9.2.1.a most organisms are active in a limited temperature range

8/14/2019 9.2.1.a Most Organisms Are Active in a Limited Temperature Range

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HSC Biology

Past Paper Answers:Maintaining a Balance

- Most organisms are active in a

limited temperature range

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1.1 Identify the role of enzymes in metabolism, describe their chemical compositionand use a simple model to describe their specificity on substrates

Multiple choice4. B to determine the effect of pH, all factors other than pH must be kept constant.

2001

5. BBoiling denatures the enzyme, which means the sugar is not converted to starch so thecorn remains sweet.

2001

7. BPoint A is the maximum level of enzyme activity. The curve is then a flat line, so enzymeactivity does not increase as the substrate concentration increases, so (B) is the only possibleanswer.

2003

10. Dan enzyme acts on a substrate to form a product(s), and remains unaltered in a chemicalreaction and so must be present before and after the reaction.

2004

1. DA substrate changes after interacting with an enzyme, whereas the enzyme itself remainsunchanged. Thus A and B are the substrate as in (D), as they are originally separate and thenchange to be joined after interacting with C, which is the enzyme.

2007

2. Ball the statements given are correct regarding enzymes, but only (B) answers the questionabout why a cell requires multiple enzymes.

2007

10. Athe enzyme activity increases until its optimum temperature is reaches. At highertemperatures it begins to denature because it is a protein. This (A) is the answer.

2009


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9. Cin both experiments, the measured enzyme activity remained zero or close to zero whenthe inhibitor was present. The pH and the temperature are the independent variables and theenzyme activity is the dependant variable. Presence or absence of an inhibitor is anotherindependent variable affecting the enzyme activity, so (C) is the answer.

2010

Short answer and extended response

29.Hypothesis: Enzymes work best at an optimal pH.

Aim: To compare enzyme activity in the two bacteria at different pH.

Equipment: 6 sterile test tubes, water bath, thermometer, heat source

Materials: Bacteria X, bacteria E, 2 identical substrates- one at pH 6 and one at pH 8

Method:

1. Using equal amounts, put substrate with pH 6 into 3 test tubes and substrate with pH 8 into 3test tubes. Label test tubes with pH used.

2. Using equal amounts, add some bacteria X into a test tube with pH 6 and to a test tube withpH 8. Repeat using the bacteria E. Label test tube with X or E. Leave remaining test tube ateach pH without bacteria as a control.

3. Place all test tubes into a water bath at 50oC and leave for 20 minutes.

4. Observe test tubes every minute and record if any gas is produces/

5. Repeat experiment several times to increase the sample size and to ensure its reliability.

6. Compare the production of gas by both bacteria at the different pH.

Risk Assessment: Sterile techniques should be used so that bacterial contamination does notoccur, disposable gloves should be worn to protect hands, and all materials should be correctlydisposed of afterwards.

Dependent Variable: Activity of the enzyme.

Independent Variable: The Different pH

2004


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2008

22. (a)To determine the optimal pH for enzyme activity OR To test the effect of pH on theactivity of an enzyme

(b)Controls without an enzyme solution should have been used at each pH, and Test a greaternumber of pH values including neutral and basic values.

(c)

Student Volume ofenzyme

solution(mL)

Temperature(oC)

pH Volume of cloudysuspension(mL)

Time(min) Observationas end of trial

1 5 37 2 10 40 Clear

2 5 37 2 10 40 Clear

3 5 37 4 10 40 Clear

4 5 37 4 10 40 Clear

5 5 37 6 10 40 Cloudy

6 5 37 6 10 40 Cloudy

2011


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1.2 identify the pH as a way of describing the acidity of a substance

Multiple Choice

12. CBubbling CO2through water would increase the [CO2] in the water over time and the pH

decreasing over time indicates that the water is becoming more acidic. Thus (C) is the answerand (B) is incorrect as it is the opposite.

2009

1.3 explain why the maintenance of a constant internal environment is important foroptimal metabolic efficiency

Multile choice

3. BEnzymes work best at specific temperatures (and pH).

2011

1.4 describe homeostasis as the process by which organisms maintain a relativelystable internal environment

Multible choice

9. D homeostasis is the process by which multicellular organisms maintain a constant internalenvironment and involves more than just controlling temperature, so (D) is the answer.

2004

4. Bhomeostasis is the maintenance a constant internal environment, and when a change fromthe stable state occurs, mechanisms in the organism act to restore the normal state. So (B) isthe answer. Enantiostasis is the maintenance of metabolic and physiological functions by anorganism in response to variation in its environment be careful not to confuse it withEnantiostasis.

2008


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1.5 explain that homeostasis consists of two stages: detecting changes from thestable state, counteracting changes from the stable state

Multiple choice

3. CA rise in body temperature results in the hypothalamus sending a nervous impulse to activatethe sweat glands. As sweat evaporates on the surface of an organism, it takes heat from theorganism, causing the body to cool down. If the body temp drops too low, the hypothalamus stopssending messages to the sweat glands, so sweat production decreases as in (C).

2001

9. D

2005

2003

26.Homeostasis maintains a constant internal environment, whereas enantiostasis maintainsmetabolic and physiological functions by altering the internal state in response to variations in theinternal environment. Estuarine plants undergo enantiostasis to survive fluctuating saltconcentrations. They can tolerate more salt in their tissue that normal plants as they havemechanisms to adjust osmotic pressure and adaptations to resist salt, e.g. mangroves exclude salt

at their roots and have special glands to pump salt out their leaves.

2009


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1.6 outline the role of the nervous system in detecting and responding toenvironmental changes


17.The nervous system maintains a constant internal body temperature. An increase/decrease inthe external temperature is detected by receptor cells. These relay this message to the CNS, whichsends the message to the hypothalamus. The hypothalamus sends messages via the nervoussystem to an effector organ to bring about an increase/decrease in temperature, e.g. to increasetemperature the muscles shiver, skin blood vessels constrict, perspiration begins. Once therequired temperature is established, negative feedback to the hypothalamus occurs to preventovercorrection.

2005


23. (a)if this technology becomes commonly used and many people are screened, it will changethe genetic diversity of the population by decreasing the frequency of this gene. However, it willhave very little effect on the population if only this one family uses the technology.

(b)Genetically engineering a transgenic species such as Bt cotton by inserting the Bt gene forinsect resistance into it has altered its genetic diversity. Therefore it has altered its evolutionarypathway because natural selection is not dictating the direction of its evolution. It will also alterevolution of the bollworm moth whose larvae feed on the cotton plants, as it decreases their chanceof survival.

24. (a)Dependent variable: changes in sweating and heart rate.

Independent variable: Temperature of the room

(b)Nervous system

(c)


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2009

1.7 identify the broad range of temperatures over which life is found compared with

the narrow limits for individual species

Multiple choice

3. DThe graph only indicates the temperature range for 4 species, not all bacteria, so (A) and (D)are incorrect. The graph shows that each of the 4 species can only reproduce within a narrow bandof temperature, with the largest band having only a range of 30oC. This (D) is the answer.

2002

8. Bthe body temperature of ectothermic animals varies with the environment, and varies over anumber of degrees. Thus species I is ectothermic. The body temperature of endothermic animals iscontrolled internally and varies by only a small number of degrees, despite external temperatures.Thus species II is endothermic.

2006

1.8 compare responses of named Australian ectothermic and endothermic organismsto changes in the ambient temperature and explain how these responses assist

temperature regulation

Multiple choice

2. CEndotherms generate heat as a result of their metabolic activity, so a sudden and prolongeddecrease in ambient temperature results in increase metabolic activity, e.g. shivering whichincreases muscle activity. A decreased blood flow to the skin surface enables the organism to havea lower skin temperature to help it maintain a more normal internal body temperature.

2002

3. Bin cold environments, mammals need a low surface area to volume ratio to reduce heat losswhich allows the body to conserve heat. This is provided by short ears, rounded body and shortlegs, so (B) is the answer.

2003

6. Dthe observation in (D) indicates that the organism is affected by the external temperature andso it is an ectotherm. Thus (D) is the answer.

2008


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20. (a)Endothermic animal: Spinifex hopping mouse OR Red Kangaroo

Ectothermic animal: Brown snake OR Blue tongued lizard

Animal Responses to Change 1 Responses to Change 2

Brown snake -moves into a sheltered orshady spot during heat of theday.-reduces daytime activity, andbecomes active in the evening.

-shelters from the cold andbasks in sunlight whenavailable.-less active, metabolism slowsdown and uses fat reserves(may hibernate)

Spinifex hopping mouse -nocturnal-shelters in undergroundburrows during hear of day.

-goes into undergroundburrows to shelter from coldconditions.-curls up, tucks legs under andcurls tail around body.-huddles in groups.

Or

Red kangaroo -sweats and pants-licks forelimbs to lose bloodheat by evaporation ofmoisture.- moves to shady spot to liedown, and sometimes digs ashallow hole to reach cooler

soil to lie in.-feeds mostly at night.

-shivers, causing muscles togenerate more heat.-moves to bask in the sunlightwhen available.-grows a thicker layer of furcloser to the skin to jeep warm(in winter)

Blue Tongued lizard -moves under dead leaves orinto shade of bushes in heat ofday.-reduces activity

-exposes a larger body surfacearea to sun to absorb moreheat by turning at right anglesto sun-flattens its body to increasesurface area exposed to Sun.Shelters from cold and movesout into sun on warmer days.

2001

16 (a)Endothermic

(b)Thorny devil lizard

(c)Organism II would move out of the sun into a shaded spot or burrow into the ground to avoidexposure to the sun. This would reduce its body temperature so that it could maintain correctbiological functioning.

2003


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27.The total increase in temp over 100 years in only 0.7oC, which is much less that the variation ofseveral oC which occurs currently from one year to another. Each species has a narrow temp rangein which they can live, according to the optimal temp for their enzymes. In the short-term, mostAustralian plants and animals have adaptations that enable them to survive the current fluctuatingtemps, e.g. sunken stomates in many plants helps them to lose less water and thus survive in hot

climates, other plants have water storage in either fleshy leaves or in their trunks like the boab tree,some marsupials such as the bilby have big ears to lose heat and avoid overheating as it lives inhot dry climates, many endothermic animals such as the spinifex hopping mouse are nocturnal andlive in burrows to escape the heat of the day, ectotherms such as snakes and reptiles move in andout of the heat of the sun to warm and cool themselves, etc. Therefore, if they are suited to theircurrent environments now they will continue to survive in these environments, as the warming trendis very slight over the life span of most plants and animals. Trees that can live several hundredyears can also survive small changes in average temperature. In the long-term, if the trend oftemperature increases continues over thousands of years, then only those species with variationsthat suit them to the changed environment will survive. These organisms with favourable variationwill survive and pass their genes to their offspring. Over time, the species as a whole will evolve,and shift towards a majority having these genes for adaptation allowing them to survive in warmer

climates, while those less suited will die out. Some species may migrate and colonise new habitatsat higher altitudes where the temperature range is more similar to the temps where they arecurrently found. Species without suitable adaptations may not be able to survive or will have to livein different ecosystems, e.g. alpine species will be the most at risk as they would have to adapt asmigration will not be an option.

2007

1.9 identify some responses of plants to temperature change

Multiple choice

1. Dthey reduce the loss of water by transpiration (evaporation through the stomata), so (D) is theanswer.

2003

6. Dplants are cooled when water evaporates from the stomata in leaf surfaces in transpiration, so(D) is the answer.

2004

11. Din a dry environment, plants must conserve water. In some desert plants, the stomata are onlyopened minimally during the day to reduce transpiration. The plant still needs CO2 forphotosynthesis, so the stomata open during the cool of the night when transpiration is reduces, Thisallows CO2 in, and it is stored in large vacuoles (as malate) until it can be used in the presence oflight during the day for photosynthesis. This is only shown in (D).

2009

9.2.1.a most organisms are active in a limited temperature range

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