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OPTIONS
Question	1	2	3	4	5	6	7	8	9	10	11	12	Total
Score
Maximum	10	10	10	8	12	10	10	10	10	10	10	10	100

1. Population growth of Lesser Reed (Phragmites australis) in a wetland has been monitored by assessing its cover over a period of fifty months following its introduction. The results of the monitoring programme are expressed in Figure 1 below:

Figure 1: surface area of wetland colonised by Phragmites australis over time.

 

1. What name is given to the form of population growth shown in Figure 1 ?

[one mark]

2. Indicate, using the symbols "H" and "L", the points on the graph where population growth is highest and lowest respectively.

[two marks]

3. What is the approximate carrying capacity of the wetland with regard to the P.australis population ?

[one mark]

 

 

4. Explain the form of the graph between months 0 and 10.

[two marks]

5. Explain the form of the graph between months 12 and 22.

[two marks]

6. Separate research indicates that the available surface area of the wetland could accommodate a population covering 10000 m². Suggest four reasons as to why this theoretical maximum population size is not actually attained.

1.

2.

3.

4.

[two marks] [total: ten marks]

 

 

2. The figure below shows the relationship between birth weight and the degree of survival in female births in a London obstetric hospital. A high proportion of mortality (70.8%) was recorded from birth weight classes outside the "optimum" 8lb class, indicating that selection against non-optimal birth weights may be occurring.



Figure 2: Relationship between birth weight and degree of survival in female births (adapted from Karn, M.N. and L.S. Penrose (1951). Birth weight and gestation time in relation to maternal age, parity and infant survival. Ann. Eugenics, 161, 147-164.)

1. What, in evolutionary terms, does "selection" represent ?

[two marks]

2. What name is given to the form of selection implied by Figure 2 ?

[one mark]

 

[continued on next page]

 

3. The data shown in Figure 2 suggest that many generations of selection would lead to uniform birth weights of 8lb for female newborns. Why is this unlikely to happen ?

[three marks]

 



Figure 3: Selection for high and low oil content in corn kernels. (adapted from Dudley, J.W. (1977). Seventy-six generations of selection for oil and protein percentages in maize. In Proceedings of the International Conference on Quantitative Genetics. Pollack, E. O. Kempthorne and T.B. Baiely, Jr. [eds.]. Iowa State University Press, Ames, pp. 459-473.)

Figure 3 shows selection for high and low oil content in oil kernels in an experiment started in 1896 at the University of Illinois and continuing to the present. Selection for high oil content still continues to yield increases, whereas selection for low oil content has tapered to the 0 percent lower limit.

 

4. What name is given to the form of selection implied in Figure 3 ?

[one mark]

5. Under what environmental conditions would you expect this form of selection to operate when encountered in natural settings ?

[one mark]

6. How may this form of selection eventually lead to speciation ?

[two marks] [total: ten marks]

 

 

3. The high-power micrographs in Figure 4 show stages in the cell cycle of root tip cells from Allium sp.

A	B	C	D
Figure 4: Cell cycle from root tip cells in Allium. From Shaw, A.C., S.K. Lazell & G.N. Foster (1965). Photomicrographs of the flowering plant. Longman.

1. What form of nuclear division is shown in the diagram ?

[one mark]

2. Arrange the four stages (A, B, C, D) in chronological order of occurrence.

[two marks]

3. Name the four stages of the cell cycle shown in Figure 4.

Stage A
Stage B
Stage C
Stage D
[two marks]

4. What form of nuclear division would you expect to observe in:

Cells from a shoot apical meristem
Microsporocytes within the microsporangia of plants
[two marks]

5. List three ways in which nuclear division can generate diversity.

1.

2.

3.

[three marks] [total: ten marks]

 

4. Complete the table below by matching the following taxa with the appropriate description:

Platyhelminthes, Crustacea, Annelida, Chlorophyta, Amphibia, Bryophyta, Echinodermata, Cnidaria

Description	Taxon
Chlorophylls a and b are the main photosynthetic pigments.
Life cycle shows alternation of generations, with the gametophyte as the dominant phase.
Sheds its exoskeleton by ecdysis; it is characterised by possession of a carapace or cephalothorax; lacks pedipalps.
Posseses a coelomic water vascular system, externally evident as muscular podia.
Dorsoventrally flattened acoelomates; cephalised; gut with multiple blind-ending branches
Animals displaying radial symmetry; the only body cavity is referred to as a coelenteron.
Semi-terrestrial vertebrates; larval stages have gills, which are usually lost in the adult.
Animal group where both internal and external anatomy exhibit metameric segmentation.
[one mark for each correct answer] [total: eight marks]

6. This question is about the structure of the human eye.



Figure 5: The Human Eye

1. Identify structures A through J shown in the diagram above.

Label	Structure
A
B
C
D
E
F
G
H
I
J

 

[one half-mark for each correct answer] [five marks]

2. Briefly describe ONE function of each of the following structures:

Structure	Function
A
E
I
J
	[four marks]

 

3. Which light sensitive cells are responsible for good visual acuity?

[one mark]

 

4. List two characteristics that adapt these cells to their function.

[two marks] [total: twelve marks]

 

 

 

7. This question concerns muscle.

1. Distinguish between sarcomeres and myofibrils.

[two marks]

 

2. Briefly describe the role of actin and myosin in contraction of striated muscle.

[four marks]

 

3. What role is played by the Z line (or Z disk) during the contraction of striated muscle fibres?

[two marks]

 

 

 

4. The presence of calcium ion is necessary for the hydrolysis of ATP. How would removal of calcium ion from the muscle fibre sarcoplasm affect contraction ?

[two marks] [total: ten marks]

 

 

8. This question is concerned with reproductive processes.

1. List ONE advantage and ONE disadvantage of asexual reproduction.

Advantage:

Disadvantage:

[two marks]

2. Several plants reproduce through vegetative propagation. What is vegetative propagation ?

[three marks]

 

3. Name FOUR plant organs that may be directly involved in vegetative propagation.

1.

2.

3.

4.

[one half-mark for each correct answer] [two marks]

 

4. Complete the table below by briefly defining each form of reproduction and by naming ONE organism that utilises each form of reproduction.

Form	Definition	Organism
Binary fission
Budding
Fragmentation

[one half-mark for each correct answer] [three marks] [total: ten marks]

 

 

9. The diagram represents a mitochondrion and surrounding organelles as viewed through an electron microscope.



Figure 6: Single mitochondrion from zymogen cell of mouse fundic gland. From: Helander, H. (1962). J. Ultrastruc. Research. Supplement 4.

1. Identify structures A, B and C shown on Figure 5.

Structure A:

Structure B:

Structure C:

[three marks]

2. What is the adaptive value of the convoluted folding of structure B ?

[two marks]

 

 

 

3. Name one type of tissue where mitochondria are abundant. Give a reason for your choice.

[three marks]

4. Name ONE technique you would use to isolate mitochondria from the tissue you have chosen.

[one mark]

5. List ONE characteristic function of structure C.

[one mark] [total: ten marks]

 

 

 

10. The diagram represents the transport of carbon dioxide in human blood. Two chemical reactions are represented by the encircled numbers within the outline of the red blood cell.

---

D

 

 

 

 

 

 

 

1. What enzyme catalyses reaction 1 ?

[two marks]

2. Name one other way, not shown in the diagram, by which carbon dioxide can be transported in the blood.

[two marks]

 

3. What is the biological importance of reaction 2 ?

[three marks]

4. The diagram shows excess hydrogen carbonate ion leaving the red blood cell. How is electrical neutrality maintained in the red blood cell following loss of this ion ?

[three marks] [total: ten marks]

 

 

 

SECTION B (Answer one question from this section):

OPTION 1: Biotechnology

11. The diagram below and the explanatory note which follows refer to the production of recombinant DNA.



Figure 7: Typical gene cloning experiment. From: Ketchum, P.A. (1988). Microbiology: Concepts and Applications. Wiley.

The diagram in Figure 7 (previous page) shows a typical gene-cloning experiment. Purified foreign DNA is inserted into a plasmid vector after both are treated with the same restriction endonuclease. These treated DNAs have complementing sticky ends that anneal to form a recombinant DNA. After nicks in the DNA are sealed by DNA ligase, the recombinant DNA is taken into a cell by artificial transformation. The foreign genes are cloned in this cell when multiple copies of the plasmid are made.

1. What is a restriction endonuclease ?

[two marks]

2. What is the role of the plasmid vector in this process ?

[two marks]

3. What is "artificial transformation" ?

[two marks]

4. What are "sticky ends" ?

[two marks]

 

 

5. Why were the purified foreign DNA and the plasmid vector both treated with the same restriction endonuclease ?

[two marks] [total: ten marks]

 

 

 

Option 2: The Diversity of Eukaryotes

12. The diagram below is a representation of Euglena.



Figure 8: Euglena. Adapted from Brusca, R.C. and G.J. Brusca (1990). Invertebrates. Sinauer Associates Inc.

1. Identify the following structures:

Label	Structure
A
C
D
E
F
G

 

[one half-mark for each correct answer] [three marks]

 

 

2. To which major taxonomic group does Euglena belong ?

[one mark]

3. Name TWO structural features, present in Euglena, which are characteristic of the major group within which it is classified.

1.

2.

[two marks]

 

4. List ONE function of each of the following structures:

Structure	Function
A
B
D
F

 

[four marks] [total: ten marks]

 

 

Option 3: Topics in Applied Botany

13. The following questions are concerned with dormancy and germination of seeds.
1. What is seed dormancy ?

[two marks]

2. List FOUR factors that may encourage dormancy of seeds.

1.

2.

3.

4.

[one half-mark for each correct answer] [two marks]

3. Why should seed dormancy be considered an adaptive strategy ?

[two marks]

4. Distinguish between synchronous and intermittent germination of seeds

[two marks]

 

5. List ONE advantage and ONE disadvantage of synchronous seed germination.

Advantage:

Disadvantage:

[one mark]

 

6. List ONE advantage and ONE disadvantage of intermittent seed germination.

Advantage:

Disadvantage:

[one mark] [total: ten marks]