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Paper Reference(s)

6106/02 (W2)

Edexcel GCEBiology

Biology (Human)Advanced

Unit Test 6 Paper 02 (W2)

Tuesday 19 May2009 Afternoon

Time: 1 hour 20 minutes

Materials required for examination Items included with question papers

Ruler Nil

Instructions to Candidates

In the boxes above, write your centre number, candidate number, your surname, initial(s) andsignature.The paper reference is shown above.Check that you have the correct question paper.Answer BOTH questions. Write your answers in the spaces provided in this question paper.Show all the steps in any calculations and state the units. Calculators may be used.Include diagrams in your answers where these are helpful.

Information for Candidates

The marks for individual questions and parts of questions are shown in round brackets: e.g. (2).There are 2 questions in this question paper. The total mark for this paper is 32.

Advice to Candidates

You will be assessed on your ability to organise and present information, ideas, descriptions and

arguments clearly and logically, taking account of your use of grammar, punctuation and spelling.

Examiners use only

Team Leaders use only

Question Leave

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No.

Paper Reference

6 1 0 6 0 2

This publication may be reproduced only in accordance with

Edexcel Limited copyright policy.2009 Edexcel Limited.

Printers Log. No.

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Answer BOTH questions.

Write your answers in the spaces provided.

1. Catclaw mimosa (Mimosa pigra) is a plant which may form dense thorny thickets as

high as 6 metres. It is an invasive weed in Northern Australia, where it is a hazard to

livestock.

One method used to control it is by the use of stem-mining moths. Plants infected by

moths produce fewer seeds, but this may not be effective in all habitats.

A group of students tested the effectiveness of this method of biological control in two

habitats: a floodplain and a woodland. Both habitats had catclaw mimosa plants growing in

them. The students selected two sites in each habitat. In each habitat, one site had mimosa

plants that were infected with stem-mining moths and the other had no infection.

At all four sites, eleven permanent 0.5 0.5 m quadrats had been prepared and the students

collected the top 2 cm of soil from each. They sieved the soil and counted the total number

of mimosa seeds they found in each sample.

The raw data table compiled by the students is shown below.

Number of seeds in each 0.5 x 0.5 m quadrat

In floodplain without mining moths

729, 500, 805, 900, 606, 825, 751, 830, 758, 505, 605

In floodplain with mining moths

350, 255, 400, 512, 200, 306, 241, 194, 369, 491, 340

In woodland without mining moths

42, 46, 61, 33, 22, 29, 38, 51, 33, 28, 48

In woodland with mining moths

52, 65, 48, 39, 60, 35, 34, 55, 62, 38, 32

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(a) Prepare a table of the raw data and organise it in such a way that the median number of

seeds with and without stem-mining moths in each of the habitats can be identified.

(4)

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(b) Use the data in your table to present the information in a suitable graphical form so

that the effects of the moths in the two habitats can be compared.

(3)

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(c) State a suitable null hypothesis for this investigation.

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(1)

(d) The students decided to apply the Mann-Whitney U test to the data. This statistical

test determines if the differences between the medians is significant.

The calculations produced two U values for each set of data. In order to support

a difference between the numbers of seeds produced by infected and non-infected

plants in each habitat, the smaller U value is required to be the same as, or less than,

the critical value.

For the floodplain sites these values were U1 = 119 and U2 = 2 and for the woodland

sites these values were U1 = 36 and U2 = 85.

The table below shows the critical values for the Mann-Whitney U test at thep = 0.05

level.

Sample size n2

7 9 11 13 15 17Sample size n1

7 8 12 16 20 24 28

9 12 17 23 28 34 39

11 16 23 30 37 44 51

13 20 28 37 45 54 63

15 24 34 44 54 64 75

17 28 39 51 63 75 87

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What conclusion can be drawn from this investigation? Use the information in the

table to explain your answer.

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(2)

(e) What other conclusion, concerning the effectiveness of this type of biological control

in different habitats, can be made from these data?

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(1) Q1

(Total 11 marks)

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2. Creeping buttercup (Ranunculus repens) reproduces sexually by seeds, but it also

reproduces asexually by means of runners. Runners are stems that grow from the parent

plant along the surface of the soil. Creeping buttercup often grows in fields of short

grass.

The structure of a creeping buttercup plant is shown in the diagram below.

Design an investigation that can be undertaken outdoors to test the hypothesis that the

number of plants reproducing asexuallyis linked to the density of plants.

Your answer should be given under the following headings.

(a) Plan of the investigation to be carried out.

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Parent plantYoung plant

Bud

Runner

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(b) Recording of raw data measurements, presentation of results and methods of data

analysis.

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(c) Limitations of your method and an indication of further work that could be undertaken

to provide additional evidence for your conclusions.

Limitations ..................................................................................................................

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(6)

TOTAL FOR PAPER: 32 MARKS

END

Q2

(Total 21 marks)

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Documents

6106-B-June-2009