BIOL2. General Certificate of Education Advanced Subsidiary Examination June Unit 2 The variety of living organisms

Transcription

1 Centre Number Surname Candidate Number For Examiner s Use Other Names Candidate Signature Examiner s Initias Genera Certificate of Education Advanced Subsidiary Examination June 2011 Question 1 2 Mark Bioogy Unit 2 The variety of iving organisms Thursday 26 May pm to 3.15 pm Time aowed For this paper you must have: a ruer with miimetre measurements. a cacuator. 1 hour 45 minutes BIOL TOTAL Instructions Use back ink or back ba-point pen. Fi in the es at the top of this page. Answer a questions. You must answer the questions in the spaces provided. around each page or on bank pages. You may ask for extra paper. Extra paper must be secured to this booket. Do a rough work in this book. Cross through any work you do not want to be marked. Information The maximum mark for this paper is 85. The marks for questions are shown in brackets. Quaity of Written Communication wi be assessed in a answers. You wi be marked on your abiity to: use good Engish organise information ceary use scientific terminoogy accuratey. (JUN11BIOL201) BIOL2

2 2 Answer a questions in the spaces provided. 1 The diagram shows an organism caed Chamydomonas. Light sensitive eyespot Cytopasm Fageum for movement Ce wa Nuceus Choropast Starch store 1 (a) Name two structures shown in the diagram that are present in pant ces but are not present in anima ces (b) Chamydomonas ives in fresh water ponds. Use your knowedge of osmosis to suggest an advantage of using starch as a carbohydrate store. (02)

3 3 1 (c) Chamydomonas has adaptations that hep it to maintain a high rate of photosynthesis. Use information in the diagram to expain what these adaptations are. (3 marks) (Extra space) (a) Expain what is meant by genetic diversity. (1 mark) 2 (b) Apart from genetic factors what other type of factor causes variation within a species? (1 mark) 2 (c) The spotted ow is a bird. Numbers of spotted ows have decreased over the past 50 years. Expain how this decrease may affect genetic diversity. 4 Turn over (03)

4 4 3 The diagram shows a short sequence of DNA bases. T T T G T A T A C T A G T C T A C T T C G T T A A T A 3 (a) (i) What is the maximum number of amino acids for which this sequence of DNA bases coud code? (1 mark) 3 (a) (ii) The number of amino acids coded for coud be fewer than your answer to part (a)(i). Give one reason why. (1 mark) (04)

5 5 3 (b) Expain how a change in the DNA base sequence for a protein may resut in a change in the structure of the protein. (3 marks) (Extra space)... 3 (c) A piece of DNA consisted of 74 base pairs. The two strands of the DNA, strands A and B, were anaysed to find the number of bases of each type that were present. Some of the resuts are shown in the tabe. Number of bases C G A T Strand A 26 Strand B 19 9 Compete the tabe by writing in the missing vaues. 7 Turn over (05)

6 6 4 The diagram shows a ce cyce. Interphase Prophase Metaphase Anaphase Teophase 4 (a) In prophase of mitosis, the chromosomes become visibe. Describe what happens in 4 (a) (i) metaphase 4 (a) (ii) anaphase. (06)

7 7 4 (b) (i) Ces ining the human intestine compete the ce cyce in a short time. Expain the advantage of these ces competing the ce cyce in a short time. (1 mark) 4 (b) (ii) The time required for a ce to compete the ce cyce was 4 hours 18 minutes. Cacuate the time required in minutes for this ce to mutipy to produce eight ces. Show your working. Answer... 4 (c) Mikanoide is a drug that inhibits the enzyme DNA poymerase. Expain why this drug may be effective against some types of cancer. 9 Turn over (07)

8 8 5 A student investigated the rate of transpiration from privet eaves. She obtained two sets of ten privet eaves. She eft the ten eaves in set A untreated. She covered the upper surfaces of the ten eaves in set B with grease. She weighed each set of eaves and then tied a the eaves in each set to a separate ength of thread. This is shown in the diagram. Thread Leaves Stand and camp She then weighed each set of eaves every 20 minutes over a period of 2 hours and potted a graph of her resuts. Set A Set B Loss in mass Time / minutes (08)

9 9 5 (a) Give two environmenta conditions that the student shoud have kept constant during this investigation (b) The student measured the water oss in miigrams. Expain the advantage of using ten eaves when taking measurements in miigrams. (1 mark) 5 (c) Expain the change in mass of untreated eaves in set A shown in the graph. (3 marks) (Extra space)... 5 (d) The resuts that the student obtained for the eaves in set B were different from those for set A. Suggest an expanation for this difference. 8 Turn over (09)

10 10 There are no questions printed on this page DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED (10)

11 11 6 Lugworms ive in mud where the partia pressure of oxygen is ow. The graph shows oxygen dissociation curves for a ugworm and for a human. 100 Percentage saturation of haemogobin with oxygen 50 Lugworm Human 0 Partia pressure (po 2 ) 6 (a) Expain the advantage to the ugworm of having haemogobin with a dissociation curve in the position shown. 6 (b) In humans, substances move out of the capiaries to form tissue fuid. Describe how this tissue fuid is returned to the circuatory system. (3 marks) (Extra space)... 5 Turn over (11)

12 12 7 Cranes are arge birds. One of the eariest methods of cassifying cranes was based on the cas they make during the breeding season. 7 (a) Expain why bioogists coud use cas to investigate reationships between different species of crane. 7 (b) More recenty, bioogists have used DNA hybridisation to confirm the reationships between different species of crane. They made sampes of hybrid DNA from the same and from different species. They measured the percentage of hybridisation of each sampe. The resuts are shown in the tabe. Species of crane from which hybrid DNA was made Percentage DNA hybridisation Grus americana and Grus monachus 97.4 Grus monachus and Grus rubicunda 95.7 Grus americana and Grus rubicunda 95.5 Grus rubicunda and Grus rubicunda 99.9 Grus americana and Grus americana 99.9 Grus monachus and Grus monachus (b) (i) Which two species seem to be the most cosey reated? Expain your answer. (12)

13 13 7 (b) (ii) The bioogists measured the temperatures at which the sampes of hybrid DNA separated into singe strands. Expain why these temperatures coud be used to find the percentage of DNA hybridisation. 7 (c) Bioogists can aso use protein structure to investigate the reationship between different species of crane. Expain why. Turn over for the next question 8 Turn over (13)

14 14 8 Costa Rica is a Centra American country. It has a high eve of species diversity. 8 (a) There are over species of pants in Costa Rica. Expain how this has resuted in a high species diversity of animas. 8 (b) The number of species present is one way to measure biodiversity. Expain why an index of diversity may be a more usefu measure of biodiversity. (14)

15 15 8 (c) Crops grown in Costa Rica are sprayed with pesticides. Pesticides are substances that ki pests. Scientists think that poution of water by pesticides has reduced the number of species of frog. 8 (c) (i) Frogs ay their eggs in poos of water. These eggs are sma. Use this information to expain why frogs eggs are very ikey to be affected by pesticides in the water. 8 (c) (ii) An increase in temperature eads to evaporation of water. Suggest how evaporation may increase the effect of pesticides on frogs eggs. (1 mark) 7 Turn over for the next question Turn over (15)

16 16 9 Erythropoietin (EPO) is a substance produced in the body. It increases the production of red bood ces. Synthetic EPO is made artificiay. It is used to treat patients who have a form of anaemia in which there is a reduced number of red bood ces. Scientists investigated the effect of synthetic EPO on vounteers with this form of anaemia. The scientists injected synthetic EPO in a sat soution into patients in the experimenta groups. They aso set up contro groups. They gave the different experimenta groups different doses of synthetic EPO and different engths of treatment. At the beginning and end of the treatment, the scientists measured each patient s haemogobin concentration. From these measurements, they cacuated the mean increase in haemogobin concentration. Some of the resuts are shown in the tabe. Number of vounteers Length of treatment / weeks Dose of synthetic EPO / units per kiogram per week Mean increase in haemogobin concentration / arbitrary units (a) Expain why treatment with synthetic EPO affects the haemogobin concentration in these vounteers. (16)

17 17 9 (b) Suggest how the contro groups shoud have been treated in this investigation. 9 (c) The scientists measured the dose of synthetic EPO per kiogram per week. Expain why they measured the dose per unit mass and per unit time. 9 (d) Expain how the information that the scientists coected might be usefu in treating patients with anaemia. Question 9 continues on the next page Turn over (17)

18 18 9 (e) Some athetes have used synthetic EPO as a performance enhancer. Expain how synthetic EPO may improve performance in ong-distance events. (4 marks) (Extra space)... 9 (f) Athetes may be tested to see if the concentration of EPO in their bood is above norma. Suggest how scientists determine the norma concentration of EPO in bood. 9 (g) Synthetic EPO can increase bood pressure. Suggest why. (1 mark) 15 (18)

19 19 10 (a) Costridium difficie is a bacterium that is present in the gut of up to 3% of heathy aduts and 66% of heathy infants. 10 (a) (i) C. difficie rarey causes probems, either in heathy aduts or in infants. This is because its numbers are kept ow by competition with harmess bacteria that normay ive in the intestine. Use this information to expain why some patients treated with antibiotics can be affected by C. difficie. 10 (a) (ii) Suggest why oder peope are more ikey to be affected by C. difficie. (1 mark) 10 (b) The antibiotic methiciin inhibits the enzyme transpeptidase. This enzyme is used by some bacteria to join monomers together during ce wa formation. Methiciin has a simiar structure to these monomers. Use this information to expain how methiciin inhibits the enzyme transpeptidase. Turn over (19)

20 20 10 (c) MRSA is a variety of Staphyococcus aureus. It is difficut to treat infections caused by this bacterium because it is resistant to methiciin and to some other antibiotics. As a resut, some patients who are aready very i may die if they become infected with MRSA. The graph shows the number of deaths in Engand and Waes between 1994 and 2008 caused by MRSA Number of deaths per Waes Engand Year 10 (c) (i) It may be difficut to identify MRSA as the actua cause of death. Expain why. (1 mark) 10 (c) (ii) Describe the change in the number of deaths caused by MRSA in Engand in the period shown in the graph. (1 mark) (20)

21 21 10 (c) (iii) Cacuate the percentage increase in the number of deaths caused by MRSA in Waes from 1996 to Show your working. Answer (d) Describe how gene transmission and seection have increased the difficuty of treating bacteria infections with antibiotics. (6 marks) (Extra space) END OF QUESTIONS (21)

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