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S295/G

Module Examination 2016

THE BIOLOGY OF SURVIVAL

PART A

Short answer questions Answer all SIX questions in this first part of the exam. Write your answers in the answer book provided, limiting your answer for each part of a question to a few sentences or more. You are advised to spend no more than 1 hour 15 minutes on this Part A of the paper, which carries 30 of the total marks for the examination. Each question is worth 5 marks.

                          Figure 1 Marine mammal phylogeny.

An example of a member of the Phocidae is Phoca vitulina, the harbour seal. An example of a member of the Otariidae family is Zalophus californianus, the Californian sea lion. The only extant member of the Odobenidae family is Odobenus rosmarus, the walrus.

(a) According to the phylogeny above, what is the sister group to the Odobenidae?

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(b) Which of the points labelled A, B or C on the figure represents a root node, and why?

 

(c) State whether the group of animals commonly referred to as seals (fur seals and true seals) is a monophyletic or paraphyletic group according to this phylogeny, and explain your reasons.

 

Question 2

Figure 2 shows the large nasal cavity and network of blood vessels in the cavernous sinus of Oryx antelopes. Explain how the countercurrent heat exchange system shown allows cooling of blood from the body before it passes to the brain. Suggest the type of environment the animal lives in to benefit from these adaptations and what other effect is achieved by this cooling system

Question 3

(a) Explain why the C2 pathway is beneficial to plant survival even though it appears wasteful.

(b) Briefly discuss the statement ‘The enzyme Rubisco is the most abundant on Earth yet one of the least efficient.’

Question 4

During the breeding season male sticklebacks build a nest in which a female can lay eggs. Once the nest is built, they display to females by shaking their bodies and fanning their fins. Fin fanning results in a twofold increase in basal metabolic rate and, in addition to display, is also used once eggs are laid in the nest to help keep them oxygenated. Researchers conducted choice tests on females to determine whether male fanning behaviour during courtship influenced their choice of mate. For each test, they placed a single female in a tank with two males as shown below and determined how many times she visited each one (indicating a preference). They found that females preferred the male that fanned his tail more frequently and for longer than the alternative male. opaque barrier male compartments female compartment.

(a) What was the reason for placing the opaque screen between the males?

(b) Explain why male fanning behaviour is likely to be an honest signal of male quality.

(c) The researchers suggested that males that fan their tails for longer and more frequently during courtship are chosen by females because they make better fathers (fan eggs more efficiently). What would the researchers need to show to establish that they are better fathers?

Question 5

Adenosine triphosphate (ATP) can be produced both by respiratory reactions and by photosynthetic reactions.

(a) Why is ATP so useful to a cell?

(b) Give an example of ATP being broken down simply to release heat rather than perform work.

 (c) When ATP loses a phosphate group it releases 30.5 kJ mol-1 of energy under standard conditions. (i) What is the full name of the molecule that is created when ATP loses a phosphate group?

 (ii) If a bee weighing 0.2 g metabolises 1.5 µmol ATP g-1 s-1 calculate the amount of energy it releases in 1 minute.

Question 6

Explain using an example(s) how genes with deleterious effects may be retained in populations due to captive breeding. Include in your answer whether natural selection is occurring within the example population with reference to predation.

PART B

Data handling and interpretation question

Answer ALL parts of the question in Part B of the examination. You are advised to spend about 1 hour on this question. This part carries 25 of the marks for this examination.

Show all your working for calculations.

 

Question 7

An investigator was interested in assessing feeding preferences of red squirrels in forests dominated by coniferous trees, as part of an investigation of squirrels’ habitat preferences. Squirrels usually feed on the seeds of conifer cones once the cones have fallen from the tree. A cone which has had its seeds eaten by a squirrel has a characteristic shape and can be easily identified in the field. The investigator planned to collect cones of three different species of conifers in areas known to be inhabited by red squirrels. Different conifer species have different numbers of seeds in their cones, and those seeds have different energetic values. Estimates of these values for the three species the investigator was interested in, taken from the scientific literature, are shown in Table 1.

Table 1

	European larch	Scots pine	Sitka spruce
Mean energy content per seed (KJ)	0.09	0.17	0.04
Mean seeds per cone	9.5	21.3	38.9
Estimated energy per cone (KJ)	0.86	3.62	1.56

 

Energy content of conifer seeds and cones of three conifer species. The investigator thinks that the high energy content of Scots pine seeds and cones should make them more attractive to squirrels than those of other conifer

species. He therefore decides to test whether squirrels will preferentially predate on Scots pine cones.

The investigator goes to his field site and spends 20 minutes collecting cones in three areas of conifer woodland: one with larch, one with pine and one with spruce. He decides that a chi-squared contingency test is the most appropriate way to assess his hypothesis.

(a) Explain why a chi-squared test is appropriate rather than a Mann-Whitney U-test, t-test or Spearman rank test in this case?

 (b)    Write down a suitable null hypothesis which the investigator could test.

Table 2 shows the numbers of predated and unpredated cones collected by the investigator from the three species of conifers. Table 3 shows the expected values for the chi-squared test.

Observed values	Larch	Pine	Spruce	Row Total
Squirrel Predated	38	36	12	86
Unpredated	73	40	46	159
Column total	111	76	58	245

 

Expected values	Larch	Pine	Spruce
Squirrel Predated	38.96	26.68	20.36
Unpredated	72.04	49.32	37.64

(c) Calculate the chi-squared value for these data. Show your working.

(d) Calculate the degrees of freedom for this test.

(e) Using Table 4 and considering your degrees of freedom from part (d), report the appropriate critical value of the chi-squared distribution and report the outcome of the chi-squared test.

(f) Refer back to the investigator’s original hypothesis. Explain whether the result of the test provides support for the hypothesis or not.

(g) What other factors might affect cone selection by squirrels?

(h) Briefly describe one further investigation that could be carried out to look into the relationship between seed energy content and feeding behaviour in squirrels. Explain which statistical test would be appropriate to analyse the data generated from your proposed investigation.

PART C

Question 8

Journal extract questions

Answer ALL parts of the question in Part C of the examination. You are advised to spend 45 minutes on this part of the paper. Your answers should be written concisely, but in sentences. You should include diagrams and calculations in your answer where appropriate. This part carries 20 marks.

This question relates to your reading of an extract from a published scientific journal paper that contrasts two hypotheses explaining the effects of eyespots on predators. It is expected that you have already read the entire extract of the journal paper, which is provided here again as a separate document.

Now read the exam questions relating to the journal extract and refer to it throughout when answering all of the question parts.

The journal extract is enclosed with this question paper.

(a) In the Introduction the authors contrast two competing hypotheses explaining the effects of eyespots on predators: the eye-mimicry hypothesis and the conspicuousness hypothesis. Briefly describe each hypothesis in your own words.

 (b)    In the Introduction, what groups of organisms does the paper identify as having evolved eyespots as an anti-predator signal?

 (c) In the Introduction the authors write that one researcher claims: ‘Mimicry… need not be invoked to explain the startling effect of eyespots on predators.’

Write down the full reference which they cite for this claim.

(d) Using your own words, describe the five different treatments used in the experiments.

(e) How did the researchers present their different treatments to their experimental birds?

(f)     In the ‘Materials and Methods’, the authors of the paper define four comparisons between their five treatments. They look for several responses from their study birds including ‘interest’ and ‘aversion’ as described in Results. Explain what the expected result of each of the four comparisons for aversion behaviour would be if:

(i) the eye-mimicry hypothesis, or

(ii) the conspicuousness hypothesis, were to be correct.

		The four comparisons
		Probability of reaction	Probability of Aversion	Intensity of Interest	Intensity of Aversion
(i)	the eye-mimicry hypothesis	Increased reaction	Average or reduced aversion	Weak intensity	Average or reduced aversion
(ii)	the conspicuousness hypothesis,	Increased reaction	Reduced aversion	Average intensity	Average aversion

 

(g)     Figure 2 (b) shows the probability of birds showing an aversion reaction when presented with the five different treatments. Write down, to the nearest 0.1, the probabilities of aversion for treatments:

(i) BR                 

(ii) BM.     

(h)     Figure 2 (d) shows the intensity (strength) of aversion responses by birds to the five different experimental treatments. Explain how the results of the experiments shown in Figure 2 (d) relate to the expectations you described in (f).

(i)     In their Discussion, the authors state: ‘It would be interesting to compare the efficacy of eyespots characterized by different levels of resemblance to predator eyes, and testing whether conspicuousness plays a larger role when lower degrees of mimicry are achieved.’ How might you explore this idea further?

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Last updated: Sep 02, 2021 10:08 AM

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