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    2008 BIOLOGY

    Monday 10 November: 9 a.m.

    Time: 3 hours

    Section A and Part 1 of Section B

    Examination material: Question Booklet 1 (20 pages)Question Booklet 2 (11 pages)one 8-page script bookone multiple-choice answer sheetone SACE registration number label

    Approved dictionaries and calculators may be used.

    Instructions to Students

    1. You will have 10 minutes to read the paper. You must not write in your question booklets or script book, oron your multiple-choice answer sheet, or use a calculator during this reading time but you may make notes onthe scribbling paper provided.

    2. This paper is in three sections: Section A and Part 1 of Section B are in Question Booklet 1; Part 2 of Section Band Section C are in Question Booklet 2.

    Section A: Multiple-choice Questions(Questions 1 to 25)Answer Section A on the separate multiple-choice answer sheet, using black or blue pen.

    Answerallquestions in Section A.

    Section B: Short-answer Questions(Questions 26 to 35)Answer Part 1 of Section B (Questions 26 to 30) in the spaces provided in Question Booklet 1.Write on page 20 of Question Booklet 1 if you need more space.

    Answer Part 2 of Section B (Questions 31 to 35) in the spaces provided in Question Booklet 2.Write on page 10 of Question Booklet 2 if you need more space.

    Section C: Extended-response Questions(Questions 36 and 37)

    Answerbothquestions in Section C in the separate script book.

    3. In Section B there is no need to fill all the space provided; clear, well-expressed answers are required. If youdelete part or all of an answer you should clearly indicate your final answer and label it with the appropriatequestion number.

    4. The allocation of marks and suggested allotment of time are as follows:

    Section A 50 marks 40 minutesSection B 120 marks 110 minutesSection C 30 marks 30 minutes

    Total 200 marks 3 hours

    5. Attach your SACE registration number label to the box at the top of this page. Copy the information fromyour SACE registration number label into the boxes on your multiple-choice answer sheet and on the frontcovers of Question Booklet 2 and your script book.

    6. At the end of the examination, place Question Booklet 2, your script book, and your multiple-choice answersheet inside the back cover of Question Booklet 1.

    External Examination 2008

    ATTACH SACE REGISTRATION NUMBER LABEL

    TO THIS BOX

    FOR OFFICE

    USE ONLY

    SUPERVISOR

    CHECK

    RE-MARKED

    QUESTION

    BOOKLET

    120 pages, 30 questions

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    STUDENTS DECLARATION ON THE USE OF

    CALCULATORS

    By signing the examination attendance roll I declare that:

    my calculators have been cleared of all memory;

    no external storage media are in use on these calculators.

    I understand that if I do not comply with the above conditions

    for the use of calculators I will:

    be in breach of the rules;

    have my marks for the examination cancelled or amended;

    be liable to such further penalty, whether by exclusion from

    future examinations or otherwise, as the SACE Board of

    South Australia determines.

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    SECTION A: MULTIPLE-CHOICE QUESTIONS(Questions 1 to 25)

    (50 marks)

    Answerallquestions in this section.

    Each of the twenty-five multiple-choice questions in Section A involves choosing from four

    alternative answers. Read each question carefully. Then indicate the onealternative that you

    consider best answers the question by shading the bubble by the appropriate letter alongside

    the question number on the multiple-choice answer sheet. Use black or blue pen. It is in your

    interest to give an answer to every question in this section of the paper, as no marks are deducted

    for incorrect answers. Each question is worth 2 marks. You should spend about 40 minutes on

    this section.

    1. Carcinogens are chemicals that

    J. increase the rate of cell division by causing harmful mutations.K. decrease the rate of cell division by causing beneficial mutations.

    L. increase the rate of cell division by causing beneficial mutations.

    M. decrease the rate of cell division by causing harmful mutations.

    2. William and Mary are brother and sister and they are twins.

    Ignoring mutations, which one of the following cells is genetically identical to a liver cell from

    William?

    J. A liver cell from Mary.

    K. A sperm cell from William.

    L. A muscle cell from William.

    M. An egg cell from Mary.

    3. Mangrove swamps occur in the sheltered intertidal zone of South Australias Spencer Gulf and

    Gulf St Vincent. These mangrove swamps are the breeding grounds for many species of fish,

    including King George whiting (Sillaginodes punctata) and yellow-eyed mullet

    (Aldrichetta forsteri).

    King George whiting and yellow-eyed mullet are members of the same

    J. biosphere but not the same population.

    K. community but not the same ecosystem.

    L. ecosystem but not the same biosphere.

    M. population but not the same community.

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    4. Which one of the following characteristics must a cell have in order to be classified as a

    eukaryotic cell?

    J. A single circular chromosome in the cytoplasm.

    K. No membrane-bound organelles.

    L. A cytoskeleton attached to the cell membrane.M. A cell wall made of cellulose.

    5. Refer to the following diagram, which shows a part of two DNA molecules from the same type of

    bacterium grown in different media:

    a part of

    two DNA

    molecules

    from thesame type

    of bacterium

    grown in medium containing

    non-radioactive nitrogen (14N)

    grown in medium containing

    radioactive nitrogen (15N)

    Bacteria were grown for several generations in a medium containing non-radioactive nitrogen.

    The medium was then replaced with a medium containing radioactive nitrogen.

    Which one of the following diagrams best represents the DNA molecules produced when the

    bacteria were allowed to divide oncein the medium containing radioactive nitrogen?

    + + + +

    J. K. L. M.

    6. Thyroxine is a hormone that is involved in the regulation of body temperature in human beings.

    Which one of the following responses will result from an increase in body temperature?

    J. An increased release of thyroxine, resulting in a decreased cell metabolism.

    K. A decreased release of thyroxine, resulting in a decreased cell metabolism.

    L. A decreased release of thyroxine, resulting in an increased cell metabolism.

    M. An increased release of thyroxine, resulting in an increased cell metabolism.

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    7. The exponential growth of the human population is not sustainable because

    J. on average, a woman produces 2.9 children during her lifetime.

    K. the input and the output of energy on the Earth are almost equal.

    L. the resources of the biosphere are limited.

    M. most of the energy that enters a community is lost as heat.

    8. Refer to the following diagrams, which show the components of a nucleotide in a DNA molecule:

    sugar phosphate basenitrogenous base

    (adenine, cytosine,

    guanine, or thymine)

    S P

    Which one of the following diagrams shows the arrangement of these components in a nucleotide

    that will pair in a DNA molecule with a nucleotide that contains guanine?

    adenine

    S

    Pcytosine

    P

    S

    J. K.

    adenine

    P

    S cytosine

    S

    P

    L. M.

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    9. Refer to the following electronmicrograph, which shows a section of an organelle:

    1m

    The main function of this organelle is

    J. semi-conservative replication.

    K. photosynthesis.

    L. translation.

    M. aerobic respiration.

    10. The synthesis of ATP from ADP and inorganic phosphate results

    J. from an input of energy from the breakdown of glucose.

    K. in an output of energy from the breakdown of glucose.

    L. in an output of energy from the synthesis of glucose.

    M. from an input of energy from the synthesis of glucose.

    11. Evidence suggests that until about 8000 years ago all human beings had brown eyes.

    Which one of the following combinations correctly matches the process by which the gene for

    blue eyes originated and the process by which the gene for blue eyes increased in frequency?

    Process by which the gene for

    blue eyes originated

    Process by which the gene for

    blue eyes increased in frequency

    J. speciation natural selection

    K. speciation geographical isolationL. mutation geographical isolation

    M. mutation natural selection

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    12. A length of DNA that codes for part of a polypeptide is known to contain 633 base pairs.

    Which one of the following combinations of number of codons and number of amino acids in the

    polypeptide is most likely to be associated with this length of DNA?

    Number of codons Number of amino acids in

    the polypeptide

    J. 1266 422

    K. 633 211

    L. 422 422

    M. 211 211

    13. Four pieces of rhubarb from the same plant were weighed separately to determine their mass.

    Solutions A, B, C, and D, each with a different salt concentration, were poured into four identical

    beakers, each containing one of the pieces of rhubarb. After 20 minutes the pieces of rhubarb wereremoved from the beakers, dried with paper towelling, and reweighed. The results are summarised

    in the table below:

    SolutionMass of piece of rhubarb (g)

    Before the experiment After 20 minutes

    A 10.2 9.8

    B 10.6 10.9

    C 9.8 10.9

    D 10.2 9.2

    Source:www.adventuresinshaw.

    wordpress.com

    Which one of the following conclusions is consistent with the information above?

    J. The solute concentration of solution A is higher than that of solution D.

    K. The solute concentration of solution C is higher than that of solution B.

    L. The solute concentration of solution A is higher than that of solution C.

    M. The solute concentration of solution B is higher than that of solution D.

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    14. Which one of the following nerve pathways represents the reflex response to the stimulus of

    stepping on a sharp object?

    J. Receptor motor nerve spinal cord sensory nerve muscle in foot.

    K. Receptor motor nerve brain sensory nerve muscle in leg.

    L. Receptor sensory nerve brain motor nerve muscle in foot.M. Receptor sensory nerve spinal cord motor nerve muscle in leg.

    15. Which one of the following processes doesnotrequire energy?

    J. The uptake of oxygen by red blood cells.

    K. The growth of a bacterial cell.

    L. The movement of the flagellum of a sperm cell.

    M. The asexual reproduction of a yeast cell.

    16. A cell with a diploid number of six is undergoing a type of cell division.

    Which one of the following diagrams could represent the arrangement of chromosomes in

    the cell?

    J. K. L. M.

    represents a maternal chromosome represents a paternal chromosome

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    17. Refer to the following diagram, which represents a map of human chromosome number 1.

    The labels show the abbreviations and names of medical conditions associated with the

    information coded for at four different places on the chromosome:

    UROD

    (Porphyria cutanea tarda)

    GBA

    (Gaucher disease)

    HPC1

    (prostate cancer)

    PS2

    (Alzheimers disease)

    The segment of human chromosome number 1 labelled GBArepresents a

    J. disease.

    K. gene.L. base triplet.

    M. polypeptide.

    18. Kelp is a marine alga, which grows to about 1 metre in height and lives for about 10 years.

    Kelp forests, which are found in temperate waters such as those off the coast of Adelaide, provide

    a habitat for fish.

    The kelp forests are being destroyed by stormwater discharged from metropolitan Adelaide

    into the coastal waters. The stormwater contains high levels of nutrient, such as nitrogen andphosphorus compounds, and high levels of sediment. Turf-forming species of alga, which grow

    to less than 5 millimetres in height and live for about 1 year, are replacing the kelp forests.

    Which one of the following statements is consistent with the information above?

    J. The impact of high levels of sediment on the kelp forests is greater than the impact of

    high levels of nutrient.

    K. The discharge of stormwater results in an increase in the population of K-selected species.

    L. A reduction in fishing off the coast of Adelaide would result in the re-establishment of

    the kelp forests.

    M. More r-selected strategies are shown by the turf-forming species of alga than by the kelpforests.

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    19. The eastern brown snake (Pseudonaja textilis) and the common death adder (Acanthophis

    antarcticus) are species of snake found throughout Australia.

    The following table provides information, for each of these species, about habitat(s), food, method

    of obtaining food, and change in population size since European settlement of Australia:

    Eastern brown snake Common death adder

    Habitat(s)cleared land with little

    vegetationcoastal dune and mallee

    Food lizards, frogs, and mice lizards and birds

    Method of obtaining foodactively searches for

    prey

    lies, covered by leaves, and

    waits for prey

    Change in population

    size since European

    settlement of Australia

    increased decreased

    Since European settlement, coastal dune and mallee habitats have been extensively cleared.

    The clearing of the remainingcoastal dune and mallee habitats should

    J. proceed because the common death adder serves no useful purpose in these habitats.

    K. not proceed because it will prevent competition between the eastern brown snake and the

    common death adder.

    L. not proceed because these habitats provide all the conditions necessary for the survival of

    the common death adder.

    M. proceed because it will assist the survival of the eastern brown snake in these habitats.

    20. In 2005New Scientistmagazine reported that green tea contains the compound epigallocatechin

    gallate (EGCG). This compound blocks the enzyme dihydrofolate reductase, which is essential to

    the growth of gastric and oesophageal tumours.

    The shape of a part of the EGCG molecule is

    J. similar to the shape of the dihydrofolate reductase molecule.

    K. similar to the shape of the active site of the dihydrofolate reductase molecule.

    L. complementary to the shape of the dihydrofolate reductase molecule.

    M. complementary to the shape of the active site of the dihydrofolate reductase molecule.

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    21. Which one of the following combinations correctly matches a type of capillary in the human body,

    a material that moves into the capillary, and the process of movement of this material into the

    capillary?

    Type of capillary in the

    human body

    Material that moves into

    the capillary

    Process of movement of this

    material into the capillary

    J.blood capillary in small

    intestinecarbon dioxide active transport

    K.blood capillary in epithelial

    tissueglucose endocytosis

    L.lymph capillary in epithelial

    tissuewater osmosis

    M.lymph capillary in small

    intestineamino acids exocytosis

    22. Which one of the following features doesnotincrease the surface area of an exchange surface?

    J. Microvilli on the epithelial cells of the small intestine.

    K. Capillary walls being one cell thick.

    L. Alveoli in lung tissue.

    M. The length of the nephron tubule.

    23. Which one of the following statements about experimental results is correct?

    J. An increase in the number of samples will decrease random errors.

    K. Results are less accurate when there is more scatter.

    L. A decrease in random errors will increase accuracy.

    M. Results are more precise when there is less scatter.

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    24. Which one of the following diagrams shows a possible sequence of the processes involved in the

    life cycle of a sexually reproducing eukaryotic organism?

    mitosis

    fertilisationmeiosis

    haploid

    diploid

    haploid

    mitosis

    fertilisationmeiosis

    diploid

    diploid

    haploid

    J. K.

    meiosis

    fertilisationmitosis

    haploid

    diploid

    haploid

    meiosis

    fertilisationmitosis

    diploid

    haploid

    haploid

    L. M.

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    25. Refer to the following diagram, which shows possible evolutionary relationships based on DNA

    evidence:

    0

    50

    100

    150

    200

    250

    300

    350

    lizards snakes crocodiles

    dinosaurs(extinct)

    birds turtles

    Millions ofyears ago

    It is reasonable to conclude from the information in the diagram above that there

    J. would be more similarity between dinosaur DNA and bird DNA than between dinosaur

    DNA and snake DNA.

    K. has been no change in lizard DNA in 350 million years.

    L. is more variation in turtle DNA than in bird DNA.

    M. is less similarity between snake DNA and lizard DNA than between snake DNA and

    crocodile DNA.

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    SECTION B: SHORT-ANSWER QUESTIONS(Questions 26 to 35)

    (120 marks)

    You should spend about 110 minutes on this section. Answers may be in note form. The allocation of

    marks is shown in brackets at the end of each part of each question. Answerallquestions in the spaces

    provided.

    Part 1(Questions 26 to 30)

    (60 marks)

    26. Refer to the following diagram, which represents part of a cellular structure:

    ATPADP + Pi

    X

    Y

    Z

    (a) Name molecule Z.

    ____________________________________________________________________________________________(2 marks)

    (b) Name the process by which molecule Ymoves through structure X.

    ____________________________________________________________________________________________(2 marks)

    (c) Explain how cyanide, a poison that inhibits aerobic respiration, could affect the

    movement of molecule Y through structure X.

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(4 marks)

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    27. Human beings use microscopic organisms such as yeasts and bacteria in a variety of ways.

    Early Europeans used fermentation by yeasts to sterilise water. Similar methods are used today in

    the production of beer and wine.

    (a) Name the substrate required for fermentation by yeasts.

    ____________________________________________________________________________________________(2 marks)

    Yeasts are eukaryotic cells that can reproduce by budding, which results in genetically identical

    offspring.

    (b) Name the type of cell division that yeasts use to reproduce by budding.

    ____________________________________________________________________________________________(2 marks)

    (c) State one disadvantage that producing genetically identical offspring has for yeasts.

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(2 marks)

    Human beings use bacteria for genetic engineering.

    (d) Selected genes can be transferred between species, using bacterial plasmids as vectors.Bacterial plasmids that contain a selected gene are called recombinant plasmids.

    Explain how a bacterial plasmid can be cut open so that a specific selected gene can be

    inserted, to form a recombinant plasmid.

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(4 marks)

    (e) Explain one advantage that the genetic manipulation of organisms has for society.

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(4 marks)

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    28. Three species of beetle living on an island are thought to have evolved from a common ancestral

    species that inhabited the island millions of years ago.

    It is thought that the rising sea level caused the island to become three separate islands. In the long

    period of isolation that followed, the three species of beetle (one species on each island) evolved

    from the common ancestral species.

    When the sea level fell, the islands re-formed into one island. The beetles remained as three

    distinct species, each with its own gene pool.

    (a) State the meaning of the term gene pool.

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(2 marks)

    (b) (i) What observation would lead biologists to be sure that two populations of beetlebelong to different species?

    __________________________________________________________________________________________________

    _______________________________________________________________________________________(2 marks)

    (ii) State one mechanism that maintains the reproductive isolation of two species.

    __________________________________________________________________________________________________

    _______________________________________________________________________________________(2 marks)

    (c) Explain how geographical isolation led to the evolution of the three species of beetle.

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(4 marks)

    (d) Describe one method that biologists could use to determine which two of the three

    species of beetle are the more closely related.

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(4 marks)

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    29. Drugs that are used in general anaesthetics bring about a reversible loss of consciousness during

    surgery.

    During anaesthesia:

    the metabolic rate is decreased by approximately 15%;

    anaesthetic drugs act as vasodilators;

    the shivering response is inhibited.

    As a result of the effects listed above, the patient experiences a mild case of hypothermia in which

    the body temperature decreases by about 3C.

    (a) Describe how vasodilation and the inhibition of shivering result in a decrease in

    a patients body temperature during anaesthesia.

    Vasodilation: ________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    Inhibition of shivering: ____________________________________________________________________________

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(4 marks)

    (b) State one benefit and one harmful effect of drugs that are used in general anaesthetics.

    Benefit: ______________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    Harmful effect: _____________________________________________________________________________________

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(4 marks)

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    30. Ecowash BBandAddcoolare commercially produced enzymes.Ecowash BBis used to pre-fade

    denim, whereasAddcoolpolishes fibres and improves the durability of the fabric.

    The effectiveness of each of these enzymes on its own substrate was tested at a range of

    temperatures. For each enzyme, ten test-tubes were set up. Each test-tube contained 30 millilitres

    of the substrate and 2 millilitres of the same concentration of enzyme. Each test-tube was held at a

    constant temperature.

    After 20 minutes the reaction mixture was tested and the percentage of the original quantity of

    substrate that remained was recorded. The results of this experiment are shown in the table below:

    Percentage of substrate remaining in

    solution after 20 minutes

    Temperature (C) Ecowash BB Addcool

    5 100 100

    15 100 88

    25 100 38

    35 98 1

    45 17 58

    55 2 99

    65 26 100

    75 71 100

    85 96 100

    95 100 100

    (a) Graph the data for Ecowash BB and for Addcoolon one set of axes on the grid below.

    Label each graph.

    (6 marks)

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    (b) State the independent variable in this experiment.

    ____________________________________________________________________________________________(2 marks)

    (c) State a conclusion that is consistent with the data in the table.

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(2 marks)

    (d) State why the enzymes are ineffective at:

    (i) 5C. _____________________________________________________________________________________________

    _______________________________________________________________________________________(2 marks)

    (ii) 95C. ___________________________________________________________________________________________

    _______________________________________________________________________________________(2 marks)

    (e) State the temperature at which Addcool is 99% effective in this experiment.

    ___________C. (2 marks)

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    SACE Board of South Australia 2008

    You may write on this page if you need more space to finish your answers to any questions in

    Part 1 of Section B. Make sure to label each answer carefully (e.g. 29(a) continued).

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    2008 BIOLOGY

    Monday 10 November: 9 a.m.

    Part 2 of Section B, and Section C

    Write your answers to Part 2 of Section B in this question booklet.

    Write your answers to Section C in the separate script book.

    External Examination 2008

    FOR OFFICE

    USE ONLY

    SUPERVISOR

    CHECK

    RE-MARKED

    QUESTION

    BOOKLET

    211 pages, 7 questions

    SACE REGISTRATION NUMBER

    FIGURES

    BIOLOGY

    CHECK

    LETTER

    SEQ BIN

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    2

    SECTION B: SHORT-ANSWER QUESTIONS

    Part 2(Questions 31 to 35)

    (60 marks)

    Answerallquestions in the spaces provided.

    31. The urine that two normal, healthy people produced over 12 hours on a hot day was analysed to

    determine the effect of water consumption on the average concentration of urea in the urine. All

    other factors were kept constant. The results of this experiment are shown in the following table:

    Person A Person B

    Water consumption over 12 hours (L) 3 0.5

    Average concentration of urea in the

    urine produced over 12 hours (%)0.5 4

    (a) With reference to the data in the table, describe the relationship between the water

    consumption and the average concentration of urea in the urine.

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(4 marks)

    (b) Explain the process that resulted in the difference between the average concentration of

    urea in the urine of person A and the average concentration of urea in the urine of

    person B.

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(4 marks)

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    (c) State one weakness in the design of this experiment and explain how it would affect the

    reliability of the data.

    Weakness in the design: __________________________________________________________________________

    _______________________________________________________________________________________________________

    Explanation: _________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(4 marks)

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    32. Micro RNA (miRNA) molecules are RNA molecules that are about 21 to 23 nucleotides long.

    These miRNA molecules are transcribed from DNA but are not translated. In bacteria they are

    known to be complementary to part of one or more messenger RNA (mRNA) molecules to which

    they can bind.

    (a) State one structural difference between DNA and mRNA.

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(2 marks)

    (b) State the complementary mRNA nucleotide sequence for the following miRNA

    nucleotide sequence by writing the appropriate letters in the boxes below.

    miRNA nucleotidesequence

    A G G C

    complementary mRNA

    nucleotide sequence

    (2 marks)

    (c) Explain how the binding of an miRNA molecule to an mRNA molecule will affect the

    role of the mRNA.

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(4 marks)

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    33. Eukaryotic cells evolved about 1.5 billion years ago in an environment that is thought to have

    been very different from todays environment.

    (a) State one piece of evidence to support the hypothesis that prokaryotic cells probably

    existed before eukaryotic cells.

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(2 marks)

    (b) State and explain one piece of evidence to support the hypothesis that the evolution of

    eukaryotic cells probably involved endosymbiotic events.

    Evidence: ____________________________________________________________________________________________

    Explanation: _________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(4 marks)

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    34. The beaver (Castor canadensis) is a large rodent that is found mainly in North American forests.

    With their chisel-like teeth, beavers cut down trees, which they use to build dams in streams and

    ponds. These dams play a major role in succession as they create new wetland environments

    for other species. The wetlands slow the erosion of soil and purify the water, but can also cause

    flooding in low-lying areas.

    Source: http://animals.nationalgeographic.com

    (a) Describe how the dams built by beavers can lead to a change in the mixture of species

    over time.

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(4 marks)

    The by-products of decomposers in North American forests are mainly carbon dioxide and

    methane (CH4), the two largest components of greenhouse emissions. It is estimated that, over a

    120-day period, decomposers in the dams built by beavers produce 678 g/m2of CO2and

    11.3 g/m2of CH4.

    (b) State the function of decomposers.

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(2 marks)

    (c) Using chemical formulae, write the chemical equation for the aerobic reaction that would

    occur in the decomposers and produce carbon dioxide.

    ____________________________________________________________________________________________(2 marks)

    This photograph cannot be reproduced here for copyright reasons.

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    7 PLEASE TURN OVER

    North American forests have been studied over long periods of time and are known as carbon

    sinks. This means that they remove carbon dioxide from the air and fix carbon in the tissues

    of plants.

    (d) Describe how carbon sinksfi

    x carbon in the tissues of plants.

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(4 marks)

    (e) Explain how a decline in the number of beavers could affect the levels of atmospheric

    carbon dioxide in these forests.

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________

    (4 marks)

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    35. Refer to the following graph and diagram, which relate to the regulation of the cell cycle by the

    proteins MPF, cyclin, and cyclin-dependent kinase (Cdk). Cyclin and Cdk combine to form MPF.

    The times shown on the diagram correspond to the times shown on the graph.

    0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34

    concentration

    of cell cycleproteins

    (arbitrary units)

    time (hours)

    MPF cyclin cyclin-dependent kinase (Cdk)

    one cell cycle

    G1 phase

    (6 hours)

    S phase(6 hours)

    mitosis andcytokinesis

    (1 hour)

    G2 phase

    (3 hours)

    checkpoint G2

    checkpoint M

    checkpoint R

    Time

    0 hours 16 hours

    Cell cycle

    [This diagram is not drawn to scale.]

    (a) Choose one external factor and describe its role in the regulation of the cell cycle.

    External factor: _____________________________________________________________________________________

    Role: ________________________________________________________________________________________________

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________

    (4 marks)

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    In 1997 researchers conducted an experiment, which showed that the chemical olomoucineacts as

    an inhibitor of Cdk in lung cancer cells grown in a cell culture.

    In the experiment it was shown that various concentrations of olomoucine resulted in a

    concentration-dependent inhibition at checkpoint G2 in the cell cycle. At the highest concentration

    of olomoucine tested, the cell cycle was completely blocked.

    (b) State one hypothesis that this experiment may have been designed to test.

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(2 marks)

    (c) State why lung cancer cells were used for this experiment.

    _______________________________________________________________________________________________________

    ____________________________________________________________________________________________(2 marks)

    (d) State two factors that would need to be kept constant in this experiment.

    Factor 1: ____________________________________________________________________________________________

    Factor 2: _________________________________________________________________________________(2 marks)

    (e) (i) Using information from the graph and the diagram opposite, describe what happensto the concentrations of cyclin and MPF that enables the cell to move past

    checkpoint G2 and checkpoint M.

    Checkpoint G2: ________________________________________________________________________________

    __________________________________________________________________________________________________

    __________________________________________________________________________________________________

    Checkpoint M: _________________________________________________________________________________

    __________________________________________________________________________________________________

    _______________________________________________________________________________________(4 marks)

    (ii) Explain how olomoucine blocks the cell cycle.

    __________________________________________________________________________________________________

    __________________________________________________________________________________________________

    __________________________________________________________________________________________________

    __________________________________________________________________________________________________

    _______________________________________________________________________________________(4 marks)

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    You may write on this page if you need more space to finish your answers to any questions in

    Part 2 of Section B. Make sure to label each answer carefully (e.g. 34(a) continued).

    Do not answer Section C on this page.

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    SECTION C: EXTENDED-RESPONSE QUESTIONS (Questions 36 and 37)

    (30 marks)

    Answerbothquestions in this section.

    Write your answers in the separate script book provided. Begin each answer on a new page.

    You should spend about 30 minutes on this section, 5 to 10 minutes planning and

    20 to 25 minutes writing. Credit will be given for clear, well-expressed answers that are well

    organised and relevant to the questions.

    36. The well-being of an ecological community is dependent on its level of productivity and the

    continued survival and reproduction of its organisms.

    Describe:

    how energy is captured and made available to organisms in a community;

    how two factors could influence the productivity of the community;

    two processes that occur in sexually reproducing organisms and that provide the

    genetic variation necessary for their continued survival and reproduction.

    (15 marks)

    37. Human stem cells have the potential to develop into a range of different cell types. One of the

    uses of cell culture could be to grow stem cells that are stimulated into making functional human

    tissues and organs.

    Describe the conditions that would be necessary to grow human cells in cell culture.

    Using examples, describe the hierarchical structure within multicellular organisms.

    Explain how genetically identical human stem cells could develop into different human

    tissues and organs.

    (15 marks)

    SACE Board of South Australia 2008