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Article TitleTest Your Understanding QuestionAnswer
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AbdomenHow does the abdominal cavity differ between mammals and other pulmonate vertebrates?In mammals, the cavity of the thorax contains the lungs. In contrast, in other pulmonate vertebrates, the pleuroperitoneal cavity contains the lungs.
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Which structures are included in the viscera?The viscera includes the stomach, liver, gallbladder, spleen, pancreas, and intestinal tract, along with their associated nerves and blood vessels.
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Which structure adheres to the abdominal wall and forms the outermost coat of the viscera?The peritoneal sac adheres to the abdominal wall and forms the outermost coat of the viscera.
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Critical Thinking: What purpose do the mesenteries serve?Sample answer: The mesenteries hold the visceral structures in their appropriate locations within the abdominal cavity.
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Absolute zeroDefine absolute zero.Absolute zero is the temperature at which matter reaches its lowest energy state and all thermal activity theoretically ceases.
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What is absolute zero on the Celsius, Fahrenheit, and Kelvin scales?Sample answer: While standard thermometers measure temperature by measuring the change in volume of a substance, there are other methods that are more practical when measuring extremely low temperatures. If the correlations between temperature and other changes are known, then, in principle, measuring any of those other changes can provide a measurement of temperature. For example, a constant-volume ideal-gas thermometer assigns a temperature to a specimen by measuring pressure. As pressure goes up, temperature goes up, and at absolute zero, the pressure of a truly ideal gas would vanish. Also, because the most probable particle speed gets smaller as temperature decreases, measuring the distribution speeds of particles can measure temperature. The Boltzmann factor can be used to measure temperature because temperature can also be expressed as the ratio of magnetic ions in a higher or lower energy state.
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Critical Thinking: Compare and contrast different methods of measuring extremely low temperatures.Sample answer: While standard thermometers measure temperature by measuring the change in volume of a substance, there are other methods that are more practical when measuring extremely low temperatures. If the correlations between temperature and other changes are known, then, in principle, measuring any of those other changes can provide a measurement of temperature. For example, a constant-volume ideal-gas thermometer assigns a temperature to a specimen by measuring pressure. As pressure goes up, temperature goes up, and at absolute zero, the pressure of a truly ideal gas would vanish. Also, because the most probable particle speed gets smaller as temperature decreases, measuring the distribution speeds of particles can measure temperature. The Boltzmann factor can be used to measure temperature because temperature can also be expressed as the ratio of magnetic ions in a higher or lower energy state.
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Critical Thinking: Describe evidence that would indicate that a specimen’s temperature is above absolute zero.Sample answer: At absolute zero, all thermal activity ceases, particle motion (except zero-point motion) stops, and the pressure of a truly ideal gas would drop to zero. Therefore, a specimen that emits heat, has observable particle motion beyond zero-point motion, or exerts a force on the walls of its container would have a temperature above absolute zero.
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Critical Thinking: Suggest potential practical applications for the ability to measure extremely low temperatures.Sample answer: Changes in temperature are associated with changes in many other properties. For example, low temperatures are associated with both the heat and electrical conductivity of metals. In some cases, we might want substances that conduct heat and/or electricity extremely well, which means we might want that substance to be kept at a very low temperature. It follows that being able to verify that substances are at very low temperatures is useful to be able to do, as verified low temperatures could be evidence that those substances will be suitable for tasks that require heat or electrical conductivity. For example, superconductors have a variety of applications and require low temperatures. Being able to verify that substances are as cold as superconductors require is a necessary step in ensuring that superconductors work properly.
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Acid and baseAccording to the Arrhenius-Ostwald theory, what substance is both a weak acid and a weak base?Water is both a weak acid and a weak base.
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How do solvents differ under the Arrhenius-Oswald theory versus the Brönsted theory?The Arrhenius-Ostwald theory only applies when the solvent is water. The Brönsted theory applies to any solvent.
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In a conjugate acid-base pair, how does the strength of a Brönsted acid relate to the strength of the base?An inverse relationship exists between the acid and base in the pairing. The stronger the acid, the weaker its conjugate base; the weaker the acid, the stronger its conjugate base.
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Which substance has a larger dissociation constant: HCl or HF? Explain why. HCl has a higher dissociation constant than HF. According to the table of conjugate acid-base pairs, HCl is a stronger acid than HF. The stronger the acid, the  higher the dissociation constant.
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Critical Thinking: Explain why virtually every cation is an acid according to the Lewis theory. Sample answer: According to the Lewis theory, acids are electron acceptors. Electrons are negatively charged. Because cations are positive ions, they attract electrons; this makes cations electron acceptors and, therefore, acids according to the Lewis theory.
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Acid-base indicatorsCan an acid-base indicator determine the precise pH of a solution? Why or why not?No. Acid-base indicators are used to visually approximate pH levels. Thus, they do not precisely measure pH.
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In what range is the pH of a solution in which the indicator phenolphthalein changes from colorless to pink? According to the table in the article, the pH of phenolphthalein is this case in the range of 8.4 to 10.0.
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Critical Thinking: A chemist places 100 mL of sodium hydroxide, pH of 13, in a flask with 2 drops of methyl orange. The chemist performs a titration of this solution with hydrochloric acid, pH of 2, until a complete color change occurs. What color change does the chemist observe, and why?The solution changes from yellow to orange. According to the table, the pH range of methyl orange is 2.8 to 4.0. This means that the indicator is orange in solutions with a pH below 2.8 and yellow in solutions with a pH above 4.0. Because sodium hydroxide is a strong base (pH = 13), the initial color of the solution is yellow. As the hydrochloric acid enters the solution, the pH of the solution decreases and changes to orange.
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Critical Thinking: Using the equilibrium equation (1) and the equation for the equilibrium constant (2), explain why adding a hydroxide base raises the pK of the indicator.According to equation (1), adding a hydroxide base converts the indicator to form (2) producing H+ and In- ions. Then, in equation (3), the log of the ratio of [In-]/[InH] results in a negative number, which is then subtracted from the pH. Because a negative number is subtracted from a positive number, the result is a higher pK.
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Acid rainCan precipitation with a pH of 5.5 be considered acid rain? Why or why not?Sample answers: No. The natural acidity of precipitation is 5.6, with a range of 4.9 to 6.5. Yes, if the normal pH of precipitation in that area is above 5.5.
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Why are locations in midlatitudes more likely to be affected by acid rain?Most precipitation in midlatitude areas comes from the flow of air from the surface level due to the action of cold and warm fronts. This carries the pollutants to the frontal cloud systems, where they attach to particles in the clouds.
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Critical Thinking: Is a drop in pH levels harmful to all species in an aquatic ecosystem? Why or why not?No. Acidification can be harmful to species and individuals that are acid-sensitive, but it could also be beneficial to acid-tolerant species. Fish tend to be affected more as they require a pH of 4–5 to maintain a proper salt balance.
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Critical Thinking: If there is no heavy industry or big city within 50 miles, is the area safe from acid rain? Why or why not?No. As pollutants can travel with the wind, areas downwind of heavy industry and urbanization can be affected by acid rain even if they are far away from the sources.
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Acquired immune deficiency syndrome (AIDS)How is HIV transmitted?A person who is infected with HIV transmits the virus to another person through the transfer of body fluids, such as semen, blood, and breast milk.It is not transmitted through casual skin contact. It is not transmitted through casual skin contact.
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Critical Thinking: Why might an individual with AIDS be instructed to wear a face mask?Individuals with AIDS are especially susceptible to lung infections, such as pneumonia and tuberculosis, because HIV attacks their immune systems, which depletes the T lymphocytes. A face mask may prevent the inhalation of pathogens that could cause these infections.
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Critical Thinking: Why is it important to give protective vaccinations to HIV-infected patients?The leading cause of death for patients with HIV is secondary opportunistic infection. Vaccines help protect these patients from pathogens that do not usually cause disease in healthy individuals.
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Activated carbonWhat properties characterize activated carbon?A powdered, granular, or pelleted form of amorphous carbon, activated carbon is characterized by very large surface area per unit volume.
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What are common uses of activated carbon?Uses of activated carbon include improving color, odor, and taste in foods and beverages, as well as removing impurities from water, gases, and various materials.
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How is carbon activated?Activation is the process of treating carbon to produce the characteristic pore structure, which typically requires the application of high temperatures or mixing with chemicals such as metal chlorides, potassium sulfide, potassium thiocyanate, or phosphoric acid.
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What advantages does activated carbon have over alternative commercial adsorbents?Compared with other commercial adsorbents, activated carbon has a broad spectrum of adsorptive activity, excellent physical and chemical stability, and ease of production from readily available waste materials.
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Critical Thinking: How might you improve the effectiveness of activated carbon in reducing a slight bitter taste in a new soft drink?Sample answer: I would choose a large-pore activated carbon, because it will work better in liquid-phase work than a finer-pore carbon. Also, mixing the carbon and liquid at lower temperature and higher pressures will increase adsorption of impurities that might cause the bitter taste. These impurities would be removed from the beverage when the activated carbon trapping them is removed by filtration.
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Addiction and addictive disordersDescribe the characteristics of addiction that are missing in people who drink alcohol but are not addicted to it.People who drink alcohol but are not addicted to it most likely do not demonstrate an increased need for alcohol or develop a tolerance that requires drinking greater amounts to feel the effects of drinking.
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Name the three opiate receptor types that have been identified. What is their role in addiction and its treatment?The three opiate receptor types are mu, delta, and kappa. In addition to binding opioids, these receptors bind opioid antagonists, such as naloxone, which displace receptor-bound opioids and can be used in the treatment of addiction.
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What are two physical and two physiological effects of cocaine addiction?The physiological effects of habitual (long-term) cocaine use include blockage of the reuptake of dopamine and disruption of the endogenous opioid system. These effects may reinforce the properties that lead to addiction and result in the physical effects, such as drug craving and relapse.
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Critical Thinking: Why could a long half-life and cross-tolerance be considered benefits of methadone?Sample answer: Because of its longer half-life (24 hours) compared with heroin and morphine (under 6 hours), methadone is effective in the prevention of the signs and symptoms of narcotic abstinence with a single daily dose. Because of its high degree of cross-tolerance for other narcotics, methadone blocks the effect of any illicit narcotics.
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Affective disordersHow are affective disorders distinguished from normal emotion?Affective disorders are distinguished from normal sadness or elation because (1) they consist of characteristic changes in brain and psychological function that affect sleep, appetite, speed of movement, energy, concentration, self-esteem, motivation, and pleasure capacity; (2) during an episode, these features are persistent, occurring day after day for at least several weeks; and (3) there is often associated impairment of functioning.
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What does research tell us about the link between brain neurochemistry and stress?Acute stress affects the release of neurotransmitters such as serotonin, norepinephrine, dopamine, and the glucocorticoid cortisol. Sustained unresolvable stress eventually depletes these neurotransmitters while cortisol levels remain high. This induces a behavioral state of "learned helplessness."
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Critical Thinking: How would you expect the occurrence of seasonal affective disorder to vary with geography and why?Sample answer: Because seasonal affective disorder comes and goes with the changing seasons—and along with that the varying amounts and intensity of sunlight—one would expect the disorder to occur relatively frequently in far northern latitudes, where sunlight is more limited, and less frequently at latitudes near the equator.
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AgingWhat is the difference between gerontology and geriatrics?Gerontology is the study of aging. Geriatrics refers to the clinical science that is concerned with health and illness in the elderly.
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Calculate the increase in life expectancy in the United States since 1900. Life expectancy in the United States has increased by 31.5 years since 1900, from 47.3 years in 1900 to 78.8 years today.
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Critical Thinking: How might the field of geriatrics have changed over the past 100 years?Sample answer: Advances in medical science have improved people’s ability to identify and treat many diseases and conditions. As a result, many problems that used to be considered natural consequences of aging can now be treated. Life expectancy has also increased, but so have expectations of the medical profession. For example, years ago, people might have thought that living in a nursing home was unavoidable when one reaches a certain age. Now, advances in techniques such as joint replacement allow the elderly to live more independently. This improves quality of life, but also spurs demand for innovations that preserve independence as people live to greater ages. In addition, as life expectancy increases, problems that tend to occur only in patients in their 70s, 80s, or 90s have become more common and are therefore a greater concern.
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Critical Thinking: What are some possible social implications as the percentage of the U.S. population that is 65 or older increases?Sample answer: As the percentage of the population that is 65 or older increases, more institutions and social programs that focus on the elderly will be needed. Health care costs are likely to rise, and a greater percentage of the population will need to work in elder care. Families and other informal caregivers will also likely have increased responsibilities. The definition of “elderly” in the context of the labor force might also change, and the retirement age could be pushed back in order to avoid unduly burdening certain governmental entitlement programs. A higher percentage of elderly people could also lead to a reduction in the number of violent crimes committed per capita, as older people tend to commit fewer violent crimes. However, elder abuse, especially in the form of financial exploitation, may also increase.
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Critical Thinking: Should research efforts focus on expanding life span or life expectancy? Explain your opinion and support it with examples. Sample answer: Although increasing life span and life expectancy are both worthy goals, increasing life expectancy should be the greater priority, in my opinion. Although some individuals have been verified to live past 110 years of age, the vast majority of people do not live to such an advanced age. Therefore, increasing the maximum age that a person can live would not affect the actual life span of most people. However, putting resources into treating or preventing diseases (such as malaria) would affect the life expectancy of millions of people. Addressing pollution, encouraging healthy habits, and improving diets would yield benefits for virtually everyone, while increasing life span would affect very few.
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Agricultural chemistryWhat are the three broad goals of agricultural chemistry?The goals of agricultural chemistry are to understand the causes and effects of biochemical reactions in plants and animals, to discover how to control those reactions, and to develop products that will provide the desired control.
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What three types of agricultural chemicals are most likely to ensure the largest commercial profit? Manufactured fertilizers, synthetic pesticides, and feed supplements are three types of agricultural chemicals that have the highest commercial value.
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Critical Thinking: Today, corn yields are significantly higher than they were in the 1950s. How have agricultural chemicals contributed to this increase?Sample answer: Agricultural chemicals have contributed to many advancements in crop yields over the last several decades, including corn. Chemicals, such as fertilizers, allow corn to gain more nutrients than otherwise possible. Herbicides help control unwanted growth of weeds that would normally compete with the corn for resources. Pesticides help control organisms that can damage the corn. All of these chemicals allow corn being planted today to thrive, as compared to the 1950s.
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Agricultural machineryGenerally speaking, how does the use of hydraulic power benefit farmers?Hydraulic power allows farmers to easily control and automate agricultural machinery and perform intricate operations that would not otherwise be possible.
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Explain the main purpose of plows, disks, and harrows.The main purpose of plows, disks, and harrows is to prepare the soil for planting. These machines facilitate tilling or breaking up and turning over the soil as well as the formation of seed beds.
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Describe some of the major drawbacks of using agricultural machinery to harvest fruits and vegetables.Most machines that harvest fruits and vegetables are nonselective and harvest all of a crop, whether or not the produce is mature. Humans must still inspect and select the desired produce.
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Critical Thinking: A crop farmer wants to prepare a field to plant soybeans. The farmer notices the field is full of weeds. How could the farmer use agricultural equipment, rather than chemicals, to eliminate the weeds?Sample answer: The farmer could use cultivating equipment to eliminate weeds from the field. Cultivating equipment would slice, bury, or rip out most of the weeds.
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Agricultural science (animal)How is the domestication of animals in today's society different than it was in primitive societies?Sample answer: Animals were originally domesticated to meet people's immediate needs, such as food, transportation, and clothing. Today, domesticated animals serve a wide variety of needs, such as consumer products other than food and as raw materials for various processing industries.
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What factors should an animal nutritionist consider when deciding what to feed farm animals?Sample answer: An animal nutritionist should take into consideration the proteins, fats, carbohydrates, vitamins, and minerals present in the type of food the animals are receiving. The nutritionist should also consider how easily those nutrients can be digested by the livestock.
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Explain selection in terms of livestock breeding.Selection is a breeding process in which animals with desirable characteristics are kept for breeding purposes, while those that don't have desirable characteristics are rejected.
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What is the reservoir stage in terms of transmission of infectious diseases among livestock? How is this stage helpful to farmers when a livestock population is at risk?The reservoir stage is the stage of infection at which the cause of the disease is localized. A farmer can stop a disease at the reservoir stage by isolating or quarantining the infected animal(s).
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Critical Thinking: Contrast the selective breeding of draft (work) horses and racehorses.Sample answer: The characteristics of each type of horse differ in their selective breeding. Draft horses are working horses that are selectively bred for characteristics such as strength, height, muscular build, and even temperament. Race horses are sporting horses, and are thus bred for characteristics such as agility, lean legs, and speed.
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Agricultural science (plant)What are the top two crop plants in the world based on acreage? Which has a higher total production?Wheat and rice are the top crop plants based on the acreage on which the plants are grown, with wheat as first and rice as second. Rice has a higher yield per area, making their total production nearly equal.
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Which environmental factor has the greatest influence on crop adaptation, and why?Temperature is the dominant influence due to its effect on enzyme activity.
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What role does seed production play in maximizing crop yield?Seed production ensures quality high-yield seed through plant hybridization and genetic engineering for use in areas otherwise not well suited to that seed.
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Critical Thinking: Why would an agricultural scientist opt to wear a protective suit and mask when working in the field?Sample answer: The use of personal protective equipment is recommended when there is a reasonable probability that injury or illness can be prevented. Protective apparel protects the body from chemical exposure, temperature extremes, and injury from sharp objects.
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Agricultural soil and crop practicesWhich type of plow would a farmer use in a field where numerous rocks and roots are present?A disk plow, which consists of a number of disk blades attached to one axle or gang bolt, would be used in a field where numerous rocks and roots are present, because the disk plow rolls over obstacles, unlike a moldboard plow.
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When in the planting process would a farmer add fertilizer to the soil?Fertilizer is usually placed in the soil at the end of the seeding process, after the seed has been placed in the furrow and covered with soil.
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What is tillage? How can tillage improve crop production?Tillage is mechanical manipulation of the soil to improve its physical condition as a habitat for plants. Effective tillage can stimulate favorable microbiological activities in soil and can also help eliminate weeds, which can take away nutrients meant for the crop so that crop seeds will germinate quickly after planting and the resulting crop plants will produce to their potential.
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Critical Thinking: Why might sustainable farming never completely replace conventional farming practices?Sample answer: Sustainable farming will probably never completely replace conventional farming because, as the demand for more crop production continue to increase as the world population increases, conventional farming allows farmers to grow crops with a much higher yield and more efficiently than with sustainable farming practices. This means that farmers can produce significantly more crops with conventional farming practices as compared to sustainable farming.
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AgricultureWhat factors contribute to the type of agriculture associated with a particular region?Factors influencing the type of agriculture common to a region include climate, soil, topography, available markets, transportation, land costs, and local economy.
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What are the main types of agricultural products? Give examples of each.Agricultural products include food crops, such as grain, legumes, roots, sugar, fruits, and vegetables; forest products, such as wood and paper; and livestock products, such as beef and poultry.
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Critical Thinking: Why do subsistence farms typically generate multiple agricultural products of great variety?In addition to planting small amounts of commercial crops to sell or trade, subsistence farmers typically grow most of the plant crops and livestock products that the families working the farm actually consume.
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Critical Thinking: How can remote sensing aid in determining the carrying capacity of rangeland for livestock?Remote sensing, such as the use of satellite data, monitors rainfall, temperature, and other factors affecting grazing plant growth rates and range readiness each year. Aerial photography can be used to monitor grazing conditions and the number of animals in a specific area.
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Critical Thinking: Would you consider farming more of a science or an art? Explain your answer.Sample answers: Farming can be described as a science because it requires knowledge and understanding of specific scientific concepts, theories, and technologies—many of which are complex and based on recent genetic research. Farming can be described as an art because it requires creativity and skill to put scientific knowledge into practice. Scientific knowledge does not replace a farmer's passion for creating food from his land.
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Air pollutionDescribe some strategies that are used to control the release of hazardous pollution from stationary sources, and some that are used to prevent pollution from such sources.Sample answer: Strategies that control the release of pollution include filters to remove particulates, adsorbent materials such as silica gel and polymers to capture chemicals, absorbers such as solvents that dissolve chemicals, and condensers that lower the temperature of a chemical stream. Most effective controls combine two or more methods. Strategies that prevent or reduce pollution include alternative chemicals that have fewer hazardous pollutants, destroying organic compounds with ultraviolet oxidizers or plasmas, and using microorganisms that feed on the pollutant as a biofilter.
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Why are liquid and compressed natural gases considered good alternatives to other fossil fuels in vehicles?Natural gas is cheap and abundant. Also, it mixes quickly and efficiently with air, has a wide air–fuel ratio selection, and has a high compression range.
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Critical Thinking: What are two reasons why the U.S. EPA has stricter regulations for fine and ultrafine particulate matter than for coarse particles?Hair in the human nose (and that of other mammals) removes larger particles from inhaled air, preventing these particles from reaching the lungs. Large particles also tend to move downward more quickly and out of the atmosphere, making them less likely to be inhaled, and therefore less of a threat to human health.
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Critical Thinking: Why can pollutants from localized events, such as chemical spills or power plant emissions, impact the environment and health on a regional scale?Sample answer: A key factor in determining the scale of an event is the variation in wind. Wind can keep pollutants in the atmosphere for several days, allowing particles to travel hundreds of miles and collect with water vapor to form acid rain, a secondary pollutant that can severely damage vegetation over large regions.
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AlcoholWhat are three ways in which alcohols can be classified?Alcohols can be classifed by the number of hydroxyl groups they possess, by the number of hydrogen atoms attached to the carbon atom bearing the hydroxyl group, and by the molecular configuration of the hydrocarbon portion.
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Critical Thinking: What is the parent hydrocarbon of ethanol? How do you know? The parent hydrocarbon of ethanol is ethane. According to the IUPAC method of classification, the parent hydrocarbon determines the name of the alcohol. The final “e” in the hydrocarbon name is dropped and replaced with “ol."
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Critical Thinking: Explain the meaning of the 2 in the name 2-Butyl alcohol.According to the IUPAC naming convention, a number before the alcohol name indicates the position location of the hydroxyl (—OH) group on the hydrocarbon longest carbon chain. In this case, the hydroxyl attaches at the second carbon atom in a chain of four carbon atoms.
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AlcoholismHow can alcoholism lead to malnutrition?Although alcoholic beverages are high in calories, they lack essential nutrients. A large part of an alcoholic's daily caloric intake is considered to be empty calories.
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How does the medication disulfiram deter an alcoholic from drinking?If alcohol is consumed, disulfiram inhibits the enzyme that normally helps break down the acetaldehyde produced from the metabolism of alcohol, resulting in nausea and vomiting for several days.
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Critical Thinking: How does the consumption of alcohol affect the ability to safely operate a motor vehicle?Alcohol impairs motor coordination, which affects steering and braking; space perception, which affects maintaining safe distances from other motor vehicles; and cognitive ability, which affects decision making.
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Critical Thinking: The legal drinking age in the United States is 21. Do you think this drinking age should be lowered? Why or why not?Sample answer: It should not be lowered. Teens who drink alcohol are more likely to become alcoholics. Therefore, lowering the drinking age would likely result in an increase in the number of alcoholics in the United States.
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AlgaeWhat characteristics (or lack thereof) are generally shared among algae? How do the shared characteristics of algae determine their ecological functions and distribution?Algae are generally oxygen-producing (via photosynthesis) and lack vascular tissue. Unlike higher plants, algae release uncovered spores. Therefore, algae are generally restricted to marine or other aquatic environments. Algae also function as producers, forming the base of many aquatic ecosystems.
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Identify several parts of algal cells used to make economically important products.The coatings of algal cells are used to make substances (for example, emulsifiers) important to food processing and manufacturing. The chloroplasts of algal cells create organic carbon compounds, making algae useful as food or animal feed.
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Identify examples of algae that demonstrate diversity in metabolism, movement, cell cycle, and reproduction.Sample answer: Some algae are heterotrophic, while others use bicarbonate instead of carbon dioxide as a carbon source. Some unicellular algae are flagellates, while many multicellular algae are sessile. Cyanobacteria are prokaryotic, while other groups are eukaryotic. Algae may be diploid or haploid, and may reproduce via spores or vegetatively, and sexually or asexually.
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Critical Thinking: Kelp, a type of brown algae, occurs mostly in the waters of the Pacific Northwest. Kelp is benthic and is known for its large size and ability to anchor to substrate. How do these distinctive characteristics allow kelp to occupy its particular niche?Light intensity at northern latitudes is limited by the angle of insolation. Therefore, being able to grow towards the ocean surface allows kelp to obtain adequate sunlight in Pacific Northwest ecosystems where kelp is commonly found.
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Critical Thinking: Do algae form a taxonomic clade? How does the classification of algae among living things relate to their diversity?Algae do not form a taxonomic clade. Rather, algae include both prokaryotic and eukaryotic organisms and, within the latter, may be classified as protists or as plants. This results in a great diversity of organisms being categorized as algae, from prokaryotic cyanobacteria (blue-green algae) to enormous eukaryotic brown algae (kelp).
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AllelopathyHow can allelochemicals promote succession to the next stage? How can they maintain the ecosystem at its current stage?Allelochemicals that are autotoxic to species of a particular stage will reduce the numbers of those species, allowing a different plant community to replace them. Allelochemicals that are beneficial to the current community will tend to maintain it.
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How can farms and orchards avoid the effects of allelochemicals?Sample answer: Farmers can clear land of plant debris before planting, avoid growing the same crop year after year, or plant nurse trees to remediate the soil.
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Critical Thinking: How can scientists, observing spacing between plants growing in a nutrient-limited ecosystem, distinguish between allelopathy and competition?Adding the limiting nutrients to the ecosystem should result in closer spacing if competition limits plant growth. However, adding limiting nutrients should not affect spacing if allelopathy inhibits plant growth.
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Critical Thinking: How can autotoxicity against a plant's offspring offer the parent plant a reproductive advantage?For plants that disperse many seeds, inhibiting the growth of seedlings too close to the parent reduces competition for resources between parents and offspring.
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Alzheimer's diseaseWhat is the difference between dementia and Alzheimer’s disease?Dementia is a group of symptoms, not a disease. Dementia can be caused by a variety of conditions, the most common of which is Alzheimer's disease.
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Why is physical testing for Alzheimer’s disease much less common than diagnoses based on behavioral evaluations and reviews of family history?Brain tissue is only available for processing postmortem or through painful, expensive, and potentially damaging brain biopsies. Alzheimer’s disease symptomatology can be diagnosed effectively from behavior and genetic history.
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Compare and contrast the two different treatment strategies for Alzheimer's disease.Sample answer: Cholinesterase inhibitors are used to boost acetylcholine levels in the brain to improve memory, while other medication-based strategies work to reduce amyloid buildup in the brain or control multiple neurotransmitter networks.
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Critical Thinking: How might a person prepare himself or herself for caring for a loved one with Alzheimer's disease?Sample answer: Consider how safe it is for the loved one to continue to live in their home without assistance. Determine what other sources of support—such as adult day care, home services, visiting nurses, or nearby family members—can assist with caring for the afflicted individual.
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Amino acidWhat are amino acids? Include the three general chemical components of amino acids in your answer.Amino acids are organic compounds that possess one or more basic amino groups (-NH2) and one or more acidic carboxyl groups (-COOH). They also have an "R" group, or substituent functional group, which helps define the biochemical properties of a given amino acid.
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Compare essential and nonessential amino acids.Essential amino acids are those that must be acquired through the diet; that is, the organism cannot make that amino acid by itself. Nonessential amino acids are those that the organism is capable of making (synthesizing) by itself and thus do not need to be consumed in the diet (although nonessential amino acids certainly may be consumed).
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Briefly describe the process of amino acid conjugation (joining), including the name of the bond created and any products formed.Amino acids join together to form a peptide when the amino group of one acid is linked to the carboxyl group of another acid. During this process, a molecule of water is lost and a peptide bond is formed.
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Critical Thinking: You are working with a newly discovered worm in the lab, and you define the properties of what appears to be a new amino acid from the muscle of this worm. Based on the information shown in Figure 2, what is the most likely type of substituent grouping of this new amino acid? Explain your reasoning.Sample answer: Based on what is known about the 20 amino acids that comprise proteins, we would expect the R group to be nonpolar as this is most common with 50% of amino acids (10/20) having a nonpolar R group. (polar = 5/20; acidic = 2/20; basic = 3/20).
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Critical Thinking: You are working in a pharmaceutical lab. You and your lab partner are tasked with developing a novel drug to kill a bacterial pathogen. Your lab partner suggests creating a drug that will target the production of bacterial amino acid synthesis. Do you think this is a good target? Explain your rationale.Sample answer: Given the importance of amino acids in organisms, this initally seems like a potential plan. However, when we apply the information that amino acid synthesis is generally the same across taxa, using this as a drug target seems impractical and likely not the best option. Given that the pathways are shared (conserved), a drug that stops production of the amino acid in the bacteria would likely also stop production in the human host, potentially resulting in severe side effects. Students may discuss finding an amino acid that is essential in humans but nonessential in the bacteria, but this approach would mean that the amino acid would then need to be limited in the diet of the infected person, which could be problematic for health.
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Animal breedingHow can animal breeders attempt to modify phenotypic traits in animals?Animal breeders can attempt to modify phenotypic traits in animals through controlled mating and selection, which can also involve genetic engineering methods.
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What is heritability? Heritability is the fraction of the total variation in a trait that results from additive genetic differences.
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Critical Thinking: If two animals that are both above average in size are bred to produce offspring, is it certain that their offspring will be above average in size? Why or why not?Sample answer: No, the offspring of two animals that are above average in size are not certain to be above average in size themselves, for a few different reasons. First, their parents’ size could have been influenced by environmental factors as well as genetic ones. Second, the parents may pass on genes that favor decreased size to their offspring. Third, size for the animal in question may depend on a complex interaction of genes that is difficult to predict.
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