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Answers to Thinking Critically About the Concepts
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Click on the appropriate chapter number to go to the answers for that chapter.

Chapter 1
Chapter 2
Chapter 3
Chapter 4
Chapter 5
Chapter 6
Chapter 7
Chapter 8
Chapter 9
Chapter 10
Chapter 11
Chapter 12
Chapter 13
Chapter 14
Chapter 15
Chapter 16
Chapter 17
Chapter 18
Chapter 19
Chapter 20
Chapter 21
Chapter 22
Chapter 23
Chapter 24
Chapter 25
Chapter 26
Chapter 27


Chapter 1: A Human Perspective

Answers to the "Thinking Critically About the Concepts" Questions

  1. Animals all begin life as a single cell, which undergoes repeated divisions. Early in the developmental process, animals have the same or similar tissues and organs. As a result, humans resemble other animals during these stages. In later stages of development, each organism takes on more of the features that make it unique.

  2. To be terrestrial, animals need four primary adaptations to survive: (1) a respiratory structure that allows them to breathe air and a means to deliver that oxygen from the air to all of the cells of the body and release carbon dioxide to the environment, (2) a way to minimize water loss from the body, (3) a means of reproduction that allows the sperm to reach the egg, and (4) a mechanism for development of the young that does not require the presence of water.

  3. In the case of humans, we have (1) specialized respiratory and circulatory systems that bring oxygen in from the environment, circulate it to all cells of the body, and remove carbon dioxide from the body; (2) layers of skin to prevent water evaporation and a specialized urinary system that regulates the amount of water released from the body; (3) internal fertilization, which isn't reliant upon an aquatic environment for sperm to reach eggs; and (4) internal development (within the mother's body) of the young.

  4. Humans differ from other animals in that they have a well-developed brain, are able to make and use tools, are able to alter their environment, and possess social skills and customs.

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Chapter 2: Chemistry of Life

Answers to the "Thinking Critically About the Concepts" Questions

  1. In the body, our blood needs to be maintained at a pH of 7.4, essentially a specific balance between acids and bases. However, when there is too much acid (pH less than 7.4) or too much base (pH greater than 7.4) present in the blood, our body is no longer healthy. The blood has buffers, carbonic acid and bicarbonate, which aid the body in maintaining a healthy blood pH of 7.4 when small excesses of acid or base are present.

    In the environment, the balance of acids or bases can be seen most dramatically in the case of acid rain. The burning of fossil fuels, such as gasoline, causes the buildup of acids (sulfuric and nitric acids) in the water vapor of the Earth's atmosphere and results in the formation of acid rain. The acid rain has profound effects on the environment over time. Such effects include the death of trees and other plants, death of fishes and other aquatic animals, and the deterioration of limestone statues and buildings.

  2. A steroid lipid has four adjacent rings, as seen in cholesterol. By changing the functional groups attached to these rings, we increase profoundly the diversity of molecules, and their effects on the body. Using cholesterol as a starting point, our bodies are able to synthesize the sex hormones, testosterone and estrogen. All three of these molecules look very similar. However, they have very diverse roles in the body. Cholesterol is the major steroid lipid of the plasma membrane. In the case of the sex hormones, testosterone is made mainly in the testes of males and estrogen mainly in the ovaries of females.

  3. The types of molecules that are found in both plant and animal cells include: carbohydrates, lipids, nucleic acids, and proteins.

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Chapter 3: Cell Structure and Function

Answers to the "Thinking Critically About the Concepts" Questions

  1. According to the vignette, the types of cells necessary for Helen to win the race would include: cells of the nervous system, muscle cells, bone cells, blood cells, cells of the digestive system, and cells of the respiratory system.

  2. Cellular respiration and lung respiration are related in that lung respiration provides the means whereby the body takes in oxygen from the air when we inhale. From the lungs, oxygen is transported by the circulatory system to the cells. The cells pick up the oxygen for use in cellular respiration and release carbon dioxide in the process. The carbon dioxide is released back to the circulatory system, where it is transported back to the lungs and released when we exhale.

  3. As a result of exercise, muscle cells will also increase in size (not in number) and, due to the increased number of mitochondria, will require more oxygen and release more carbon dioxide.

  4. The heart, like skeletal muscle, needs regular exercise to function properly. However, exercise that is done too strenuously or stopped too suddenly (out of balance) may be harmful, as the cardiac muscle cells have not become accustomed to a higher level of activity or have not had time to adjust to a lesser amount of activity. The result may be a heart attack.

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Chapter 4: Organization and Regulation of Body Systems

Answers to the "Thinking Critically About the Concepts" Questions

  1. Excess water loss is known as dehydration. When dehydration is severe, the signs include: a dry or sticky mouth, minimal urine production, any urine produced is very concentrated urine (appears dark yellow), tears are not produced, one may become sluggish or go into a coma. Many of these signs are the result of the body attempting to retain as much water as possible. Furthermore, dehydration has a dramatic impact on brain function. If left untreated, the result can be seizures, permanent brain damage, or death.

  2. Just like anything to do with the human body, balance (homeostasis) is essential. Our bodies are designed to work optimally at a given temperature (37°C or 98.6°F). If the body temperature rises to 107.6°F (42°C), brain damage can result. In contrast, if the body temperature drops to 95°F (35°C), one becomes sluggish, may go into shock, or a coma, or death may occur. These temperature extremes have such an impact on health because the body is at a temperature where it no longer functions optimally.

  3. In addition to melanin, the body defenses against ultraviolet radiation include: the dead outer layer of skin, presence of hair on the body, and dilation of the pupils to protect the eye.

  4. An advantage of multiple cell types within an organ is to allow for several processes to take place within an organ. In this manner, the body is being efficient. A disadvantage of multiple cell types within an organ is that a problem with one of the cell types may affect the function of the entire organ.

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Chapter 5: Cardiovascular System: Heart and Blood Vessels

Answers to the "Thinking Critically About the Concepts" Questions

  1. The recommended dietary changes for decreasing the possibility of a stroke include: increasing consumption of fruits and vegetables, eating whole grain foods, decreasing saturated fats (from meat and dairy products) and cholesterol, decreasing the amount of salt, and reducing alcohol intake.

    Lifestyle changes include: regular exercise, weight loss (if obese), and smoking cessation.

  2. Risk factors for stroke include: high blood pressure, smoking, diabetes, high blood cholesterol (elevated low density lipoprotein levels-LDL), sedentary lifestyle, obesity, excessive alcohol consumption, age, heredity, and gender (males more frequently than females).

  3. Due to the blockage in the artery, the heat pumps harder in order to move the amount of blood it should throughout the body. As a result, there can be changes in the heart beat that often make stroke victims feel as though they are having a heart attack. In addition, the blockage may increase blood pressure.

    Perhaps the organ most greatly affected by stroke is the brain. When oxygen and other nutrients are not available to the brain, function is impaired. This loss of function is observed as loss of speech, vision, memory, pain and numbness, or paralysis. In addition, the kidneys and other organs may be affected.

  4. The blood is responsible for delivering oxygen and nutrients to cells and removing carbon dioxide and cellular waste products. If the flow of blood is impaired in any fashion, the affected cells in that region of the body have too little oxygen and nutrients available for functioning and increased levels of carbon dioxide and waste. As a result, many of these cells die.

  5. Based on the vignette, the possible directly contributing risk factors would include high blood pressure, atherosclerosis of blood vessels, age, and diet.

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Chapter 6: Cardiovascular System: Blood

Answers to the "Thinking Critically About the Concepts" Questions

  1. Severe blood loss will mean that organs, such as the brain, do not have sufficient oxygen and nutrients and too much carbon dioxide and metabolic wastes. In the brain, this may lead to unconsciousness and shock. The blood pressure will decrease; the hands and feet will become cold due to decreased circulation; the heart will beat too quickly trying to circulate as much blood as possible; due to the lack of nutrients and accumulation of wastes, many organs will begin to fail and ultimately death will result.

  2. Alice will need to drink plenty of fluids, eat a healthy diet, and exercise regularly. Fluids will keep enough water in the blood plasma; proper nutrition will help the body to replenish the blood cells and will make sure that adequate nutrients are available for all of her cells; and lastly regular exercise will help maintain good blood flow throughout the body.

  3. When a person is given blood of the wrong type, the body undergoes a transfusion reaction. A transfusion reaction is the body fighting and destroying the blood cells from the transfusion because they are recognized as a foreign invader, like a bacteria or virus cell. The net result is that the body destroys the very thing that it needs during the transfusion. The outcome of this error depends upon the amount of blood the patient has received. If it is a small amount, the problem can be corrected with little problem to the person. For larger volumes, the result is often death.

  4. Other problems that result from blood transfusions are the transmission of various diseases, including hepatitis C, HIV, and many others.

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Chapter 7: Digestive System and Nutrition

Answers to the "Thinking Critically About the Concepts" Questions

  1. A radical procedure like this will have tremendous impact on the physiology of Monica's digestive system. Essentially, the result is a reduction in the amount of food the system can intake, limiting the number of calories and nutrients that can be absorbed by the system. Other organs will be affected if nutrients become too restricted, particularly the brain.

  2. Her ability to properly digest food and absorb nutrients will obviously be compromised. Much of the nutritional value of her food will be released from the body unused. As a result, she will need to make sure that she receives as much nutrition as possible in the small portions of food she will be able to ingest following the surgery. This includes chewing the food thoroughly to maximize the amount of nutrients obtained from the food. She will not be able to drink fluids while eating, as she will feel full before she has taken in enough food. Furthermore, she will need to omit desserts and other items with sugar listed as one of the first three ingredients, carbonated drinks, high-calorie nutritional supplements, milk shakes, high-fat foods and foods with high-fiber content.

  3. Her dietary restrictions will obviously affect her development, as growth and maturation processes in the body are nutritionally demanding. As a result, these processes will not occur as they normally would due to the limited amount of nutrients in the body.

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Chapter 8: Respiratory System

Answers to the "Thinking Critically About the Concepts" Questions

  1. When exercising, the body's demand to increase oxygen intake and carbon dioxide release is approximately five times higher than at rest. As a result, the body needs to meet these demands in order to perform optimally. In cold weather, skeletal muscle maximum strength, muscular endurance, and aerobic capacity are all reduced. In addition, ventilation rate increases and peripheral blood flow is reduced. These factors combined lead to a lesser performance.

  2. When exercising, the body's demand to increase oxygen intake and carbon dioxide release is approximately five times higher than at rest. As a result, the body needs to meet these demands in order to perform optimally. During hot weather, more blood is sent to the skin for cooling so less blood flows to working muscles. This means that a lesser amount of oxygen is able to reach the muscle cells, thus compromising performance.

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Chapter 9: Urinary System and Excretion

Answers to the "Thinking Critically About the Concepts" Questions

  1. Kidney stones can block urine formation by interfering with any one of the three basic steps associated with urine formation.

  2. The presence of kidney stones and their interference with renal function may damage the kidney over time. The presence of stones interferes with the proper filtration of metabolic wastes from the blood. Ultimately, the glomeruli are no longer able to filter properly and the proteins and blood cells that were to remain in the blood are now able to be excreted with the urine.

  3. Our "backup" system in case one kidney is blocked by a very large stone is the fact that we have two kidneys. A person can do fine, from a homeostasis perspective, with one functioning kidney.

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Chapter 10: Skeletal System

Answers to the "Thinking Critically About the Concepts" Questions

  1. The advantage of a curved vertebral column over a straight vertebral column is that the curvature gives added strength and resilience for an upright posture.

  2. Your leg muscles are many times stronger than your back muscles. As a result, you cannot lift as much weight using your back muscles as you can using your leg muscles.

  3. X-rays can be used to examine injuries, such as fractures or broken bones, arthritis, vertebral disk dislocation, degeneration of the disks, tumors, scoliosis, or other abnormalities of the spine. Muscle or soft tissue injuries will generally not show up on an X-ray.

  4. Healthy bones are maintained through a diet containing the recommended amounts of calcium and vitamin D, maintaining a healthy weight, and regular exercise.

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Chapter 11: Muscular System

Answers to the "Thinking Critically About the Concepts" Questions

  1. At the cellular level, fast-twitch and slow-twitch muscle fibers have very few differences. Fast-twitch muscle fibers grow in size more than slow-twitch when trained. Slow-twitch muscles are dependent upon an oxygen supply for aerobic respiration and have many mitochondria, while fast-twitch muscles can function by glycolysis and produce lactic acid.

  2. Fast-twitch muscle fibers are better for short bursts of speed because they are able to contract more quickly, allowing a repeated, fast series of contractions.

  3. Other things that influence performance include: amount of stored cellular carbohydrate available, temperature, and general health.

  4. A chicken's legs are mainly made up of slow twitch fibers. Their legs are used for walking and standing, which doesn't use much energy. In contrast, a chicken's wings and breast are largely made up of fast twitch muscle fibers. Their wings are used for brief bursts of flight, which require lots of energy and the muscles involved tire very quickly.

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Chapter 12: Nervous System

Answers to the "Thinking Critically About the Concepts" Questions

  1. If the spinal cord injury is due to a car accident and the result is a severed spinal cord, then there is no progressive nerve degeneration. Depending on the location of the injury, the injury is also not fatal. ALS is characterized by nerve degeneration, and it is progressive and fatal.

  2. In the case of ALS, only motor neurons are affected. Therefore, sensory perceptions are not lost.

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Chapter 13: Senses

Answers to the "Thinking Critically About the Concepts" Questions

  1. Changing the shape of the cornea changes the way light focuses on the retina, allowing the image to be less distorted and thus more focused.

  2. Problems that cannot be corrected with LASIK surgery include glaucoma, cataracts, and corneal scars.

  3. LASIK surgery will not prevent or slow the aging process, so the lens will still become more rigid around age 45. In that case, the individual will most probably need glasses or contacts in spite of the LASIK treatment.

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Chapter 14: Endocrine System

Answers to the "Thinking Critically About the Concepts" Questions

  1. "Increasing secretion by the hypothalamus is credited with jump starting puberty" is a reasonable hypothesis because the hypothalamus stimulates gonadotropin-releasing hormone to be secreted from the anterior pituitary gland. This, in turn, stimulates the maturation and development of the gonads and their respective hormones that influence the production of secondary sex characteristics.

  2. If the sry gene is on the X chromosome of an XX individual, he/she will be phenotypically male (this phenomenon has been observed in mice). Therefore, maleness can be defined as the presence of a sry region not just XY.

  3. The anabolic steroids most abused by athletes are those that chemically resemble testosterone, as these act to increase muscle mass and enhance performance. Females taking these steroids experience the negative side effects of growth of facial hair, male-pattern baldness, changes in the menstrual cycle, clitoris enlargement, and a deepened voice.

  4. Sex hormones can affect the brain. The most obvious example, as indicated on p. 270, gonadotropin-releasing hormone is triggered to be released from the pituitary gland by the hypothalamus. The gonadotropin-releasing hormone, in turn, stimulates either the testes or the ovaries to produce gametes and release their respective sex hormones. Those hormones in turn influence the brain by chemically communicating with the hypothalamus with regard to secretion of hormones.

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Chapter 15: Reproductive System

Answers to the "Thinking Critically About the Concepts" Questions

  1. This particular question has multiple answers as it asks how individuals view government intrusion. Use your best judgment in evaluating answers, which will range from (1) no government intrusion, as it is a right to have children, to those who (2) worry about individuals solving infertility issues by human cloning that may involve some governmental control.

  2. This is an ethical issue, so answers will vary. Answers can range from (1) the "survival of the fittest" issue should not influence a decision to aid infertile couples from reproducing to (2) reproduction in this manner should be scrutinized so that "bad genes" are not maintained in the gene pool.

  3. The problems associated with developing a male birth control pill are as follows: the reversibility of sperm production; inactivation by any substances (such as antibiotics); affects on the body other than sperm production need to be assessed; and the transmission of sexually transmitted diseases cannot be influenced by use of a male contraceptive other than condoms.

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Chapter 16: Development and Aging

Answers to the "Thinking Critically About the Concepts" Questions

  1. Development is a lifelong process. As we age, we see physiological and physical changes in ourselves over time. There is the middle age spread, stiffening of the lenses of the eyes, decreased reaction times, and menopause, for instance.

  2. Even though genes determine our destiny to an extent, they are not necessarily concrete. If genetically, your hemoglobin contains information associated with the formation of sickle-shaped red blood cells, then you will suffer with sickle-cell anemia. However, in other instances they are not as concrete. If you are destined to be short in height, how short may be dependent upon your nutrition when your long bones are lengthening.

  3. Development is also influenced by factors in the environment where the development is taking place. For example, nutrition availability and hormones within the womb or nutrition ingestion and hormones produced by the body (depending upon what point in the developmental process we are examining) can influence the developmental process.

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Chapter 17: Cell Division and the Human Life Cycle

Answers to the "Thinking Critically About the Concepts" Questions

  1. During embryonic development, apoptosis is appropriate for the death of structures that are no longer needed, such as the webbing between the fingers and the toes. During adulthood, apoptosis is important in cells where cell division has not occurred correctly, cell turnover, and cancer cells.

  2. To turn on apoptosis, cells of the immune system must stimulate the target cell to apoptosis by interacting with a cell surface protein, which in turn may activate "executioner" capases.

  3. The protein that is activated is the Fas receptor on the surface of the cell to undergo apoptosis.

  4. The cells are not able to regulate the cell cycle, as with the loss of p53 activity.

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Chapter 18: Patterns of Inheritance

Answers to the "Thinking Critically About the Concepts" Questions

  1. We don't have enough information from the vignette about the inheritance to fit into any pattern other than a dominant/recessive inheritance pattern. Another possibility would be X-linked inheritance, but we would need information about Michael Douglas' mother to evaluate that possibility.

  2. All of the children would have cleft chin (heterozygous) and a recessive type hairline.

  3. Crossing over would have no affect in this case because Michael is homozygous for the cleft chin gene. Therefore, there would be no change in the phenotypes of his children.

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Chapter 19: DNA Biology and Technology

Answers to the "Thinking Critically About the Concepts" Questions

  1. As chromosomes are inherited in pairs (one from each parent), then parent and child should share half a DNA fingerprint. The likelihood of two people sharing a common DNA fingerprint by random chance is very small.

  2. The greater number of regions that can be used in creating a DNA fingerprint, the more unique that DNA fingerprint becomes. A DNA fingerprint that allows for the greatest number of regions to be examined will be totally unique for a single individual. As a result, person to person variation between DNA fingerprints is much more apparent between individuals (except identical twins).

  3. The problem with eyewitnesses is that they don't always remember detail exactly. During stress our brains can fill in detail that wasn't very apparent to complete a mental image. DNA sequence is concrete; the details do not change as long as the DNA has not been damaged.

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Chapter 20: Genetic Counseling

Answers to the "Thinking Critically About the Concepts" Questions

  1. Normally, each individual has two copies of each chromosome. This is because one copy is received from the paternal parent and one copy from the maternal parent.

  2. Epigenomics, the science of how genomes and proteomes interact, would indicate that the amount of purines in the blood (influenced by the Gart gene) influences the level of retardation observed among different Down syndrome individuals.

  3. With genes associated with the X-chromosome in humans, those who are heterozygous are often seen to have patches with and without expression, termed mosaics. The mosaic gene expression pattern is due to the random inactivation of one of the X chromosomes during development.

  4. Genomics can be helpful from a variety of perspectives, including knowledge of disorders that can be corrected somewhat with lifestyle changes, identification of potential targets for gene therapy to correct some chromosomal disorders, and in making reproductive choices.

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Chapter 21: Defenses Against Disease

Answers to the "Thinking Critically About the Concepts" Questions

  1. Other autoantibody-mediated conditions include: systemic lupus erythematosus , myasthenia gravis, rheumatoid arthritis, Goodpasteure's syndrome, Hashimoto's thyroiditis, and type I diabetes.

  2. Antibodies are part of the specific (acquired) defense system, as they are made in response to a specific encounter.

  3. The B lymphocytes, which transform into antibody secreting plasma cells, are the cell type responsible for antibody production.

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Chapter 22: Parasites and Pathogens

Answers to the "Thinking Critically About the Concepts" Questions

  1. Using PCR for a detection method indicates the laboratory in question is testing for the SARS-CoV nucleic acid.

  2. Public health practitioners can prevent further SARS epidemics by isolation/quarantine of sick individuals if possible, frequent hand washing, cleaning surfaces where body fluids may be, and the use of gloves and masks if appropriate.

  3. To protect yourself from SARS, frequent hand washing, routine cleaning of surfaces, and covering your nose and mouth with a tissues when sneezing or coughing are recommended.

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Chapter 23: Sexually Transmitted Diseases

Answers to the "Thinking Critically About the Concepts" Questions

  1. Genital herpes is caused by a virus. In this case, the virus can be latent in the body for indefinite periods of time. In many cases, the symptoms recur as the result of some of the viruses awakening from the latent state. As a result, Jennifer will always have the virus.

  2. Antibiotics will not cure Jennifer because antibiotics target cellular structures or cellular processes within cells, such as bacteria. However, viruses are reliant on the host (infected) cell to perform the cellular process (of making virus particles) for them. As a result, antibiotics are not effective against viral diseases.

  3. The surest way of reducing transmission of sexually transmitted diseases is to practice abstinence. Other practices include monogamous relationships, checking the STD status or intravenous drug use of a potential partner, and using latex condoms.

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Chapter 24: Cancer

Answers to the "Thinking Critically About the Concepts" Questions

  1. Smoking cigarettes and using chewing tobacco can increase the risk of cancer, such as pancreatic cancer, because the compounds present in the tobacco (either form) have ready access to the bloodstream or to circulation at some point. As a result, those compounds are able to circulate throughout the body and potentially cause cancer anywhere in the body.

  2. Statistics conclude that smoking is the cause of 87% of all lung cancers and 30% of all cancer deaths. In addition to lung cancer, smoking has been linked to cancer of the bladder, throat, pancreas, mouth, and cervix.

  3. The compounds in tobacco would be expected to be mutagenic as they are able to induce cancer. To do this, there must be a change (mutation) in the DNA of a proto-oncogene or tumor suppressor gene, ultimately resulting in the uncontrolled growth that is characteristic of cancer cells.

  4. The types of genes that would be expected to undergo mutation would include proto-oncogenes and tumor-suppressor genes.

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Chapter 25: Human Evolution

Answers to the "Thinking Critically About the Concepts" Questions

  1. Genes govern our metabolism in that genes encode the enzymes that mediate our metabolic reactions. The enzymes then influence the overall efficiency of our metabolism.

  2. If ATP is readily available in the body, then high storage fat will occur as there is no need for it to be utilized immediately for energy.

  3. A "thrifty gene" hypothesis would suggest that a gene regulates the amount of mass the body maintains. A possible role would be the down-regulation of our metabolic rates when the body is starved for nutrients. As a result of the lowered metabolism, less of the body's stores are utilized, as indicated by the lack of weight loss when on a restricted diet. Such a hypothesis could be tested by a variety of means, but the best way would be to look at genetically identical mice, one with the gene and one genetically engineered to lack the gene, and the effect of diet on the mice. If our hypothesis is true, only the mice lacking the gene will lose mass on a restricted diet.

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Chapter 26: Global Ecology

Answers to the "Thinking Critically About the Concepts" Questions

  1. For examples that demonstrate that our society is based on resource consumption, one need only go as far as the local refuse dump. We continually burn fossil fuels for transportation, many reusable items are discarded as trash, and disposable items (such as diapers and wipes) are the norm.

  2. The gross national product is the quantitative measure of a nation's total economic activity; currently the best indicator of a country's economic status. The gross national product is the sum of the gross domestic product plus income earned by domestic residents through foreign investments minus the income earned by foreign investors in the domestic market. The gross domestic product is calculated from the total value of goods and services produced in an economy over a specified period of time.

  3. One of the best ways to teach people to think about the environment is through education. The earlier people are made aware of the factors that affect the environment, the more they consider the environment in their decisions about life, as with Jessica and Miguel.

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Chapter 27: Human Population, Planetary Resources, and Conservation

Answers to the "Thinking Critically About the Concepts" Questions

  1. One of the best ways to get farmers to adopt the four farming practices would be to provide some sort of incentive to keep those practices in place and some sort of fines or other punishment for noncompliance.

  2. The environmental reason for becoming a vegetarian is that the "meat agriculture" industry today is a very resource-demanding industry. In addition to the large volumes of water used for animals, there are tremendous problems with waste disposal and diseases that may be transmissible to humans.

  3. Answers may vary. The recent gas prices of well over $2.00 a gallon had some people contemplating alternative energy sources, such as solar-hydrogen. However, others are harder to convince, especially when one considers the tremendous cost associated with the dedicated conversion to solar-hydrogen energy nationwide.








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