Chapter 9 Review, pages 460-465
Knowledge
1. b
2. a
3. a
4. b
5. c
6. a
7. b
8. d
9. b
10. True
11. False. Homeostasis is an ongoing condition that is dynamic.
12. False. The set point is the optimal value for a given variable of a system.
13. False. Signals from the hypothalamus are what enable humans to sense a lowered body
temperature.
14. True
15. False. Thermal acclimatization is the gradual adjustment to seasonal variations in
temperature.
16. False. Osmoregulation ensures that the intracellular and extracellular fluids are isosmotic.
17. False. Filtration refers to the process in which fluid and small molecules pass into Bowman’s
capsule.
18. (a) iii
(b) v
(c) i
(d) ii
(e) v
19. (a) iv
(b) v
(c) ii
(d) iii
(e) i
20. Homeostasis is the condition of equilibrium of the body’s internal environment through the
interplay of all the body’s regulatory processes.
21. It is important for an organism to maintain homeostasis because homeostasis is required to
maintain optimal conditions for bodily functions. If an organism does not maintain homeostasis,
the organism will not be able to perform at an optimal level.
22. Homeostasis is regulated by feedback loops that consist of a stimulus, a receptor, an
integrator, an effector, and a response. The stimulus is changing environmental conditions, the
receptor monitors changes in conditions and sends that information to the integrator. The
integrator compares the information with the desired condition and tells the effector to make a
change if required. The effector makes the appropriate change. The response is a return to
homeostasis.
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23. Answers may vary. Sample answer:
24. Frogs are best described as poikilotherms because a frog’s body temperature varies with, and
sometimes matches, the temperature of its external environment.
25. Ectotherms have an advantage over endotherms in terms of energy requirements because
ectotherms absorb thermal energy from their environment to maintain their body temperature.
Therefore, they do not use as much of their own energy to maintain their internal temperature.
They require much less energy for the same body mass than endotherms do.
26. Shivering and “goose bumps” help to maintain homeostasis because muscle contractions
during shivering produce heat and the raised hairs in the skin trap air, which reduces heat loss,
helping to maintain body temperature.
27. Osmotic pressure and hydrostatic pressure are two factors that determine whether osmosis
occurs. Osmotic pressure: Water will move across a membrane when the solutions on either side
of the membrane have different concentration gradients until both solutions are isoosmotic.
Hydrostatic pressure: Water will flow across a membrane until the internal hydrostatic pressure
balances the external osmotic pressure.
28. Turgor pressure in plants occurs when water surrounding plant roots is hypoosmotic relative
to the inside of the plant cells. This pushes water into the root, stem and leaf cells exerting
pressure against the cell walls. This turgor pressure gives plants rigidity and allows them to stand
erect. A drop in turgor pressure will cause the plant to wilt.
29. Ammonia is produced by most aquatic animals. Urea is produced by mammals, amphibians
and sharks. Uric acid is produced by many reptiles, birds, insects and snails.
30. Metanephridia are excretory organs that open internally to the coelom and the waste flows
out as urine. Malphighian tubules have dead end tips immersed in circulatory fluid that is
connected to the digestive system so most waste exits along with feces.
31. The nephron is the tiny filtering structure in the kidneys. Each of the kidneys contains more
than a million nephrons that help clean the blood. Nephrons remove water and solutes including
wastes from the blood by filtration. The nephrons then return water and substances like sodium,
potassium, and phosphorus to the blood to maintain optimal levels in the body. The nephron
consists of a glomerulus enclosed within Bowman’s capsule and a tubule consisting of the
proximal convoluted portion, loop of Henle, and distal convoluted portion.
32. Aquaporins are openings in the plasma membrane, which selectively conduct water
molecules in and out of the cell, while preventing the passage of ions and other solutes.
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33. The filtrate crosses the membranes from the glomerulus to the Bowman’s capsule due to high
arterial pressure in the renal arteries and vessels that feed the glomerulus and due to the relatively
low pressure on the inside of the Bowman’s capsule. Diffusion gradients also aid the passage of
materials.
34. (a) 1 — Cortex, 2 — medulla, 3 — renal pyramids, 4 — renal pelvis
(b) B — the renal vein
(c) the medulla
Understanding
35. Answers may vary. Answers should include three of the following: Nervous system: receives
sensory data from the external environment and transmits signals throughout the body.
Endocrine system: regulates hormone levels. Circulatory system: carries hormones and other
chemicals needed for homeostasis throughout the body. Immune system: protects the body from,
and fights, infections. Digestive system: liver controls amino acid levels, detoxifies harmful
chemicals, and manufactures blood proteins. Integumentary system: helps control body
temperature.
36. In a negative feedback system, the body senses a change and activates mechanisms that slow
down or decrease that change. When the body temperature rises too high, this is sensed by
specialized neurons in the hypothalamus of the brain. They signal other nerve centres, which in
turn send signals to the blood vessels of the skin. As these blood vessels dilate, more blood flows
close to the body surface and excess heat radiates from the body. If this is not enough to cool the
body back to its set point, the brain activates sweating. Evaporation of sweat from the skin has a
strong cooling effect and the body temperature returns to normal.
37. Answers may vary. Sample answer: Increasing contractions during labour is an example of a
positive feedback mechanism used by the body. Uterine contractions stimulate the release of
oxytocin from the pituitary gland. This increased oxytocin in the blood intensifies the
contractions. The intensified contractions, in turn, stimulate further release of oxytocin,
amplifying the effect.
38. Four mechanisms of heat loss are: 1) Conduction: heat loss due to contact with another
surface, 2) Convection: heat transferred in a fluid, 3) Radiation: transfer of heat through
electromagnetic radiation, and 4) Evaporation: thermal energy is required in the process of
evaporation, so heat is transferred from the body as sweat evaporates.
39. Endotherms rely on internal mechanisms that generate thermal energy to regulate body
temperature while ectotherms use behavioural mechanisms, regulating their body temperature by
absorbing thermal energy from their environment.
40. Torpor is a short-term drop in metabolic rate and body temperature to conserve energy.
Hibernation is an extended state of inactivity with a significantly decreased metabolic rate to
conserve energy when food is unavailable in the winter.
41. The jackrabbit is able to dissipate thermal energy through the large surface area of its ears.
The blood vessels in the ears are very close to the surface. This allows thermal energy to be
transferred from the blood to the surrounding air.
42. (a) Osmoregulation is the process by which the water content and the ion concentration
inside a cell are regulated and kept stable.
(b) The kidneys perform both excretion and osmoregulation.
43. Nitrogenous wastes are the residues from the degradation of proteins. They are made from
the chemical transformation of the amine group of amino acid molecules.
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44. The three main types of nitrogenous wastes excreted by organisms are ammonia, uric acid,
and urea.
45. The main nitrogenous waste that is produced by humans is urea. Urea is formed as a byproduct of the degradation of amino acids. The lost amine group is changed into ammonia. In the
liver the ammonia reacts with carbon dioxide to form urea and water.
46. Three interrelated processes that result in the formation of urine are filtration, reabsorption
and secretion. Filtration is the process by which water and solutes pass out of blood through a
selectively permeable membrane; reabsorption is the transfer of water, ions, and nutrients from
the nephron back to the capillaries; and secretion is the movement of materials such as ammonia
and some drugs, from the blood back to the distal convoluted tubule.
47. Answers may vary. Sample answer: Technically, bears do not hibernate in any environment.
In winter conditions they find protected areas like a cave or hollow log and conserve energy by
taking extended naps. In zoos, because temperatures in cages and enclosures remain warm
throughout the year and the bears have access to a food supply that is continually replenished,
they remain active year-round.
48. Water would move into the cell. If the osmolarity of the cell is higher than the osmolarity of
the solution surrounding the cell, the concentration of water is greater outside the cell. Since the
cell membrane is permeable to water, water would flow in. Since the cell membrane is not
permeable to other substances, they would not move in or out of the cell.
49. Two factors that can influence the rate at which water can cross a membrane are temperature
and membrane permeability. Temperature affects osmosis because when temperature increases,
molecules move faster and the rate of osmosis will increase. Decreased temperature reduces the
rate of osmosis. Membrane permeability affects osmosis because the more permeable the
membrane is, the more readily the water can cross the membrane.
Analysis and Application
50. (a) Malpighian tubules
(b) uric acid
51. Answers may vary. Sample answer: The loop can be drawn vertically, horizontally or a
combination of the two, but should include the following: sweating ↑ & water intake ↓, → solute
concentration ↑, blood volume ↓, & blood pressure ↓, → osmoreceptors in hypothalamus →
posterior pituitary → ADH ↑, → reabsorption of water in kidneys↑, blood pressure ↑, blood
volume ↑ & solute concentration ↓.
52. (a) Doctors ask patients for a urine sample as part of an annual physical examination because
urinalysis is a useful way to diagnose certain illnesses and conditions. The doctor knows what
should normally be found in urine and at what levels. If substances are present that should not be
or in levels that are not normal, they could indicate a problem.
(b) Urinary tract infections or diabetes are two conditions that can be diagnosed by urinalysis.
53. We need to drink six to eight glasses of water per day because water is needed by the body
for many different functions. The excretory system requires water to dilute wastes filtered by the
kidneys. Normally the kidneys excrete 500 – 2000 mL of water daily, so the recommended daily
amount of water would be to make up for this water loss as well as water lost through the skin,
lungs, and feces.
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54. (a) After playing soccer in hot weather, the urine would be concentrated (dark yellow colour)
and the volume would be low. Water loss from sweating would cause the kidneys to retain as
much water as possible.
(b) Alcohol is a diuretic, so alcohol consumption would cause a person to urinate frequently.
After several hours, this would reduce the urine volume and concentrate the urine (dark yellow
colour).
(c) After exercising, consuming a litre of water would replace any water loss from the moderate
exercise. This would return the volume of urine to normal or above normal and cause the urine to
be slightly diluted and clearer than normal.
55. Proteinuria is considered a sign of damage or injury to the glomerulus because proteins are
generally too big to be filtered through the glomerulus and are rarely seen in the urine. When
higher levels of protein are apparent, disease or damage is suspected.
56. Hematuria (blood in the urine) is less specific to the kidneys because even though the
glomerulus blocks blood cells and platelets from entering the urine due to their large size, blood
could enter the urine from an injury/disease in the lower parts of the urinary tract.
57. Coffee and colas increase urination because they contain caffeine. Caffeine increases the
glomerular pressure, causing increased filtration. It also inhibits Na+ reabsorption, causing
decreased water reabsorption. This leads to increased urination.
58. (a) Sample 1 has normal specific gravity, low pH, high glucose, and is positive for ketones .
These results are typical of diabetes. Sample 2 has a reddish-brown colour, high specific gravity,
and is positive for blood and leukocytes, which is indicative of urinary tract or kidney infection.
(b) Glucose is not normally found in the urine because at normal blood sugar levels, the glucose
is reabsorbed in the proximal tubule of the nephron. In diabetes, much higher blood sugar levels
are found. The excess sugar remains in the nephron and is secreted with the urine.
(c) Other reasons that may cause ketones to appear in the urine include bulimia, anorexia,
consuming insufficient calories, and high protein diets.
59. (a) Filtration
(b) in the glomerulus
(c) proteins and cells
(d) In urine formation, filtration forces water and small solutes out of the glomerular vessels into
the nephron tubule. Nutrients, salts, and water are recovered in the proximal and distal tubule.
Glucose and amino acids are returned to the bloodstream by active transport. Salts and water are
reabsorbed from the proximal tubule. Tubular excretion moves uric acid, creatinine, hydrogen
ions, ammonia, and antibiotics from the peritubular capillary into the distal convoluted tubule.
Glomerular filtrate exists as urine and is excreted.
In the coffee scenario, water is filtered through the ground coffee. Some water remains in the
coffee grounds, but most moves through absorbing some of the coffee, water and coffee are
retained, and the grounds are discarded.
60. Crocodiles really cry to get rid of nitrogenous wastes.
61. Amphibian larvae are aquatic and therefore can dilute the ammonia. Adults are terrestrial and
cannot. Undiluted ammonia would be toxic.
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Evaluation
62. Pitocin is often administered to women during labour because labor sometimes stalls or is
delayed. If the health of the mother or baby needs labor to continue more quickly, induction by
pitocin is one option. Pitocin creates a positive feedback loop, like its natural counterpart
oxytocin, that increases the rate and strength of the contractions, moving labour forward.
63. (a) With loss of the ability to sweat or vasoconstrict the patient becomes poikilothermic and
needs to carefully control their environmental conditions. Therefore, if a high paraplegic or
quadriplegic is in an outside temperature over 32 °C, especially when the humidity is high, the
body temperature will begin to rise (poikilothermia). Likewise in a cold environment, the body
may not be able to get the messages through to the brain that the body is cooling down, and if
left untreated, the person will soon become hypothermic.
(b) Answers may vary. Sample answer: To cool a person with a spinal cord injury, a cold wet
towel wrapped around the back of the neck could be used. The skin should also be dampened to
allow the water to evaporate from the skin, and hence cool the body down. To warm a person
with a spinal cord injury, layers of clothing should be worn, and warm fluids should be
consumed to bring the core temperature back up to normal.
(c) This condition is called poikilothermia because a person’s body temperature varies with the
environmental temperature like poikilotherms’ does, rather than being regulated internally.
64. (a) Osmosis occurs across the semi-permeable barrier of the plasma membrane. That barrier
allows water molecules to pass in certain directions, depending on the concentration of water
solutions on each side. Under normal circumstances, the saltiness of water in your cells is the
same as the saltiness outside your cells — an isotonic state. When your cells use water, the
internal solution becomes more concentrated, and the natural process of osmosis allows water
from outside your cells to pass into your cells to achieve equilibrium or osmoregulation.
(b) Our cells are isotonic to about 0.9 % saline solution. If the salinity of the solution outside the
cells decreases, our cells absorb more water to get back to an isotonic state. For example, when
endurance athletes drink too much fresh water, the salinity of the solution outside their cells
drops rapidly and osmosis allows water to pass into the cells as a part of osmoregulation. If they
absorb too much water, the cells can swell and burst, which can lead to a quick death.
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(c) The opposite happens when drinking sea (salt) water. The salinity outside our cells increases
rapidly. Osmoregulation effects a movement of water out of our cells to achieve an isotonic state.
Even though you may be dehydrated, your cells will actually release, rather than absorb, the
water around them.
(d) Drinking salt water could lead to death sooner than not drinking anything at all, decreasing
your chances of being rescued.
65. Cells of the nephron have many mitochondria because many of the substances either secreted
or reabsorbed in these tubules do so by active transport that requires energy (ATP). Many
mitochondria are required to supply the much needed ATP for the active transport.
66. Doctors examine the urine of diabetic patients because kidney problems occur in about 20 –
40 % of all people with diabetes. The high concentrations of blood glucose place a strain on the
functioning of the nephrons and can lead to disease. Doctors also examine the urine of diabetic
patients to check for ketones. If cells are not able to absorb glucose, they often use lipids to meet
their energy needs. A byproduct of this is ketones, which will show up in the urine.
67. (a) The class mate is incorrect; the kidneys perform several life-sustaining roles.
(b) Answers may vary. Sample answer: I would explain that the kidneys cleanse your blood by
removing waste and excess fluids, they help maintain the balance of salt and minerals in your
blood, and they help regulate blood pressure.
68. The health of the heart depends on a stable, normal blood pressure. Having the heart secrete
ANF allows the heart to be a check and balance in the renal control of blood pressure.
69. The fetus excretes nitrogenous wastes by passing the wastes to the mother’s blood through
the placenta, which is then excreted in the mother’s urine as well.
70. Infants are more susceptible to dehydration than adults because infants’ kidneys are not yet
functioning at full capacity. In addition, infants have a high surface area to volume ratio, so they
may be more susceptible to losing fluids in hot conditions, causing dehydration.
71. Answers may vary. Sample answer: People taking prescription drugs that make them more
sensitive to heat would be more susceptible to a heat illness. Therefore, they should avoid
extended periods of time out in the heat, avoid alcohol and caffeinated beverages that would
make them lose more fluids, drink more water than usual to keep their body hydrated, avoid hot
cars etc.
Reflect on Your Learning
72. (a) Answers may vary. Sample answer: I think that urine testing for drug use in sports is
necessary to ensure that athletes are not using illegal substances that could artificially enhance
their performance. This is required to maintain the integrity of the sport.
(b) Answers may vary. Sample answer: I do not think this type of testing will stop the problem
of drug abuse as athletes may still use the drugs while training and stop using long enough to
clear the drugs from their system just before testing. In some cases, however, it may be a
deterrent for some athletes to not use performance-enhancing drugs.
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(c) Answers may vary. Sample answer: No, I do not think that athletes should have the option of
refusing or requesting urine testing. Testing should be mandatory to ensure an equal playing field
and it should also be random and spontaneous so that the athlete cannot “prepare” for the test.
73. (a) Answers may vary. Sample answer: No, I do not think that selling organs is an
acceptable practice. Putting a price tag on an organ may lead to people donating organs for
money who otherwise would not have wanted to donate the organ. Additionally, it may lead to
“stealing” organs from people.
(b) Answers may vary. Sample answer: If I needed an organ or someone I knew needed an organ
and I had enough money to purchase one, I would not buy the organ. I believe that money should
not be a motivation for organ donation. Additionally, black market organs may not be fully
screened for disease/health. For these reasons, I would want to take my chances with waiting on
a transplant list.
74. (a) Answers may vary. Sample answer: Yes, I have known someone to donate an organ.
Since then, I have recognized the importance and life-saving ability of organ transplants.
(b) Answers may vary. Sample answer: I would certainly consider organ donation, especially for
a loved one. On one hand, I would be thrilled to save the life of someone I love, but on the other
hand, I have concerns about my own future needs. I would be concerned that I would need the
organ in the future, if my other kidney should fail, for example.
(c) Answers may vary. Sample answer: There are a few questions that I would like to have
answered before agreeing to donate an organ. These include: How long will the transplanted
organ last in the recipient? How will my health change after the transplant? Will I have to make
any lifestyle changes after the surgery? What are the chances that I will require an organ
transplant in the future?
(d) Answers may vary. Sample answer: To get these questions answered, I could speak to a
doctor/surgeon, I could speak to previous transplant recipients and donors, or I could find a
support group for transplant patients.
Research
75. (a) The mammalian diving reflex is an innate response to cold water exhibited by mammals,
including humans. Cold water contacting the face triggers the reflex, which shunts blood and
available oxygen to the heart and brain.
(b) Bradycardia is the first process that is triggered. As soon as the face makes contact with cold
water, the human heart rate slows down. Next, peripheral vasoconstriction sets in. When under
high pressure induced by deep diving, capillaries in the extremities start closing off, stopping
blood circulation to those areas. This leaves more blood for use by the heart and brain. Finally,
during very deep dives, organ and circulatory walls allow plasma to pass freely throughout the
thoracic cavity, so its pressure stays constant and the organs are not crushed.
(c) Hypothermia is a physical condition that occurs when the body’s core temperature falls below
a normal 37 °C to 35 °C or cooler. The heart rate slows and the blood flow is concentrated on the
internal organs and shunted away from the extremities. Conversely, the mammalian diving reflex
lowers the heart rate and limits blood circulation to all but the body’s core so that the core
temperature will not fall below 37 °C.
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76. Answers may vary. Reports should include the following:
• Glomerulonephritis is inflammation of the glomerulus and may be caused by problems with the
body's immune system. Often, the precise cause of glomerulonephritis is unknown. Damage to
the glomeruli causes blood and protein to be lost in the urine.
• Another name for the disease is Bright’s disease.
• Risk factors for the disease include infection, history of cancer, exposure to some solvents,
diabetes, some over-the-counter and prescribed drugs. Symptoms include blood in the urine,
foamy urine, and swelling of the hands, face, and ankles. Treatments include medication, dietary
restrictions, plasmapheresis, and dialysis. The disease may or may not resolve on its own. There
is no known cure for this disease. If left untreated or problems persist for a long period of times,
it could result in end stage kidney failure.
77. Answers may vary. Reports should include personal reflections, and the following:
• Xenotransplantation is transplantation of an organ or tissue from one species to another.
• The main benefit is that organs for transplant are more readily available, reducing the death rate
of people on the transplant list. Other benefits include xenotransplantation is less costly and
donor and recipient do not need to be in close proximity. Disadvantages include higher risk of
tissue rejection, religious or cultural objections, animal rights objections, and the risk of
spreading diseases not seen before in humans.
• There have only been a few attempts at human xenotransplantation over the years, but no
xenotransplantation projects are currently approved for transplanting organs into humans.
• Xenotransplantation is currently not prohibited in Canada; however, the live cells, tissues and
organs from animal sources are considered to be therapeutic products (drugs or medical devices)
in Canada. Therefore, xenotransplantations are subject to the requirements of the Food and
Drugs Act, the Food and Drug Regulations or the Medical Devices Regulations. To conduct a
human clinical trial, a sponsoring company or research institute would have to apply to Health
Canada for approval before proceeding.
78. Pamphlets or posters will vary, but should include the following:
• Gout is the first diagnosed and most common form of arthritis.
• Gout is considered a disease of the excretory system because it is caused by uric acid crystal
build up in the joint, leading to inflammation. The body normally forms uric acid when breaking
down cells and proteins, releasing it into the bloodstream. The uric acid normally stays dissolved
in the blood and ends up being flushed out by the kidneys. If there is too much uric acid in the
blood, or if the kidneys cannot eliminate it quickly enough, it may begin to form crystals that
collect in the joints and even in the kidneys, skin, and other soft tissues.
• Researchers believe that drinking alcohol can lead to gout because alcohol contains purines or
oxypurines, leading to an increased purine load. This causes too much uric acid to be produced,
triggering gout.
• The alcohol that seems to be the worst offender is beer because it contains the most purines.
• Other factors that increase the number and severity of gout attacks include diet, age, gender,
dehydration, flying, and injury to the foot prior to onset.
• Gout attacks can be reduced or prevented by cutting down on dehydrating drinks such as
alcohol, coffee, tea, and cocoa; animal proteins such as seafood, liver, kidney, heart, gizzard,
sweetbreads, meat extracts, and gravy; and vegetables such as peas, beans, spinach, and lentils.
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79. Pamphlets/posters/videos may vary, but should include the following:
• Heat exhaustion and heatstroke are heat-related illnesses caused by exposure to extreme heat.
Untreated heat exhaustion can develop into heat stroke, which is a much more serious heatrelated illness that affects the central nervous system.
• Athletes, children, and the elderly are most susceptible.
• Signs and symptoms of heat exhaustion to watch out for include malaise, headache and nausea.
Symptoms of heatstroke can include, stroke, delirium, coma, breakdown of muscle tissue, liver
failure, arrhythmias, disseminated intravascular coagulation, and death.
• Heat exhaustion and heatstroke can be avoided by preparing for heat waves; staying in a cool,
shaded place; drinking water to help the body’s natural cooling mechanisms function; and
reducing physical activity in extreme heat.
• If someone exhibits signs of heat exhaustion or heatstroke, try to cool them immediately by
wetting them and using evaporation or by immersing them in ice-water.
80. Articles may vary. Articles should include the following:
• When temperatures drop below freezing, the metabolism of wood frogs slows dramatically so
the frog’s cells can survive on very little oxygen and energy.
• The frog’s liver begins to pump out glucose, raising the concentrations of glucose in the
bloodstream.
• Ice crystallizes in the frog’s body cavities drawing some of the water from the cells in the tissue
and organs. This further concentrates the glucose inside the cells, turning it into a substance
similar to antifreeze that keeps the remaining water from solidifying and damaging the tissues.
• A frog can remain in this state until spring, when its metabolism returns to normal.
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