Middle Level: Sample 1
The diagram below shows a model for the circulation of air in Earth's atmosphere. In the model above, the rotation of Earth is ignored and Earth's surface is considered to be smooth with no land or sea interactions. Which of the following best describes the primary mechanism causing the circulation of air in this model? A. warm air at the top of the atmosphere flows toward cooler air at Earth's surface. B. warm air at the equator rises while cool air from the poles sinks and moves toward the equator. C. warm air in the lower atmosphere prevents cold air at higher altitudes from sinking and vice versa. D. warm air at the equator spreads along the surface of Earth and rises to displace cold air at the poles.
B. warm air at the equator rises while cool air from the poles sinks and moves toward the equator. The general circulation of air in Earth's atmosphere is the result of uneven heating of the planet's surface, with solar heating being greatest at the equator. Heated air near the equator rises and then spreads both north and south toward the poles. At the poles, the relatively cold air is more dense, sinking and then flowing back toward the equator. The net pattern of overall circulation is thus a flow of surface air from the poles to the equator and a simultaneous movement of upper-level air from the equator to the poles.
Occasionally snow falls into air that is above freezing. Although initially some of the snow melts, under the right atmospheric conditions substantial snow can continue to fall with temperatures several degrees above freezing. Which of the following best describes the conditions that make it possible for snow to fall when it is above freezing? A. the rapid fall of heavy snow into a saturated air mass reduces melting of the falling snow. B. evaporation of some of the precipitation into a dry air mass cools the air and precipitation. C. a high rate of condensation near the surface removes heat energy from the surrounding air. D. expansion of a saturated parcel of air as it spreads out across Earth's surface cools the air.
B. evaporation of some of the precipitation into a dry air mass cools the air and precipitation. The process of evaporation absorbs energy from the surrounding environment. People experience this most directly when they step out of a shower or pool and are chilled by the evaporation of water from their skin. When the air is very dry, precipitation that is falling evaporates rapidly into the surrounding air, cooling the remaining precipitation to below freezing. This allows snow to fall when air temperatures are above freezing. When the air becomes saturated and evaporation no longer lowers the temperature, the precipitation turns to rain.
A student is reading a general science text and encounters a section that does not make sense to the student. Which of the following strategies would be most appropriate for the student to use in this situation to improve and repair reading comprehension? A. using contextual analysis to deduce the meaning of any unfamiliar words encountered in the section. B. making connections between concepts previously read or learned and those presented in the section. C. identifying the topic sentences throughout the section and analyzing each of the sentences syntactically. D. increasing reading rate and fluency by skipping over the parts of the section that are most confusing.
B. making connections between concepts previously read or learned and those presented in class. As described, the student's comprehension difficulty is limited to a particular section of a text and therefore the student has understood the sections of text that preceded the problematic section. Typically, the concepts and information presented in different sections of an informational passage are related and are organized so that foundational concepts and information are presented first. Making connections between concepts in the confusing section and concepts previously learned in earlier sections is an effective metacognitive strategy for actively constructing meaning during reading. The concepts previously presented are likely to provide relevant background information to support comprehension of the difficult section.
Two scientists present two different hypotheses to explain the same phenomenon. Both hypotheses are reasonable, testable, and explain the existing data. Given that both hypotheses are scientifically valid, the hypothesis that will be favored by the scientific community typically is the one that: A. aligns with existing theories in other fields. B. requires the fewest new assumptions. C. supports previous research in the field. D. requires the least expensive testing to verify.
B. requires the fewest new assumptions. The principle that science tends to prefer a hypothesis that requires the fewest new assumptions only holds if the hypotheses being evaluated are equal in all other respects. The principle, known as Occam's razor, is based on the premise that all other things being equal, scientists should not invoke unnecessary assumptions to explain a phenomenon when a simpler valid explanation is equally supported by existing evidence.
As seen from the viewpoint of an observer in Earth's northern hemisphere, which of the following is a characteristic of the movement of stars across the celestial sphere? A. all stars appear to rise on the eastern horizon and set in the west. B. stars that are close to the pole never appear to rise or set completely. C. all stars appear to flicker more frequently the further that they travel. D. stars that enter the southern portion of the sky become red-shifted.
B. stars that are close to the pole never appear to rise or set completely. From the point of view of an observer in the northern hemisphere, stars appear to rotate in paths that are circular around the North Pole. Stars that are closest to the pole rotate in small circles and, as a result, never appear to move below the horizon, remaining visible in the night sky.
Which of the following provides the best example of a negative feedback system? A. melting of sea ice caused by a warming atmosphere increases absorption of solar energy by the newly exposed dark ocean. B. sweating and the evaporation of sweat from a person's skin reduces body temperature. C. injured tissue releases chemicals that activate platelets and these activated platelets activate more platelets to produce clotting. D. a public address system microphone picks up noise from its own speakers, producing feedback.
B. sweating and the evaporation of sweat from a person's skin reduces body temperature. The human body's temperature regulation system is an example of a system in which negative feedback prevents overheating of the body. The stimulus for the body's systemic response to overheating is increased body temperature. The thermostat in the hypothalamus recognizes the body is too warm and activates blood vessel dilation and sweating. The evaporation of the sweat and blood vessel dilation reduce the body's temperature in a classic negative feedback system that acts to reverse the warming of the body and prevent overheating.
Which of the following describes the primary reason why the seasonal change in daylight is greater at higher latitudes than it is at lower latitudes? A. the elliptical shape of Earth's orbit. B. the tilt of Earth's rotational axis. C. the variation in Earth's orbital speed. D. the orientation of Earth's orbital plane.
B. the tilt of Earth's rotational axis. As Earth orbits the sun, the 23.4-degree tilt of its rotational axis relative to its orbital plane does not change; however, the tilt of Earth's axis means that the Northern and Southern hemispheres will receive different amounts of solar energy depending on which hemisphere is tilted toward the sun. In the Northern Hemisphere summer, the northern end of Earth's rotational axis is tilted toward the sun. This positioning of the axis is the cause for the increased hours of daylight during the summer and the increased solar heating of the Northern Hemisphere between the equinoxes.
A General Science teacher regularly reads aloud short, complex informational texts that are related to the current unit of study but are written above students' instructional reading levels. During reading, the teacher pauses frequently to use think-aloud and discussion to highlight new vocabulary, deconstruct syntactically complex sentences, and develop students' conceptual understanding of the text's content. The teacher's approach to read-alouds promotes students' content-area reading development primarily by: A. enhancing their ability to select and use comprehension strategies. B. building their academic language and background knowledge. C. helping them distinguish between oral and written language conventions. D. motivating them to use effective study and research strategies.
B. building their academic language and background knowledge. Vocabulary knowledge and concept development are closely interrelated; discipline-specific vocabulary development involves concept learning, while concept learning supports academic vocabulary development. Both academic language knowledge and background knowledge play important roles in the comprehension of content-area texts. By incorporating more difficult vocabulary into the instruction, the students' base knowledge is widened, giving the students new words to build upon. In discussing the text, students further cement the relationships of the new information to their background knowledge.
Radioactive isotope labeling using elements such as carbon and nitrogen has contributed most significantly to biology by facilitating the: A. creation of diffraction images for deducing the chemical structure of nucleotides. B. use of spectral analysis to determine the chemical composition of biomolecules. C. analysis of the movement of molecules during biochemical processes. D. ability to physically separate large macromolecules such as proteins from the cell cytoplasm.
C. analysis of the movement of molecules during biochemical processes. Carbon and nitrogen atoms are present in a wide variety of biomolecules and play an important role in many of the biological processes that take place in cells. When biomolecules are labeled radioactively, one atom is replaced with a radioactive isotope. This radiolabeled biomolecule can then be traced as it moves throughout a cell or organism by using any one of a variety of imaging systems. By tracing the movement of the biomolecule in this way, scientists can discover how a biomolecule is used and where it is distributed within a cell or organism, as well as a variety of other information about biochemical processes that cannot be monitored otherwise.
Which of the following is an example of a nonpoint source of water pollution? A. chemicals from a train car leak into a stream after a derailment. B. effluent from a treatment plant is discharged upstream from a town. C. antifreeze salt from roads washes into a lake after snow melts. D. bacteria from a faulty septic tank leach into an aquifer.
C. antifreeze salt from roads washes into a lake after the snow melts. A nonpoint source of water pollution is one in which a given pollutant that contaminates a body of water is not the result of a single, easily traceable source. Instead, the pollutant's presence in the body of water occurs occasionally, varies in intensity, and is associated with an irregular event or set of events. Consequently, a nonpoint source of water pollution is more difficult to monitor and control.
Scientists have determined that many galaxies in the universe, including the Milky Way, are rotating around a central region containing a: A. supernova. B. globular cluster. C. black hole. D. neutron star.
C. black hole. Extremely massive black holes appear to be the central organizing structure of a variety of different types of galaxies, including the Milky Way. Theory predicts that as matter is swept toward a black hole, it becomes incredibly hot, giving off abundant X-rays as it is finally pulled into the black hole. This is in fact what astronomers have observed from a variety of galactic nuclei, including the one at the center of the Milky Way. In addition, the high orbital speed of stars near the cores of many galaxies suggests that a huge mass, such as a black hole, is preventing them from flying away from the galactic core.
The development of the East African Rift Valley is primarily a result of which of the following geologic processes? A. crustal uplift and fracturing at the interface of two colliding tectonic plates. B. subduction of an oceanic plate at its boundary with a continental margin. C. breaking apart of a continental plate along a zone of crustal extension. D. erosion of sediments in a structural basin of the continental interior.
C. breaking apart of a continental plate along a zone of crustal extension. The East African Rift Valley is a classic example of the separation or rifting of a single continental plate as it begins to break into two separate plates. Tectonic extensional forces drive the rifting of a continental plate and it is typically accompanied by volcanic activity as magma moves upward into the fractures produced by the rifting.
Which of the following processes is a major mechanism helping drive the movement of tectonic plates? A. the gravitational force exerted by the sun and moon on Earth's crust. B. variations in the intensity and polarity of Earth's magnetic field. C. the flow of heat between warmer and colder parts of Earth's interior. D. changes in Earth's orbital velocity as it travels around the sun.
C. the flow of heat between warmer and colder parts of Earth's interior. The unequal distribution of heat within Earth's interior is the fundamental cause of the slow movement of tectonic plates. Convective flow in the mantle, resulting from the unequal distribution of heat, is the driving force causing the movement of tectonic plates. Warm, buoyant rock in the mantle rises, while cooler dense materials, such as the leading edge of a subducting plate, sink. Ultimately, mantle convection and plate tectonics are part of the same system that recycles tectonic plates back into Earth's interior. Relatively cool, dense subducting oceanic plates drive the downward component of mantle convection, while the upwelling of near-surface magma along oceanic ridge systems and rising mantle plumes support the upward component of mantle convection.
In using the scientific approach to analyze and investigate socioeconomic issues, such as hunger in developing countries, it is most challenging to determine which of the following components of the investigation? A. the goals. B. the essential problem. C. the variables. D. the affected populations.
C. the variables. When scientists investigate large-scale socioeconomic problems, it is difficult and sometimes not possible to identify all the variables that may be important causal factors underlying the problem.
Funding for scientific research may come from a variety of different sources, including government grants, non-profit organizations, and private companies. Which of the following situations is an ethical concern associated with the increase of scientific funds provided by private companies? A. scientific studies occur at relatively accelerated rates. B. multiple businesses are interested in pursuing the same field of study. C. certain fields of study have less monetary support than others. D. commercial interests influence the conclusions of scientific studies.
D. commercial interests influence the conclusions of scientific studies. Work associated with industry and private sources of funding may be proprietary in nature. As such, it may be subject to delays in publication or withholding of information or data that normally would be subject to peer review. In some cases, only certain research gets published and made available to the public.
In many regions of the world, alpine glaciers have been dramatically reduced in size over the last 100 years. Scientists have determined that a significant factor in this process has been an increase in the: A. intensity of ultraviolet light at high latitudes. B. concentration of ozone in the stratosphere. C. variability of precipitation during winter months. D. deposition of soot from the atmosphere.
D. deposition of soot from the atmosphere. Soot has been identified as a major cause for the increased melting of alpine glaciers over the past 100 years. The dark color of soot is the primary reason it is believed to be a climate forcing agent. Soot on snow or glacial ice decreases the albedo (i.e., reflectivity) of the snow or ice when sunlight strikes its surface. This increased absorption of solar energy by alpine glaciers increases the rate at which they melt during warmer times of the year, thereby reducing the annual accumulation of ice.
A geologist encounters an outcrop of sandstone that contains well-rounded sand grains of uniform size and composition. Given these characteristics, in which of the following depositional environments would the sand grains most likely have been originally deposited before they became sedimentary rock? A. flood plain. B. surf zone. C. river delta. D. dune field.
D. dune field. Wind effectively rounds sand grains by abrasion as the individual grains constantly collide with each other. Wind also sorts sand by size as the smaller grains are separated from the larger grains over time, creating the well-sorted sand typical of sand dunes. Wind sorting occurs because the size and mass of a grain that can be moved by wind is limited by the wind's velocity. As a sand dune moves over thousands of years, larger, more massive grains are left behind, while the smallest ones are blown away. This sorting process ultimately leaves a deposit of well-rounded sand grains of uniform size that may ultimately be lithified through compaction and cementing to form sandstone.
Which of the following tools would be most effective for measuring several millimeters of a liquid substance? A. volumetric flask. B. beaker. C. graduated cylinder. D. pipette.
D. pipette. For the small volumes of fluids involved, only a pipette would be an effective tool for precisely measuring millimeters of a liquid.
As cancer deaths increased in frequency, scientists began to investigate them more thoroughly and found that many cancers have hereditary components. Explorations into the specific genes that could be linked to cancer were initially slow. As technology developed, researchers were able to look at an increasingly wide range of genes until they were able to begin comparing whole genomes. As a result of these efforts, ever greater numbers of genes and mutations are being linked to different forms of cancer. Which of the following technologies played a key role in these research advances? A. X-ray crystallography. B. restriction enzyme digest. C. embryonic stem cell lines. D. polymerase chain reaction.
D. polymerase chain reaction. The polymerase chain reaction (PCR) has allowed rapid progress in the field of genetics. PCR is used to quickly make a multitude of copies of DNA from a quantity of DNA that would otherwise be too small to study. As sequencing techniques continue to improve, the time and cost that it takes to sequence an entire genome of an organism has decreased drastically. As genomic sequencing occurs on larger and larger scales, more patterns can be detected, allowing for newly recognized genes to be linked to a wide variety of characteristics. In this way, the genomes of individuals with cancer can be screened rapidly for genetic sequences that are common to individuals with the same type of cancer.
A wildlife biologist is conducting research to determine the cause of a rapid decline in a local population of raccoons. Which of the following statements concerning the decline of the raccoon population provides a testable hypothesis that would be the most practical to evaluate experimentally? A. random changes in genetic fitness have reduced the birth rate of the raccoon population. B. changes in diet have led to the outbreak of an unknown infectious disease in the raccoons. C. stress from changing climate conditions has reduced the health of the raccoon population. D. rabies has become widespread in the raccoon population and has increased mortality rates.
D. rabies has become widespread in the racoon population and has increased mortality rates. While all the response options could be topics for investigation, the only testable hypothesis that would be practical to evaluate experimentally is the hypothesis that widespread rabies has increased the mortality rate in the local raccoon population. Since both deceased and living raccoons could be tested for rabies, the hypothesis that rabies is the cause of the decline could be tested and either confirmed or rejected.
At approximately 30° north and south latitude the surface conditions are typically arid or semiarid. Which of the following atmospheric phenomena is primarily responsible for the climate conditions at this latitude? A. diverging winds aloft produce surface low pressure. B. converging surface winds produce strong updrafts. C. near-surface air is heated by tropical ocean currents. D. sinking air produces high pressure at the surface.
D. sinking air produces high pressure at the surface. Global atmospheric circulation produces a persistent high-pressure belt at approximately 30° north and south latitude. The existence of this subtropical high-pressure belt is connected to the solar heating of the equatorial regions. Solar energy drives convection of warm, moist air at the equator, causing heavy rainfall in many equatorial regions. This air then travels toward the poles until it cools sufficiently to sink at approximately 30° north and south latitude. As the air mass sinks, it compresses, becoming hotter and drier. This belt of sinking air in the subtropics is the underlying cause for the dry conditions that typify the climate at 30° north and south latitude.
The diagram below shows a geologic cross section. According to the diagram, which of the following statements about the sequence of geologic events must be true? A. the top layer of shale eroded before the faulting. B. the limestone was intruded into the shale deposition. C. the faulting occurred before the limestone was deposited. D. the basalt dike formed after the faulting occurred.
D. the basalt dike formed after the faulting occurred. Using the laws of stratigraphy, it is possible to analyze the sequence of events shown in the diagram above. According to the Law of Superposition, the oldest rock layers are on the bottom in an undeformed sequence. Therefore, in this sequence, shale is the oldest rock layer while limestone is the next oldest. Since the fault only cuts through these two layers, it follows that they were the only ones present during the faulting event because the principle of cross-cutting relationships states that an igneous intrusion is younger than the rock it crosses. The basalt dike cuts across the shale and limestone layers, meaning that it is younger than these two layers. Since the fault does not cross through the dike, the dike must have formed after faulting occurred.
The cross section below shows a confined aquifer and an unconfined aquifer located in unconsolidated sediments. There are four drinking water wells located in the geologic deposits. The wells take in water from the bottom 5 feet of the well casings, where the well casing is screened to allow the uptake of water. Hazardous waste is spilled on the surface over a 20-foot area indicated in the cross section. Given the characteristics of the two aquifers and the location of the wells and hazardous waste spill, which of the following wells is most likely to be contaminated by the spill? A. well A. B. well B. C. well C. D. well D.
D. well D. Wells A and D are both in the unconfined aquifer that will be most directly affected by the hazardous waste spill. Since the unconfined water table slopes away from Well A, it is highly unlikely that it would be contaminated. Well D, on the other hand, is down gradient from the spill and is at risk of becoming contaminated as the hazardous waste plume will most likely flow down gradient following the slope of the water table. The wells that are drilled into the confined aquifer are protected from the spill by the thick layer of clay, which is impermeable to water.
Valleys and coastal regions surrounded by large mountains occasionally experience atmospheric conditions that increase the concentration of locally produced air pollutants to dangerous levels. Which of the following is typically the underlying mechanism for concentrating air pollution in these geographic settings? A. hot air at the surface becomes saturated as it cools down overnight, creating fog. B. air temperature drops sharply with increasing elevation. increasing atmospheric instability. C. cold air at the surface becomes trapped beneath a layer of warm air, limiting convection. D. high pressure at the surface is overlain by low pressure aloft, producing downdrafts.
C. cold air at the surface becomes trapped beneath a layer of warm air, limiting convection. The presence of a temperature inversion—cold air at the surface located beneath a layer of warmer air—can concentrate locally produced pollutants. This occurs because the cold air is denser than the warmer air and the warm air acts as a lid preventing mixing of the layers and reducing the ability of pollutants below the warm layer to dissipate into higher levels in the atmosphere. This problem most often develops in northern valleys during winter months, but is also a problem in the Los Angeles Basin, where cooler marine air gets trapped at the surface beneath a layer of warmer air aloft.
Which of the following scientific breakthroughs provided the foundation for modern wireless communications between cell phones? A. research on sound transmission carried out by Alexander Graham Bell B. invention of the phonograph by Thomas Edison C. investigations of electromagnetic waves conducted by Heinrich Hertz D. discovery of the quantization of light by Max Planck
C. investigations of electromagnetic waves conducted by Heinrich Hertz. Heinrich Hertz was the first person to successfully show that electromagnetic waves existed by building and testing a device to transmit and detect radio waves. This accomplishment was built upon by many others, ultimately leading to the development of wireless communication systems for cell phones.
Which of the following strategies would be most effective in promoting students' understanding and retention of new earth science vocabulary words associated with a unit of study that focuses on earth systems? A. using weekly quizzes to assess students' knowledge of the newly introduced vocabulary words. B. having students look up definitions of the new vocabulary words in both a textbook glossary and a standard dictionary. C. providing multiple opportunities for students to use the new vocabulary words in discussions and in their writing. D. encouraging students to enter the new vocabulary words in a personal dictionary of words they find interesting or useful.
C. providing multiple opportunities for students to use the new vocabulary words in discussion and in their writing. Vocabulary learning is an incremental process; more exposure to new vocabulary and opportunities to use it in context result in greater depth of understanding. Providing students with multiple opportunities to use the vocabulary from a new unit of study both in discussions and in their writing promotes the students' vocabulary learning while simultaneously strengthening their understanding of associated concepts.
A teacher is putting together an investigation that explores the force required to move a toy car. In the investigation, the teacher wants the students to be able to compare the amount of force it takes to pull the toy car across surfaces with different amounts of friction. To perform this investigation, the teacher would normally have the students use a spring scale. However, the spring scale is missing and the teacher's class is about to start. Which of the following objects would be the best substitute for a spring scale in the proposed investigation? A. elastic ball. B. lead weight. C. rubber band. D. nylon rope.
C. rubber band. A spring scale is a device typically used to measure force. It stretches as more force is applied; the more force that is applied, the longer it stretches. In order to replace the spring scale in the investigation, the new object must also be able to stretch to different lengths. Since a rubber band is the only one of the four objects that stretches, it is the best option to use as a substitute for a spring scale.
Soils in regions of the tropics with high year-round rainfall tend to have which of the following characteristics? A. high organic matter content related to consistent warmth. B. low levels of soluble nutrients as a consequence of leaching. C. deep soils produced by centuries of stable climate conditions. D. anaerobic conditions resulting from a seasonally high water table.
low levels of soluble nutrients as a consequence of leaching. The high rainfall and warm temperatures common in some parts of the tropics cause the leaching of soluble nutrients from the soils, depleting the soils of nutrients other than iron and aluminum. Even though tropical rain forests have lush vegetation, rapid bacterial decay rates limit the development of humus. In tropical regions with high year-round rainfall, the nutrients needed for plant growth are typically held in the decaying organic matter on the forest floor and not in the underlying soils.
The surface temperature of Venus is greater than the highest temperatures that are reached on Mercury, although it is almost twice as far from the sun. Which of the following physical characteristics of Venus is the primary cause of the planet's high surface temperature? A. the occurrence of massive volcanic eruptions. B. the extremely slow rate at which it rotates on its axis. C. the absence of liquid water on the surface. D. the presence of high levels of carbon dioxide in the atmosphere.
D. the presence of high levels of carbon dioxide in the atmosphere. Due to the extremely high levels of carbon dioxide in Venus's atmosphere, a very strong greenhouse effect keeps temperatures extremely high. Venus's carbon dioxide-rich atmosphere allows solar radiation to warm the planet's surface, but limits the rate at which infrared energy can escape from the planet into space. Over time, the greenhouse effect has made Venus's surface hotter than Mercury's surface even though it is farther from the sun.
A General Science teacher would like to promote students' ability to read informational texts closely (e.g., identifying a text's essential vocabulary and main ideas; tracing an author's argument, claims, and evidence). The teacher could best support students' close reading by providing them with explicit modeling and guided practice in which of the following comprehension strategies? A. annotating a text during reading. B. predicting a text's outcomes before reading. C. using visualization and mental imagery during reading. D. identifying a text's organizational structure before reading.
A. annotating a text during reading. Annotating a text requires students to use various means (e.g., sticky notes, highlighting, notes in the text's margins) during reading to identify the text's key ideas and details, including the author's argument and claims, as well as the text's important vocabulary and evidence. Text annotation also supports students' participation in text-based collaborative discussions and enhances their comprehension and retention of essential text content.
A science teacher is reorganizing the room used for chemical storage. In order to appropriately store specific chemicals in a safe manner, the teacher should use a: A. container of mineral oil to store alkali metals. B. fume hood for long term storage of volatile compounds. C. d glass jar to store radioactive elements. D. metal cabinet for long term storage of strong acids.
A. container of mineral oil to store alkali metals. In order to safely store chemicals, it is necessary to first separate them into classes based on their properties. Each class of chemicals must then be handled with regard to its reactive properties. Alkali metals are highly reactive with water, including water in the atmosphere. By storing the metals in a hydrophobic environment such as a container of mineral oil, their contact with water is minimized.
Warming of Earth's surface on a sunny summer morning plays a major role in the formation of cumulus clouds and, when conditions are right, thunderstorms. Which of the following physical processes is central in this transfer of energy from the surface into the atmosphere? A. convection. B. conduction. C. radiation. D. evaporation.
A. convection. Solar heating of Earth's surface leads to the release of infrared energy by heated surface materials such as soils, vegetation, and pavement. On a hot summer morning, as the warming land surface heats the overlying air, the air rises into the atmosphere by convection. The heated air at the surface rises because as the air warms, it expands and becomes less dense than cooler air further up in the atmosphere. As this warmed parcel of air rises into the troposphere, it cools down both as a result of expansion and by the loss of heat by conduction to the surrounding cooler air. If there is sufficient water vapor in the convecting air parcel, it will condense into water droplets when it cools to the dew point, creating cumulus clouds and, if other conditions are right, thunderstorms.
In the past 20 years, research in a variety of fields has led to the development of advanced medical technologies for treating chronic and rare diseases. Which of the following questions presents the most serious ethical and economic issue associated with society's support for the development of these advanced medical technologies? A. how many people will benefit from these new technologies and at what cost to everyone else's health care? B. who is funding the research and will the use of these new technologies have unintended consequences? C. should animals be used for testing of these new technologies when there are some risks involved and uncertain benefits? D. is it appropriate to allow scientists and medical professionals to profit from the development of these technologies?
A. how many people will benefit from these new technologies and at what cost to everyone else's health care? Advanced medical technology is often extremely expensive and its use has driven up the overall cost of health care, reducing the availability of health care for the general population.
The geologic cross section shown in the diagram represents sedimentary deposition on top of ancient granitic basement rocks. The type of sedimentary rocks in the sequence and the order of the sequence suggest that these rocks were first deposited as sediments: A. in a coastal region where sea level rose and fell over time. B. in the semiarid continental interior near a seasonal lake. C. along a major river valley in the foothills of a mountain range. D. along the margin of a continental glacier that was melting.
A. in a coastal region where sea level rose and fell over time. Although sandstone and shale could have formed in a variety of freshwater settings, the sandstone-limestone-shale sequence indicates that these sedimentary rocks formed in a coastal environment, where sandstone was deposited near or on shore, the limestone in shallow marine waters, and the shale either in deeper marine waters or in estuarine swamps. The repetitive nature of the sequence suggests that the changes in the depositional environment were cyclical, such as might be caused by the repeated rise and fall of sea level associated with continental glaciations.
In 1928, Bell Labs wanted to investigate the possibility of using long wave electromagnetic radiation (wavelengths of 10-to20 m) for transatlantic communication. Physicist Karl Jansky built a directional antenna to look for potential sources of interference in this band. He found that interferences were caused by a variety of sources, including an unknown source that rose and fell once a day with a period of 23 hours 56 minutes. To which of the following inventions and subsequent discovery did Jansky's directional antenna lead? A. invention of the radio telescope and discovery of cosmic background radiation. B. invention of the satellite and discovery of planetary orbits. C. invention of the cell phone and discovery of digital communications principles. D. invention of the laser and discovery of quantum mechanics.
A. invention of the radio telescope and discovery of cosmic background radiation. Jansky's invention of the directional radio antenna and identification of a source of radio interference from the center of the Milky Way led to the invention of the radio telescope by Grote Reber, and thus to the development of the field of radio astronomy. Further investigations into interferences of radio telescopes led to the discovery of the cosmic background radiation left over from the Big Bang.
All of the planets within the solar system, with the exception of Venus and Mars, have a magnetic field. Which of the following planetary characteristics generates a planet's magnetic field? A. movement of a liquid conductive core. B. presence of plate tectonic activity. C. conduction of heat evenly over the surface. D. activity of a hydrological cycle.
A. movement of a liquid conductive core. Convective currents within liquid conductive cores allow interior heat to escape and generate magnetic fields around certain planets within our solar system. In the case of Mercury and Earth, the liquid core is an iron compound. The four gas-giant outer planets have cores of metallic hydrogen and liquid water.
When monitoring an active volcano that is at risk of a major eruption, geologists evaluate seismic data of local earthquake swarms by creating a network of seismometers surrounding the volcano. The evaluation of the local seismic data is most often used by geologists to monitor which of the following variables involved in a volcanic eruption? A. the movement of magma beneath a volcano. B. the changing composition of gases building up under a volcano. C. the rate of melting of volcanic rock beneath a volcano. D. the explosiveness of a particular magma body under a volcano.
A. the movement of magma beneath a volcano. The movement of magma into a near-surface magma chamber is a potential trigger for a volcanic eruption. As the magma moves into place below an active volcano, it releases seismic energy that produces distinctive signals, known as harmonic tremors, that seismologists study to determine if an eruption is likely.
An astronomer observes a distant star and analyzes slight blue and red Doppler shifts in the light emitted by the star. This information has been extensively used by astronomers to determine: A. the presence of an extrasolar planet orbiting the star. B. the composition of the star's core. C. the existence of gravity waves emitted by the star. D. the size of the star's photosphere.
A. the presence of an extrasolar planet orbiting the star. As a faraway object moves away from an observer on Earth, the spectrum of light emitted by the object is shifted toward the red end of the spectrum. Conversely, an object moving toward an Earth-based observer is shifted toward the blue end of the spectrum. A planet orbiting a star causes the star to wobble ever so slightly toward and away from Earth. It is this slight wobble that causes the spectrum of the star to cycle between a red shift in its spectrum and a blue shift. This has been the primary means for establishing the existence of extrasolar planets orbiting distant stars.
In a year-long study, scientists enclose a section of rain forest in a temporary greenhouse structure and raise the carbon dioxide levels 20 percent. They regulate the greenhouse to approximate conditions in a nearby section of rain forest that will be used as a control. The scientists find that the enclosed rain forest produced 5 percent more biomass per square foot than the control rain forest. Based on the results, the scientists conclude that increased atmospheric carbon dioxide will significantly increase worldwide agricultural productivity. Which of the following is the most significant problem with this conclusion? A. variables that affect plant growth in other regions were not accounted for. B. the study did not investigate all of the different components of the carbon cycle. C. tropical plants use carbon dioxide differently that most crop plants. D. the nutritional needs of rain forest plants were not evaluated during the study.
A. variables that affect plant growth in other regions where not accounted for. The major problem with the conclusion described in the question is that it did not account for many variables that affect plant growth in different parts of world. For example, soils in many regions may be depleted of nutrients or have insufficient water, sunlight, and warmth—all limiting factors affecting plant growth. No matter what the level of atmospheric carbon dioxide is in these regions, the plants will be unable to create significantly more biomass.
A General Science teacher wants to improve students' ability to comprehend print and digital academic texts at the discourse level by helping them recognize a text's organizational structure (e.g., comparison/contrast, chronological, cause/effect). Which of the following instructional strategies would likely be most effective in achieving this goal? A. ensuring that the texts selected for a given lesson include an example of each type of organizational text structure. B. teaching the students the transition markers, or signal words and phrases, commonly associated with each text structure. C. providing students with guided practice using various note-taking strategies, such as outlining and creating two-column notes. D. modeling for students key morphological strategies, such as applying knowledge of common roots and affixes and structural analysis skills.
B. teaching the students the transition markers, or signal words and phrases, commonly associated with each text structure. Helping students recognize transition markers promotes their ability to make logical connections between the ideas or events in a text. Each transition marker is commonly associated with a particular text structure. For example, texts that follow a comparison/contrast structure often use words/phrases such as "in the same way," "likewise," "in similar fashion," "nonetheless," "however," "though," and "on the other hand," while chronologically organized texts use terms such as "first," "next," "before," "as soon as," "eventually," "subsequently," and "preceding." Teaching students to scan a text for common transition words/phrases before reading will help them recognize the text's organizational structure and anticipate how the ideas in the text will relate to one another, and thus improve their comprehension of the text.