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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 10 10 10 8 14 10 8 10 10 10 100 Score Maximum © The MATSEC Examinations Board reserves all rights on the examination questions in all examination papers set by the said Board. AM 05/I.16m DO NOT WRITE ABOVE THIS LINE _________________________________________________________________________________________________ 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. Accept ANY ONE of the following: It helps us remember the organisms and their characteristics. 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. 1 mark 1 mark [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 and a taxonomic rank Option 2 A species is defined as a group of similar organisms Which are capable of interbreeding/ exchange genes to produce fertile offspring 1 mark 1 mark 1 mark 1 mark [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: Genus 1 mark 1.5.ii. melitensis: species 1 mark [two marks] [Total: Ten marks] Page 2 of 12 AM 05/I.16m DO NOT WRITE ABOVE THIS LINE _________________________________________________________________________________________________ 2. This question is about biomolecules. Figure 1 represents the molecular structure of ATP. Figure 1: Molecular structure of ATP (Source: http://chemwiki.ucdavis.edu/@api/deki/files/25707/800px-ATP_chemical_structure.png?revision=1) 2.1 2.2 What does ATP stand for? Adenosine Triphosphate 1 mark Reject if answer is not complete [one mark] 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] Page 3 of 12 AM 05/I.16m DO NOT WRITE ABOVE THIS LINE _________________________________________________________________________________________________ 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 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] Page 4 of 12 AM 05/I.16m DO NOT WRITE ABOVE THIS LINE _________________________________________________________________________________________________ 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] Page 5 of 12 AM 05/I.16m DO NOT WRITE ABOVE THIS LINE _________________________________________________________________________________________________ 4. 4.1 This question is about hormonal control. Which hormones are responsible for the regulation of blood glucose in the body? Insulin 1 mark glucagon 1 mark [two marks] An experiment was carried out to investigate how the blood glucose level fluctuates following ingestion of glucose. At the start of the experiment, each member of a group of volunteers ingested a syrup containing 50 g of glucose. The concentration of glucose was determined in blood samples at intervals over a period of 2 hours. The results shown in the graph next page (Figure 3) are mean values for the group of volunteers. Mean blood glucose concentration / mmolL-1 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 0 20 40 60 80 100 120 140 Time / minutes Figure 3: Graph showing mean blood glucose concentration versus time 4.2 Describe and explain the changes in the concentration of glucose during the following time intervals. 4.2.i 0 to 30 minutes Blood glucose level increases Peaks at 7.5 mMol/L Due to absorption of glucose from gut/ enters blood stream 4.2.ii 30 to 120 minutes Concentration decreases Rise of glucose stimulates insulin secretion Uptake by liver/muscle/taken into cells/ Change into glycogen 1 mark 1 mark 1 mark [three marks] 1 mark 1 mark 1 mark [three marks] [Total: Eight marks] Page 6 of 12 AM 05/I.16m DO NOT WRITE ABOVE THIS LINE _________________________________________________________________________________________________ 5. This question is about genetics. 5.1 Explain what is meant by the following terms: 5.1.i Allele: One of the forms of a gene that are found on the same loci of a chromosome. 1 mark [one mark] 5.1.ii Dominant: An allele that will always show in the phenotype if present 5.1.iii Heterozygous: Two different alleles of a gene In a particular locus 1 mark [one mark] 0.5 mark 0.5 mark [one mark] 5.1.iv Genotype: Accept ANY of the following: Alleles present in an organism Particular alleles of a gene Gene constitution 1 mark [one mark] 5.2 Melopsittacus undulatus, commonly known as the budgerigar, is a small parrot which can have green, blue, yellow or white feathers. Feather colour is controlled by two genes, B/b or Y/y according to the following genotypes: Colour of bird Genotype Green At least one dominant B allele and one dominant Y allele Blue At least one dominant allele B but are homozygous recessive for y Yellow At least one dominant allele Y but are homozygous recessive for b White Homozygous recessive for both b and y 5.2.i If two green-feathered budgerigars which are heterozygous at both loci were crossed, what is the probability of producing offspring with blue feathers? A genetic diagram should be included. BY BY BBYY By BBYy bY BbYY by BbYy Probability = 3/16 or 18.75% By BBYy BByy BbYy Bbyy Parents BbYy x BbYy Gametes BY By bY by Correct Punnett square (or genetic diagram) Page 7 of 12 bY ByYY BbYy bbYY bbYy by BbYy Bbyy bbYy bbyy 1 mark 1 mark 3 marks AM 05/I.16m DO NOT WRITE ABOVE THIS LINE _________________________________________________________________________________________________ Correct probability 1 mark [six marks] 5.2.ii Two blue budgerigars were crossed and over the years, they produced 22 offspring, five of which were white. Deduce the most likely genotypes for the two blue birds. Blue birds can be BByy or Bbyy 1 mark Since ~ 25% were white, b must have been present in both parents 1 mark Correct punnett square (or genetic diagram)/explanation 1 mark Therefore the parents were Bbyy and Bbyy 1 mark [four marks] [Total: Fourteen marks] 6 This question is about biotechnology. 6.1 Define biotechnology. Accept ANY of the following: The application of organisms, biological systems or biological processes to manufacture certain services. Manipulation of DNA to produce genetically modified products 1 mark [one mark] 6.2 List the FOUR main stages that are employed in genetic engineering using bacteria Gene extraction 1 mark Recombinant DNA formation 1 mark Introduction of vector DNA into host cell 1 mark Screening/DNA proofing 1 mark DNA amplification/ cloning can also be accepted [four marks] 6.3 The following are techniques used in analysing DNA organisation. Give the function of each: Gel electrophoresis Separation of DNA fragments 1 mark Southern blotting Detection of fragments/identification of 1 mark genes/visualisation of DNA fragments [two marks] PCR is an important tool used in biotechnology. 6.4 6.5 What does PCR stand for? Polymerase chain reaction 1 mark Reject if answer is not complete [one mark] Explain the function of PCR in biotechnology. PCR enables one to amplify (to generate a large number of copies) a specific fragment of DNA 1 mark 1 mark [two marks] [Total: Ten marks] Page 8 of 12 AM 05/I.16m DO NOT WRITE ABOVE THIS LINE _________________________________________________________________________________________________ 7 This question is about reproduction. 7.1 Briefly mention the main advantages and disadvantages of asexual reproduction. Advantages: Accept any two: 1 mark each 1 parent needed – MAX 2 No energy waste in mating marks No energy wasted in gamete production Fast/efficient Disadvantages: 1 mark Slow rate of generation of genetic variation (relies only on mutations) Low genetic variation within population results in susceptibility 1 mark [four marks] 7.2. The following hormones are involved in the control of the human menstrual cycle. For each hormone, state where it is produced and the organ/s on which it acts. Oestrogen: ovary / granulosa cells/ ovarian/ Graafian 0.5 marks follicle affects ovary, uterus and anterior pituitary 0.5 marks Reject if organs in bold are not mentioned gland Progesterone: ovary / corpus luteum 0.5 marks affects the lining of uterus and pituitary gland 0.5 marks Reject if organs in bold are not mentioned [two marks] The placenta plays an important role in pregnancy. 7.3. 7.3.i State ONE important role of the placenta in the: protection of the embryo. Accept any of the following: Prevents certain harmful pathogens from passing to the embryo. Releases progesterone to prevent the wall to contract. Protects against the high blood pressure. Passage of antibodies from the mother which gives the embryo a way of defence. Passage of waste from embryo to mother – avoids intoxication of embryo 1 mark [one mark] 7.3.ii nutrition of the embryo. Accept any of the following: It transfers nutrients, food and necessary vitamins from the blood of the mother to the embryo. Responsible for oxygen exchange between mother and embryo. 1 mark [one mark] [Total: Eight marks] Page 9 of 12 AM 05/I.16m DO NOT WRITE ABOVE THIS LINE _________________________________________________________________________________________________ 8 This question is about excretion and osmoregulation. The water balance of the body in different situations was investigated. The results were recorded on three separate days, namely, a warm day, a cold day and a day during which the individual did heavy exercise (Figure 5). The total water intake by the body was the same as the water output in each situation. Figure 5: Water balance for 3 different days – a warm day, a cold day and a day whereby heavy exercise was performed. 8.1 Explain what is meant by oxidation of food and how it produces water in the body. Oxidation of food - during cellular respiration, organic molecules are 1 mark broken down to release energy OR addition of oxygen to food molecules to release energy or produce water During the final stage of electron transport chain oxygen accepts hydrogen 1 mark and electrons forming water OR by cytochrome oxidase [two marks] 8.2.i Describe the differences in water output between the cold day and the day of heavy exercise. On a cold day, the volume of urine was more than that on the day of heavy 1 mark exercise. Sweat was higher on heavy exercise day 1 mark More water lost from lungs on the heavy exercise day 1 mark [three marks] 8.2.ii Explain what is causing these differences Cool temperatures mean less sweating. Sweat due to body heat generation and thermoregulatory mechanisms to let out heat. since more heavy breathing to provide more oxygen for activity Page 10 of 12 0.5 mark 0.5 mark 1 mark AM 05/I.16m DO NOT WRITE ABOVE THIS LINE _________________________________________________________________________________________________ [two marks] 8.3 Explain why more water is produced by the oxidation of food on the day of heavy exercise. A lot of food being respired. 1 mark More energy for the exercise. 1 mark Respiration of fats therefore more water in the oxidation chain. 1 mark [three marks] [Total: Ten marks] 9 This question is about the immune system. 9.1 Explain the term disease. A particular abnormal condition, a disorder of a structure function/impairment of the normal state of the individual that is a response to a pathogen, the environment or genetic disposition . or 1 mark 1 mark [two marks] An individual can acquire two types of immunity. Table 6 represents the different types of immunity. Table 6: Different types of immunity Immunity Type of immunity Production of memory acquired cells / yes or no Injection with an antibody against Artificial Passive No specific disease- causing organism Injection with a live, weakened Artificial Active Yes disease-causing organism 0.5 marks each point 9.2 Complete Table 6. [two marks] When a pathogen enters the body, a primary immune response occurs. This can include the production of antibodies. 9.3 9.4 Define the term antibody. Accept any of the following: Option 1 A molecule that is made by an animal in response to the presence of a pathogen/ substances known as antigens Option 2 a Y-shaped protein with 2 heavy chains and 2 light chains (held by disulphide bridges) Bind to epitope 1 mark 1 mark 1 mark 1 mark [two marks] Describe the events in the immune response which lead to antibodies being produced. Antigen binds to receptor or membrane of B-cells/ B-lymphocytes 1 mark T helper cell or T lymphocyte, activate the B-cells 1 mark Page 11 of 12 AM 05/I.16m DO NOT WRITE ABOVE THIS LINE _________________________________________________________________________________________________ Killer T cells release cytokines to stimulate the B-cells Plasma cells form and produce antibodies 1 mark 1 mark [four marks] [Total: Ten marks] 10 This question is about evolution. 10.1 Explain what is meant by biological evolution. Biological evolution involves a change in the gene pool (allele and genotype frequencies) of a population from one generation to the next. Small differences accumulate with each generation and can, over time, cause substantial changes in the organisms. 1 mark 1 mark [two marks] 10.2 An important factor for natural selection to occur is the variation in the phenotypes of the population. Explain. Variation means the presence of different characteristics within a population 1 mark Results in different survival rates 1 mark More successful phenotypes are passed on to next generation 1 mark [three marks] 10.3 Briefly differentiate between sympatric and allopatric speciation. Allopatric speciation is speciation that results when a population is separated by a physical barrier. It is also referred to as geographic speciation. Sympatric speciation is speciation that occurs without physical separation of members of the population but is the product of divergent evolution/ specialisation. 1 mark 1 mark [two marks] 10.4 Briefly explain how geographic isolation can lead to the evolution of a new species. Populations separated by physical barrier therefore no mixing of gene pools/ Separated population experiences founder effect and there is no mixing of gene pools Due to different selection pressures, become adapted to local environment Mutation in one group adds to changes in allele frequency 1 mark 1 mark 1 mark [three marks] [Total: Ten marks] Page 12 of 12