3. The following diagram is a summary of a homeostatic mechanism for compound X.

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1 VCAA EXAM QUESTIONS MULTIPLE CHOICE QUESTIONS 1. Homeostasis is the condition of a relatively stable internal environment. The internal environment of a multicellular organism includes A. tissue fluid. B. digestive fluid. C. cytosol. D. urine. 2. Homeothermy is the A. regulation of blood solute concentrations. B. maintenance of a relatively constant body temperature. C. increase in metabolic rate with increasing external temperatures. D. maintenance of body temperature the same as that of the external environment. 3. The following diagram is a summary of a homeostatic mechanism for compound X. In organ Y A. the cells must act as exocrine glands. B. there must be sensors for compound X levels. C. compound Z must act to increase blood levels of compound X. D. compound X sensors and compound X effectors are part of the nervous system. TEMPERATURE REGULATION 4. An elephant maintains its body temperature within a narrow range. In conditions of extreme heat, factors that contribute to increased heat loss from an elephant include A. folding the ears against the body. B. decreased blood flow to the ears. C. huddling with others. D. flapping the ears. 5. Woolly mammoths are an extinct species of elephant that lived in very cold climates. They had very small ears. Compared with the large ears of modern elephants, small ears would have assisted the survival of the mammoths by A. decreasing the core body temperature. B. increasing the effects of heat conduction. C. increasing the radiation of heat from the body. D. decreasing the surface area through which heat is lost. 6. Mammals that live in very cold environments have behavioural adaptations that help reduce the rate at which they lose heat. One behavioural adaptation could be A. decreasing food intake. B. having fur that fluffs out. C. curling up into the shape of a ball. D. isolating themselves from other individuals. 1

2 One way in which the general principle of homeostasis can be outlined is given in the following diagram. 7. Consider homeostasis in the control of body temperature. If body temperature rises above normal limits then A. responses 2 involve constriction of the blood vessels. B. responses 2 involve an increase in shivering. C. the sensor is the anterior pituitary gland. D. the sweat glands act as an effector. 8. Consider homeostasis in the control of body water. If a person becomes dehydrated, the concentration of the solutes in their body ß uids increases and A. this change is detected by sensor cells within the hypothalamus. B. as a consequence responses 1 become relevant. C. effectors include cells within the digestive tract. D. as a consequence responses 2 involve a decrease in water reabsorption from nephron tubules. 9. Considering the diagram above, the component that is being kept relatively constant is A. the variable. B. input to the sensor. C. input to the effectors. D. output from the effectors. 2

3 The body temperature of two different mammals was recorded over 24 hours. The average daytime temperature was 40 C and average night-time temperature was 20 C. The temperatures of the mammals over the 24 hours are shown in the graph below. 10. From the information given it would be reasonable to conclude that A. between midnight and 6.00 am, mammal H would be gaining heat by conduction. B. at noon, mammal H would be gaining heat by radiation. C. at noon, mammal G is losing heat by radiation. D. between midnight and 6.00 am, mammal G would be losing heat through evaporation of sweat. The graph below shows the effect of environmental temperature on the metabolic rate of two mammals. The zero rate of metabolism represents the basal metabolic rate for each mammal. 11. From the information given you could conclude that A. mammal A would be shivering when the air temperature is 50 C. B. mammal B would be sweating when the air temperature is 20 C. C. mammal B would have a thicker insulating layer of fat than mammal A. D. vasodilation of skin blood vessels of mammal A would occur when air temperature is 10 C. 3

4 OSMOREGULATION Biologists investigating the regulation of body water in Peking ducks, Anas platyrhynchos, put forward the hypothesis that Peking ducks drink more as the saltiness of their drinking water increases. The drinking water was to be supplied in 70 litre wading pools and replenished twice each day. Twelve adult Peking ducks, males and females, were available and two experimental designs were suggested. Design 1 The same twelve ducks are provided with drinking water of increasing saltiness over a 24-week period. Design 2 The twelve ducks are divided into four groups of three ducks and each group is exposed to drinking water of a different saltiness. 12.The variable being investigated is the A. time. B. species of duck. C. gender of the ducks. D. saltiness of the drinking water. 4

5 13. Design 1 was chosen for the investigations because it better accounted for A. variation between individual ducks. B. homeostatic regulation of body water. C. other factors that could affect drinking. D. time taken for the ducks to acclimatise to the conditions. The kidney plays a vital role in homeostasis in mammals. The basic functional unit of a mammalian kidney is a nephron which is shown in the following diagram. 14. Normal functioning of a nephron relies on a A. decrease in renin production as blood pressure falls. B. secretion of ADH (antidiuretic hormone) by kidney cells. C. reabsorption of water into the blood from the Loop of Henle. D. decrease in water movement from distal tubules as ADH increases in the blood. 15. Fish living in freshwater A. actively transport water into their body cells from their surroundings. B. produce urine with a high solute concentration. C. produce urine that contains ammonia. D. produce small volumes of urine. 16. A group of students studied water balance in mice. Each student placed a mouse in a cage with dry food and a water bottle. They measured the amount of water consumed by each mouse every 24 hours. The students assumed that if a mouse was in water balance then the amount of water consumed would be equal to the volume of urine lost by the mouse each day. In making their assumption about water balance, students had overlooked the point that A. larger mice would drink more water. B. water would be lost in faeces and saliva. C. more water would be consumed on hotter days. D. urine volume would vary with volume of water consumed. 5

6 HOMEOSTASIS OF PH AND CO 2 The following diagram shows the regulation of carbon dioxide concentration in arterial blood. 17. The effector in the regulation of carbon dioxide concentration is the A. respiratory muscles. B. efferent nerve impulses. C. respiratory centre in brain. D. afferent nerve impulses. 18. When the concentration of carbon dioxide returns to normal it would be reasonable to conclude that the A. respiratory muscles stop contracting. B. rate and depth of breathing decrease. C. number of afferent nerve impulses increase. D. respiratory centre in the brain fails to send efferent nerve impulses. GLUCOSE HOMEOSTASIS 19. Cats that have not been fed for two to three days are able to maintain a constant blood glucose concentration. After 24 hours without food, the structure from which glucose is released into the cat s blood is the A. liver. B. brain. C. pancreas. D. digestive tract. 6

7 CONTROL OF THYROXINE The following diagram shows the regulation of thyroxine secretion. 16. A person who lacks sufficient iodine in the diet is unable to manufacture thyroxine. This is because iodine is required by the thyroid gland to manufacture thyroxine. It is reasonable to conclude that when a person lacks sufficient iodine in the diet A. TSH production would increase. B. TRH production would decrease. C. the negative feedbacks would cease to operate. D. the metabolic rate of cells in the body would increase. SHORT ANSWER QUESTIONS SPRAY ON SKIN 1. Treatment of burns has been improved by the use of spray on skin. Spray on skin consists of a suspension of individual skin cells from the patient that is sprayed directly onto the burnt area. These cells then grow and divide rapidly to produce a continuous layer of skin cells. Spray on skin results in rapid healing of the burnt area. a. Describe one way in which intact skin contributes to homeostasis. Spray on skin uses the body fluids of the patient as a culture medium for the skin cells. A continuous layer of skin cells can be produced more rapidly with spray on skin than with another technique in which the patient s skin cells are grown in vitro until a sheet of skin cells is formed. b. Suggest a reason for more rapid cell growth and division with the spray on skin technology. 7

8 GLUCOSE HOMEOSTASIS 2. The concentration of glucose in human blood is kept within a narrow.normal. range. All body cells need a continuous supply of glucose. The uptake of glucose into the muscle cells occurs by facilitated diffusion. a.explain how the process of facilitated diffusion enables the uptake of glucose. To prevent the concentration of glucose in the blood falling below the normal range the pancreas releases a hormone. b.i What is the name of the hormone? b. ii. What is the target organ for this hormone? biii. How does this hormone cause an increase in blood glucose concentration? When the concentration of glucose in the blood rises above the normal range the pancreas releases another hormone. Some humans cannot make enough of this hormone and must have regular injections of this hormone.different forms of this hormone have been produced by pharmaceutical companies. The table below showsinformation on three forms of the hormone. c. State one advantage of form C. d. Describe one situation when it would be advantageous to use form A. 3. Regulation of blood-glucose concentration relies upon functioning B cells in the Islets of Langerhans in the pancreas. These cells produce a hormone. Diabetes mellitus develops when B cells are destroyed. a. Name the hormone produced by B cells. A characteristic sign of a person suffering from diabetes mellitus is a high concentration of glucose in the blood. b. Describe the action of the hormone produced by B cells. Currently, individuals with diabetes mellitus are treated with injections of the missing hormone. These injections are usually given several times each day. Recently, a pump capable of delivering the hormone continuously in response to changing blood-glucose concentration has been developed. The pump turns on and off automatically when the blood glucose changes. 8

9 c. What would be the signal for the pump to turn on and begin delivering the hormone? d. Episodes of abnormally low concentration of blood glucose are reported to be less frequent in individuals when the hormone pump is used rather than hormone injections. Explain why this would be the case. 4. The table below shows the mean levels of glucose and insulin in two groups of people sampled one hour after the ingestion of 75 g of glucose. One of the experimental groups consisted of people with diabetes; the other acted as a control. a. What is the purpose of the control group? b. Using the above data, give two reasons to explain which group (X or Y) included the people with diabetes. Group Reason 1 Reason 2 No other food or drink was ingested in the three hours following the conclusion of the experiment. Neither group received an injection of insulin. In that time the mean plasma glucose concentration in the control group returned to 5.3 mmol/l. c. Explain how this change occurred. Another hormone involved in the control of plasma glucose concentration is glucagon. d. From which organ is glucagon secreted? e.explain how high levels of glucagon would affect the plasma glucose level. 9

10 5. Insulin is a hormone involved in the regulation of blood sugar levels. Failure to produce insulin results in insulin-dependent diabetes, and persons with this condition must have regular injections of insulin. A common insulin used has been NPH insulin and it is given from two to four times daily. Recently the activity of a new type of insulin, called LANTUS insulin, has been tested and compared with NPH insulin. Participants in the test were divided into two groups. One group received NPH insulin. The second group received LANTUS insulin. All participants received the same amount and concentration of the appropriate insulin. The following graph shows the average results for participants in each of the two groups. Insulin is regarded as being effective when the glucose uptake by cells is above 0.4 mg/kg/min. f. After the injections, for how long was each kind of insulin effective? NPH insulin LANTUS insulin g. Assuming there are no undesirable side effects from using LANTUS insulin, suggest why using LANTUS insulin may be an advantage for a person who has insulin-dependent diabetes. OSMOREGULATION 6. A study was carried out comparing camels, cattle and sheep. The average amount of body water the mammals lost per day when the temperature was 42 C was calculated. The results are shown in the table below. 10

11 a. Using the information given, explain which animal will survive for the longest time in a hot dry environment. Water can be lost from a mammal due to evaporative cooling. b. i. Explain how evaporative cooling leads to a reduction in body temperature. ii. Describe one other way in which a mammal may lose water. In another mammalian study, the relative contribution of sweating or panting to evaporative cooling was investigated when the animals were exposed to a hot, dry environment. c. Describe one advantage to a mammal of panting rather than sweating. d. Mammals that live in hot, dry environments have physiological adaptations that help them to survive. Describe one of these adaptations. 7. Springhares are large nocturnally active rodents that live in arid regions of southern and eastern Africa. They spend much of the day sheltering in burrows. Biologists studied the characteristics of springhares that enable them to cope with the scarcity of water and extremes of temperature in their habitat. Eighteen adult springhares were caught and brought to the laboratory for study. Each springhare was placed in an experimental chamber and the rate at which it used up oxygen was measured. The measurements were repeated for each springhare at a range of chamber temperatures. a. Explain why studying oxygen usage for each springhare enabled the scientists to calculate the metabolic rate of each animal. The average results are shown in the following graph. 11

12 The thermoneutral zone (TNZ) for an animal is that range of temperatures at which their energy expenditure is the lowest. b. What is the thermoneutral zone for these springhares during the experiment? The biologists observed the springhares as the temperature of the experimental chamber was changed. c. Explain how each of the observations listed below (i., ii. and iii.) would contribute to regulation of body temperature. i. As the chamber temperature decreased below 15 C, the springhares curled up with their heads between their hind legs and their tails wrapped around their backs. ii. As the chamber temperature decreased below 15 C, shivering became increasingly apparent. iii. At 35 C, blood vessels in the ears and legs were visibly dilated and the springhares spread saliva over their faces and throats. After the experiment, the springhares were kept for a week in the laboratory animal house which was maintained at 20 C. Dry food and drinking water were provided; however, there was no evidence that the animals ever drank. d. What would be the water source for these animals if they do not normally drink when the environmental temperature is 20 C? The biologists returned to the region in which the springhares had been caught to investigate the temperatures in their burrows. They found that although outside day and night temperatures varied significantly between 33 C and 3 C, temperatures within burrows remained stable at about 12 C. e. Explain how spending most of the daytime in burrows helps springhares maintain their water balance. 8. Several hormones are involved in maintaining homeostasis in mammals. Antidiuretic hormone is important in controlling water balance. The following graph shows changes in the concentration of this hormone as plasma solute concentration increases. a. At what plasma solute concentration is the release of antidiuretic hormone triggered? 12

13 b. Which organ of the body releases antidiuretic hormone? c. Explain the action of antidiuretic hormone in controlling water balance. 9. A group of scientists investigated two species of mammals living in their natural habitat. The scientists recorded the ways in which water was lost and gained by the mammals. The findings are summarised in the table below. a. State two pieces of evidence from the table that suggest that mammal species A is suited to survive in a hot, dry environment. Evidence 1 Evidence 2 Consider the ways in which the two species of mammals are losing water. The evaporation of water includes the water lost during respiration and water lost through the skin. b. Describe one way in which a mammal may behave to reduce the amount of water lost in evaporation. c.suggest the third avenue of water loss that may account for 4% of losses in each of the mammal species. 13

14 d. The percentage of water lost in urine varies between the two mammal species. Describe a structural adaptation which would explain the difference. THERMOREGULATION The diagram below summarises the response to an increased body temperature in a person. a.explain what happens when body temperature increases. b. Explain what happens when body temperature decreases. CALCIUM HOMEOSTASIS 11. Human blood-calcium concentrations are under homeostatic control. When the concentration of calcium in the blood begins to fall the parathyroid gland releases parathyroid hormone. This hormone stimulates bone cells called osteoclasts to break down bone and release calcium into the blood. When the concentration of calcium rises in the blood, specialised cells associated with the thyroid gland release the hormone calcitonin. Calcitonin acts on bone and increases the amount of calcium that is deposited into bone. This information can be presented in a flowchart such as that in the figure below. Note that some parts of the flowchart have been completed. 14

15 a. What is the general name given to structures that detect the changes in blood-calcium concentrations? b. The control of blood-calcium concentrations involves negative feedback. What is negative feedback? c. Use the information given above to complete the flowchart by filling in the six empty boxes. d. Explain what happens when calcium level decreases e. Explain what happens when calcium level increases 15

Homeostasis. - Homeostasis literally means same state and it refers to the process of keeping the internal body environment in a steady state.

Homeostasis. - Homeostasis literally means same state and it refers to the process of keeping the internal body environment in a steady state. www.sureshkumarbio.wordpress.com Form 4 : Chapter 2 : Cell Structure and Cell Organisation Homeostasis - Homeostasis literally means same state and it refers to the process of keeping the internal body