Cell Biology

1. The diagram shows how vesicles are used to transport materials in a cell.

(a) (i) State the name of organelle A. [1]

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(ii) State the process occurring at B. [1]

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Answer

1. (a) (i) Golgi apparatus/complex/body Reject Golgi vesicle and Golgi unqualified. [1]

(ii) endocytosis/phagocytosis/pinocytosis Reject exocytosis. [1]

(b) fluidity of membrane allows change of shape/invagination/formation of vesicles;phospholipids can move / phospholipid bilayer makes membrane fluid/flexible;weak bonding between phospholipid tails;bends/kinks in the phospholipid tails prevent close packing;cholesterol affects membrane fluidity; [2 max]

Molecular Biology

1. (a) Define the active site of an enzyme. [1]

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(b) Explain how the active site promotes enzyme–substrate specificity. [2]

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(c) Outline possible effects of acids on enzyme activity. [2]

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2. Two foods were measured with a calorimeter to determine the energy in each. Five trials on potato chips and five trials on walnuts were performed. The results are shown in the table below.

(a) Calculate the mean energy for the walnut. [1]

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(b) Explain how this data shows which food had the greatest variation in its energy content. [2]

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(c) Both potato chips and walnuts contain lipids. State one function of lipids. [1]

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ANSWER

1)(a) region/site where a substrate binds [1]

(b) shape of active site matches that of the substrate; chemical properties/charges of active site attract the substrate; active site can change to induce fit of substrate; [2 max]

(c) changes the charge/ionization of amino acids/R-groups; changes 3-D structure (of active site)/tertiary structure / denatures enzyme; substrate no longer binds/fits so decreases activity; could increase activity if optimum pH of enzyme is acidic; [2 max]

2)

(a) 25.8 kJ g–1 (units needed) [1]

(b)a. walnut has the greatest variation in energy content;b. because the standard deviation/range (much) greater for walnuts than for potato chips;c. the small standard deviation/range for potato chips indicates that the data are clustered closely around the mean/the large standard deviation/range for

walnuts indicates that the data are spread out further from the mean;d. 68 % of the values will fall within one standard deviation of the mean which is 2.0 (kJ g–1) for walnuts but only 0.1 (kJ g–1) for the potato chip / OWTTE; [2 max](c) energy source/storage / insulation / provision of essential fatty acids / hormones / waterproofing / component of membranes / buoyancy / bile salts / protection of internal organs [1]

Only award marks to the first function if candidate gives more than one function.

Genetics

1. a) In a strain of soybeans, high oil content (H) in seeds is dominant to low oil content (h) and four seeds in a pod (F) is dominant to two seeds in a pod (f). A farmer crosses two soybean plants, both with high oil content and four seeds in a pod. The offspring have a phenotypic ratio of 9:3:3:1.

(i) Identify the genotypes of the soybean plants with high oil content and four seeds in a pod that were used in the cross. [1]

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(ii) Determine the genotypes of the gametes and offspring using a Punnett grid. [2]

(iii) Identify the phenotypes of each part of the phenotypic ratio. [2]

Ratio Phenotypes9

3

3

1

(b) The image shows the karyotype of a person who developed as a female.

(i) Deduce the reason for the person developing as a female. [1]

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(ii) Determine, with a reason, whether this karyotype shows that non-disjunction has occurred. [1]

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Answer

(a) (i) HhFf X HhFf / (both) HhFf; [1]

(ii)

all gametes shown correctly on Punnett grid;all offspring genotypes correct; [2]

(iii)

(b) (i) no Y chromosome [1]

(ii) yes as there is only one X chromosome/chromosome missing/only 45 chromosomes [1]

Ecology

1. (a) Distinguish between autotrophs and heterotrophs. [2]

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(b) Define saprotroph. [1]

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(c) State an external feature that is different in:(i) Cnidaria and Mollusca. [1]

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(ii) Mollusca and Annelida. [1]

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2. The greenhouse effect is a naturally occurring process.

(a) (i) State one greenhouse gas. [1]

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(ii) Explain how radiation of different wavelengths is involved in the greenhouse effect. [2]

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(b) The enhanced greenhouse effect can cause a rise in atmospheric temperature.

(i) Outline two consequences of a global temperature rise on arctic ecosystems. [2]

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(ii) Outline one effect of a temperature rise on plants. [1]

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Answer

1)(a) autotrophs make their own food/organic molecules/organic matter and heterotrophs feed on/obtain their food/organic molecules from other organisms; autotrophs use/require inorganic molecules/CO2 and heterotrophs require (complex) organic molecules; [2]

(b) an organism that lives on/in non-living/dead (organic) matter and secretes digestive enzymes/digestive juices into it / OWTTE [1]

(c) (i) Cnidaria have radial symmetry while Mollusca have bilateral symmetry; Cnidaria have tentacles/nematocysts/stinging cells while Mollusca do not; Mollusca (may) have a (hard) shell while Cnidaria do not; Mollusca have a mouth and anus while Cnidaria have only one opening; Mollusca have a muscular/large foot while Cnidaria do not; other valid external difference; [1 max]

(ii) Annelida are segmented while Mollusca are not (visibly segmented); Annelida may have bristles/chetae/chaetae while Mollusca do not; Mollusca (may) have a (hard) shell while Annelida do not; Mollusca have a muscular/large foot while Annelida do not; other valid external difference; [1 max] 2) (a) (i) carbon dioxide / methane / oxides of nitrogen / water vapour / ozone / CFCs [1]

(ii) incoming shorter-wave radiation/UV/visible passes through Earth’s atmosphere; converted to longer-wave radiation/heat/infrared;atmosphere absorbs/traps longer-wave radiation/infrared/heat; [2 max]Answers can be given in the form of an annotated diagram.Answers must specify long wave/infrared/heat and short wave radiation.

(b) (i) increased rates of decomposition (of detritus in permafrost);expansion of the range of habitats available to temperate species;loss of ice habitat;changes in distribution of prey species affecting higher trophic levels;increased success of pest species/pathogens;rise in sea levels; [2 max]Mark only the first two answers given.

(ii) rate of photosynthesis increases as temperature increases;rate of transpiration increases as temperature increases;shift in plant distribution / OWTTE; [1 max

Evolution and Biodiversity

1. The probability of extinction of a species increases if the population is small with low genetic variation.

(a) State two processes that cause population size to decrease. [2]

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(b) Explain how meiosis promotes variation. [3]

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Answer

1)(a) mortality / fatal disease / predation / competition / other cause of death; emigration; [2] (b) (in prophase I) crossing over/chiasmata formation (between homologous chromosomes); random alignment of homologues/bivalents in metaphase I / independent assortment of homologues / chromosomes; second division of meiosis separates alleles further; combinations of alleles in gametes is unlimited/2n; [3 max]

Human Physiology

1. (a) Outline the mechanisms involved in the control of heartbeat. [3]

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(b) Explain how the direction of blood flow in the heart is controlled. [2]

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2. (a) Outline the process of in vitro fertilization (IVF). [3]

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(b) The diagram below shows a small portion of the tissue in a transverse section of a testis.

(i) Identify the cell labelled X. [1]

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(ii) Outline the function of this cell. [1]

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(c) Explain how meiosis results in genetic variation in gametes. [2]

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3.(a) Blood transports molecules throughout the body. State where the blood absorbs

(i) hormones. [1]

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(ii) carbon dioxide. [1]

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(b) Describe three features of alveoli that adapt them to gas exchange. [3]

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. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .(c) Explain how the structure of capillaries relates to their functions. [3]

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4. (a) Label I, II, III and IV on the diagram of the human elbow. [2]

[© International Baccalaureate Organization, 2013]

(b) Outline the functions of I and III. [2]

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4. The diagram shows the structure of a nephron.

(a) (i) Label I and II. [1]

[© International Baccalaureate Organization, 2013]

(ii) Outline the function of III. [1]

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(b) Estimate the content of glomerular filtrate and urine of a healthy person by completing the following table. [2]

Plasma proteins /mg 100 ml–1

Glucose /mg 100 ml–1

Urea /mg 100 ml–1

Blood plasmain renal artery

740 90 30

Glomerularfiltrate

90

Urine(c) Explain the role of the medulla and the collecting duct of the kidney in the maintenance of the water balance in blood. [3]

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ANSWER

1)(a) myogenic contraction / muscles contract without stimulus from a nerve;pacemaker/SA node initiates each heart beat/stimulates atria to contract;nerves carry impulses from the brain to speed up and slow down the heart;medulla (of the brain) monitors blood pressure;epinephrine/adrenaline increases rate/strength of contractions;[3 max]

(b) valves open/close due to blood pressure differences;valves prevent backflow/only allow unidirectional flow;atrioventricular valves between ventricles and atria;semilunar valves between arteries and ventricles; [2 max]Accept mitral/bicuspid and tricuspid in place of atrioventricular.Accept aortic and pulmonary in place of semilunar valves.

2)(a) mother receives hormone treatment/FSH to stimulate egg development;eggs and sperm collected/harvested / eggs taken from ovary;egg fertilized outside the body/in a dish/in a lab;develops into embryo;embryo(s) implanted (artificially) in mother’s body/uterus;

[3 max]Do not accept egg/fertilized egg/zygote implanted.

(b) (i) Sertoli cell / nurse cell [1]

(ii) nourishes maturing sperm(atozoa) / protects sperm from lymphocytes [1]

(c) crossing over in prophase 1/between chromatids;random orientation of bivalents/homologous pairs in metaphase 1;random orientation of chromatids/chromosomes in metaphase 2; [2]

3)(a) (i) endocrine glands / named endocrine gland (e.g. pancreas/hypothalamus/pituitary/ovary/testes) [1]Do not accept gland alone.

(ii) cells / tissues / named cells/tissue (e.g. muscles / muscle tissue / muscle cells /epithelial tissue / other reasonable example) [1]Do not accept alveolus or named organ.

(b) a. high density of capillaries surrounding alveoli;b. large surface area due to shape / large number of alveoli;c. thin walls / walls one cell thick; (do not accept membranes)d. moist layer covering the (inner) surface of the alveoli; [3 max]

Award [2 max] for a list of features.

(c) a. capillaries walls thin/one cell thick for better diffusion;(Do not accept membranes)b. small diameter/narrow lumen to fit into small places/between cells;c. small diameter for greater surface area for molecular exchange;d. pores between cells of the walls so plasma can leak out;e. pores between cells of the walls allow phagocytes/immune components to enter tissues;f. only one red blood cell allowed to pass at a time for efficient oxygen uptake; [3 max]

4)(a) Award [1] for two correct labels.I. biceps;II. humerus;III. cartilage;IV. synovial fluid/synovial cavity; [2 max]

(b) I. (contracts to) move/raise forearm/lower arm/radius / flex/bend arm at elbow;II. reduces friction / prevents bone rubbing on bone / absorbs shock; [2]Do not accept answers that do not specify the movement caused by I, or state that I lifts the arm.Do not allow ECF answers.

5)(a)

(i)I: glomerulus;II: (descending limb of) loop of Henle;(both needed) [1]

(ii) III: selective re-absorption of glucose/minerals/amino acids/water/ useful substances;absorption by active transport/using ATP of glucose/minerals/ amino acids/useful substances; [1 max]

b)

[2]Award [1] for each correct row.

(c) collecting duct has water channels/aquaporins/is permeable to water;high solute concentration of medulla / medulla is hypertonic;

plasma proteins /

mg100ml –1

glucose/mg100ml–1

urea / mg 100 ml –1

Blood plasma in renalartery

740 90 30

Glomerular filtrate

0 90 30(or slightlyless)

Urine 0 0 (much) greater than 30

reabsorption of water allows excretion of concentrated urine (antidiuresis);secretion of ADH/vasopressin increases permeability of collecting duct to water / vice versa; [3 max]

Nucleic acids

1. (a) DNA replication involves a number of enzymes including DNA polymerase. Identify one other enzyme involved in DNA replication. [1]

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(b) Explain the role of Okazaki fragments in DNA replication. [2]

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(c) The diagram below shows the process of transcription

(i) Label the sense and antisense strands. [1]

(ii) Draw an arrow on the diagram to show where the next nucleotide will be added to the growing mRNA strand. [1]

Answer

1)(a) helicase / RNA primase / (DNA) ligase [1]

(b) DNA fragments/sections (formed) on the lagging strand;because replication must be in the 5–3 direction;replication starts repeatedly and moves away from replication fork; [2 max]

(c) (i) both strands clearly labelled [1]Check carefully whether the correct strand has been labelled if the labelsare shown in helical parts of the DNA.Reject if the sense strand label points to the mRNA.

(ii) a clearly drawn arrow pointing at the free 3 end of the mRNA strand or to the first free nucleotide on the antisense strand to the left of the mRNA or to a nucleotide added by the candidate to the left hand end of the mRNA [1]

Metabolism, Respiration and Photosynthesis

1. The following diagram shows the synthesis and regulation of some amino acids.

(a) State the type of inhibition shown in this diagram. [1]

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(b) Explain how this type of regulation could affect the synthesis of an amino acid. [2]

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(c) Outline the models that describe how substrates bind to enzymes. [2]

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ANSWER

1)(a) end-product/non-competitive/(negative) feedback inhibition [1]

(b) amino acid/end product produced if used up/not enough present; production stops if amino acid/end product unused/accumulates/in excess; amino acid/end product changes active site of (first) enzyme of pathway; (this is an example of) negative feedback; [2 max]

(c) lock-and-key where substrate (exactly) fits the active site of the enzyme/where substrate is complementary to the active site; induced fit where active site/substrate changes shape so substrate can bind/fit; [2]

Plant Biology

1. The diagram shows a cross section of a leaf.

(a) Identify the tissues labelled X, Y and Z.

(i) X: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(ii) Y: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(iii) Z: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

(b) Outline two adaptations of xerophytes that help to reduce transpiration from the leaves. [2]

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(c) Angiospermophyta have vascular tissue (xylem and phloem) that bryophyta lack. Suggest advantages that vascular tissue confers. [3]

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ANSWER

1)(a)

(i) palisade mesophyll/layer [1]

(ii) guard cells [1]

(iii) vascular bundle/tissue / xylem (vessel) [1]

(b)a. reduced/few leaves/needles to lower surface area;b. rolled leaves to increase humidity around stomata;c. spines to collect water;d. waxy cuticle;e. fewer stomata/closing of stomata;f. stomata in pits to increase humidity;g. CAM metabolism so stomata can remain closed during light;h. C4 photosynthesis so stomata can remain closed during light; [2 max]

(c) a. would make it easier to stand upright (against gravity)/structural support / allows (angiospermophytes) to be bigger;b. could put leaves higher in the air to get more sunlight;

c. transport of water supply/nutrients from roots to other tissues;d. could (more efficiently) transport/translocate sugars/food from leaves for storage; [3 max]