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MAY/JLTNE 2017

CARIBBEAN EXAMINATIONS COUNCIL

CARIBBEAN ADVANCED PROFICIENCY EXAMINATION@

BIOLOGY

UNITl-Paper02

2 hours 30 minutes

DO NOT TURN THIS PAGE UNTIL YOU ARE TOLD TO DO SO.

1

READ THE FOLLOWING INSTRUCTIONS CAREFULLY.

This paper consists of SIX questions in TWO sections. Answer ALLquestions.

Write your answers in the spaces provided in this booklet.

Do NOT write in the margins.

You may use a silent, non-programmable calculator to answer questions.

You are advised to take some time to read through the paper and plan youranswers.

If you need to rewrite any answer and there is not enough space to do so

on the original page, you must use the extra lined page(s) provided at theback of this booklet. Remember to draw a line through your originalanswer.

If you use the extra page(s) you MUST write the question numberclearly in the box provided at the top of the extra page(s) and, whererelevant, include the question part beside the answer.

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Copyright O 2015 Caribbean Examinations CouncilAll rights reserved.

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SECTION A

AnswerALL questions.


1. (a) Figure I is a stained animal cell as seen under a light microscope.

Figure l. Animal cellSource : http : //imgarcade. com/

(i) In the box below, make a detailed drawing of the cell in Figure I and label FOURstructures seen in the cell.

[6 marks]

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(ii) Using the magnification provided, calculate the actual size of the cell, highlightedby the bar line at the left of the image. State the calculated value to the nearestmicrometer. Show your working.

Size

[2 marks]

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r 6 -lAn experiment is conducted to determine the amount of reducing sugar and starch inbananas at different degrees of ripeness. Extracts of equal quantities of tissue samples ofbananas, at three different stages of ripeness, are prepared by mashing and grinding thesamples in water. For eaeh stage, sample extracts are placed in two sets of test tubes. Afourth test tube is set up with only water and no banana extract. Tests for reducing sugar

and starch are conducted on all four test samples. The findings of the experiment are

summarized in Table 1.

Note: For the Fehling's test the amount of the precipitate is measured as the height ofprecipitate (cm) at the bottom of the test tube.

TABLE 1: OBSERVATIONS OF SAMPLE EXTRACTS AFTER TESTING

F'ood TestGreen RawBanana

Half-ripeBanana

RipeBanana

Waterwithno BananaExtract

Fehling'sSolution

Observationafter heating

Greenishsolutionwith redprecipitate



Blue solution

Height ofprecipitate(cm)

0.2 0.4 1.0 0.0

IodineIntensity ofcolour

Intense blue-black colour

Mediumblue-blackcolour

Pale blue-black colour

Browncolour

(D Suggest a hypothesis for this experiment.

[1 markl

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(b)

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r -7 - -l(ii) Compare the results obtained for the amount of reducing sugar and starch in the

banana samples. Include in your comparison reference to the observations recorded.

[3 marksl

(iii) Comment on the significance of the findings of this experiment in relation to theuse of bananas as a food item.

[2 marks]

(iv) State the purpose of testing a sample with no banana extract.

[1 markl

Total 15 marks

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Haemophilia is a recessive sex-linked condition in humans in which the blood does notclot properly, leading to excessive bleeding. Use the symbols XH for the normal alleleand Xh for the haemophilia allele in your responses.

(i) State the genotypes of the following

A normal clotting male ..............

A normal clotting carrier female

[2 marksl

(iD Using the genotypes stated in (i) as parental genotypes, construct a Punnett squarediagram to show how haemophilia-affected offspring can result from normalclotting parents. State the phenotype of all offspring.

[3 marksl

(iiD Give an explanation as to why a man with haemophilia cannotpass on the conditionto his son.

[1 markl

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2. (a)

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A geneticist crossed two types of pea and obtained 5474 plants with round seeds and

1850 plants with wrinkled seeds in the F, generation. You are required to use the Chi-square test to show that these results are consistent with the 3:1 ratio normally expectedfrom a monohybrid cross.

(D State the null hypothesis for this test.

[1 mark]

(ii) Calculate Chi-square using the formula, Chi-square : I(O - E)'lE, where O isthe observed and E the expected number of plants. Show your working in tabularform as follows.

Plant1}pe Observed Expected o-E (o - E)' (o - E)r/E

Roundseeds

Wrinkledseeds

Chi-square

[2 marksl

(iii) Use the data in Table 2 on page l0 to make an inference based on your calculatedChi-square value.

[2 marks]


-l(b)

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Degrees ofFreedom

Number ofClasses

12 Yalues

I 2 0.46 1.64 2.71 3.84 6.64 10.83

2 ) r.39 3.22 4.61 5.99 9.21 13.82

J 4 2.37 4.64 6.25 7.82 1r.34 16.27

4 5 3.36 5.99 7.78 9.49 t3.28 18.47

Probability [p] thatchance alone couldproduce the deviation

0.50(s0%)

0.20(20%) (

0.10r0%)

0.0s(s%)

0.0i(r%)

0.001(0.r%)

-lt- -10-

TABLE 2: STATISTICAL TABLE - CRITICAL VALUES OF CHI.SQUARE DISTRIBUTION

(c) The variation in size of an organism in a population is depicted in Figure 2.

Size

Figure 2.Slr,e distribution of an organism in a population

(i) Using the axes provided in Figure 3, illustrate the effect of disruptive selection onthe population distribution in Figure 2. I mark]

Size

Figure 3. Effect of disruptive selection

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(iD Using Darwin's theory of natural selection, explain how disruptive selection canlead to the formation of new species.

[3 marks]

Total 15 marks

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An experiment is conducted to investigate the effects of type of culture medium and

sucrose concentration on the pollen germination rate of a species of palm. Pollen grainsare collected from newly opened flowers of the same bunch on the same day. The grains

are inoculated into two types of medium: a liquid culture medium and a solid culturemedium. The solid culture medium consists of different concentrations of sucrose in agar.

The liquid medium is similar to the solid medium with respect to the sucrose concentrationsbut does not contain agar. The results of the investigation are given in Table 3.

3. (a)

TABLE 3: EF.FECTS OF CULTURE MEDIUM AND SUCROSE CONCENTRATIONON POLLEN GERMINATION RATE IN A SPECIES OF'PALM

7o Pollen Germination

Sucrose Concentration(el')

Liquid Culture Medium Solid Culture Medium

0 5l 27

20 52 39

40 73 87

60 50 57

80 4I 66

100 0 4l

Source: AmericanJournal of Plant Sciences. 2013, 4, 1669*1674

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(i) On the grid provided in Figure 4, plot line graphs for the data given in Table 3.

[4 marksl

Figure 4. Effects of culture medium and sucrose concentration on pollen germination

(iD Briefly describe the overall trend for the effect of different sucrose concentrations,in both culture media, on the germination rate of the palm pollen.

[2 marksl

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(b)

(iii) Based on the results shown in Table 3, what can be deduced about the effect ofthe type of culture medium on the maximum rate of pollen germination?

[2 marks]

Figure 5 is a drawing of a section through a human placenta in situ.

I

Allantois

Fallopiantube

Developingembryo

Cervix

Figure 5. Section through a human placenta

(D Identifu and describe the main function of EACH of the structures labelled I, IIand III.

II:

[3 marksl


III

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(ii) Comment on TWO roles of the structure labelled Y in the development of the

foetus.

[2 marksl

(iii) Outline TWO ways in which the placenta acts as a protective barrier for the

developing foetus.

[2 marksl

Total 15 marks


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SECTION B

AnswerALL questions.


4. (a) (i) Compare the cell size and THREE structural features ofprokaryotic and eukaryoticcells

[4 marks]

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Outline the endosymbiont theory for the origin of eukaryotic cells. Explain how

characteristics of mitochondria and chloroplasts provide evidence in support ofthis theory.

[5 marksl


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(ii)

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(b) Discuss the importance of protein structure for determining enzyme specificity and modeof action.

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[6 marks]

Total 15 marks

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5. (a) Describe the roles of DNA and RNA in protein synthesis.

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potential for improving human health.

(i) Outline the principle of genetic engineering, including a brief description of thebasic steps of this technique.

[5 marks]

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(ii) Despite its promising potential, one of the arguments sometimes raised against

the use of gene therapy is that it is technically too dangerous. With reference to

cystic fibrosis, discuss reasons for this viewpoint.

[5 markslTotal 15 marks


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6. (a) Giving examples, discuss TWO advantages of vegetative propagation of plants.

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[5 marks]

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(b) Discuss TWO genetic consequences of sexual reproduction.

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[4 marks]


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(c) Describe the development of fruit and seed structures from floral structures after fertilization.

[6 marksl

Total 15 marks

END OF TEST

IF YOU FINISH BEFORE TIME IS CALLED, CHECK YOUR WORK ON THIS TEST.

021070201cAP82017

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