• Write your index number in the space at the top right-hand corner of this page.

1. This question is concerned with the role of nitrogen in the biosphere:
1. Why is nitrogen essential for living organisms?

[one mark]

2. Why is nitrogen generally a significant limiting factor in agriculture?

[one mark]

3. Briefly describe each of the following processes in the context of the nitrogen cycle:
1. Nitrogen fixation

[two marks]

2. Nitrification

[two marks]

3. Denitrification

[two marks] [Total: eight marks]

3. How may each of the following observations be interpreted in the light of evolutionary theory?

1. Humans possess a vestigial appendix.

[two marks]

2. Viral DNA has the same basic structure as the DNA of prokaryotes and eukaryotes.

[two marks]

3. The survival rate of the melanic form of the Peppered Moth (Biston betularia) in industrial areas was higher than that of the non-melanic form.

[two marks]

4. At least four different sub-species of the Maltese Wall Lizard (Podarcis filfolensis) are recorded from different islands of the Maltese Archipelago (Podarcis filfolensis maltensis from Malta, Gozo and Comino; Podarcis filfolensis kieselbachi from St.Paul’s Islands; Podarcis filfolensis generalensis from General’s Rock and Podarcis filfolensis filfolensis from Filfla).

[two marks] [Total: eight marks]

5. The phenotypic expression of a dominant gene in Ayrshire cattle is a notch in the tips of the ears. In the pedigree below, square symbols represent male animals, circles represent female animals and solid symbols represent notched individuals.



1. What is pedigree analysis?

[two marks]

 

Use the pedigree diagram to determine the probability of notched progeny being produced from each of the following matings. Your working and reasoning must be shown.

2. III 1 x III 3

[two marks]

3. III 2 x III 3

[two marks]

4. III 3 x III 4

[two marks]

5. III 1 x III 5

[two marks]

 

6. III 2 x III 5

[two marks] [Total: twelve marks]

7. This question is concerned with diversity of plants:
1. Complete the table below:

	Mosses	Ferns	Flowering Plants
Presence or absence of vascular tissue (xylem and phloem)	Non- vascular
Relative importance of gametophyte and sporophyte generations in life cycle			Sporophyte dominant
Male gametes		Free-swimming sperm (water required)
Habitat			Wide range of habitats
[four marks]

 

2. Briefly describe the structure of the mature sporophytes of mosses, ferns and flowering plants:

Mosses:

Ferns:

Flowering Plants:

[six marks] [Total: ten marks]

9. What forms of behaviour or learning are illustrated by each of the following observations?

1. Some birds avoid eating black and orange cinnabar moth larvae because of their unpleasant taste and avoid all similarly coloured larvae even though they may be nutritious.

[one mark]

2. Mice will immediately explore a new burrow thoroughly, even though this knowledge seems to have no apparent immediate value.

[one mark]

3. When presented with wooden boxes and bananas too high to reach, chimpanzees stacked up the boxes beneath the bananas and climbed up to get them.

[one mark]

4. Goslings and ducklings deprived of a parent will follow a human being and use it as a substitute parent.

[one mark]

5. An adult male robin (Erithacus rubecula) will attack a stuffed male robin displaying a red breast and will also attack an isolated clump of red breast feathers. It will not attack a stuffed young male robin that does not have a red breast.

[one mark]

6. What is habituation?

[one mark]

7. How does habituation differ from other forms of learning?

[one mark] [Total: seven marks]

10. The figure below is a diagrammatic representation of the menstrual cycle in a human female. The layer in the lower part of the figure represents state of the uterine endometrium.



(adapted from Eckert, R., Randall, D. & Augustine, G. 1988. Animal Physiology: mechanisms and adaptations. W.H. Freeman and Company.)

1. Identify structures A and B; name ONE hormone secreted by each structure and list ONE function of each hormone you mentioned.

Label	Structure	Hormone secreted	One function of hormone
A
B
[three marks]

2. Identify the process marked as X. What hormone induces this process and what is the source gland of this hormone?

Process X:

Hormone:

Source Gland:

[one mark]

3. Give a brief description of the processes that would be expected to operate during the phase marked as Y.

[one mark]

4. Briefly describe the hormonal changes that bring about phase Y.

[one mark]

5. What would you expect to happen to structure B in case of fertilisation?

[one mark]

6. What is the role of the placenta in nutrition of the embryo?

[one mark]

7. What is the role of the placenta in protection of the embryo?

[one mark] [Total: nine marks]

 

 

 

 

12. The figure below is an electron micrograph of mammalian muscle tissue.



1. What type of muscle tissue is shown in the figure?

[one mark]

2. What name is given to the region delimited by the horizontal arrows in the diagram?

[one mark]

3. Briefly describe the structure of this region.

[two marks]

5. Give a brief outline of the role of actin, myosin and ATP in the functioning of this type of muscle.

[three marks] [Total: seven marks]

 

 

 

 

13. This question concerns the properties and importance of water in living organisms.

1. The following table lists some physical properties of water. Complete the table by stating how each physical property contributes to making water such a biologically important molecule.

Physical Property	Biological Significance
High latent heat of vaporisation
Expansion on freezing
High surface tension
High specific heat capacity
[eight marks]

 

3. Describe the chemical structure of the water molecule and indicate the main characteristic that gives water the physical properties listed in the previous part of the question.

[three marks]

 

Water molecules are mobile and can cross membranes.

4. Give the name of the process that refers to the movement of water molecules.

[one mark]

5. Give two examples of this process happening in biological systems.

[two marks] [Total: fourteen marks]

15. The liver is an organ of major importance in the body.

1. Name the vessel that supplies the liver with oxygenated blood at high pressure.

[one mark]

2. Name the vessel that delivers blood rich in the soluble products of digestion to the liver.

[one mark]

3. Name the vessel that supplies the liver with blood rich in insulin.

[one mark]

Distinguish between the following pairs of processes that occur in the liver.

4. Deamination and Transamination

[one mark]

5. Glycogenesis and Gluconeogenesis

[one mark]

Describe the role of the following cells that are found in the liver:

6. Küppfer cell

[one mark]

7. Macrophage

[one mark] [Total: seven marks]

17. This question is concerned with biological systematics and nomenclature:

1. What is a biological species?

[two marks]

2. List three criteria on the basis of which organisms are classified into different taxonomic groups.

[one mark]

3. Re-arrange the following classification categories in descending order of taxonomic rank:

Order, Phylum, Class, Family, Phylum, Species, Kingdom, Genus

[two marks]

 

4. Identify the errors of biological nomenclature in each of the following names of species:

Triops Cancriformis:

Triops cancriformis:

triops cancriformis:

[three marks] [Total: eight marks]

 

SECTION B (Answer one question from this section):

Option 1: Biotechnology

18. Monoclonal antibodies have several applications in biotechnological industry, one of which is pregnancy testing. In this context, detection of pregnancy is based on antibodies to Human Chorionic Gonadotrophin (HCG), a hormone produced only during pregnancy. The basic sequence of events is as follows:

Stage I	A mouse is injected with HCG
Stage II	After a few weeks, the mouse is killed and the spleen removed.
Stage III	Lymphocytes are washed out and centrifuged.
Stage IV	Lymphocytes are fused with myeloma cells to form a hybridoma.
Stage V	The hybridoma cells are cloned and tested for antibody production.
Stage VI	Clones that produce the required monoclonal antibody are sub-cultutred.

 

1. What are monoclonal antibodies?

[one mark]

2. Why does Stage II occur several weeks after Stage I?

[one mark]

3. What differences would be evident if Stage II occurred:

1. Within minutes of Stage I:

[one mark]

2. Years after stage I:

[one mark]

5. Why are lymophcytes centrifuged in Stage III?

[one mark]

 

6. Why do lymphocytes need to be fused with myeloma cells?

[two marks]

 

7. Give a brief outline of a method through which hybridoma cells could be cloned.

[three marks] [Total: ten marks]

 

 

 

Option 2: The Diversity of Eukaryotes

19. The figure below represents Trichoplax adhaerens, which has often been described as the simplest of all animals. The organism is approximately 0.3mm across.



(adapted from Margulis, L. & K.V. Schwartz 1988; Five Kingdoms. Second Edition. W.H .Freeman)

1. In what major taxonomic group (apart from the Animalia) would you classify Trichoplax adhaerens? Give reasons for your answer.

[two marks]

2. Briefly outline the structure and function of the mesenchyme layer.

[two marks]

3. Use your knowledge of biology to suggest how Trichoplax adhaerens may acquire its food.

[one mark]

Suggest ONE function for each of the following structures visible in the diagrams:

4. Ciliated epithelium

[one mark]

5. Fluid-filled cavity

[one mark]

6. Lipid vesicles

[one mark]

 

Suggest reasons for the following observations:

7. Trichoplax adhaerens is similar to the planula larva of cnidarians.

[one mark]

8. There is no known fossil record for Trichoplax adhaerens.

[one mark] [Total: ten marks]

 

Option 3: Topics in Applied Botany

20. Taking cuttings is a common horticultural practice for the propagation of plants. The cut end of a stem is often dipped into a rooting powder.
1. What is a cutting?

[one mark]

 

2. What chemical substances would you expect to be present in the rooting powder?

[one mark]

 

Another widely used method for propagation of woody species is grafting, in which the plant to be propagated (the scion) is grafted on to another plant (the stock).

3. How does grafting permit propagation?

[one mark]

4. Why is grafting generally only successful if the scion and stock are from closely related species?

[one mark]

 

Plants can also be propagated through plant tissue culture and micropropagation techniques.

5. Suggest two advantages of micropropagation over more conventional propagation techniques.

[two marks]

7. Construct a concise outline (in point form) of the steps followed when culturing plant tissue.

[three marks]

8. It has been reported that addition of silver nitrate to a plant culture medium increases the probability of successful culture. Suggest a reason for this observation.

[one mark] [Total: ten marks]