreme cold. Finally, it is possible that the improved tools and hunting implements of the late Neanderthal period made the powerful Neanderthal physique less of an advantage than it had been previously. At the same time, the Neanderthals' need for a heavy diet to sustain this physique put them at a disadvantage compared to the less massive moderns. If this was the case, then it was improvements in human culture -- including some introduced by the Neanderthals themselves -- that made the Neanderthal obsolete.

  All of the following are hypotheses about the disappearance of the Neanderthals EXCEPT:

  A. the Neanderthal physique became a handicap instead of an advantage.
  B. the Neanderthals failed to adapt to climatic changes.
  C. the Neanderthals evolved into modern humans.
  D. modern humans exterminated the Neanderthals.
  C. the Neanderthals evolved into modern humans.

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  Explanation/Reference:

  The hypotheses about the disappearance of the Neanderthals are all in Paragraph 5. Of the choices listed, only Choice C is not put forward in this paragraph as a possible explanation. Even if humans did evolve from an isolated group of Neanderthals, as Trinkaus and Howells suggest, knowing this would not shed light on the mystery of the disappearance of the entire population of Neanderthals.

• Question 64:

  If a gas occupies 0.1L at 200atm, what will its volume be at 1atm?

  A. slightly less than 20L
  B. 20L
  C. slightly more than 20L
  D. 2000L
  A. slightly less than 20L

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  Explanation/Reference:

  Ideal gases undergoing pressure and volume changes are related by the expression P1V1/T1=P2V2/T2. Here, temperature is not involved and P1V1= P2V2. However, since P1 is greater than 10atm, the size of the molecules cannot be

  ignored and volume V1 is slightly greater than it should be for an ideal gas. Therefore, the calculated volume V2=20L is slightly larger than it should be. Choice A is correct. B ?incorrect. The initial volume at a pressure of 200atm includes a

  small contribution from the molecules themselves, and therefore, the initial volume of 0.1L is larger than the volume of an ideal gas.

  C ?incorrect. See explanations for A and B.

  D ?incorrect. This answer choice incorrectly divides the initial pressure by the initial volume.

• Question 65:

  Although we know more about so-called Neanderthal men than about any other early population, their exact relation to present-day human beings remains unclear. Long considered sub-human, Neanderthals are now known to have been fully human. They walked erect, used fire, and made a variety of tools. They lived partly in the open and partly in caves. The Neanderthals are even thought to have been the first humans to bury their dead, a practice which has been interpreted as demonstrating the capacity for religious and abstract thought. The first monograph on Neanderthal anatomy, published by Marcelling Boule in 1913, presented a somewhat misleading picture. Boule took the Neanderthals' lowvaulted cranium and prominent brow ridges, their heavy musculature, and the apparent overdevelopment of certain joints as evidence of a prehuman physical appearance. In postulating for the Neanderthal such "primitive" characteristics as a stooping, bent-kneed posture, a rolling gait, and a forward-hanging head, Boule was a victim of the rudimentary state of anatomical science. Modern anthropologists recognize the Neanderthal bone structure as that of a creature whose bodily orientation and capacities were very similar to those of present-day human beings. The differences in the size and shape of the limbs, shoulder blades, and other body parts are simply adaptations which were necessary to handle the Neanderthal's far more massive musculature. Current taxonomy considers the Neanderthals to have been fully human and thus designates them not as a separate species, Homo neanderthalensis, but as a subspecies of Homo sapiens: Homo sapiens neanderthalensis. The rise of the Neanderthals occurred over some 100,000 years -- a sufficient period to account for evolution of the specifically Neanderthal characteristics through free interbreeding over a broad geographical range. Fossil evidence suggests that the Neanderthals inhabited a vast area from Europe through the Middle East and into Central Asia from approximately 100,000 years ago until 35,000 years ago. Then, within a brief period of five to ten thousand years, they disappeared. Modern human, not found in Europe prior to about 33,000 years ago, thenceforth became the sole inhabitants of the region. Anthropologists do not believe that the Neanderthals evolved into modern human beings. Despite the similarities between Neanderthal and modern human anatomy, the differences are great enough that, among a population as broad-ranging as the Neanderthals, such an evolution could not have taken place in a period of only ten thousand years. Furthermore, no fossils of types intermediate between Neanderthals and moderns have been found. A major alternative hypothesis, advanced by E. Trinkaus and W.W. Howells, is that of localized evolution. Within a geographically concentrated population, free interbreeding could have produced far more pronounced genetic effects within a shorter time. Thus modern human could have evolved relatively quickly, either from Neanderthals or from some other ancestral type, in isolation from the main Neanderthal population. These humans may have migrated throughout the Neanderthal areas, where they displaced or absorbed the original inhabitants. One hypothesis suggests that these "modern" humans immigrated to Europe from the Middle East. No satisfactory explanation of why modern human beings replaced the Neanderthals has yet been found. Some have speculated that the modern humans wiped out the Neanderthals in warfare; however, there exists no archeological evidence of a hostile encounter. It has also been suggested that the Neanderthals failed to adapt to the onset of the last Ice Age; yet their thick bodies should have been heat-conserving and thus well-adapted to extreme cold. Finally, it is possible that the improved tools and hunting implements of the late Neanderthal period made the powerful Neanderthal physique less of an advantage than it had been previously. At the same time, the Neanderthals' need for a heavy diet to sustain this physique put them at a disadvantage compared to the less massive moderns. If this was the case, then it was improvements in human culture -- including some introduced by the Neanderthals themselves -- that made the Neanderthal obsolete.

  It can be inferred from the passage that the rate of evolution is directly related to the:

  A. concentration of the species population.
  B. anatomical features of the species.
  C. rate of environmental change.
  D. adaptive capabilities of the species.
  A. concentration of the species population.

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  Explanation/Reference:

  According to the fourth paragraph, interbreeding in a concentrated population can produce more pronounced genetic effects in a shorter period of time than interbreeding in a sparser population would. From this it can be inferred that the rate

  of evolution is directly related to the concentration of the species population (Choice A).

  Changes in the anatomical features of a species (Choice B) may be a way to measure the rate of evolution, but anatomical features do not directly affect the rate of evolution. The rate of environmental change (Choice C) and the adaptive

  capabilities of a species (Choice D) may both affect a species' survival, but they too do not speed evolution up in the way that concentrating the population can.

• Question 66:

  Which of the following fungi is poisonous?

  A. Morchella
  B. Amanita
  C. Agaricus
  D. Rhizopus
  B. Amanita

• Question 67:

  In order to determine the Doppler shift in perceived sound frequency, the following variables must be known:

  speed of sound in medium time of interaction between sound source and detector distance between source and detector frequency of emitted sound

  A. I only
  B. I and III
  C. II and IV
  D. I an IV
  D. I an IV

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  Explanation/Reference:

  The equation for calculating the Doppler effect on perceived frequency relies on the actual frequency of emitted sound, speed of sound in the transmitting medium, and the relative velocities of the source and detector.

  A ?incorrect. Choice IV is also required.

  B ?incorrect. Distance is not a variable in the Doppler equation.

  C ?incorrect. Time of interaction is not a variable in the Doppler equation.

  D ?correct. Furthermore, the relative velocities of the detector and source are required.

• Question 68:

  Which one of the following chemicals would UNLIKELY be involved in the onset of a panic attack?

  A. Melatonin
  B. Epinephrine
  C. Norepinephrine
  D. Serotonin
  A. Melatonin

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  Explanation/Reference:

  A is correct. Melatonin helps to sustain people's circadian rhythms. It is mainly involved in the sleep-wake cycle regulation. It is secreted into the bloodstream at night, inducing drowsiness and making the person feel sleepy. It has been found to be effective in the treatment of anxiety due to its calming effects. These effects suggest that melatonin is not involved in the outset of acute anxiety episodes. Moreover, no findings have yet associated low or high levels of melatonin with anxiety disorders. B and C. These are incorrect. The hormone epinephrine (or adrenaline) and the neurotransmitter norepinephrine (or noradrenaline) are released in greater quantities during stressing, threatening situations. Anxiety disorders involve experiencing normal situations as menacing. This perception prompts fight-or-flight, stress-related responses. For example, the person's blood flow, arousal, alertness, attention and memory are boosted; and the chemicals epinephrine and norepinephrine are released in great quantities. Thus, these substances could be present during the onset of a panic attack. D. This is incorrect. Serotonin is a neurotransmitter. It is mainly involved in the regulation of homeostatic processes, such as sleep and appetite. It also plays an important role in the regulation of mood. Low levels of serotonin can result in the development of both depressive and anxiety disorders. Thus, serotonin levels might decrease during the onset of panic attack.

• Question 69:

  A helium-neon gas discharge laser as shown in Figure 1 below generates a coherent beam of monochromatic light at a wavelength of 632.8 nm.

  

  Figure 1

  A discharge current of electrons is created in the tube by an applied voltage. When these electrons collide with the helium atoms, they can excite ground-state helium electrons to an energy level of 20.61 eV. The excited electrons cannot decay back to the ground state by emitting a photon because such a transition does not conserve angular momentum. Instead, if the excited helium atom collides with a neon atom, a ground-state electron in the neon atom can be excited to an energy level of 20.66 eV, and the helium electron can return to its ground state. The above process occurs quite often in the tube until the percentage of neon atoms with electrons in the 20.66-eV energy level is greater than the percentage of neon atoms with electrons in lower levels. This condition is called a population inversion. An excited electron in one of the neon atoms can then spontaneously decay by emitting a photon of wavelength 632.8 nm in a random direction. The photon will stimulate the same transition in another excited electron in a neon atom. The photon radiated by this stimulated emission process travels in the same direction as the original photon. The resulting light is then reflected back and forth inside the tube until it escapes through the partially transparent mirror. (Note: A photon's energy in eV is given by E = 1240/, where is the photon's wavelength in nm. The helium and neon ground-state energies are both 0 eV.)

  A population inversion exists in the laser tube when:

  A. the percentage of neon atoms with electrons in the ground state is greater than the percentage of neon atoms with electrons in higher energy levels.
  B. the percentage of neon atoms with electrons in a higher energy level is greater than the percentage of neon atoms with electrons in lower energy levels.
  C. the percentage of neon atoms with electrons in a higher energy level is equal to the percentage of neon atoms with electrons in the ground state.
  D. all the neon atoms have electrons in the ground state only.
  B. the percentage of neon atoms with electrons in a higher energy level is greater than the percentage of neon atoms with electrons in lower energy levels.

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  Explanation/Reference:

  To answer this question, you have to refer back to the passage to find the description of the condition called a population inversion. The passage states that a population inversion exists when the percentage of neon atoms with electrons in the 20.66 eV energy level is greater than the percentage of neon atoms with electrons in lower levels. The distinctive characteristic of this distribution is that the percentage of atoms with electrons in a higher energy level is greater than the percentage of atoms with electrons in lower levels. The only choice that is consistent with this is choice B, so it is the correct answer.

• Question 70:

  One of the basic principles of ecology is that population size is to some extent a function of available food resources. Recent field experiments demonstrate that the interrelationship may be far more complex than hitherto imagined. Specifically, the browsing of certain rodents appears to trigger biochemical reactions in the plants they feed on that help regulate the size of the rodent populations. Two such examples of phytochemical regulation (regulation involving plant chemistry) have been reported so far. Patricia Berger and her colleagues at the University of Utah have demonstrated that instrumentality of 6- methoxybenzoxazolinone (6-MBOA) in triggering reproductive behavior in the mountain vole (Microtus montanus), a small rodent resembling the field mouse. 6-MBOA forms in young mountain grasses in response to browsing by predators such as voles. The experimenters fed rolled oats coated with 6-MBOA to non-breeding winter populations of Microtus. After three weeks, the sample populations revealed a high incidence of pregnancy among the females and pronounced swelling of the testicles among the males. Control populations receiving no 6- MBOA revealed no such signs. Since the timing of reproductive effort is crucial to the short-lived vole in an environment in which the onset of vegetative growth can vary by as much as two months, the phytochemical triggering of copulatory behavior in Microtus represents a significant biological adaptation. A distinct example is reported by John Bryant of the University of Alaska. In this case, plants seem to have adopted a form of phytochemical self-defense against the depredations of the snowshoe hare (Lepus americanus) of Canada and Alaska. Every ten years or so, for reasons that are not entirely understood, the Lepus population swells dramatically. The result is intense overbrowsing of early and mid-successional deciduous trees and shrubs. Bryant has shown that, as if in response, four common boreal forest trees favored by Lepus produce adventitious shoots high in terpene and phenolic resins which effectively discourage hare browsing. He treated mature, non-resinous willow twigs with resinous extracts from the adventitious shoots of other plants and placed treated and untreated bundles at hare feeding stations, weighing them at the end of each day. Bryant found that bundles containing only half the resin concentration of natural twigs were left untouched. The avoidance of these unpalatable resins, he concludes, may play a significant role in the subsequent decline in the Lepus population to its normal level. These results suggest obvious areas for further research. For example, observational data should be reviewed to see whether the periodic population explosions among the prolific lemming (like the vole and the snowshoe hare, a small rodent in a marginal northern environment) occur during years in which there is an early onset of vegetative growth; if so, a triggering mechanism similar to that found in the vole may be involved.

  It can be inferred that the study of lemmings proposed by the author would probably:

  A. fully explain the interrelationship between food supply and reproductive behavior in northern rodent populations.
  B. disprove the conclusions of Berger and her colleagues.
  C. be irrelevant to the findings of Berger and her colleagues.
  D. provide evidence indicating whether the conclusions of Berger and her colleagues can be generalized.
  D. provide evidence indicating whether the conclusions of Berger and her colleagues can be generalized.

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  Explanation/Reference:

  The author recommends research on the reproductive behavior of lemmings because lemmings are similar in kind and in habitat to voles. Knowing whether lemmings have a reproductive trigger mechanism similar to that of voles would allow

  us to determine whether Berger's findings about voles are true of other species as well. This idea is captured by Choice D.

  Choices B and C contradict this notion entirely. Choice A goes way too far: there is no way one study of lemmings could tell us all there is to know about the interrelationship between food supply and reproductive behavior in northern rodent

  populations.