MATRICULATION AND SECONDARY ... - University of Malta

Index No.:______________

AM 05/I.16m

MATRICULATION AND SECONDARY EDUCATION CERTIFICATE EXAMINATIONS BOARD UNIVERSITY OF MALTA, MSIDA

MATRICULATION EXAMINATION ADVANCED LEVEL MAY 2016

SUBJECT: PAPER NUMBER: DATE: TIME:

BIOLOGY

I 5th May 2016

4.00 p.m. to 7.05 p.m.

Directions to Candidates ? Write your index number in the space at the top left-hand corner of this page. ? Answer ALL questions. Write all your answers in the spaces provided in this booklet. ? The mark allocation is indicated at the end of each question. Marks allocated to parts of questions are

also indicated. ? You are reminded of the necessity for good English and orderly presentation in your answers. ? In calculations you are advised to show all the steps in your working, giving your answer at each stage. ? The use of electronic calculators is permitted.

For examiners' use only:

Question

1

2

3

4

5

6

7

8

9 10 Total

Score

Maximum 10 10 10 8 14 10 8 10 10 10 100

? The MATSEC Examinations Board reserves all rights on the examination questions in all examination papers set by the said Board.

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1 This question is about taxonomy.

1.1 Why is it advantageous to have a system of classification for organisms?

It helps us clarify the evolutionary relationships among organisms.

1 mark

Accept ANY ONE of the following:

It helps us remember the organisms and their characteristics.

1 mark

It lets us communicate clearly regarding the identity of the organisms being

studied.

It provides stable names to organisms in order to avoid ambiguity of

common names.

[two marks]

1.2 Define the term species.

Accept ANY of the following options:

Option 1 A species is one of the basic units of biological classification

1 mark

and a taxonomic rank

1 mark

Option 2 A species is defined as a group of similar organisms

1 mark

Which are capable of interbreeding/ exchange genes to 1 mark

produce fertile offspring

[two marks]

Euphorbia melitensis is an endemic flowering plant found in the Maltese islands.

1.3 Identify TWO major taxonomical groups within the plant kingdom for Euphorbia melitensis.

Tracheophyta

1 mark

Magnoliophyta / Angiosperm

1 mark

Dicot; Magnoliopsida (class); Malpighiales(order); Euphorbaceae (family) can also be

acceped

[two marks]

1.4 Euphorbia melitensis is the scientific name of this plant. Mention TWO advantages of using the binomial system for naming organisms.

Accept TWO of the following: Universal in the scientific community/eliminates use of several common names. No misunderstanding of the organisms being studied/attributed to a particular species. Gain information about plant

1 mark each MAX 2 marks

[two marks]

1.5 What do the following represent in the taxonomic rank?

1.5.i. Euphorbia: 1.5.ii. melitensis:

Genus species

1 mark 1 mark [two marks]

[Total: Ten marks]

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2. This question is about biomolecules.

Figure 1 represents the molecular structure of ATP.

Figure 1: Molecular structure of ATP

(Source: )

2.1 What does ATP stand for? Adenosine Triphosphate

1 mark

Reject if answer is not complete

[one mark]

2.2 Mention THREE reasons why ATP is an optimal energy currency in living organisms.

Accept any THREE of the following: Gives off small packets of energy Small and water-soluble so can move around the cell Immediate energy donor Rapid turnover

1 mark each reason ? MAX 3 marks

[three marks]

Proteins are made up of amino acids. Twenty amino acids make up polypeptides and proteins in animals.

2.3 What is an amino acid?

Accept ANY of the following: An organic molecule consisting of the basic amino group (NH2), a hydrogen atom, an acidic carboxylic group (COOH) and an organic side group (R) which is attached to the carbon atom. A biochemical with the following formula: NH2CHRCOOH. The basic chemical unit that makes up proteins. An amino acid is the chemical which is coded for by a triplet codon on the DNA molecule.

1 mark [one mark]

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2.4 Name the type of reaction that occurs when two amino acids form a dipeptide.

Condensation reaction

1 mark

Reject dehydration reaction

[one mark]

2.5 Valine and Glycine are two of the twenty amino acids found in animals. Their molecular structure is represented below in Figure 2.

Valine

Glycine

Figure 2: Molecular structure of valine and glycine

In the space below, draw the molecular structure of the dipeptide formed between these two molecules.

Correct R-groups Amino and carboxylic acid ends are showing Water is eliminated Peptide bond drawn correctly.

2.6.i Describe the primary structure of a protein. The linear sequence of amino acids that form the molecule.

2.6.ii What is the importance of the primary structure of a protein? Accept any of the following: The primary structure is the basis of identity of the protein. Forms the basis of all other proteins

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0.5 marks 0.5 marks 0.5 marks 0.5 marks [two marks]

1 mark [one mark]

1 mark

[one mark] [Total: Ten marks]

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3 This question is about gaseous exchange.

3.1 List TWO characteristics of a respiratory surface. Accept any TWO of the following Large surface area One cell thick / thin An extensive blood network Concentration gradient present Moist

1 mark each ? MAX 2 marks

[two marks]

3.2 How does the countercurrent system found in the gills of fish provide efficient gaseous

exchange?

Water and blood flow in opposite directions.

1 mark

Concentration gradient maintained all along length of lamellae /Equilibrium is 1 mark

not reached

Water always next to blood with a lower concentration of oxygen.

1 mark

Accept diagram if clearly annotated with above points

[three marks]

Neoparamoeba perurans is a parasite which causes amoebic gill disease in fish. This disease causes the lamellae to thicken and to fuse together.

3.3 Explain why these two effects give rise to a reduction in the efficiency of gaseous exchange in fish.

Thicker lamellae mean a bigger diffusion distance. Lamellae fuse therefore the surface is reduced/ Reduced surface area to volume ratio.

1 mark 1 mark

[two marks]

3.4 Use the information in Table 1 to calculate the volume of water that would have to pass over

the gills every hour to provide a fish, weighing 0.6 kg, with the required oxygen. Show your

working.

Table 1: Hypothetical features of gaseous exchange in fish at rest

Oxygen required by fish

85 cm3kg-1hour-1

Volume of oxygen absorbed by the gills from each Litre of water

8 cm3

Oxygen required by fish = 0.6 x 85 = 51 Volume = 51/8 Correct answer 6.375L

1 mark 1 mark 1 mark

Deduct 0.5 marks if units are not given or incorrect

[three marks]

[Total: Ten marks]

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