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© Harry Leather and Jan Leather 2014

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Maintaining a Balance: Solutions Explained

Question 1 Enzymes are biological catalysts. This means

A. they lower the activation energy of biochemical reactions and cannot be reused B. they increase the activation energy of biochemical reactions and can be reused C. they increase the activation energy of biochemical reactions and cannot be reused D. they lower the activation energy of biochemical reactions and can be reused

Question 1 Solution: D Activation energy refers to the energy required to start a reaction. Enzymes lower the activation energy, therefore an organism’s body temperature can be lower. Enzymes can be reused. Question 2 Which of the following graphs best represents an enzyme controlled biochemical reaction as temperature is increased?

Question 2 Solution: B Enzymes have an optimal temperature. Reaction rates will decrease on either side of the optimal temperature. Question 3 All enzymes

A. are made of the same amino acids B. contain a non-‐protein co-‐factor such as a zinc or iron C. are proteins D. have the same shape

Question 3 Solution: C Enzymes are proteins and are made of amino acids. Different enzymes are made of different amino acids therefore they have different shapes.



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Question 4 Lactase is an enzyme produced by human babies. It catalyses the breakdown of lactose to glucose. 5 ml of lactose syrup and 0.5 ml of lactase were added to two test tubes. Test tube A was incubated at 37oC while test tube B was incubated at 100oC. After 10 minutes the amount of glucose present in test tube A would be

A. higher than test tube B because the enzyme in test tube B had been denatured B. lower than test tube B because the enzyme in test tube A had been denatured C. lower than test tube B because there would be fewer collisions between the lactase and the

lactose D. higher than test tube B because there would be more collisions between the lactase and the

lactose Question 4 Solution: A The number of collisions between lactase and lactose would be higher in test tube B but the enzyme would have been denatured by the high temperature of incubation. Question 5 Each enzyme can only catalyse a specific reaction because

A. enzymes are carbohydrates B. enzymes are able to alter their shape to allow them to bind with many different substrates C. part of the enzyme molecule has a particular shape that allows it to bind with a specific

substrate D. enzymes have different optimal temperatures

Question 5 Solution: C Enzymes are proteins with a specific shape. This shape allows bonds to form with substrate that has a complementary shape. Question 6 In the diagram below

A. G is an enzyme-‐substrate complex B. F is the reactant C. E is the product D. H is the enzyme

Question 6 Solution: A E is the reactant, F is the enzyme and H is the product.

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Question 7 In an experiment students bubbled carbon dioxide through water. Measurements showed that the pH of the water decreased as carbon dioxide was added. This indicated that

A. the water became more acidic as dissolved carbon dioxide increased B. the water became less acidic as dissolved carbon dioxide increased C. the water became more acidic as dissolved carbon dioxide decreased D. dissolved carbon dioxide did not change the acidity of water

Question 7 Solution: A Bubbling carbon dioxide through water increases the amount that dissolves in water. Lowering the pH shows increased acidity. Question 8 The internal environment includes

A. blood plasma B. contents of the intestines C. air in the lungs D. urine in the bladder

Question 8 Solution: A All others are beyond the membranes of the body and therefore in the external environment. Question 9 Homeostasis refers to the maintenance of a relatively stable internal environment. A variable that is within a narrow range within the human body is

A. urea concentration in the blood B. rate of breathing C. blood pressure D. sweat production

Question 9 Solution: A The other items vary to allow the body to maintain homeostasis. Question 10 Homeostasis

A. occurs only in mammals B. provides the conditions for optimal enzyme activity allowing for a rate of metabolism that

can sustain life C. reduces the rate of metabolism allowing for more efficient use of resources D. occurs only in endotherms

Question 10 Solution: B Homeostasis occurs not just in mammals or endotherms. It results in optimal conditions for metabolic activity.



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Question 11 The two stages of homeostasis are

A. Stage 1 increasing a change from the stable state and Stage 2 decreasing a change from the stable state

B. Stage 1 counteracting changes from the stable state and Stage 2 detecting changes from the stable state

C. Stage 1 detecting changes from the stable state and Stage 2 increasing the change from the stable state

D. Stage 1 detecting changes from the stable state and Stage 2 counteracting changes from the stable state

Question 11 Solution: D When a change occurs it must be identified and then brought back to the best conditions for metabolic activity. Question 12 Which is not an example of a body response that results from negative feedback?

A. rising blood sugar levels after a meal B. rising blood sugar levels several hours after a meal C. a rise in breathing rate during exercise D. a decrease in urea concentration in the blood

Question 12 Solution: A This is a consequence of sugar being absorbed from the intestines. Over time the body will respond to remove sugar from the blood to maintain a constant sugar level. Question 13 When a baby suckles, nerve impulses are sent to the spinal cord and hypothalamus. The hypothalamus then stimulates the pituitary gland to produce more prolactin leading to an increase in milk production. This is an example of

A. homeostasis B. negative feedback C. positive feedback D. negative response

Question 13 Solution: C The response amplifies rather than counteracts the original stimulus. Question 14 Which of the following statements about the nervous system is correct?

A. Afferent neurons carry sensory information from the brain B. Afferent neurons carry sensory information to the spinal cord C. Efferent neurons carry motor information from sense organs D. Efferent neurons carry motor information from effector cells

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Question 14 Solution: B Afferent or sensory neurons carry sensory information to the CNS of which the spinal cord is a part. Question 15 Which of the following statements about the nervous system is correct?

A. The peripheral nervous system consists only of sensory neurons B. The motor division consists of an autonomic nervous system and a somatic system C. The involuntary system is under conscious control D. Sensory neurons carry information to sense organs

Question 15 Solution: B This is a fact. The others are all incorrect statements. Question 16 The distinguishing feature of endocrine system is:

A. hormones control all aspects of growth of the body B. hormones are produced in large amounts and circulate in the blood C. hormones are produced by endocrine glands and are secreted directly into the bloodstream D. hormones are produced by endocrine glands and are carried directly to specific target

organs Question 16 Solution: C Hormones control many of the body’s systems and have long-‐term effects. They are carried all around the body but specific hormones are detected by target organs. Question 17 Which one of the following statements is incorrect?

A. Life on Earth exists at temperatures ranging from negative 40oC to 120oC but individual species can only exist in a narrower range of temperatures

B. Life is limited at extremes of temperature because proteins are denatured C. Life is limited at temperatures below 0oC because ice crystals tend to form in cells D. Life is limited at temperatures above 45oC because enzymes tend to denature

Question 17 Solution: B Proteins are not denatured by low temperatures rather the reaction rate is decreased because there are less collisions between reactants. All other statements are correct. Question 18 Which of the following does not allow regulation of body temperature on a daily basis?

A. dilation or constriction of superficial blood vessels B. moulting – loss of body hair in summer C. increased sweating D. contraction or relaxation of muscles at base of hairs, allowing the hairs to stand up or lie

down



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Question 18 Solution: B Moulting does allow temperature regulation but on a seasonal rather than daily basis. Question 19 Which is the greatest source of heat loss for a human being?

A. radiation B. evaporation C. conduction to air D. conduction to a cold surface

Question 19 Solution: A Radiation accounts for about 60% of heat loss hence the need for clothing to reduce this source of heat loss. Question 20 With respect to mammals and birds, which one of the following is correct?

A. all have a constant body temperature of 37°C B. all are ectothermic C. all are endothermic D. all are ectothermic and homeothermic

Question 20 Solution: C This is a definition question. Ectothermic refers to the ability to produce heat within the body. Question 21 Ectothermic animals can gain heat through all but one of the following:

A. direct radiation B. evaporation C. conduction D. reflected radiation

Question 21 Solution: B Evaporation only results in heat loss. The other alternatives can allow heat loss or gain. Question 22 Directing blood flow to and away from the body surface allows heat loss and/or gain depending on an organism’s body temperature. Flow is regulated by

A. constriction of blood vessels found deep within the body B. constriction of peripheral veins C. constriction of capillaries allows blood to be redirected D. relaxation or constriction of arteriole walls

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Question 22 Solution: D Peripheral veins are thicker than capillaries but have little control over blood flow and capillaries with one cell thick walls have none. It is the muscular walls of arteries and arterioles that can control blood flow. Question 23 Which of the following adaptations would enable plants to live in a cold environment?

A. ability to drop leaves for parts of the year B. ability to open and close stomata C. the presence of large flat leaves D. seeds that germinate during winter

Question 23 Solution: A This reduces the surface area of the plant over which heat can be lost. Large flat leaves would increase the area of over which heat could be lost, and seeds germinating in winter would have a lower survival rate than those germinating in warmer months. Evaporation of water through stomata increases heat loss. Question 24 Blood consists of a number of components. By volume the largest component is

A. red blood cells B. plasma C. white blood cells D. platelets

Question 24 Solution: B Plasma is 90% water. Question 25 Oxygen is carried in the blood mainly

A. dissolved in the plasma as bicarbonate ions B. within red blood cells C. combined with haemoglobin in red blood cells D. on the surface of white blood cells

Question 25 Solution: C Question 26 Carbon dioxide is carried in the blood mainly

A. dissolved in the plasma as bicarbonate ions B. within red blood cells C. combined with haemoglobin in red blood cells D. on the surface of white blood cells

Question 26 Solution: A



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Question 27 Haemoglobin

A. allows more carbon dioxide to be carried in the blood B. allows more oxygen to be carried in the blood C. binds irreversibly with carbon dioxide D. binds irreversibly with oxygen

Question 27 Solution: B Haemoglobin combines with oxygen in the lungs and is released by haemoglobin in the tissue. Question 28 Both arteries and veins

A. mainly carry oxygenated blood B. contain valves C. have a three-‐layer wall – an endothelium, muscular layer and non-‐elastic connective tissue

layer D. carry blood both away from and towards the heart

Question 28 Solution: C Arteries except the pulmonary artery carry oxygenated blood whereas veins except the pulmonary vein carry deoxygenated blood. Veins carry blood towards the heart and arteries do not contain valves. Question 29 As blood travels through the capillaries of the lung

A. oxygen binds strongly to haemoglobin B. carbon dioxide binds strongly to haemoglobin C. nitrogen binds strongly to haemoglobin D. glucose binds strongly to haemoglobin

Question 29 Solution: A Carbon dioxide is transported as bicarbonate ions in the plasma. Question 30 Energy is made available to cells through respiration. Aerobic respiration

A. requires carbon dioxide as a reactant and produces oxygen as a waste product B. requires oxygen as a reactant and produces carbon dioxide as a waste product C. releases less energy than anaerobic respiration D. results in the release of oxygen which in turn lowers the pH of the blood

Question 30 Solution: B Anaerobic respiration releases less energy than aerobic respiration and it is the release of carbon dioxide that results in a decrease in pH of the blood.

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Question 31 Movement of materials through flowering plants occurs through phloem and xylem tissue. Both mature xylem cells and phloem cells

A. are living B. contain chloroplasts C. contain cytoplasm D. have a cell wall

Question 31 Solution: D Mature xylem cells are dead and do not contain chloroplasts or cytoplasm. Parts of the cell walls remain. Phloem cells are living, have cell walls and contain cytoplasm. Question 32 Movement through the xylem involves

A. forces of cohesion between water molecules and the walls of the xylem B. forces of adhesion between water molecule and water molecule C. the evaporation of water from the leaf surface D. energy released during cellular respiration in the xylem cells

Question 32 Solution: C Adhesion refers to forces of attraction between water molecules and the walls of the xylem vessels, while cohesion refers to the force of attraction between one water molecule and another. The energy source for movement in the xylem comes from the heat of the sun evaporating water at the leaf surface. Question 33 The pressure-‐flow or mass-‐flow model of phloem transport involves

A. a sugar source in photosynthetic tissue and a sugar sink in storage areas B. a sugar sink in photosynthetic tissue and a sugar source in storage areas C. movement in one direction only D. evaporation of water from the leaf surface

Question 33 Solution: A Movement can occur both up and down the stem and requires metabolic energy rather than evaporation of water from the leaf surface. Question 34 Which of the following statements is not a reason why the concentration of water in cells should be maintained within a narrow range?

A. Water is the major solvent for metabolic reactions in living cells B. Water is a reactant in many biological reactions C. Water expands when it freezes D. Water is a good transport material and has a high specific heat



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Question 34 Solution: C This is a property of water but is not related to why its concentration should be maintained within a narrow range. All other alternatives maintain conditions within the cell for optimal activity. Question 35 Metabolic wastes

A. are major reactants in chemical reactions occurring within cells B. increase the rate of metabolic reactions within cells by combining with enzymes C. include nitrogenous wastes that are toxic to cells D. increase the permeability of cell membranes resulting in an increase in the rate of metabolic

reactions within cells Question 35 Solution: C Metabolic wastes are products, not reactants, in chemical reactions within cells. Their accumulation results in a decrease in metabolic activity. Question 36 The kidneys in fish and mammals are responsible for

A. the production and excretion of urea B. the removal of nitrogenous wastes and maintenance of water levels within the organism C. the excretion of salt and conservation of water within the organism D. the excretion of water and conservation of salt within the organism

Question 36 Solution: B Nitrogenous wastes are the by-‐products of the breakdown of proteins and nucleic acids by all cells, especially liver cells. The kidneys maintain water balance by adjusting the amount of water and salt that is reabsorbed. Question 37 Goannas excrete their nitrogenous waste mainly in the form of uric acid. This is an adaptation to

A. conserve water B. increase water loss C. conserve salt D. increase excretion of salt

Question 37 Solution: A Uric acid is insoluble and is excreted as a paste containing very little water. Question 38 Marine and freshwater fish produce

A. concentrated urine B. dilute urine C. different concentrations of urine with marine fish producing more dilute urine D. different concentrations of urine with marine fish producing more concentrated urine

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Question 38 Solution: D Marine fish live in an environment containing a higher salt concentration than their body fluids therefore they tend to lose water by osmosis. Producing concentrated urine is an adaptation to reduce water loss. Question 39 Many organisms are unable to effectively remove nitrogenous wastes by osmosis and diffusion because

A. diffusion occurs too slowly resulting in an accumulation of nitrogenous wastes within the organism

B. osmosis occurs too slowly resulting in an accumulation of nitrogenous wastes within the organism

C. osmosis occurs faster than diffusion therefore the organism would lose too much water D. diffusion occurs faster than osmosis therefore the organism would lose too much water

Question 39 Solution: A Osmosis refers to the movement of water, not nitrogenous waste. Question 40 The diagram below shows the movement of molecules across a semi-‐permeable membrane.

The movement of molecules occurs by A. diffusion B. osmosis C. passive transport D. active transport

Question 40 Solution: D The molecules are moving from where they are in low concentration to where they are in high concentration.



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Question 41 The diagram below is of a mammalian nephron.

As the fluid within the nephron passes from A to B

A. the urea concentration decreases B. the glucose concentration decreases C. the protein concentration decreases D. the concentration of urea and glucose increases

Question 41 Solution: B Glucose is reabsorbed back into the blood. Question 42 Fluid travels through the nephron in the following order:

A. glomerulus to Bowman’s capsule to proximal tubule to descending tubule to ascending tubule to distal tubule to collecting duct

B. Bowman’s capsule to glomerulus to proximal tubule to descending tubule to ascending tubule to distal tubule to collecting duct

C. glomerulus to Bowman’s capsule to proximal tubule to ascending tubule to descending tubule to distal tubule to collecting duct

D. Bowman’s capsule to glomerulus to descending tubule to ascending tubule to distal tubule to proximal tubule to collecting duct

Question 42 Solution: A Question 43 Anti-‐diuretic hormone is secreted when

A. blood pressure and blood volume decrease B. a person drinks a large volume of water C. the solute concentration of the blood increases D. the solute concentration of the blood decreases

Question 43 Solution: C ADH acts on the distal tubules and collecting ducts, resulting in greater reabsorption of water.

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Question 44 Both homeostasis and enantiostasis

A. maintain an organism’s internal environment close to ideal conditions B. maintain an organism’s internal environment over a narrow range C. allow an organism to function in a changing environment D. allow organisms to function at optimal efficiency

Question 44 Solution: C Homeostasis maintains the internal environment over a narrow range close to ideal conditions for cellular functioning whereas enantiostasis results in wider fluctuations that allow the organism to function but not necessarily at optimal efficiency. Question 45 Which of the following is not an adaptation to reducing water loss for plants living in a dry environment?

A. waxy leaves B. sunken stomata C. hairy leaves D. stomata that open during daylight

Question 45 Solution: D Water evaporates from open stomata. Stomata that are open during the day will lose more water. Question 46 The best definition of biological evolution is:

A. when one species changes into another species B. change in the gene pool of a population over many generations C. when species become extinct D. when one species changes into two new species

Question 46 Solution: B Evolution may occur within a population or between populations. It may or may not result in new species or extinction. Question 47 Which of the following is an example of the impact of physical conditions in the environment on the evolution of an organism?

A. the extinction of the Tasmanian tiger after the introduction of the dingo to Australia B. the increase in number of bacteria that are resistant to antibiotics C. Wollemi pines that are virtually identical to ancient fossil forms D. fossilised teeth of ancient kangaroos that were unspecialised whereas modern kangaroo

teeth are specialised for grinding grasses that grow in dry climates



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Question 47 Solution: D Physical conditions refer to the environmental conditions such as climate, temperature and availability of water. Question 48 Which of the following is an example of the impact of the chemical conditions in the environment on the evolution of an organism?


teeth are specialised for grinding grasses that grow in dry climates Question 48 Solution: B Chemical conditions refer to the environmental conditions such as the presence of salt, heavy metals, pH, antibiotics and pesticides. Question 49 An example of the impact of competition for resources in the environment on the evolution of an organism is


teeth are specialised for grinding grasses that grow in dry climates Question 49 Solution: A The Tasmanian tiger and the dingo both ate the same food. The dingo hunted in packs and was therefore a more efficient predator. Question 50 The following points summarise the steps involved in natural selection. They are not in the correct order.

1 over time there is an increase in frequency of individuals with the favoured characteristic 2 genetic and phenotypic variation exists in a population 3 offspring inherit the favoured characteristic from their parent 4 there is a struggle to survive 5 more individuals with favoured characteristics survive and reproduce than those individuals

lacking the favoured characteristic 6 some individuals have characteristics that increase their chance of survival in the

environment

The correct order of events in natural selection is A. 3, 4, 2, 5, 1, 6 B. 6, 3, 1, 5, 2, 4

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C. 2, 4, 6, 5, 3, 1 D. 1, 3, 5, 2, 4, 6

Question 50 Solution: C Variation exits, there is a struggle to survive, differential reproduction, offspring inherit, change in allele frequency. Question 51 It has been suggested that reptiles evolved from fish-‐like ancestors. 375-‐million-‐year-‐old fossils of Tiktaalik rosteae have been found in Canada. These fossils suggest that Tiktaalik rosteae had scales, fins and a lower jaw similar to modern fish. Other features such as the skull, neck and forelimbs are more similar to early reptiles. Given the similarity to both fish and reptiles, Tiktaalik rosteae is an example of

A. convergent evolution B. interbreeding C. an index fossil D. a transitional form

Question 51 Solution: D The fossils show characteristics of both fish and reptiles, therefore it is an intermediate form. Index fossils are used to date sediments; they are of organisms that had a wide distribution for a short period of time. Convergent evolution refers to organisms that have been subject to the same selection pressure but do not have a recent common ancestor. Question 52 The study of the distribution of organisms in relation to the movement of continental plates is called

A. biodiversity B. convergent evolution C. comparative anatomy D. biogeography

Question 52 Solution: D Biodiversity refers to the diversity of organisms, convergent evolution refers to organisms that have been subject to the same selection pressure but do not have a recent common ancestor and comparative anatomy involves comparing the physical structures of different organisms. Question 53 Comparative embryology suggests that

A. as vertebrates have different embryos they do not have a common ancestor B. as vertebrates have similar embryos they have been subject to the same selection pressures C. as vertebrates have different embryos they have been subject to different selection

pressures D. as vertebrates have similar embryos they have a common ancestor



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Question 53 Solution: D This suggests a fundamental step in the development of an ancestral organism that has been inherited by all groups therefore a common ancestor. Vertebrate embryos are similar but they have not been subject to the same selection pressures. Question 54 The forelimbs of a frog, a whale, a lion, a bat and a human have the same basic structure. This suggests

A. these organisms live in the same environment B. these organisms were subject to similar selection pressures C. convergent evolution D. divergent evolution

Question 54 Solution: D This suggests that in the past there was a common ancestor and that adaptive radiation has occurred. Question 55 The table below shows a comparison of the α-‐globin polypeptide between humans and a number of other vertebrates newt cow carp kangaroo shark Number of amino acid different to humans in α-‐globin

62 17 68 27 79

Based on this information:

A. newts and carp share a more recent common ancestor B. humans share a more recent common ancestor with kangaroos than sharks C. humans share a more recent common ancestor with newts than cows D. these organisms do not share a recent common ancestor

Question 55 Solution: C The smaller the difference, the more recent the common ancestor. These results compare the similarity between humans and these organisms not the similarity between the other organisms and each other. Question 56 Sharks and dolphins live in water. Both have a similar shape but sharks are fish and dolphins are mammals. This is an example of

A. convergent evolution B. divergent evolution C. adaptive radiation D. mimicry

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Question 56 Solution: A Both the shark and the dolphin live in water and are subject to the same selection pressure. Question 57 Which of the following did not contribute to Mendel’s success?

A. the offspring of a large number of crosses were observed B. peas can be grown from cuttings C. peas are easy to grow and produce many offspring D. peas can self fertilise

Question 57 Solution: B Cuttings are a form of asexual reproduction. Question 58 Mendel ensured the reliability of his results by

A. using easy-‐to-‐grow peas B. controlling the fertilisation process C. studying characteristics that had two easily identifiable forms D. using thousands of plants in each experiment

Question 58 Solution: D Increasing the number in the experiment increases statistical reliability. Each of the other alternatives contributed to the success of Mendel’s experiments but not to statistical reliability. Question 59 In watermelons, the presence of spotting on the skin is controlled by a single gene with two alleles. The allele coding for spots has dominant expression. If a heterozygous plant is crossed with a plant with solid colour melons, the chance that the offspring produces solid colour melons is:

A. 100% B. 50% C. 25% D. 0%

Question 59 Solution: B Let S = allele for spotting and s = allele for solid. P genotype is Ss x ss gametes gam

etes

S s

s Ss ss

Therefore 50%.



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Question 60 Tay Sachs disease is an inherited progressive neurological disorder in humans. Below is a pedigree of a family with a history of Tay Sachs disease. This pedigree indicates that the pattern of inheritance of Tay Sachs disease is

A. non-‐sex-‐linked dominant B. non-‐sex-‐linked recessive C. sex-‐linked dominant D. sex-‐linked recessive

Question 60 Solution: B Two parents give rise to a different offspring therefore the pattern of inheritance is recessive. If it was sex-‐linked then the father must also show the trait. Question 61 Mendel self-‐pollinated a tall pea plant. 750 of the offspring were tall plants and 250 were short plants. These results indicate that

A. short offspring are heterozygous for height B. all tall offspring have the same genotype C. tall offspring may have different genotypes D. short offspring may be heterozygous or homozygous for height

Question 61 Solution: C Parents are tall but some of their offspring are short, therefore short individuals are homozygous for short height. The parents must be heterozygous, therefore their tall offspring may be heterozygous or homozygous for height. Question 62 Peas may produce flowers that are either violet or white. In this example

A. the gene for violet colour has two alleles, one coding for white and one coding for colour B. the gene for flower colour has two alleles, one coding for violet and one coding for white C. the allele for flower colour has two genes, one coding for violet and one coding for white D. the allele for violet colour has two genes, one coding for white and one coding for colour

Question 62 Solution: B Gene refers to the general characteristic whereas allele refers to the alternative forms of the characteristic.

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Question 63 Individuals with the same phenotype

A. must be related B. must have the same genotype C. may have the same genotype D. must have the same parents

Question 63 Solution: C Individuals showing the dominantly expressed phenotype may be heterozygous or homozygous and therefore may have the same or different genotypes. Question 64 Boveri contributed to the ‘Sutton-‐Boveri Chromosome Theory’ by

A. concluding that chromosomes are carriers of hereditary units B. showing that a complete set of chromosomes is required for the normal development of an

organism C. suggesting that Mendel’s results could be explained if genes were parts of chromosomes D. showing that chromosomes are distinct entities

Question 64 Solution: B The other alternatives refer to the work of Sutton. Question 65 Chromosomes are made of

A. DNA and carbohydrate B. DNA and RNA C. DNA and protein D. RNA and protein

Question 65 Solution: C Chromosomes are 40% DNA and 60% histone – a protein. Question 66 Which of the following best describes the structure of DNA?

A. two strands of DNA nucleotides held together by bonds between deoxyribose sugar units B. two strands of DNA nucleotides held together by bonds between nitrogen bases C. two strands of DNA nucleotides held together by bonds between phosphate units D. two strands of RNA nucleotides held together by bonds between phosphate units

Question 66 Solution: B The building blocks of DNA are DNA nucleotides. Deoxyribose sugar and phosphate form the backbone of the structure.



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Question 67 Twenty per cent of the nucleotides in human DNA are guanine. What is the percentage of thymine?

A. 10% B. 20% C. 30% D. 40%

Question 67: C 20% guanine therefore 20% cytosine, as cytosine binds with guanine. This leaves 60% for adenine and thymine, half of which will be thymine. Question 68 Gametes are formed when a cell undergoes meiosis. Gametes

A. contain a quarter of the number of chromosomes as the parent cell B. contain half the number of chromosomes as the parent cell C. contain the same number of chromosomes as the parent cell D. contain double the number of chromosomes as the parent cell

Question 68 Solution: B Cells containing one of each homologous pair are the result of meiosis. Question 69 Offspring of sexually reproducing organisms show greater genetic variation than offspring of asexual reproduction. This increased genetic variation is due to

A. random segregation of chromosomes during meiosis B. mutation C. DNA replication D. polypeptide production

Question 69 Solution: A Random segregation of chromosomes results in gametes with a different combination of alleles. Mutation results in genetic variability, but it occurs in both sexually and asexually reproducing organisms. Question 70 Colour blindness is more common in men than women. This is because

A. the gene locus for colour blindness is found on the Y chromosome B. the gene locus for colour blindness is found on the X chromosome C. the gene locus for colour blindness is found on an autosome D. colour blindness shows a dominant pattern of inheritance in men but shows a recessive

pattern of inheritance in women

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Question 70 Solution: B It is more common in men than women because as males have only one X chromosome the presence of one allele for colour blindness will result in its expression. Females have two X chromosomes therefore two alleles for colour blindness must be present before it is expressed. Question 71 A pedigree is shown below.

The pattern of inheritance shown in the pedigree could be

A. X-‐linked recessive or non X-‐linked recessive B. X-‐linked dominant or non X-‐linked dominant C. X-‐linked recessive or X-‐linked dominant D. non X-‐linked dominant only

Question 71 Solution: B It cannot be X-‐linked recessive or non X-‐linked recessive as II4 and II5 do not show the trait. Question 72 ABO blood grouping is controlled by a single gene that has three alleles.

IA = presence of protein A on red blood cells IB = presence of protein B on red blood cells i = lack of protein A or B on red blood cells

IAIB individuals have both A and B proteins on red blood cells. IA and IB show dominant expression over i. If the mother has protein A on her red blood cells and the father has protein B on his red blood cells it is possible for their child to

A. have neither A nor B proteins on red blood cells B. have either A or B proteins on red blood cells C. have both A and B proteins on red blood cells D. have all of the above

Unaffected female Affected female

Unaffected male Affected male

Key



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Question 72 Solution: D Parents could be homozygous or heterozygous with an i. If both parents are heterozygous, i.e. IAi and IBi, then it is possible to produce an ii child. Question 73 When Himalayan rabbits are born they have white fur. If these rabbits are reared in environmental conditions of 20oC or less the hair at the tips of their ears, nose, tail and feet become black. If they are reared in environmental conditions of above 30oC the tips remain white. This is an example of

A. codominance B. X linkage C. mutation D. environment affecting gene expression

Question 73 Solution: D Temperature is affecting the production of pigment. Question 74 The following points summarise the steps involved in DNA replication. They are not in the correct order.

1 DNA double helix 2 two DNA double helices 3 matching bases pair up 4 strands separate

The correct order of events in DNA replication is A. 4, 2, 3, 1 B. 1, 4, 3, 2 C. 2, 4, 3, 1 D. 1, 4, 2, 3

Question 74 Solution: B The process begins with a DNA double helix. The bases are exposed when hydrogen bonds between the base pairs break. This separates the strands and allows matching bases to pair with the exposed bases resulting in two DNA double helices. Question 75 The following points summarise the steps involved in the production of polypeptides. They are not in the correct order.

1 exposed bases are used as a template for the synthesis of mRNA 2 DNA double helix unzips 3 mRNA is translated by tRNA carrying a specific amino acid 4 bonds form between amino acids forming a polypeptide 5 mRNA leaves the nucleus and moves to the ribosome

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The correct order of events in the production of polypeptides is A. 2, 3, 5, 1, 4 B. 2, 1, 5, 3, 4 C. 1, 2, 5, 3, 4 D. 1, 4, 2, 3, 5

Question 75 Solution: B The DNA unzips, is transcribed into mRNA, the mRNA leaves the nucleus and moves to the ribosome where it is translated into a chain of amino acids. Question 76 DNA and mRNA

A. are both single stranded B. both contain thymine C. both contain uracil D. both contain nucleotides consisting of a sugar, a phosphate and a nitrogen base

Question 76 Solution: D DNA is double stranded, thymine is not found in mRNA and uracil is not found in DNA. Question 77 Proteins

A. are made of one or more polypeptides which are formed from a chain of amino acids B. are made of one or more amino acids which are formed from a chain of polypeptides C. are made of one or more poly peptides which are formed from a chain of fatty acids D. are made of one or more nucleotide strands

Question 77 Solution: A Fatty acids are a component of lipids and nucleotides are the building blocks of nucleic acids. Question 78 Mutations

A. are always harmful B. only occur in sexually reproducing organisms C. may be induced by high levels of radiation D. are not inherited

Question 78 Solution: C Some mutations may be beneficial, occur in both sexually and asexually reproducing organisms and can be inherited.



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Question 79 A section of a polypeptide was found to have the following sequence of amino acids. Lys-‐Cys-‐Ala-‐Ile-‐ Asn

Amino acid Codons Lys AAA AAG Cys UGC UGU Ala GCA GCC GCG GCU Ile AUU AUC AUA Asn AAC AAU

Using the above table, the sequence of DNA coding for this section of polypeptide could be: A. TTTACGCGTTATTTG B. TTTTCGCGTTATTTG C. TTTACTCGTTACTTG D. TTCACACGATATTTT

Question 79 Solution: A B’s fourth base, C’s sixth and twelfth bases and D’s last 3 bases are incorrect. Question 80 According to modern evolutionary theory, mutations can only be inherited by the next generation if

A. they make the species fitter B. they make the individual fitter C. they occur in somatic tissue D. they occur in reproductive tissue

Question 80 Solution: D Mutations in somatic tissue are not passed on to the offspring. An individual may be fit but that does not mean that they reproduce or pass on their advantageous characteristics to their offspring. Question 81 Darwin’s theory of evolution differs from the concept of punctuated equilibrium in that according to Darwin, evolutionary change is

A. fast, whereas punctuated equilibrium results in gradual evolutionary change B. slow and gradual, whereas punctuated equilibrium results in continual rapid evolutionary

change C. slow and gradual, whereas punctuated equilibrium results in long periods of little

evolutionary change followed by short periods of rapid change D. fast, whereas punctuated equilibrium results in long periods of little evolutionary change

followed by short periods of rapid change Question 81 Solution: C Darwin referred to slow gradual change in populations, whereas punctuated equilibrium refers to short bursts of rapid change.

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Question 82 The gene that codes for the production of human insulin has been inserted into bacteria. These bacteria can now produce human insulin that can be used by people with diabetes. This is an example of

A. artificial selection B. artificial insemination C. genetic engineering D. cloning

Question 82 Solution: D The genome of the bacteria has been altered to include a human gene. The altered bacterium is then cloned. Question 83 The following points summarise the steps involved in the production of transgenic bacteria. They are not in the correct order.

1 plasmids from bacteria are isolated 2 gene to be inserted is isolated 3 ligase is added 4 recombinant plasmid is transformed into bacterial cells 5 plasmids and gene for insertion are mixed and cut with the same restriction enzyme

The correct order of events in the production of transgenic bacteria is A. 2, 1, 5, 3, 4 B. 2, 1, 4, 3, 5 C. 1, 2, 3, 4, 5 D. 1, 4, 2, 3, 5

Question 83 Solution: A Gene and plasmid are isolated from their sources, mixed and cut with the same restriction enzyme, ligase joins the pieces together producing a recombinant plasmid which is then inserted into a bacterial cell. Question 84 Artificial insemination

A. reduces genetic variability as one male animal can pass on his genes to many offspring B. increases genetic variability as one male can father many offspring C. reduces genetic variability as all offspring will be identical to the father D. increases genetic variability as one female may produce more offspring

Question 84 Solution: A One male can pass on his genes to many offspring, meaning there is an increase in the proportion of his alleles in future population, and thus reduced genetic variability. The offspring will not be identical as they are still the result of the sperm fertilising an ova.



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Question 85 Which of the following is an example of a non-‐infectious disease?

A. measles B. skin cancer C. malaria D. influenza

Question 85 Solution: B The other alternatives are caused by pathogens. Question 86 Why are travellers to Bali advised to drink bottled water instead of tap water?

A. it reduces the chance of ingesting disease causing bacteria found in the local water B. it reduces the chance of ingesting dirt found in the local water C. water is in short supply in Bali D. bottled water contains an antiseptic

Question 86 Solution: A Pathogens cause disease not dirt. Question 87 Pasteur contributed to an understanding of disease by

A. developing a method to identify the organism causing an infectious disease B. disproving the theory of spontaneous generation C. discovering how the body recognises foreign cells D. showing bacteria cause anthrax

Question 87 Solution: B A and D are the work of Koch and C is attributed to Macfarlane Burnet. Question 88 Viral pathogens

A. are destroyed by antibiotics B. release toxins into the body of the host C. manipulate the host cell to produce more viral particles D. do not contain nucleic acids

Question 88 Solution: C Antibiotics are used to treat bacterial diseases, bacteria release toxins and virus particles contain nucleic acids. Question 89 Prions are a type of

A. nucleic acid B. protein

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C. bacterium D. virus

Question 89 Solution: B Prions are an infectious particle made of protein. Question 90 Which list shows pathogens in order of decreasing size?

A. protozoan, macro-‐parasite, prion, bacterium, virus B. prion, virus, protozoan, bacterium, macro-‐parasite C. bacterium, macro-‐parasite, virus, prion, protozoan D. macro-‐parasite, protozoan, bacterium, virus, prion

Question 90 Solution: D Macro-‐parasites are multicellular, protozoans are large unicells, viruses and prions are infectious particles. Question 91 In humans, the first line of defence against disease includes

A. the production of antibodies B. inflammation C. production of histamines D. production of mucus on respiratory and urogenital surfaces

Question 91 Solution: D Inflammation and production of histamine are part of the second line of defence and the production of antibodies occurs in the third line of defence. Question 92 The human body has three lines of defence against pathogens:

1 barriers 2 inflammation and phagocytosis 3 the immune response.

Which of the following statements is correct? A. B and T cells are mainly involved in the second line of defence B. histamines are involved in the first line of defence C. the first and second lines of defence are non-‐specific whereas the third line of defence is

specific D. antibodies are produced in the second line of defence

Question 92 Solution: C Antibodies, B and T cells are mainly involved in the third line of defence and histamines are involved in the second line of defence.



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Question 93 Inflammation involves

A. the production of antibodies B. the production of antibiotics C. B and T cells D. dilation of blood vessels at the site of infection

Question 93 Solution: D Antibodies and T and B cells are involved in the immune response. Antibiotics are used to treat bacterial infections. Question 94 White blood cells

A. are only present in blood vessels B. release clotting agents at sites of bleeding C. are similar in shape to red blood cells D. are primarily designed to fight infection

Question 94 Solution: D White blood cells are carried in the blood but many are found in lymph and tissue fluids. Question 95 Antigens are

A. molecules that trigger an immune response B. produced by B cells C. produced by T cells D. chemicals that attract phagocytes to the site of infection

Question 95 Solution: A Antibodies are produced by B cells and histamines attract phagocytes to the site of infection. Question 96 The following points summarise the steps involved in the interaction between T cells and B cells. They are not in the correct order.

1 Helper T cells produce chemicals that cause B cells to multiply 2 T cells interact with antigens presented by macrophages 3 Activated T cells differentiate into helper T cells

The correct order of events in the interaction between T cells and B cells is: A. 1, 2, 3 B. 2, 3, 1 C. 2, 1, 3 D. 3, 2, 1

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Question 96 Solution: B The antigen is presented to the Helper T cell, which then produces chemicals which activate B cells. Question 97 The diagram below is of a disease causing bacterium

Which of the following antibodies would be most effective against this bacterium? A.

B.

C.

D.

Question 97 Solution: D The shape of the antibody must fit the shape of the antigen. Question 98 Organ transplant patients are given anti-‐rejection drugs to

A. stimulate B cells to produce antibodies B. destroy bacteria C. increase the activity of phagocytes D. prevent T cell growth

Question 98 Solution: D This reduces the identification of the transplant tissue as foreign.



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Question 99 The bacterium Corynebacterium diphtheria causes the disease diphtheria. A baby whose parents both had diphtheria as children will develop active immunity against diphtheria if the baby is

A. injected with dead Corynebacterium diphtheria B. given a blood transfusion from the mother C. breastfed D. given antibiotics

Question 99 Solution: A This will bring about active immunity whereas alternatives B and C will result in passive immunity. Antibiotics are used to treat not prevent bacterial diseases. Question 100 The graph below shows the level of antibodies in a person after they have been vaccinated against a viral disease.

First injection Booster The blood antibody concentration rose faster and higher after the booster injection because

A. antibodies are only produced by the body after a second exposure B. the booster injection contained more virulent viral particles C. the first injection resulted in the presence of memory cells in the blood at the time of the

boost shot D. the first injection resulted in the presence of cytotoxic T cells

Question 100 Solution: C Antibodies are produced after the first injection and cytotoxic T cells destroy viral infected cells.

blood antibody

concentration

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