Analysis, Conclusions and Evaluation

In March 2008, the scientists measured four variables at each coffee farm, as shown in Table 2.1.

Table 2.1

Farmers from each coffee farm completed a questionnaire to record when elephants entered the farm.

The scientists decided to use Spearman’s rank correlation to investigate the relationship between each of the four variables in Table 2.1 and the number of months that elephants entered each coffee farm per year.

State two conditions that allow Spearman’s rank correlation to be used in this investigation.

State a null hypothesis for testing whether there is a correlation between water availability and the number of months that elephants entered each coffee farm per year.

For each variable in Table 2.2, decide whether the $r_s$ value is significant or not significant. Record your decision in the third column of Table 2.2, headed significance. Write yes if the value is significant or no if the value is not significant.

Describe what can be concluded from Table 2.2 about the relationship between the density of December trees and the number of months that elephants entered each coffee farm per year.

A coffee farmer living close to a different national park in India wanted to reduce the number of times that elephants entered the farm.

The farmer analysed data from the investigation and concluded that reducing the number of ponds, lakes and water holes on the farm would reduce the number of times that elephants entered the farm.

Explain how the information provided and the data in Table 2.2 support and do not support this conclusion.

support ______

do not support ______

Calculate the percentage decrease in transpiration rate from 0 to $400\ \mu\text{mol dm}^{-3}$ of ABA for the mutant variety.

Show your working.

percentage decrease = ______

With reference to Fig. 2.1, suggest conclusions that can be made about the effect of different concentrations of ABA on the transpiration rates of the mutant variety.

State the evidence that supports your conclusions.

The scientists used a mutant variety of thale cress that has stomata that do not respond to ABA.

The scientists concluded that ABA reduces water loss in thale cress by ways other than stomatal closure.

Suggest additional information that is required to increase the confidence in this conclusion.

The ecologists sampled the plant species in peat bog A and peat bog B.

The ecologists decided to use two suitable indices of biodiversity:

• Simpson’s index of diversity
• Shannon diversity index.

The ecologists had read that the two indices can lead to different conclusions.

The Shannon diversity index gives values in the range 1.5–3.5, where 1.5 is low biodiversity and 3.5 is high biodiversity.

The results are shown in Table 2.1.

Table 2.1

The ecologists concluded that one index indicated peat bog A had more biodiversity, but the other index indicated peat bog B had more biodiversity.

Suggest how the differences in the data in the two samples, shown in Table 2.1, may have led to the different conclusions.

The ecologists sampled invertebrate species in peat bog A:

• between 13:00 and 16:00 on three different days within a 30-day period
• at 10 random sites along the edge of a path in the peat bog
• by sampling the invertebrates within a $1\ \text{m}^2$ quadrat placed at each site
• by using an identification key to identify the species
• by counting the number of individuals of each species.

Describe how this sampling method could be improved to make sure the results are more representative of all invertebrates in the whole of peat bog A.

Table 2.2 shows the results of the invertebrate sampling in peat bog A.

The formula for Simpson’s index of diversity ($D$) is:

$n$ = number of individuals of each species present in the sample
$N$ = total number of all individuals of all species present in the sample

Complete Table 2.2 and use the formula provided to calculate Simpson’s index of diversity.

Table 2.2

Simpson’s index of diversity ($D$) = ______

The ecologists calculated a $D$ value of 0.710 for peat bog B.

Use your value of $D$ from (b)(ii) to compare the biodiversity of peat bog A and peat bog B.

The ecologists sampled the plant species in peat bog A and peat bog B.

The ecologists decided to use two suitable indices of biodiversity:

• Simpson’s index of diversity
• Shannon diversity index.

The ecologists had read that the two indices can lead to different conclusions.

The Shannon diversity index gives values in the range 1.5–3.5, where 1.5 is low biodiversity and 3.5 is high biodiversity.

The results are shown in Table 2.1.

Table 2.1

The ecologists concluded that one index indicated peat bog A had more biodiversity, but the other index indicated peat bog B had more biodiversity.

Suggest how the differences in the data in the two samples, shown in Table 2.1, may have led to the different conclusions.

The ecologists sampled invertebrate species in peat bog A:

• between 13:00 and 16:00 on three different days within a 30-day period
• at 10 random sites along the edge of a path in the peat bog
• by sampling the invertebrates within a $1\ \text{m}^2$ quadrat placed at each site
• by using an identification key to identify the species
• by counting the number of individuals of each species.

Describe how this sampling method could be improved to make sure the results are more representative of all invertebrates in the whole of peat bog A.

Table 2.2 shows the results of the invertebrate sampling in peat bog A.

The formula for Simpson’s index of diversity ($D$) is:

$n$ = number of individuals of each species present in the sample
$N$ = total number of all individuals of all species present in the sample

Complete Table 2.2 and use the formula provided to calculate Simpson’s index of diversity.

Table 2.2

Simpson’s index of diversity ($D$) = ______

The ecologists calculated a $D$ value of 0.710 for peat bog B.

Use your value of $D$ from (b)(ii) to compare the biodiversity of peat bog A and peat bog B.

State one reason why the chi-squared test ($\chi^2$ test) was used.

State the null hypothesis that the biologist would use for this test.

Complete Table 2.2 and calculate the value of $\chi^2$ for the results of the F2 generation.

The equation for the calculation of $\chi^2$ is:

$O = \text{observed result}$
$E = \text{expected result}$
$\sum = \text{sum of}$

Table 2.2

$\chi^2 = \_\_\_\_\_\_$

Table 2.3 shows some critical values of $\chi^2$ at different probability levels.

Table 2.3

State the critical value at $p < 0.05$ for this $\chi^2$ test.

Use your calculated value of chi-squared ($\chi^2$) to:

• explain whether the null hypothesis should be accepted or rejected
• suggest a conclusion the biologist could make about the inheritance of the genes controlling flower colour and flower position in pea plants.

State one reason why the chi-squared test ($\chi^2$ test) was used.

State the null hypothesis that the biologist would use for this test.

Complete Table 2.2 and calculate the value of $\chi^2$ for the results of the F2 generation.

The equation for the calculation of $\chi^2$ is:

$O = \text{observed result}$
$E = \text{expected result}$
$\sum = \text{sum of}$

Table 2.2

$\chi^2 = \_\_\_\_\_\_$

Table 2.3 shows some critical values of $\chi^2$ at different probability levels.

Table 2.3

State why the student used the critical value of 7.82 in this investigation.

Use your calculated value of $\chi^2$ to:

• explain whether the null hypothesis should be accepted or rejected
• suggest a conclusion the biologist could make about the inheritance of the genes controlling wing shape and eye colour in fruit flies.

Describe the trend shown by the scatter graph in Fig. 2.2.

State three reasons why this statistical test is a suitable way to analyse the data about species diversity in Fig. 2.2.

State the null hypothesis for this investigation.

The student calculated the value of Spearman’s rank correlation coefficient, $r_s$, as -0.359.

Table 2.1 shows the probability table for Spearman’s rank correlation test.

Table 2.1

Discuss, with reference to Table 2.1, the conclusions that can be made from the analysis of the data collected by the student.

The student was investigating the statement ‘species diversity decreases with increasing distance from the equator’.

Discuss the limitations of the sampling method and of the data collected in supporting this statement.

Small birds such as the ruby-crowned kinglet, Regulus calendula, are found throughout North America.

Fig. 2.3 shows a ruby-crowned kinglet caught in a mist net. Mist nets are used in surveys of bird populations.

Describe how the mark-release-recapture method can be used to estimate the population size of small birds, such as the ruby-crowned kinglet.

Calculate the percentage change in the number of new cases of ash dieback in plant nurseries, between 2013 and 2015.

Show your working and give your answer to the nearest whole number.

percentage change = ______ $\%$

Describe and explain the differences between the changes in the numbers of cases of ash dieback from 2013 to 2015 in the environments shown in Table 2.1.

Explain how the cDNA in samples from the ash trees hybridises onto the microarray slide.

Suggest how the level of each gene expression is determined.

Explain why it was important that samples from healthy trees were taken from trees growing next to very heavily diseased trees.

Describe how the study ensured that a diverse range of ash trees was selected for sampling.

Suggest why a numeric scale was used to record the degree of damage to the trees caused by ash dieback.

State which base is associated with tolerance to ash dieback.

Suggest how a change in one nucleotide base could result in a change of tolerance to a pathogen.

State a null hypothesis for this test.

Complete Table 2.2 to show how the values for $D^2$ were calculated.

Table 2.2

Complete the steps of the calculation to find the value of $r_s$. Give your answer to two decimal places.

$r_s =$ ______ (2 d.p.)

Table 2.3 shows the critical values of $r_s$ at the 0.05 probability level.

Table 2.3

Explain why the scientists rejected the null hypothesis.

Suggest why there is a higher proportion of cyanogenic clover plants at locations with high mean January temperatures compared with the other locations studied.