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S295/D

Module Examination 2019

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.

Question 1

Figure 1 shows a simplified suggested phylogeny for a number of orders of monocotyledons. Monocotyledons are flowering plants (angiosperms) whose seeds typically contain only one embryonic leaf, or cotyledon. Monocotyledons include palm trees, grasses, lilies and many other families and include many important food crops. Note that the taxa in the group comprising Arecales, Poales, Commelinales and Zingiberales are together known as the commelinids, as shown in Figure 1.

1. What is meant by the term ‘sister group’, and what is the sister group of:

(i) the Pandanales, and (ii) the Asparagales? Explain your reasoning.

Ans: Sister groups or sister taxa are any taxa derived from a common ancestral node

1. Dioscoreales (e.g. yam)
2. The Commelinids

REASON: They have the same most recent common ancestor

2. (i)   Are the Arecales (true palms) monophyletic or paraphyletic? Explain your reasoning.

Ans: The Arecales (true palm) are paraphyletic. It does not include all descendants of its most recent common ancestor.

(ii) The Pandanales include several palm-like species in the Pandanus genus, which are known as screw palms. Using the information given in Figure 1, explain why screw palms are not true palms.

Ans: Screw palms are not true palms as they do not share the same parent

3. (iii) Are palms (true palms plus screw palms) monophyletic, paraphyletic or polyphyletic? Explain your reasoning.

Ans: True palms and screw palms are polyphyletic; their most recent common ancestor is not included

Question 2

A researcher observes a queen buff-tailed bumblebee (Bombus terrestris) on cherry plum flowers in early spring.

(a) Is the bee likely to be collecting nectar, pollen or both pollen and nectar? Explain your answer.

(b)    Towards the end of the summer some of the eggs laid by the queen develop into new queens and some into male bees. Name the phenomenon by which this occurs and explain how it results in both male and female offspring.

Question 3

White storks (Ciconia ciconia) mostly migrate from Europe (Germany) to Africa to overwinter but recently, increasing numbers have shortened their migrations to overwinter in southern Europe, particularly in Spain. In a study to determine fitness-related differences in the two populations, researchers determined that the survival of birds that overwintered in Spain was significantly higher than those that overwintered in Africa.

(a) What factors might contribute to an increase in the number of storks overwintering in Spain compared with overwintering in Africa?

(b) A decrease in migratory distance is becoming more common in some species of birds and there is evidence that this change is a result of natural selection. What kind of evidence is required to support this theory?

Question 4

The process of producing stored energy in the form of carbohydrate from light energy is known as photosynthesis. Different photosynthetic pathways have evolved in plants to capture this light energy.

(a) Compare the C3 and C4 pathways highlighting the efficiency of carbon fixation and resource use of each pathway.

(b) Some species of plant are able to switch between the CAM and C3 photosynthetic pathways depending on the environmental conditions. Explain why this is beneficial to the plant.

Question 5

(a) Name an example of a chasing predator and describe three physical and/or behavioural characteristics that enable it to hunt prey successfully.

(b) Describe two physiological characteristics of spiders that enable them to catch prey much larger and stronger than themselves.

(c) Explain how neurotoxins in snake venom cause paralysis of prey.

Question 6

Eukaryotes are thought to have evolved around two billion years ago. Fungi, animals and plants are just three of the recognised eukaryotic kingdoms. Fungi and animals have a common evolutionary history distinct from plants.

(a) Describe the features that reveal this shared history between fungi and animals and separates them from plants.

(b) Many fungi have evolved biotrophic relationships with plants. How would you describe this relationship and the type of interaction that can occur between plants and fungi?

 

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

Two students were asked independently to investigate the salt tolerance of a particular population of a common species of grass, Festuca rubra. To do this, they compared the yield of grass grown under a ‘no salt’ and a ‘high salt’ watering regime. They each sowed seeds in pots (same number in each pot), and watered half of the pots with water containing no added salt, and the other half with water containing a concentration of salt which is similar to that which might be found in a salt marsh area near the coast. After three weeks, they harvested the grass from all the pots from each watering regime, dried it and measured the dry mass of grass to estimate the yield per pot.

(a) What was their null hypothesis?

(b) How many degrees of freedom are there for this t-test? Show how you obtained your answer.

(c) Using the equation given above calculate the value of t which should have been obtained by student A, showing how you obtained your answer.

(d) How does the value of t you obtained compare with the critical value?

(e) How would you interpret the outcome of this t-test in terms of the hypotheses involved?

(f) What would you conclude from the test result?

(g) How many degrees of freedom are there for this t-test? Show how you obtained your answer.

(h) Using the equation given above calculate the value of t which should have been obtained by student B, showing how you obtained your answer.

(i) How does the value of t you obtained compare with the appropriate critical value?

(j) How would you interpret the outcome of this t-test in terms of the hypotheses involved?

(k) What would you conclude from the test result?

(l) Which statistical outcome from the two performed t-tests is likely to be more reliable and why? Why was the conclusion of the investigation different for student A and student B?

(m) Explain why plants growing near the coast tend to be more salt-tolerant than those growing inland.

(n) In plants affected by marine waters, or those growing in desert areas, water uptake is made particularly difficult by the presence of dissolved salts. Explain how plants adapt to this situation.

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 on the diet and digestibility of seagrass in bonnethead sharks. It is expected that you have already read the entire extract of the journal paper, which is provided here again as a separate document.

Answer the following exam questions relating to the journal extract and refer to it throughout when answering all the question parts.

The journal extract is enclosed with this question paper.

From their ‘Background’:

(a) The authors contrast the diet and digestion systems of carnivores and omnivores.

(i) Briefly summarise their descriptions in your own words.

(ii) State all the observations of bonnethead sharks described by the authors, which seem to suggest that bonnethead sharks might not be carnivores.

From the ‘Methods’:

(b) (i) In your own words, briefly summarise how the bonnethead sharks were captured for the study and how seagrass was prepared for the study.

(ii) How did the researchers ensure that sharks received the appropriate diet?

From the ‘Results and conclusions’:

(c) Calculate the value for the mean increase in body mass during the experimental study and also the difference in mean calories consumed and digested.

(d) The authors determined the digestibility of the food they fed to the bonnethead sharks. What comparisons do they make with other species in their discussion of these data?

(e) In their study of enzyme activity:

(i) Why did the authors perform their enzyme assays in duplicate or triplicate?

(ii) What is approximately the highest level of amylase activity reported and in which gut region is it found?

(iii) How do the amylase activities compare between the laboratory-fed and wild-caught animals?

(f) Describe the data presented by the authors for their findings about amino acids. Why is this observation important?

(g) What is the journal reference given by the authors for published findings indicating that the spiral intestine is the site of amino acid and fatty acid absorption in bonnethead sharks?

(h) Briefly outline the implications from the findings discussed by the authors about the understanding and management of seagrass meadow ecology.

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