UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Level BIOLOGY 9700/04 Paper 4 A2 Structured Questions December 2009 Class A2 2 hours Candidates answer on the Question Paper. Additional Materials: Answer Paper available on request. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may use a pencil for any diagrams, graphs, or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions in Section A and one question from Section B. Circle the number of the Section B question you have answered in the grid below. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner s Use Section A 1 2 3 4 5 6 7 8&9 Section B 10 or 11 Total This document consists of 18 printed pages, 2 lined pages. [Turn over
1 (a) The inheritance of coat colour in horses is complex but all horses have one of two base colours, red (chestnut) or black. The base colour is controlled in a simple monohybrid way. 2 When chestnut stallions and mares are mated the foals are always chestnut. When black stallions are mated with black mares, either black or chestnut foals may be produced. Draw a genetic diagram to show how two parents with black coat colour can produce a chestnut foal and the probability of such an event occurring. Choose a letter symbol to represent coat colour. [4]
(b) Five other genes can modify the base coat colour. 3 One of these genes is the C gene. There are two alleles of this gene, C and C CR. C does not affect the base coat colour. C CR may modify the base coat colour. If a chestnut horse has at least one C CR allele its phenotype will be palomino, which is a light cream colour. If a black horse has at least one C CR allele its effect will not be noticeable in the phenotype. Complete the genetic diagram below. parental genotype aacc CR AaCC parental phenotype gametes offspring genotypes offspring phenotypes [4] [Total: 8] [Turn over
2 (a) Fig. 2.1 shows a scanning electron micrograph of a section through a leaf of the Christmas rose, Helleborus niger. 4 M { } N Name M and N. Fig. 2.1 M... N... [2] (b) Gases leave and enter the leaf through pores called stomata. Describe and explain how a stoma is opened... [6]
(c) Fig. 2.2 outlines the main reactions in the light-dependent stage of photosynthesis. 5 2e reduced NADP 2e 2e S H 2 O R photosystem I light photosystem II increasing energy level light Fig. 2.2 (i) Name the process shown by the dotted arrows ( ).... [1] (ii) Describe what happens to water at R.... [2] (iii) State the product formed as electrons flow along S.... [1] (iv) Explain briefly the role of reduced NADP in the light-independent stage.... [ 2][Total: 14]
6 3 Colour blindness is a condition characterised by the inability of the brain to perceive certain colours accurately. The most common form is termed red-green colour blindness (RGC). RGC results from a recessive allele. 0.6% of females worldwide have RGC. 8.0% of males worldwide have RGC. Fig. 3.1 shows the occurrence of RGC in one family. = male = female = male with RGC 1 2 3 4 5 6 7 8 9 Fig. 3.1 10 (a) Explain the meaning of the terms allele and recessive. allele......[1] recessive......[1] (b) Explain why females are less likely than males to have RGC....[2] (c) With reference to Fig. 3.1, and using the symbols R for the dominant allele and r for the recessive allele, state the genotypes of the individuals 1, 4, 6 and 7. 1... 4... 6... 7... [4] [Total: 8]
4 (a) An absorption spectrum is a graph of the absorption of different wavelengths of light by a photosynthetic pigment. An action spectrum is a graph of the rate of photosynthesis at different wavelengths of light. 7 Fig. 4.1 shows the absorption spectra of chlorophyll a and chlorophyll b as well as an action spectrum. 100 action spectrum 90 80 rate of photosynthesis chlorophyll b chlorophyll a 70 60 50 40 30 percentage light absorption 0 400 450 500 550 600 650 700 0 20 10 wavelength of light / nm Fig. 4.1 With reference to Fig. 4.1, (i) compare the absorption spectra of chlorophyll a and chlorophyll b,...[3]
8 (ii) explain the shape of the action spectrum,...[3] (iii) explain why plants appear green....[2] (b) Fig. 8.2 is an electron micrograph showing a section through part of a chloroplast. Fig. 4.2 On Fig. 4.2, draw label lines and use the letters W and Y to identify the following structures: W where the light-independent reactions occur Y where chlorophyll is found [2]
9 (c) Explain why increasing the concentration of carbon dioxide may increase the rate of production of carbohydrates at high light intensities....[5] [Total: 15]
5 The Atlantic herring, Clupea harengus, lives in large populations called shoals and may grow up to 40 cm long. Fig. 5.1 shows the appearance of C. harengus. 10 Fig. 5.1 The length of C. harengus shows wide variation. Fig. 5.2 shows the numbers of fish of different lengths in a population of C. harengus. The arrows show the selection pressures, P and S. selection pressure P selection pressure S number of fish 0 0 10 20 length of fish / cm 30 40 Fig. 5.2
11 (a) (i) Sketch a graph on the axes below to show the distribution of length of C. harengus, when selection pressures P and S operate for a few years. number of fish 0 0 10 20 length of fish / cm 30 40 [2] (ii) Name this type of natural selection...[1] (b) (i) Sketch a graph on the axes below to show the distribution of length of C. harengus, when selection pressure S alone operates for a few years. number of fish 0 0 10 20 length of fish / cm 30 40 (ii) Name this type of natural selection...[1] (iii) Suggest two examples of selection pressure S. 1.... 2....[2] [2] [Total: 8]
6 Fig. 6.1 shows the structure of ATP. 12 NH 2 N N B P P P CH 2 N N O H H H H OH OH S Fig. 6.1 (a) (i) Name the nitrogenous base labelled B....[1] (ii) Name the sugar labelled S....[1] (b) ATP is described as having a universal role as the energy currency in all living organisms. Explain why it is described in this way....[4]
13 (c) State precisely two places where ATP is synthesised in cells. 1... 2......[2] [Total: 8]
7 In mice there are several alleles of the gene that controls the intensity of pigmentation of the fur. The alleles are listed below in order of dominance with C as the most dominant. 13 C = full colour C ch = chinchilla C h = himalayan C p = platinum C a = albino The gene for eye colour has two alleles. The allele for black eyes, B, is dominant, while the allele for red eyes, b, is recessive. A mouse with full colour and black eyes was crossed with a himalayan mouse with black eyes. One of the offspring was albino with red eyes. Using the symbols above, draw a genetic diagram to show the genotypes and phenotypes of the offspring of this cross. [6] [Total: 6]
8 In the majority of photosynthetic organisms, fixation of carbon dioxide occurs in the Calvin cycle. Fig. 8.1 is an outline of this cycle. 15 CO 2 ribulose bisphosphate (RuBP) 2 glycerate phosphate (GP) 2 triose phosphate (TP or GALP) (a) State, Fig. 8.1 (i) the name of the five carbon sugar in the cycle...[1] (ii) the name of the enzyme that fixes carbon dioxide...[1] (iii) where in the chloroplast the Calvin cycle occurs...[1] (iv) the name of another compound that is produced in the light-dependent stage of photosynthesis that is used in the Calvin cycle....[1]
16 (b) Fig. 8.2 shows the changes in the relative concentrations of RuBP and GP produced in the Calvin cycle before and after a light source is switched off. All other conditions are constant. light switched off light dark concentrations and RuBP of GP GP RuBP time Fig. 8.2 Explain the changes in the relative concentrations of RuBP and GP after the light source is switched off....[4] [Total: 8]
17 9 (a) Outline the symptoms of cystic fibrosis (CF)... [5] (b) CF is caused by a recessive mutation, b, on an autosome. Draw a genetic diagram to show, for parents with genotypes BbXX and BbXY, the probability of having a daughter who suffers from CF. In your genetic diagram, show the genotypes of the gametes and the genotypes and phenotypes of the offspring. genetic diagram parental genotypes BbXX x BbXY genotypes of gametes genotypes and phenotypes of offspring [5] [Total: 10]
18 Section B Answer one question. Circle the number of the question you have answered in the grid on the front cover. 10 (a) Describe the structure of photosystems and explain how a photosystem functions in cyclic photophosphorylation. [9] (b) Explain briefly how reduced NADP is formed in the light-dependent stage of photosynthesis and is used in the light-independent stage. [6] [Total: 15] 11 (a) Explain how meiosis and fertilisation can result in genetic variation amongst offspring. [7] (b) Explain, using examples, how the environment may affect the phenotype of an organism. [8] [Total: 15]................................................
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