students guied( ohanyan)

IB Biology ( Anania Shirakatsy Lyceum)

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STUDENT’S GUIED

IB BIOLOGY

Teacher: Mariam Ohanyan 2015 November

ANANIA SHIRAKATSY LYCEUM


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Content

Topic Pages (Total 110)

1. The cell 3-9 2. Molecular Biology 10-21 3. Genetics 22-25 5. Evolution and Ecology 26-47 6.Human Physiology 48-66 7. DNA and Proteins 67-70 8. Respiration and Photosynthesis

71-74

9. Plant Physiology 75-80 10. Genetics 81-82 11. Animal Physiology 83-88 Option C Ecology 89-99 Option H Further Human Physiology

100-110


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Topic 1:The Cell

Paper 1

1. Which hypothesis can be tested using the t-test?

A. The difference in variation between two samples is not significant.

B. The difference between observed values and expected values is not significant.

C. The change in one variable is not correlated with a change in another variable.

D. The difference between the means in two samples is not significant. (Total 1 mark)

Answer: D [1]

2. What does a small standard deviation signify?

A. The data is not correlated.

B. The data is widely spread around the mean.

C. The data shows a close relationship between two variables.

D. The data is clustered closely to the mean value. (Total 1 mark)

Answer: D [1]

3. The levels of iron in liver tissue from 12 rats fed on beef and 11 rats fed on plant oils were compared using the t-

test to see if there was a significant difference at the 5% level.

Part of the table showing the critical values for the t-test is shown below.

Degrees of freedom p = 0.1 p = 0.05 p = 0.01 p = 0.001

19 1.729 2.093 2.861 3.883

20 1.725 2.086 2.845 3.850

21 1.721 2.080 2.831 3.819

22 1.717 2.074 2.819 3.792

23 1.714 2.069 2.807 3.767

What is the critical value above which the two samples can be considered significantly different?


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A. 2.086

B. 2.080

C. 2.074

D. 2.069 (Total 1 mark)

Answer: B [1]

4. What do error bars on graphs show?

A. If the data is correct or not.

B. How variable the data is.

C. Which result is closest to the true result.

D. What statistical technique was used to eliminate incorrect results. (Total 1 mark)

Answer: B [1]

5. A red blood cell is 8 μm in diameter. If drawn 100 times larger than its actual size, what diameter will the

drawing be in mm?

A. 0.08 mm

B. 0.8 mm

C. 8 mm

D. 80 mm (Total 1 mark)

Answer: B [1]

6. What do diffusion and osmosis have in common?

A. They only happen in living cells.

B. They require transport proteins in the membrane.

C. They are passive transport mechanisms.

D. Net movement of substances is against the concentration gradient. (Total 1 mark)


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Answer: C [1]

7. The diagram below shows a cell during mitosis.

What are the structures and stage of mitosis?

Stage of mitosis Structure I Structure II

A. metaphase chromatid nuclear membrane

B. anaphase centromere plasma membrane

C. anaphase chromatid nuclear membrane

D. metaphase centromere plasma membrane

(Total 1 mark)

Answer: D [1]

8. Which of the following are features of prokaryotes and eukaryotes?

70S ribosomes 80S ribosomes Naked DNA

DNA associated

with proteins

A. prokaryote eukaryote prokaryote eukaryote

B. eukaryote prokaryote eukaryote prokaryote

C. eukaryote prokaryote prokaryote eukaryote

D. prokaryote eukaryote eukaryote prokaryote

(Total 1 mark)

Answer: A


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Paper 2

1. The electron micrograph below shows the ultrastructure of part of an animal cell.

[Source: Reproduced with the kind permission of the Electron Microscopy Facility, Trinity College, Hartford, Connecticut, USA, and

Professor Daniel G. Blackburn.]

(a) Identify the structure labelled I.

...................................................................................................................................... (1)

(b) Explain briefly how materials produced in the structure labelled I are transported to the plasma

membrane.

......................................................................................................................................

...................................................................................................................................... (2)

(c) Outline the function of the mitochondria in the cell.

......................................................................................................................................

...................................................................................................................................... (2)

(d) Suggest why the two labelled mitochondria are different shapes in the micrograph.

...................................................................................................................................... (1)

(Total 6 marks)

Answer:

(a) rough endoplasmic reticulum/RER/rough ER / ribosome 1


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(b) vesicles are formed (from the rough ER);

they are received by Golgi apparatus;

Golgi apparatus forms vesicles that transport substances to membrane; 2 max

(c) aerobic respiration takes place in the mitochondria;

important for energy/ATP production;

pyruvate broken down into carbon dioxide and water; 2 max

(d) they are cut in different planes / due to three-dimensional nature/shape 1 [6]

2. (a) Define osmosis.

.....................................................................................................................................

..................................................................................................................................... (1)

(b) Outline how transport occurs across membranes by facilitated diffusion.

.....................................................................................................................................

..................................................................................................................................... (2)

(c) Explain how the properties of phospholipids help to maintain the structure of cell membranes.

.....................................................................................................................................

..................................................................................................................................... (3)

(Total 6 marks)

Answer:

(a) (osmosis is) the passive movement of water / solvent molecules from a

more dilute solution / region of lower solute concentration to a more

concentrated solution / region of higher solute concentration through

a partially permeable membrane 1

(b) facilitated diffusion is a form of passive transport / molecules move from a

region of higher concentration to a region of lower concentration / down a

diffusion gradient;

requires specific protein channels in plasma membrane; 2

(c) phospholipds have hydrophilic and hydrophobic regions;

hydrophilic heads attracted to water and hydrophobic / fatty acid tails repelled

by / not attracted to water;

phospholipd bilayer forms with heads in contact with water on both sides of

membrane / with environment and cytoplasm;

hydrophobic tails found in centre (of bilayer) away from water;

stability to membrane brought about by attraction between hydrophobic

tails / between hydrophilic heads and water; 3 max [6]


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Paper 3

Rice (Oryza sativa) is usually intolerant to sustained submergence under water, although it grows rapidly in height

for a few days before dying. This is true for one variety, Oryza sativa japonica. The variety Oryza sativa

indica is much more tolerant to submergence.

Three genetically modified forms of O. sativa japonica, GMFA, GMFB and GMFC, were made using

different fragments of DNA taken from O. sativa indica.

The plants were then submerged for a period of 11 days. The heights of all the plants were measured at the

beginning and at the end of the submergence period.

[Adapted by permission from Macmillan Publishers Ltd, Xu et al. 2006. ―Sub1A is an ethylene-response-factor-like gene that confers

submergence tolerance to rice.‖ Nature. Vol 442. Pp 705–708. Copyright 2006. http://www.nature.com/]

(a) (i) State which group of rice plants were the shortest at the beginning of the experiment.

........................................................................................................................... (1)


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(ii) Calculate the percentage change in height for the O. sativa japonica unmodified variety during

the submergence period. Show your working.

...........................................................................................................................

........................................................................................................................... (2)

(b) Explain how the error bars can be used to compare the results for O. sativa indica.

......................................................................................................................................

...................................................................................................................................... (2)

(c) Deduce the general relationship between the growth of all the japonica varieties and their stated

tolerance level.

......................................................................................................................................

...................................................................................................................................... (1)

Total 6 marks

Answer:

(a) (i) (GMF) C 1

(ii) × 100;

=127% ; (units required) (allow answers in the range of 127 to 127.3) 2

(b) error bars show the range/variability/uncertainty of the data / OWTTE;

error bars/standard deviation about the same length for day 0 and day 11 /

spread of data (around the means) about the same;

overlapping bars indicate that there is no (significant) difference in the

data/ means;

68% of population within one standard deviation; 2 max

(c) inversely proportional / the higher the tolerance, the less the

growth / vice versa 1

22

)2250(


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Topic 2:Molecular Biology

Paper 1

1. Which of the following are connected by hydrogen bonds?

A. Hydrogen to oxygen within a molecule of water

B. Phosphate to sugar in a DNA molecule

C. Base to sugar in a DNA molecule

D. Hydrogen to oxygen between two different molecules of water (Total 1 mark)

Answer: D

2. The graph below shows the effect of substrate concentration on enzyme activity. What conclusion can be drawn

about section X of the graph?

A. The enzyme has started to denature and the reaction slows down.

B. The reaction has finished and the substrate has been used up.

C. The enzyme is saturated and is working at its maximum reaction rate.

D. Some of the enzyme has been consumed and the reaction has reached a plateau. (Total 1 mark)

Answer: C

3. Which type of molecule is shown in the diagram below?


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A. Peptide

B. Carbohydrate

C. Lipid

D. Nucleic acid (Total 1 mark)

Answer: A

4. How do cells capture the energy released by cell respiration?

A. They store it in molecules of carbon dioxide.

B. They produce glucose.

C. The energy is released as pyruvate.

D. They produce ATP. (Total 1 mark)

Answer: D

5. What is the source of the oxygen released into the air as a product of photosynthesis?

A. Chlorophyll

B. Carbon dioxide only

C. Water only

D. Both water and carbon dioxide (Total 1 mark)

Answer: C

6. What is denaturation?

A. A structural change of a protein that results in the loss of its biological properties

B. A change in the genetic code of an organism


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C. A change in the amino acid sequence of a protein causing a disruption of its 3D shape

D. The process by which amino acids are broken down and ammonia is released (Total 1 mark)

Answer: A

7. What property of water makes it a good evaporative coolant?

A. High latent heat of evaporation

B. Relatively low boiling point

C. Volatility

D. Transparency (Total 1 mark)

Answer: A

8. Which variable has the least effect on enzyme activity?

A. Temperature

B. Light intensity

C. pH

D. Substrate concentration (Total 1 mark)

Answer: B

Paper 2 1. (a) State one example of a fibrous protein and one example of a globular protein.

Fibrous protein: ...........................................................................................................

Globular protein: ......................................................................................................... (1)

(b) Compare the structure of fibrous and globular proteins.

......................................................................................................................................

...................................................................................................................................... (2)

(c) Amino acid polarity is an important factor in determining the functions of proteins.

Explain the importance of polar and non-polar amino acids in membrane proteins.

......................................................................................................................................


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...................................................................................................................................... (3)

(Total 6 marks)

Answer:

(a) Fibrous protein:

keratin / elastin / fibroin / collagen / myosin / actin / other named

example;

Globular protein:

hemoglobin / myoglobin / named enzyme / named peptide hormone /

named antibody / albumin / other named example; 1 max

Example of both fibrous and globular protein needed to gain the

mark. Check any other answers for validity.

(b) both are polypeptides / chains of amino acids joined by peptide

bonds / have primary structure;

globular proteins have tertiary structure whereas fibrous proteins

do not (may have extended secondary structure);

globular proteins are rounded in shape while fibrous proteins

are elongated / OWTTE;

globular proteins are (generally) soluble while fibrous tend

to be insoluble; 2 max

(c) polar amino acids are soluble/have stable interactions in water/

extracellular fluid/cytoplasm;

non-polar amino acids are soluble/have stable interactions in

the lipid bilayer;

polar amino acids strongly hydrophilic and non-polar amino

acids are repelled by water/are hydrophobic;

(help to) retain protein in position in the membrane;

polar amino acids form hydrophilic channels/protein pores

in membranes;

transmembrane proteins have polar amino acids on either

side of the membrane; 3 max [6]

2. The diagram below shows one DNA nucleotide and part of a second nucleotide.

(a) State the names of structures I and II.

I. ..................................................................................................................................


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II. ................................................................................................................................. (1)

(b) On the diagram above, draw the structures that are missing from the second nucleotide. (1)

(c) The two nucleotides would be permanently separated during DNA replication. State one process

during which they would be temporarily separated.

...................................................................................................................................... (1)

(d) Outline the method that can be used to amplify small quantities of DNA to obtain large enough

quantities for DNA profiling.

......................................................................................................................................

...................................................................................................................................... (2)

(Total 5 marks)

Answer: (a) Both must be correct for the mark to be awarded.

I. phosphate and II. hydrogen bond(s) 1

(b) deoxyribose and phosphate added to base to show antiparallel orientation 1

Labels are not required but location of bonds and shape of deoxyribose

must be correctly shown.

(c) transcription 1

(d) polymerase chain reaction/PCR;

(DNA obtained from) blood/semen/hairs/other source of tissue;

combined with necessary raw materials/one example of raw material;

in thermal cycler / (PCR) machine;

DNA replicated many times; 2 max [5]

3. (a) State the location of high proton concentration caused by electron transport in the mitochondrion.

...................................................................................................................................... (1)

(b) Outline the role of oxygen in cellular respiration.

......................................................................................................................................

...................................................................................................................................... (2)


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(c) Explain how any two structural features of the mitochondrion are related to its function.

......................................................................................................................................

......................................................................................................................................

...................................................................................................................................... (2)

(Total 5 marks)

Answer: (a) inter-membrane space / outside inner membrane / between

outer and inner membrane 1

(b) in the electron transport chain;

final electron/hydrogen acceptor;

combines with H+ (and electrons) to produce water; 2 max

(c) cristae for increasing surface area;

small inter-membrane space for rapid build-up of concentration gradient;

matrix with chemical concentration to support unique chemical reactions; 2 max [5]

Paper 3

The rate of photosynthesis in the marine seagrass, Zostera marina, was investigated under a range of pH conditions.

After a period of darkness, the plants were illuminated at a constant light intensity at 15°C and the rate of

photosynthesis was measured. Zostera marina can use both dissolved carbon dioxide (CO2) and hydrogen

carbonate ions for photosynthesis. The rate of photosynthesis is plotted on the y-axis on the left. In addition,

the concentration of carbon dioxide was measured for each pH investigated and is plotted on the y-axis on the

right.


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(a) State the carbon dioxide concentration at pH 7.2.

......................................................................................................................................

...................................................................................................................................... (1)

(b) Calculate the percentage decrease in the rate of photosynthesis from pH 7 to pH 7.5.

......................................................................................................................................

...................................................................................................................................... (1)

(c) Outline the relationship between pH and the rate of photosynthesis.

......................................................................................................................................

...................................................................................................................................... (2)

(d) Suggest how Zostera marina can perform photosynthesis even at very low carbon dioxide

concentrations.

......................................................................................................................................

...................................................................................................................................... (1)

(e) Based on the information and data provided, discuss the role of one limiting factor, other than carbon

dioxide, and suggest how this would affect the rate of photosynthesis.

...................................................................................................................................... (2)

(Total 7 marks)

Answer: (a) 200 μM (units required) 1

(b) (77–51)/77×100 = 35% (Units required. Allow answers

in the range of 32–37%.) 1

(c) highest rate of photosynthesis at pH 7;

decrease (in rate of photosynthesis) between pH 7 and pH 7.5;

little change (in rate of photosynthesis) at higher pH values;

rate of photosynthesis falls again (slightly) at pH 9; 2 max

(d) uses hydrogen carbonate ions;

uses stored carbon dioxide / carbon dioxide from respiration; 1 max

(e) pH

optimum pH may be less than 7;

reducing the pH below 7 may lead to a higher rate (of photosynthesis);

(but) enzyme activity can be affected by low pH;


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or

Temperature

optimum temperature may not be 15ºC;

enzyme activity is affected by temperature;

temperatures above (or below) 15ºC may lead to a higher rate

(of photosynthesis);

or

Light intensity

light intensity may not be optimal/may be limiting;

too low light intensity produces less ATP/NADPH + H+;

higher light intensities may result in a higher rate (of photosynthesis);

as light intensity/temperature increases rate of photosynthesis

may not increase as another factor becomes limiting; 2 max

[1] for named limiting factor and [1] for effect on photosynthesis. [7]


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Topic 2(Cambridge University Press)

1 a Copy and complete the following table, which shows some elements needed by living organisms. (4)

Element Use in organisms

calcium

phosphorus

iron

sodium

b Water is important in organisms because of its solvent properties.

i What is a solvent? (1)

ii Why is this property of water so important to organisms? (1)

2 Identify these molecules andgive one use for each. (4)

a b

3 Copy this paragraph about DNA structure and fill in the spaces with suitable words. (7)

A DNA molecule is made up of ________________ sugars, phosphate groups and four types of base. Within the

DNA molecule, bases are held together in pairs by ________________ bonds. Guanine is always paired with

________________ and thymine is always paired with ________________. This arrangement is known as

________________ base pairing. The two strands of nucleotides coil around one another to form a

________________ ________________.

4 Copy and complete the information in this table to compare the structures of DNA and RNA. (3)

DNA RNA

a double stranded molecule

contains ribose sugar

contains adenine, guanine, cytosine and thymine bases


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5 Transcription and translation are processes necessary for protein synthesis. Arrange these sentences in the correct

order to explain the sequence of events. (10)

A RNA polymerase forms an mRNA strand that is complementary to DNA.

B A chain of amino acids linked together is known as a polypeptide.

C The mRNA molecule consists of a series of triplets of bases known as codons.

D The ribosome travels along the mRNA.

E Amino acids are joined by peptide bonds.

F One codon codes for one amino acid.

G mRNA moves into the cytoplasm from the nucleus.

H tRNA brings amino acids to the ribosome.

I Each tRNA molecule corresponds to one codon and can carry the appropriate amino acid.

J A ribosome attaches to the mRNA.

6 The graph below shows the rate of an enzyme-catalysed reaction at different temperatures. Describe the events that

are taking place at points A, B and C on the graph. Use the terms ‗molecular collisions‘, ‗active site‘ and

‗denaturation‘. (6)

7 The table below summarises the results of an experiment in which light of different intensities was shone onto a

sample of Canadian pondweed and the rate of oxygen released was measured. The experiment was conducted at

two different carbon dioxide concentrations, which were achieved by enriching the water with sodium

hydrogencarbonate. The different light intensities were obtained by placing a lamp at different distances from the

container of pondweed.

Distance of lamp from plant/m 2.00 1.50 1.00 0.75 0.50 0.25

Rate of oxygen release/mm3min

–1

1% CO2

0.2 0.4 0.7 1.4 1.4 1.4

Rate of oxygen release/mm3min

–1

2% CO2

0.6 0.8 1.1 1.6 1.8 1.8

a Plot the results on graph paper using the same axes for both curves. (4)

b Use the 2% CO2 line on your graph to outline the relationship between light intensity and the rate of

photosynthesis. (2)


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c Explain how and why the rates of photosynthesis at 1% CO2 and 2% CO2 are different. (2)

Answers 1 a (4)

Element Use in organisms

calcium component of bones, involved in transmission of nerve impulses

phosphorus found in ATP, in phospholipid bilayer and in nucleic acids

iron important in the blood pigment hemoglobin, and in cytochromes in plants

sodium used in transmission of messages across membranes, and in nerve impulses along nerves

b i A solvent is a substance in which a solute will dissolve. (1)

ii Most chemical reactions in organisms occur in water and many organic molecules in organisms are

water soluble. (1)

2 a glucose – used to supply energy (2)

b triglyceride (fatty acid + glycerol) – used as reserves of energy, insulating layers or for buoyancy (2)

3 A DNA molecule is made up of deoxyribose sugars, phosphate groups and four types of base. Within the DNA

molecule, bases are held together in pairs by hydrogen bonds. Guanine is always paired with cytosine and thymine

is always paired with adenine. This arrangement is known as complementary base pairing. The two strands of

nucleotides coil around one another to form a double helix. (7)

4 (3)

DNA RNA

a double stranded molecule a single stranded molecule

contains deoxyribose sugar contains ribose sugar

contains adenine, guanine, cytosine and thymine bases

contains uracil instead of thymine

5 A, C, F, G, J, H, I, E, B, D (10)


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6 A – As the temperature rises, molecules have more kinetic energy. This means that molecular collisions between

the enzyme and substrate molecules increase in frequency, so the rate of reaction increases. (2)

B – The reaction has reached its optimum point and the rate of reaction cannot increase any further. All the active

sites in the enzyme molecules present are full and no more substrate can be processed. (2)

C – As the temperature increases further, the shape of the active site of the enzyme molecule is altered. The rate of

reaction decreases rapidly as the enzyme denatures and can no longer catalyse the reaction. (2)

7 a Graph should have:

correctly labelled axes (1)

points plotted correctly, with lines to connect them (2)

lines labelled with carbon dioxide concentration (1)

b As light intensity increases, the rate of photosynthesis also increases until the lamp is 0.50 m from the plant,

after which the rate remains constant even if the light intensity is increased. (1)

After this point, the rate of reaction is limited by another factor. (1)

c The rate of photosynthesis is higher in the higher concentration of carbon dioxide at all intensities of light.

(1)

Carbon dioxide is essential for photosynthesis and is a limiting factor for the reaction. (1)


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Topic 3 :Genetics( Cambridge University Press)

1 A gene controlling fur colour in cats is sex-linked. Two alleles, black and orange, occur on the X chromosome only:

XB

= black pigment and XO

= orange pigment.

So, black cats have the genotype XBX

B (females) and X

BY (males).

Orange cats have the genotype XOX

O (females) and X

OY (males).

Tortoiseshell (mixed orange and black) cats can only be female XBX

O.

a What are the possible offspring of a black female cat and an orange male cat? Show the possible phenotypes

and genotypes of the kittens. (4)

b A tortoiseshell female cat mated with an unknown male cat and produced six kittens: two were orange

females, two were orange males, one was a black male and there was one tortoiseshell female. Deduce the

genotype of the unknown male. (4)

2 a Outline the main differences between mitosis and meiosis. (3)

b Explain why two brothers may not look alike but identical twins do look alike. (2)

c A couple have three children, all boys. They feel certain that their next child will be a girl. Do you think they

are correct? Explain your answer. (2)

d What is non-disjunction and what is its effect in a gamete? (2)

e Cells that are collected during amniocentesis must be allowed to develop for a period of time before they can

be used in karyotyping. Suggest why this is so. (2)

3 Study the DNA profile diagram below. It is a representation of the result of gel electrophoresis of DNA samples.

a Why do smaller DNA fragments travel further down the gel? (1)

b Suggest why the band in column 2 is thicker and darker than the other bands? (1)

c Suggest why there is no band in the third column. (1)


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d Explain which of the alleged fathers (A or B) in the profiles below is most likely to be the parent of the child.

(1)

e What is the purpose of the marker columns in each case? (1)

4 a Explain the meanings of the following terms used in biotechnology and genetic engineering.

i transgenic organism (1)

ii plasmid (1)

b How are the following enzymes used in biotechnology?

i restriction enzymes (endonucleases) (1)

ii ligase (1)

5 Dolly the sheep was a cloned animal produced from an ovum that was not fertilised by a sperm. The ovum had its

nucleus removed and replaced with the nucleus from a somatic cell from a donor sheep. The ovum containing this

nucleus was allowed to develop in the uterus of a surrogate mother sheep.

a Dolly was a clone of which sheep?

A the sheep whose ovum was used

B the sheep whose nucleus was used

C the surrogate mother sheep

Explain your answer. (2)

b How does the nucleus removed from the ovum differ from the nucleus from the donor sheep? (1)

c Outline the advantages of producing animal clones. (2)

d Give two disadvantages of the procedure. (2)


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Answers 1 a All female kittens would be tortoiseshell, with the genotype X

BX

O, while all males would have black fur and

have the genotype XBY. (4)

b The kittens had the genotypes XOY (orange male), X

BY (black male), X

BX

O(tortoiseshell female), X

OX

O

(orange female).

This information can be put into a Punnett grid as follows:

tortoiseshell female

XB X

O

un

kno

wn

mal

e

X? X

BX

O X

OX

O

Y XBY X

OY

The unknown male must have been an orange male, XOY. (4)

2 a Mitosis is nuclear division that results in the production of two genetically identical cells.Meiosis is nuclear

division that results in the production of four gametes that are not genetically identical. (2)

Meiosis occurs only in testes and ovaries, while mitosis occurs in somatic cells and in ovaries and testes

during the early stages of gamete formation. (1)

b Brothers develop from different ova and sperm cells, which will contain different combinations of parental

alleles. Identical twins develop from one ovum that has been fertilised by one sperm cell and subsequently

separated into two at an early stage of development. The two parts contain the same alleles and are

genetically identical. (2)

c For each fertilisation there is a 50/50 chance of the baby being a boy or a girl, unrelated to the sex of previous

children. Therefore, the couple cannot predict that their next (or any subsequent children) will be girls.

(2)

d Non-disjunction occurs when chromatids fail to separate correctly during meiosis. It results in gametes with

one additional chromosome (in humans, 24 instead of 23). Most trisomies (having three copies of a

chromosome rather than two) are fatal so that zygotes do not develop, but a trisomy in chromosome 21 leads

to Down‘s syndrome. (2)

e Chromosomes only condense and become visible at certain stages of the cell cycle. Cells sampled during

amniocentesis must be allowed to divide so that their chromosomes can be seen and analysed. (2)


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3 a Gel electrophoresis draws DNA fragments through agarose gel depending on their size and charge. Small

fragments are able to move more quickly than large ones, and so they travel further down the gel in the time

allowed. (1)

b The second sample may have been larger than the others and in the time allowed for the gel to ‗run‘ it has not

yet separated into bands. (1)

c No sample has been applied to the third position. This may be to check that there are no anomalies due to

impurities in the gel or apparatus. (1)

d Father A shares no DNA bands in common with the child whereas father B has one band in common so is

more likely to be the father. (1)

e The reference bands show the commonly used markers that are checked in forensic or paternity tests. They

indicate that the samples have moved correctly and minimise the risk of errors being made. (1)

4 a i A transgenic organism contains DNA from more than one species. The term is usually applied to

organisms whose DNA has been modified by genetic engineering. (1)

ii A plasmid is a small circular piece of DNA found in bacteria. Genes can be introduced into plasmids

from other organisms and the bacteria will then transcribe them to produce the protein specified by the

genes. (1)

b i Restriction enzymes cut DNA at specific (known) locations so that genes can be introduced at that

point (for example, into a plasmid). (1)

ii Ligase enzymes rejoin fragments of DNA so that the introduced genes are fixed into the chromosome

of another organism. (1)

5 a B – the sheep whose nucleus was used. The nucleus contains two sets of chromosomes from which the ovum

then developed. (2)

b The removed nucleus was haploid, while the inserted donor nucleus was diploid. (1)

c advantages:

cloned animals are all genetically identical;

the technique is used in producing animals that can (for example) manufacture proteins useful to humansin

their milk, such as blood clotting factorsor treatments for CF (2)

d disadvantages:

many cloned animals have been found to be born with abnormalities, because ‗old‘ genes from mature donor

animals are used to produce them and these have already differentiated to produce different cells which may

cause long-term problems;

the technique is expensive and requires advanced technology (2)


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Topic 4: Ecology

1. Which of the following is the best definition of a population?

A. A group of individuals that can interbreed and produce fertile offspring

B. The number of individuals of the same species in a given area

C. A group of species living and interacting with each other in a given area

D. The total number of individuals in a given area (Total 1 mark)

Answer: B

2. The diagram below shows a simplified food web.

3. What is the role of the snake in this food web?

A. Primary consumer

B. Secondary consumer

C. Tertiary consumer

D. Producer (Total 1 mark)

Answer: B

4. The graph below represents a sigmoid (S-shaped) population growth curve. Three sections of the curve are

indicated (1, 2 and 3).

In which of the sections is natality plus immigration greater than mortality plus emigration?


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A. 1 only

B. 2 only

C. 1 and 2 only

D. 3 only (Total 1 mark)

5.

Two different trees have been classified as Pinus pinea and Pinus nigra. Which of the following statements is

correct?

A. Both trees belong to the same class but a different genus.

B. Both trees belong to the same family and same genus.

C. The species name of both trees is Pinus.

D. The family names are pinea and nigra. (Total 1 mark)

B

6. A collection of four animal specimens is observed and a dichotomous key is applied. Which specimen is an

arthropod?

1. Non-segmented body ......................................... go to 2

Segmented body ................................................. go to 3

2. Body is not symmetrical ..................................... specimen A

Body is symmetrical ........................................... specimen B

3. Jointed appendages present ................................ specimen C

Jointed appendages absent ................................. specimen D

A. Specimen A

B. Specimen B


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C. Specimen C

D. Specimen D (Total 1 mark)

Answer: C

7. Which of the following ecological units includes abiotic factors?

A. A community

B. An ecosystem

C. A population

D. A trophic level (Total 1 mark)

B

8. In the forest zone between Gabon and the Republic of Congo it is estimated that an epidemic of the Zaire strain

of the Ebola virus (ZEBOV) killed nearly 5000 gorillas, significantly reducing the population. Which

statement is supported by this information?

A. Natality was greater than mortality.

B. Mortality was equal to natality.

C. Natality and immigration was greater than mortality and emigration.

D. Mortality was greater than immigration and natality. (Total 1 mark)

D

9. If humans become infected with the Ebola virus it can have devastating effects. Strong, but not certain, evidence

suggests that trading in animal products is the main reason for the spread of the Ebola virus to humans.

Which statement about the precautionary principle is correct?

A. In the absence of certainty about cause and effect, people should not be asked to stop trading in animal

products.

B. The burden of proof regarding a cause and effect relationship lies with scientists.

C. Because it is a probable cause, trading in animal products should be banned because of the potentially

devastating consequences.

D. The precautionary principle is not relevant in this case. (Total 1 mark)

C


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10. If humans become infected with the Ebola virus it can have devastating effects. Strong, but not certain, evidence

suggests that trading in animal products is the main reason for the spread of the Ebola virus to humans.

Which statement about the precautionary principle is correct?

A. In the absence of certainty about cause and effect, people should not be asked to stop trading in animal

products.

B. The burden of proof regarding a cause and effect relationship lies with scientists.

C. Because it is a probable cause, trading in animal products should be banned because of the potentially

devastating consequences.

D. The precautionary principle is not relevant in this case. (Total 1 mark)

C

11. Which group of organisms in the carbon cycle converts carbon into a form that is available to primary

consumers?

A. Decomposers

B. Saprotrophs

C. Detritus feeders

D. Producers (Total 1 mark)

D

12. Up to two additional marks are available for the construction of your answers. (2)

(a) Living organisms at every trophic level are part of the carbon cycle. Draw a labelled diagram of the

carbon cycle to show the processes involved. (9)

(b) Explain, using an example of a food chain, how trophic levels can be deduced. (4)

(c) Explain methods that can be used to measure the rate of photosynthesis. (5)

(Total 20 marks)

(a) Award [1] for each of the following shown on a diagram of the

carbon cycle.

Award [5 max] for points not shown on a diagram.

The following show carbon which is static within the cycle at this

point in time.


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carbon dioxide in air/water;

(sugars/carbon compounds in) plants/producers;

(carbon compounds in) animals/consumers;

(carbon trapped in) coal/oil/gas/fossil fuels;

The following should show arrows in direction of carbon flow.

carbon dioxide absorbed by plants/producers and used in

photosynthesis;

carbon dioxide released by (cell) respiration in plants/producers;

plants/producers eaten by animals/primary consumers/herbivores;

primary consumers eaten by secondary consumers;

carbon dioxide released by (cell) respiration in animals/consumers;

plants/animals die and are decomposed by (saprotrophic) bacteria/fungi;

carbon dioxide released by combustion of coal/oil/gas/fossil fuels;

carbon dioxide released by (cell) respiration in bacteria/fungi/

decomposers;

forest fires/combustion releases carbon dioxide from trees/plants;

carbon dioxide emitted by volcanoes; 9 max

(b) diagram of food chain showing at least three organisms and two

linkages with arrows showing direction of energy flow;

trophic level is a step/position in the movement/flow of energy

through an ecosystem;

(in a field situation) observe which organisms eat each other;

producer/name from example (first trophic level) does not eat other

organisms/captures energy through photosynthesis;

primary consumer/name from example (second trophic level) feeds

on producers;

secondary consumer/name from example (third trophic level) feeds

on primary consumers; 4 max

Since the command term is explain, the answer must be explicit to

gain marking points d–f. Named examples for producer and

consumers in diagram or explained example must represent

a coherent food chain. Reject chains using general names

such as fish or tree or grass. But, accept sardine or oak.

(c) measure production of oxygen;

because oxygen is a by-product of photosynthesis;

example of technique for measuring oxygen production (count

bubbles/use sensors/other);

measure uptake of carbon dioxide;

because carbon dioxide is used during photosynthesis;

example of technique for measuring carbon dioxide production

(sensor, aquatic pH shift);

measure biomass of (batches of) plants;

increase in biomass gives (indirect) measure of rate of photosynthesis;

Since the command term is explain, reasons must be given to

receive full marks. 5 max

(Plus up to [2]for quality)

[20]


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(a) Describe what is meant by a food chain using an example with four named organisms. (4)

(b) Outline how global warming may affect arctic ecosystems. (5)

(c) Explain how natural selection can lead to evolution using antibiotic resistance in bacteria as an

example. (9)

(Total 20 marks)

(a) food chains describe the feeding relationships between species;

arrows show (one) path of energy flow in an ecosystem / energy

flow described;

food chain with arrows pointing in the correct direction;

producer first step in chain;

three other named organisms making a realistic food chain; 4 max

Accept explicit common names exact enough to identify the food

source e.g. Oak not tree, sparrow not bird, rye grass not just grass, etc.

(b) global warming is an increase in temperature of the atmosphere/

oceans/Earth;

may result in climate change / changes in amount of precipitation /

greater ranges in temperature;

melting ice leads to rising of sea level;

leading to loss of habitat / example of organism that would lose

habitat;

changes in salinity / changes in ocean currents change distribution

of nutrients;

changes in predator-prey relationships (due to ecosystem disruption);

increased success of pest species;

temperate species with bigger range of habitats as ice melts;

increased rate of decomposition of detritus; 5 max

(c) members of a population of the same species show variation;

some organisms are more likely to survive due to selective

advantage / survival of the fittest;

some organisms have a reproductive advantage;

these variations may be genetically controlled/heritable;

these genes are most likely to be passed on to offspring;

this can change the characteristic of the population;

bacteria can normally be killed with antibiotics;

antibiotics impose a selection pressure;

if a few bacteria have natural resistance to the antibiotic

they will survive;

if the resistance is heritable they will pass it on to their offspring;

they will reproduce/evolve to form bacterial colonies resistant

to the antibiotic;


32

example of organism selected by use of antibiotic;

(e.g. MRSA bacteria / resistant TB bacteria) 9 max

(Plus up to [2] for quality)

[20]

14. The food web below shows some of the feeding relationships found between the organisms living in or near a

river in England.

(a) Identify an organism in the food web that is

(i) an autotroph.

........................................................................................................................... (1)

(ii) both a secondary and tertiary consumer.

........................................................................................................................... (1)

(b) Explain how the flow of energy in the food web differs from the movement of nutrients.

......................................................................................................................................

...................................................................................................................................... (2)

(c) Discuss reasons why the levels of a pyramid of energy differ in size.

......................................................................................................................................

...................................................................................................................................... (2)

(Total 6 marks)


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(a) (i) diatoms / (other) algae 1

(ii) trout 1

(b) nutrients are recycled in a food web and energy enters and

leaves/is not recycled;

nutrients are recycled by saprotrophs/returned to environment and reused;

while energy (enters as light and) is dispersed as heat; 2 max

(c) (the shape of pyramid) shows energy lost from base to top of

pyramid/80 to 90% lost at each trophic level;

(because) energy is used/released through cell respiration/heat/

metabolism/movement (at each trophic level);

not all tissues are eaten i.e. bone/hair/cellulose/excretion/

undigested/die (so energy is not available for next trophic level); 2 max [6]

15. Which phylum does the plant below belong to?

A. Angiospermophyta

B. Bryophyta

C. Coniferophyta

D. Filicinophyta (Total 1 mark)

D

16. Why do food chains in an ecosystem rarely contain more than five organisms?

A. Nutrients are recycled by the decomposers back to the producers.

B. Nutrients are lost from the ecosystem when organisms die.

C. The conversion of food into growth by an organism is not very efficient.


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D. Energy is recycled by the decomposers back to the producers. (Total 1 mark)

C

17. Slime moulds (Acrasiomycota) are protoctists. They feed on decaying organic matter, bacteria and protozoa.

Which of the terms describes their nutrition?

I. Detritivore

II. Autotroph

III. Heterotroph

A. I only

B. I and II only

C. I and III only

D. I, II and III (Total 1 mark)

C

18. (a) Define the terms species, population and community.

Species: ............................................................................................................

............................................................................................................

Population: ............................................................................................................

............................................................................................................

Community: ............................................................................................................

............................................................................................................ (3)

(b) Explain the shape of the pyramids of energy that are constructed by ecologists to represent energy flow

in an ecosystem.

......................................................................................................................................

......................................................................................................................................


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...................................................................................................................................... (3)

(Total 6 marks)

(a) species: group of organisms that can interbreed to produce

fertile offspring;

population: group of organisms of the same species living in the same

area at the same time;

community: group of populations living and interacting with each

other in an area; 3

(b) energy flows up from one trophic level to the next (in a community);

energy is lost at each stage by waste products/feces/not all the organism

is consumed;

most energy is lost through respiration/heat;

each level on the pyramid is about 10%–20% of the size of the one

below it / 80%–90% energy lost between levels;

labelled diagram of pyramid of energy (indicating trophic levels); 3 max [6]


36

Topic 5:Ecology(Cambridge University Press)

1 Use the following information to construct a food web. For each organism, indicate the trophic level.

(10)

Grass and seeds are eaten by mice, rabbits and crickets.

Rabbits and mice are eaten by hawks.

Crickets are eaten by frogs, mice and snakes.

Frogs are eaten by snakes.

Snakes are eaten by hawks.

2 The table below shows the concentration of some greenhouse gases in the atmosphere.

Greenhouse gas Concentration in atmosphere/ppm

Pre 1850 1999

carbon dioxide 275 355

methane 0.8 1.8

nitrous oxides 282 308

a Calculate the % increase in each gas in the 150-year period. (3)

b For each, give an example of a source of the greenhouse gas. (3)

c Outline three potential consequences for ecosystems of increased global warming caused by rising levels of

greenhouse gases. (3)

3 a Write a short description of the theory of evolution by means of natural selection using the following words:

(5)

overpopulation, competition, adaptation, variation, selection

b How does a plant or animal breeder produce a new variety using artificial selection? (3)

4 a What effect may an increase in global temperature have on:

i decomposition of material trapped in permafrost (2)

ii distribution of species from temperate climates? (2)

b What problems could be caused by these changes? (2)

5 a Draw a graph to show the growth of a population of animals introduced into a new habitat where resources

are plentiful. (3)


37

b Show the stages that will occur as the population changes and indicate the factors that influence the changing

size of the population as it becomes established. (3)

c In most communities, the population of an organism fluctuates in response to factors in the environment. List

three factors that might cause such changes and explain why they do so. (3)

Answers

1 (10)

2 a carbon dioxide: % increase = (355 275) ÷ 275 100 = 29%

methane: % increase = (1.8 0.8) ÷ 0.8 100 = 125%

nitrous oxides: % increase = (308 282) ÷ 282 100 = 9.2% (3)

b carbon dioxide – burning fossil fuels

methane – digestive systems of cows

nitrous oxides – car exhaust fumes (burning petrol products) (3)

c rising sea levels and loss of habitat for organisms;

changes in worldwide weather patterns;

change in distribution of species and changes in established food webs (3)

3 a All species are capable of producing more offspring than are needed to replace them when they die. Despite

this, it is unusual for overpopulation to occur because there iscompetition between the offspring. As there

are variations between offspring, some will have adaptations that are better suited to the environment where

they live. Natural selection will favour these individuals, who will be more likely to survive and reproduce.

Gradually, over generations, the population may change so that it contains more individuals with these

favourable characteristics. (5)


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b An animal breeder chooses individuals with the required characteristics for a breeding programme. These

animals are mated and the breeder selects only the offspring with the required characteristics to breed from.

The same procedure is used for several generations and eventually most of the offspring will have the

required characteristics. (3)

4 a i As permafrost melts, material trapped in it decomposes, causing the release of more carbon dioxide

and methane. (2)

ii Species from temperate climates may be able to move northward to Arctic

regions. (2)

b The greenhouse effect may be enhanced by decomposition. The movement of species could mean the

takeover of habitats or the spread of pest species that cause disease – for example, there is concern that

mosquitoes may move north. Pest species may attack animals or plants in the borders of the Arctic region and

reduce their populations still further. (2)

5 a (3)

b During the exponential phase, resources are abundant and the population grows at its maximum rate.

During the transition phase, a resource is becoming limiting or a toxin is accumulating so that the rate of

growth of the population decreases.

During the plateau phase, there are sufficient resources to support the population, which maintains more or

less constant numbers. (3)

c three from:

availability of space will limit a population;

abundance of food limits the number of individuals that can survive in an area;

presence of predators, or incidence of disease can limit a population or cause its numbers to fall;

immigration and emigration, births and deaths affect population numbers (3)


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Evolution

1. What is evolution?

A. A measure of the relative survival and reproductive success of an individual

B. A cumulative change in the genetically controlled characteristics of a population

C. A physical change during an organism‘s life that is inherited by its offspring

D. A random change in the proportions of alleles from generation to generation (Total 1 mark)

B [1]

2. Explain how natural selection can lead to evolution using antibiotic resistance in bacteria as an example. (11 mark)

Answer: members of a population of the same species show variation;

some organisms are more likely to survive due to selectiveadvantage / survival of the fittest;

some organisms have a reproductive advantage;these variations may be

geneticallycontrolled/heritable;these genes are most likely to be passed on to offspring;

this can change the characteristic of the population;bacteria can normally be killed with antibiotics;

antibiotics impose a selection pressure;if a few bacteria have natural resistance to the antibiotic

they will survive;if the resistance is heritable they will pass it on to their offspring;

they will reproduce/evolve to form bacterial colonies resistantto the antibiotic;example of organism

selected by use of antibiotic;

(9 max)

3. Which of the following are used as evidence for evolution?

I. Homologous structures

II. Selective breeding of domesticated animals

III. Overproduction of offspring

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

Answer: A

(Total 1 mark)


40

4. Which of the following will promote variation in a species?

I. Meiosis

II. Fertilization

III. Natural selection

A. I only

B. II only

C. I and II only

D. I, II and III (Total 1 mark)

Answer: C

5. Which process tends to reduce variety within a population?

A. Natural selection

B. Random fertilization

C. Independent assortment

D. Crossing over (Total 1 mark)

Answer: A [1]

6. Charles Darwin used domesticated animals to provide evidence for evolution by natural selection.

What is this evidence?

A. Differences between breeds show that selection can cause species to change.

B. The ancestors of domesticated animals can be found in the fossil record.

C. Some domesticated animals die because the environment cannot support them all.

D. Variation in domesticated animals is due to sexual reproduction. (Total 1 mark)

Answer: A [1]

7. Which process has the greatest effect in determining which members of a population are most likely to

survive until reproductive age?


41

A. Evolution

B. Natural selection

C. Meiosis

D. Hybridization (Total 1 mark)

B [1]


(a) Draw and label a diagram of the molecular structure of DNA. (4)

(b) Explain the consequences of a base substitution mutation in relation to the processes of

transcription and translation. (8)

(c) Outline the evidence for evolution provided by homologous structures. (6)

(Total 20 marks)

Answer: (a) Award [1] for each of the following clearly drawn and correctly labelled.

Simple shapes may be used but must have a key or be clearly labelled.

two nucleotide strands (note that strands must be drawn antiparallel

although it does not need to be labelled as such);

alternating sugar-phosphate backbone;

complementary base pairs shown, A-T and C-G;

hydrogen bonds between base pairs;

covalent bonds between sugar and phosphate groups / between sugar and bases;

nucleotide including sugar, phosphate and base (with parts correctly

connected); 4 max

(b) mutation is a change in the genetic make-up;

base substitution mutation occurs when one (nitrogenous) base in DNA chain is

replaced by another;

this is a gene mutation / change in the base sequence of a gene;

effect of mutation ranges from no effect / no change in amino acid sequence to

drastic changes;

sickle-cell anaemia involves change in gene for one of polypeptides in

hemoglobin / Hb / HBA

;

GAG has mutated to GTG (on DNA);

adenine replaced by thymine in DNA;

transcription of DNA produces the triplet GUG instead of GAG on mRNA;

one codon is different in mRNA;

new codon is for valine rather than glutamic acid;

tRNA brings amino acid to ribosome during translation;

different amino acid placed in polypeptide chain being formed by translation;


42

the two amino acids differ in solubility / have different properties / valine causes

HBS to be less soluble;

causes red blood cells to become sickle shaped / carry oxygen less efficiently;

HBS allele causes sickle-cell anaemia but gives resistance to malaria; 8 max

(c) comparative anatomy of groups of animals or plants shows certain

structural features are basically similar;

homologous structures are those that are similar in shape in different types

of organisms;

structural similarities imply a common ancestry;

(homologous structures) used in different ways;

example is pentadactyl limb in vertebrates / modification of ovary wall or

pericarp to aid seed dispersal / other suitable example;

adapted to different mode of locomotion in particular environment /

example of two differences such as bat‘s wing and human hand;

illustrates adaptive radiation since basic plan adapted to different niches;

the more exclusive the shared homologies the closer two organisms are related;

certain homologous structures in some species with no apparent function such as

human appendix (homologous with functional appendix in herbivores); 6 max


[20]

9. Define evolution.

(Total 2 marks)

Answer: Evolution is the cumulative change in the heritable characteristics

of a population.

If we accept not only that species can evolve, but also that new

species arise by evolution from preexisting ones, then the whole

of life can be seen as unified by its common origins.

Variation within our species is the result of different selection

pressures operating in different parts of the world, yet this

variation is not so vast to justify a construct such as race

having a biological or scientific basis.

10. Explain two examples of evolution in response to environmental

change.

(Total 2 marks)

Answer: one must be antibiotic resistance in bacteria.

Other examples could include: the changes in size and shape of

the beaks of Galapagos finches; pesticide resistance, industrial

melanism or heavymetal tolerance in plants.


43

11. Why has antibiotic resistance evolved in bacteria?

A. All bacteria reproduce very quickly.

B. Bacteria exposed to antibiotics developed a resistance to them.

C. Varieties of bacteria resistant to antibiotics reproduce faster than non-resistant varieties.

D. Bacteria showing resistance to antibiotics survive after antibiotics are used. (Total 1 mark)

Answer: D [1]


44

Topic 6: Human Physiology ( Cambridge University Press)

1 a Copy and complete the table to show the functions of the different parts of the intestine. (6)

Stomach Small intestine Large intestine

Function

b Explain the importance of capillary networks in the absorption of food. (2)

2 a The atrioventricular valves in the heart are attached to the ventricle walls by non-elastic tendons. Suggest

why these tendons must be non-elastic. (2)

b What effect does atrial systole have on the pressure of blood in the atria? (1)

c The base of the veins which enter the atria contract during atrial systole. How does this affect blood flow?

(1)

d The table below shows human blood pressure in different situations.

Part of the body Blood pressure in kPa

Standing up Lying down

head 9.1 13.3

heart 13.4 13.4

feet 27.1 13.2

i Why is the blood pressure in the head and feet of a person who is standing up different from a person

who is lying down? (2)

ii Why are the blood pressures in the head and feet of a person who is lying down lower than that in the

heart? (2)

iii Red blood cells (erythrocytes) contain enzymes and hemoglobin. Why is it more efficient to have these

substances enclosed inside a cell membrane? (2)

3 a The number of deaths from HIV/AIDS in developed countries has reduced as antiviral drugs have been

developed. Why has a similar reduction in deaths not occurred in sub-Saharan Africa? (2)


45

b HIV infection causes the gradual but progressive loss of T-cells. Why does this lead to an increase in the

number of other infections in AIDS patients? (2)

c Explain why a course of antibiotics should always be finished completely, even if the symptoms of the

disease have disappeared. (4)

4 The table shows the percentage composition of inspired, expired and alveolar air.

Gas Inspired air Expired air Alveolar air

oxygen 20.6 14.9 13.5

carbon dioxide 0.04 3.9 5.2

water vapour 1.4 6.4 6.4

nitrogen 78.0 74.8 74.9

a Explain the differences between the percentages of oxygen in inspired, expired and alveolar air. (3)

b Explain why the percentage of water vapour is different in inspired and expired air. (2)

c Suggest one other difference between inspired and expired air and give a reason for your suggestion. (2)

5 a Draw a flow diagram to show the events that follow the arrival of a nerve impulse at a synapse. (5)

b Consider the information in this table:

Neuron Myelinated? Diameter/µm Speed of transmission of

impulse/ms–1

mammal axon N 1.0 3.0

mammal axon Y 10.0 50.0

frog axon Y 10.0 30.0

squid axon N 1000.0 30.0

i What is the relationship between the speed of impulse and the properties of the different axons?

(3)

ii Give possible explanations for the differences between the axons. (3)

6 a Outline the hormonal changes that trigger ovulation. (2)

b Arrange the following structures in the order in which an ovum would pass them on its journey through the

female reproductive system, during a menstrual cycle. (2)

cervix, oviduct, ovary, uterus, vagina

c During IVF (in vitro fertilisation), FSH and/or LH may be used in a woman‘s treatment. Outline why these

hormones are used. (3)


46

Answers 1 a (6)

Stomach Small intestine Large intestine

Function physical digestion –

mixing with protease

and hydrochloric acid

digestion and

absorption

reabsorption of water

and storage of faeces

b any two points from:

capillaries absorb nutrients from the villi;

the blood flowing through the capillaries maintains a concentration gradient so nutrients can be absorbed by

diffusion;

the thin walls of capillaries reduce the diffusion distance to a minimum (2)

2 a Tendons must be strong and non-elastic to withstand the pressure of blood, which might otherwise ‗invert‘

the valve and allow blood to flow in the wrong direction. (2)

b Blood pressure in the atria increases during atrial systole. (1)

c It prevents blood flowing backwards into the veins. (1)

d i Blood pressure is affected by gravity. Pressure in lower parts of the body increases and pressure in

higher parts decreases when a person stands up. (2)

ii Blood that flows to the head and feet is affected by friction in the blood vessels, which causes a

reduction in its pressure. (2)

iii Membranes enclose the chemicals and ensure they are present at a sufficiently high concentration.

Reactants are kept in close proximity to the enzymes that catalyse reactions. (2)

3 a New drugs are expensive and may be unaffordable in less-developed countries. There are fewer medical

facilities to administer drugs in less-developed countries (or similar statements). (2)

b either of the following:

T-cells form an important part of the immune response – as numbers of T-cells decline, a person cannot fight

off opportunistic infections;

T-cells activate B-cells, which produce antibodies – without antibodies it is not possible to resist infections

adequately. (2)

c any four points from:

antibiotics interfere with metabolic processes in prokaryotic cells;

some work at specific times in the lifecycle of a bacterium;

symptoms may disappear as the numbers of live bacteria fall;

if antibiotics are not completed, these live organisms can reproduce again;

the last bacteria to be killed may be more resistant to the antibiotic so not completing the course may lead to

a build-up of antibiotic-resistant organisms (4)


47

4 a Atmospheric air contains about 20% oxygen. In the alveoli, oxygen is removed and exchanged for carbon

dioxide so the percentage falls to 13.5%. However, as this air is exhaled it mixes with some air in the bronchi

and trachea which is higher in oxygen, and so the final percentage in expired air increases to 14.9%. (3)

b Water vapour is a product of respiration and the alveoli are lined with aqueous surfactant so the percentage in

expired air is greater than in inspired air. (2)

c Expired air will be warmer than inspired air as heat lost from the pulmonary circulation raises the

temperature of the air in the alveoli. (2)

5 a Ca2+

ions enter the synaptic knob

→ neurotransmitter diffuses across the synaptic cleft

→ neurotransmitter binds to receptors on post-synaptic membrane

→ ion channels open

→ action potential is generated

→ neurotransmitter is deactivated and reabsorbed (5)

b i Myelinated neurons conduct impulses faster than non-myelinated neurons of the same diameter.

(1)

Thicker unmyelinated neurons conduct impulses faster than thinner ones. (1)

Mammalian axons that are myelinated conduct impulses faster than those of squid or frogs. (1)

ii Mammals have a fast metabolic rate and have more energy to conduct impulses more quickly.

Resistance to the flow of an impulse is lower in a thicker axon.

Myelinated neurons enable impulses to ‗jump‘ between sections of myelin, making transmission faster.

(3)

6 a Ovulation follows a peak in the level of estrogen and of FSH. (2)

b ovary, oviduct, uterus, cervix, vagina (2)

c LH and FSH stimulate the development of follicles in the ovary. LH stimulates the oocyte to resume meiosis

and the growth of the follicle, and also stimulates the

formation of the corpus luteum, which produces progesterone to sustain a pregnancy. Higher levels of LH

and FSH stimulate the ovaries to produce several oocytes, which

can be collected. (3)


48

Topic 6 : Human Physiology

1. The table below shows the level of hemoglobin measured in two different groups of athletes.

Hemoglobin /

grams per 100 cm3

Number of

athletes tested

Standard deviation /

grams per 100 cm3

Group A 12.6 200 0.8

Group B 11.9 220 3.2

Which of the following statements is correct?

A. Results from group B are more accurate because more athletes were tested.

B. Results from group B are more reliable because it has a higher standard deviation.

C. More athletes have their hemoglobin concentration close to the mean in group A than in group B.

D. These results indicate that the level of hemoglobin follows a normal distribution. (Total 1 mark)

Answer: C [1]

2. Celiac disease causes the destruction of the villi cells. Which of the following is most likely to happen to people

with celiac disease?

A. Incomplete digestion of fats

B. Poor absorption of calcium

C. Increased levels of glucose in blood

D. Damage in the esophagus caused by increase in acid content of the stomach (Total 1 mark)

Answer:B [1]

3. Is the blood in the aorta, left ventricle and pulmonary artery oxygenated or deoxygenated?

Aorta Left ventricle Pulmonary artery

A. oxygenated deoxygenated deoxygenated

B. deoxygenated oxygenated oxygenated

C. oxygenated oxygenated deoxygenated


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D. oxygenated oxygenated oxygenated

(Total 1 mark)

C [1]

4.Which of the following statements about antibodies is correct?

A. Antibodies are polypeptides.

B. Antibodies are produced by the bone marrow.

C. Antibodies are pathogenic foreign substances.

D. Antibodies kill bacteria but not viruses. (Total 1 mark)

A [1]

5.What normally prevents the membranes of the alveoli from sticking together during expiration?

A. The thickness of the single-cell layer of alveoli membranes

B. The secretion of fluids in the inner surface of the alveoli

C. The pressure within the thoracic cavity

D. The dense net of capillaries covering the alveoli (Total 1 mark)

B [1]

6.The diagram below shows the male reproductive system.


50

Which are the epididymis and the seminal vesicle in the diagram?

Epididymis Seminal vesicle

A. IV I

B. III II

C. I V

D. III I

(Total 1 mark)

D [1]

7.A number of different proteins are involved in nerve function. Which of the following does not require a

membrane protein?

A. Active transport of sodium

B. Diffusion of K+ into the cell

C. Diffusion of the neurotransmitter across the synapse

D. Binding of the neurotransmitter to the post-synaptic membrane (Total 1 mark)

C [1]

8. This question refers to the following diagram of the digestive system.

9. Which organs are associated with the transformation of glucose into glycogen?

A. 1 and 4


51

B. 2 and 3

C. 2 and 4

D. 1 and 3 (Total 1 mark)

A [1]

10. Which vessel directly supplies the heart muscle with blood?

A. The aorta

B. The pulmonary artery

C. The coronary artery

D. The pulmonary vein (Total 1 mark)

C

11.

(a) State the missing source, optimum pH requirement, substrate and product of the human enzymes in the table

below.

Enzyme Source Optimum pH Substrate Products

Amylase Salivary gland 7

Lipase Lipids Fatty acids and glycerol

(2)

(b) Explain the need for enzymes in digestion.

......................................................................................................................................

...................................................................................................................................... (2)

(c) Draw a labelled diagram to show the interconnections between the gall bladder, pancreas and small

intestine.

(3)

Answer:

(a) Award [1] for every two correct.


52


Amylase Salivary

gland

7 starch/amylose/

glycogen;

maltose/short

polysaccharides

/disaccharides

/dextrin;

Lipase Pancreas; Allow any pH in

range 7–9

Lipids Fatty acids and

glycerol

2 max

(b) rate of digestion at body temperature would be too slow / enzymes

increase the rate of digestion;

enzymes break large molecules down into small/soluble molecules;

for absorption/diffusion into blood; 2 max

(c) labelled sac-shaped gall bladder with a duct;

tubule/(bile) duct shown connecting gall bladder directly to small

intestine/duodenum / tubule/(bile) duct merging with the pancreatic

duct before entering small intestine; Alternative answers are

accepted because of variations in human anatomy.

pancreas drawn with pancreatic duct connected to small intestine

and pancreas labelled; 3

A duct is preferred to a line, but since this is a diagram, both are acceptable. [7]

12.What stimulates the production of antibodies?

A. AIDS

B. Antibiotics

C. Anticodons

D. Antigens (Total 1 mark)

D [1]


(a) Draw and label a diagram of the digestive system. (5)

(b) Discuss factors that affect enzyme activity. (9)

(c) Outline one industrial use of lactase.


53

(5)

(Total 21 marks)

Answer:

(a) Award [1] for each structure correctly drawn and labelled.

esophagus — attached to both mouth and stomach;

stomach — j-shaped sac attached to esophagus and u-shaped portion of

small intestine;

large intestine — wider diameter than small intestine, attached to small intestine;

pancreas — leaf-shaped, in u-shaped region of small intestine with small duct

connected to small intestine;

liver — large, triangular, to left of stomach;

gall bladder — small sac drawn on top of liver with tube connected to small

intestine at same region as duct from pancreas;

anus —at end of large intestine but narrower in diameter; 4 max

(b) at low temperatures, rate of reaction increases as temperature increases

(or vice versa);

more kinetic energy / faster movement of molecules means more collisions

between enzyme / active site and substrate;

optimum temperature is temperature at which rate of enzyme-catalyzed

reaction is fastest;

at high temperatures enzymes are denatured and stop working;

denatured means change of structure in enzyme / protein resulting in loss of its

biological properties / no longer can carry out its function;

too much kinetic energy / vibrations breaks bonds that give enzyme specific

shape;

optimum pH is one at which rate of enzyme-catalyzed reaction is fastest;

rate of reaction reduced as increase or decrease pH (from optimum);

strong acids and alkalis can denature enzymes;

affect (weak, ionic, hydrogen) bonds that hold enzyme in specific shape;

at low substrate concentrations, as increase concentration get increase in rate

of reaction;

more chance of collision between substrate and enzyme / active site;

at high substrate concentration, have no change in rate as increase

concentration;

all active sites occupied; 9 max

(c) lactose intolerance high in some human populations / Asian / African / native

American and Australian aboriginal populations;

lactase used to produce lactose-free / low-lactose milk;

lactase breaks down lactose to glucose and galactose;

source of lactase is usually yeast / many sources such as bacteria, moulds;

milk passed over immobilized lactase / lactase bound to inert substance;

increase sweetness of milk;

no need to add extra sugar in manufacture of flavoured milk drinks /

frozen desserts;

can add (harmless) bacterium such as L.acidophilus which has same effect on

lactose as in yoghurt; 5 max


[20]


54

Topic 7 and 8

1. A number of different proteins are involved in nerve function. Which of the following does not require a

membrane protein?

A. Active transport of sodium

B. Diffusion of K+ in: to the cell

C. Diffusion of the neurotransmitter across the synapse

D. Binding of the neurotransmitter to the post-synaptic membrane (Total 1 mark)

Answer: C

2. The effect of temperature on photosynthesis was studied in sweet orange (Citrus sinensis) using leaf discs. The

production of oxygen was used to measure the rate of photosynthesis.

Gross photosynthesis refers to the sum of net photosynthesis and respiration. Net photosynthesis was

calculated by subtracting the rate of respiration in the dark from gross photosynthesis.

[Source: Adapted from R Ribeiro et al. 2006. Ciência e Agrotecnologia. Vol 30. Pp 670–678.]

(a) Identify the optimum temperature for photosynthesis in this plant.

...................................................................................................................................... (1)

(b) Determine the difference between gross photosynthesis and net photosynthesis at 40°C and 50°C.

40°C: ..........................................................................................................................

50°C: ..........................................................................................................................


55

(2)

(c) Deduce what happens to the rate of respiration as the temperature increases between 40°C and 50°C.

...................................................................................................................................... (1)

(d) (i) Describe the general pattern of change in photosynthesis in sweet orange as the temperature

increases.

........................................................................................................................... (1)

(ii) Compare the effect of temperature on photosynthesis with the effect of temperature on

respiration in sweet orange.

...........................................................................................................................

........................................................................................................................... (2)

(Total 7 marks)

Answer: (a) 40°C 1

(b) 40°C: 3.5 µmol m–2

s–1

; (units required)

Accept answers between 3.0 µmol m–2

s–1

and 4.0 µmol m–2

s–1

.

50°C: 10 µmol m–2

s–1

; (units required) 2

Accept answers between 9 µmol m–2

s–1

and 11 µmol m–2

s–1

.

(c) rate of respiration is increasing 1

(d) (i) rate increases as the temperature increases up to a point/40°C

and then decreases 1

(ii) at low temperatures/between 25°C and 35°C the rate of

photosynthesis increases and the rate of respiration is

(approximately) constant;

between 35°C and 40°C both increase;

as temperature continues to increase the rate of

photosynthesis reaches optimum whereas rate of respiration

decreases less/stays constant/increases;

at high temperatures/between 40°C and 50°C photosynthesis

decreases as respiration decreases less/stays constant/increases; 2 max [7

3. (a) Distinguish between fibrous proteins and globular proteins giving one example of each.

...................................................................................................................................... (3)

(b) Outline the differences between competitive and non-competitive inhibitors. (4)

(Total 7 marks)


56

Answer: Enzymes

7.6.1 State that metabolic pathways consist of chains and cycles of

enzyme - catalysed reactions. Obj 1

7.6.2 Describe the induced - fit model. Obj 2

This is an extension of the lock-and-key model. Its importance in

accounting for the ability of some enzymes to bind to several

substrates should be mentioned.

TOK: Scientific truths are often pragmatic. We accept them as true

because they give us predictive power, that is, they work. The

German scientist Emil Fischer introduced the lock-and-key model for

enzymes and their substrates in 1890. It was not until 1958 that Daniel

Koshland in the United States suggested that the binding of the

substrate to the active site caused a conformational change, hence

the induced-fit model. This is an example of one model or theory,

accepted for many years, being superseded by another that offers

a fuller explanation of a process.

7.6.3 Explain that enzymes lower the activation energy of the chemical reactions

that they catalyse. Obj 3

Only exothermic reactions should be considered. Specific energy

values do not need to be recalled.

7.6.4 Explain the difference between competitive and non - competitive inhibition,

with reference to one example of each. Obj 3

Competitive inhibition is the situation when an inhibiting molecule

that is structurally similar to the substrate molecule binds to the

active site, preventing substrate binding.

Limit non - competitive inhibition to an inhibitor binding to an

enzyme (not to its active site) that causes a conformational change in

its active site, resulting in a decrease in activity.

Reversible inhibition, as compared to irreversible inhibition, is not

required.

7.6.5 Explain the control of metabolic pathways by end - product inhibition,

including the role of allosteric sites. Obj 3

4. Explain the link reaction that occurs between glycolysis and the Krebs cycle.

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................

................................................................................................................................................ (Total 4 marks)


57

Answer: Cell respiration

8.1.1 State that oxidation involves the loss of electrons from an element, where

as reduction involves a gain of electrons; and that oxidation frequently

involves gaining oxygen or losing hydrogen, whereas reduction

frequently involves losing oxygen or gaining hydrogen. Obj 1

8.1.2 Outline the process of glycolysis, including phosphorylation, lysis,

oxidation and ATP formation. Obj 2

In the cytoplasm, one hexose sugar is converted into two

three - carbon atom compounds (pyruvate) with a net gain of two

ATP and two NADH + H+.

8.1.3 Draw and label a diagram showing the structure of a mitochondrion as

seen in electron micrographs. Obj 1

8.1.4 Explain aerobic respiration, including the link reaction, the Krebs

cycle, the role of NADH + H+, the electron transport chain and the

role of oxygen. Obj 3

In aerobic respiration (in mitochondria in eukaryotes), each

pyruvate is decarboxylated (CO2 removed). The remaining two

carbon molecule (acetyl group) reacts with reduced coenzyme A,

and, at the same time, one NADH + H+ is formed. This is known as

the link reaction.

In the Krebs cycle, each acetyl group (CH3CO) formed in the link

reaction yields two CO2. The names of the intermediate compounds

in the cycle are not required. Thus it would be acceptable to

note: C2 + C4 = C6 C5 , and so on.

8.1.5 Explain oxidative phosphorylation in terms of chemiosmosis. Obj 3

8.1.6 Explain the relationship between the structure of the mitochondrion

and its function. Obj 3

Limit this to cristae forming a large surface area for the electron

transport chain, the small space between inner and outer

link reaction

C3 (pyruvate)

C4

CO2

C6

C5

CO2

C2 (acetyl CoA)


58

membranes for accumulation of protons, and the fluid matrix

containing enzymes of the Krebs cycle.

5. What does a nucleosome consist of ?

A. DNA and histones

B. DNA and chromatin

C. Chromatin and nucleotides

D. Mature RNA and histones (Total 1 mark)

Answer: A

6. What are Okazaki fragments?

A. Short lengths of RNA primase attached to the DNA during replication

B. Short sections of DNA formed during DNA replication

C. Nucleotides added by DNA polymerase I in the same direction as the replication fork

D. Sections of RNA removed by DNA polymerase III and replaced with DNA (Total 1 mark)

Answer: B [1]

7. The sequence of nucleotides in a section of RNA is:

GCCAUACGAUCG

What is the base sequence of the DNA sense strand?

A. CGGUAUGCUAGC

B. GCCATACGATCG

C. CGGTATGCTAGC

D. GCCAUACGAUCG (Total 1 mark)

Answer: C [1]

8. The electron micrograph below shows an organelle in a eukaryotic cell. What is the area labelled X and what is

the type of reaction occurring there?


59

[Source: http://scienceblogs.com/clock/2006/11/cell_structure.php]

X Reaction

A. matrix photolysis

B. stroma Krebs cycle

C. stroma photolysis

D. matrix Krebs cycle

(Total 1 mark)

Answer: D [1]


(a) Membrane proteins vary in their positions within the membrane and in their functions.

Outline the positions and functions of proteins in membranes. (8)

(b) Explain how polar and non-polar amino acids help channel proteins and enzymes carry out their

functions. (5)

(c) Compare competitive and non-competitive inhibition of enzymes. (5)

(Total 20 marks)

Answer: (a) integral proteins are embedded in the membrane/phospholipid bilayer;

peripheral proteins are on the surface of the membrane;

some integral proteins (are transmembrane proteins that) extend from

one side of the membrane to the other;

hormone binding sites;

e.g. insulin;

enzymes;

e.g. sucrase / succinate dehydrogenase;

cell adhesion;


60

cell-to-cell communication recognition / antigenic markers /

glycoproteins / contact inhibition;

channels/pores for passive transport/facilitated diffusion;

pumps/carriers for active transport;

receptors for neurotransmitters;

such as acetylcholine;

electron carriers;

e.g. electron transport chain of cellular respiration;

pigments (in rods/cones); 8 max

Award any of the above points if clearly drawn in an annotated diagram.

(b) non-polar amino acids cause channel proteins to embed in a

membrane;

polar amino acids at either end cause channel proteins to be

transmembrane / retain protein position in membrane;

polar amino acids lining pore allow polar particles to pass through/

form hydrophilic channels through membranes;

polar amino acids on surface of enzyme allow it to dissolve in water;

polar and non-polar amino acids contribute to the specificity of

an enzyme;

non-polar amino acids of surface of enzyme allow it to embed

in a membrane;

polar amino acids at active site of enzyme attract polar substrates;

positively charged amino acids attract negatively charged

substrate / vice versa;

non-polar amino acids at active site attract non-polar substrate; 5 max

Award any of the above points if clearly drawn in an annotated diagram.

(c) Answers do not need to be shown in a table format. Award marks

only when there is a comparison of both types of inhibition.

Competitive inhibition Non-competitive inhibition

substrate and inhibitor are

(chemically) similar/same shape

substrate and inhibitor are (chemically)

not similar/different shape;

inhibitor binds to active site inhibitor binds away from the active

site/allosteric site / diagram to illustrate

difference;

inhibitor does not change the shape

of the active site

inhibitor changes the shape of the active

site;

increases in substrate concentration

reduce the inhibition

increases in substrate concentration do

not affect the inhibition / annotated

graph to illustrate the difference;

both types of inhibitor reduce enzyme activity;

both types of inhibitor bind to the enzyme;

both types of inhibitor prevent the substrate from binding to the active site;

example e.g. succinate

dehydrogenase is inhibited by

example e.g. pyruvate kinase is inhibited


61

malonate by alanine;

5 max


10. Where is carbon dioxide produced in the mitochondrion?

(Total 1 mark)

Answer: D

11. Genetic engineering allows genes for resistance to pest organisms to be inserted into various crop plants.

Bacteria such as Bacillus thuringiensis (Bt) produce proteins that are highly toxic to specific pests.

Stem borers are insects that cause damage to maize crops. In Kenya, a study was carried out to see which

types of Bt genes and their protein products would be most efficient against three species of stem borer. The

stem borers were allowed to feed on nine types of maize (A–I), modified with Bt genes. The graph below

shows the leaf areas damaged by the stem borers after feeding on maize leaves for five days.


62

[Source: S Mugo et al., Figure 3 from ―Developing Bt maize for resource-poor farmers—Recent advances in the IRMA project‖,

African Journal of Biotechnology (2005), volume 4, number 13, pp. 1490-1504]

(a) Calculate the percentage difference in leaf area damaged by Sesamia calamistis between the control

and maize type H. Show your working.

......................................................................................................................................

...................................................................................................................................... (2)

(b) Discuss which species of stem borer was most successfully controlled by the genetic engineering of the

maize plants.

......................................................................................................................................

...................................................................................................................................... (3)

Before the use of genetically modified maize as a food source, risk assessment must be carried out. A 90-day

study was carried out in which adult male and female rats were fed either:

• seeds from a Bt maize variety

• seeds from the original non-Bt maize variety

• commercially prepared rat food.

All the diets had similar nutritional qualities.

[Source: Linda A. Malley et al. 2007. ―Subchronic feeding study of DAS-59122-7 maize grain in Sprague-Dawley rats‖. Food and

Chemical Toxicology. Vol 45, issue 7. Pp 1277–1292]


63

(c) Calculate the change in mean mass of male and of female rats fed on Bt maize from day 14 to 42.

......................................................................................................................................

...................................................................................................................................... (2)

(d) Evaluate the use of Bt maize as a food source on the growth of the rats.

......................................................................................................................................

...................................................................................................................................... (2)

(e) Comment on the use of Bt maize as a food source compared to the other diets tested.

......................................................................................................................................

...................................................................................................................................... (1)

Studies have shown that Bt proteins are released by plant roots and remain in the soil.

One study looked at the biomass of microorganisms in soil surrounding the roots of:

• Bt maize

• non-Bt maize

• non-Bt maize with an insecticide (I).

The graph below shows the biomass of microorganisms at two different times in the growth cycle of the

plants (Flower and Harvest). Error bars represent standard error of the mean.

[Source: Devare, M et al. ―Neither transgenic Bt maize (MON863) nor tefluthrin insecticide adversely affect soil microbial activity or

biomass: A 3-year field analysis‖. Soil Biology and Biochemistry. Vol 39, issue 6. Pp 2038–2047. © Elsevier. Reproduced with

permission.]


64

(f) State one role of bacteria in a soil ecosystem.

......................................................................................................................................

...................................................................................................................................... (1)

(g) Compare the biomass of microbes in the soils surrounding the roots of Bt maize and non-Bt maize.

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................

...................................................................................................................................... (2)

(h) The researchers‘ original hypothesis stated that microorganisms would be negatively affected by the Bt

protein released by the plant roots. Discuss whether the data supports the hypothesis.

......................................................................................................................................

...................................................................................................................................... (2)

Bt proteins act as toxins to insects, primarily by destroying epithelial cells in the insect‘s digestive system.

Below is the three-dimensional structure of one such protein.

[Reprinted from Mario Soberón. 2007. ―Mode of action of mosquitocidal Bacillus thuringiensis toxins‖. Toxicon. Vol 49, issue 5. Pp

597–600. Copyright (2007), with permission from Elsevier and the International Society on Toxicology.]

(i) (i) State the type of structure shown in the region marked A in the diagram above.

...........................................................................................................................


65

(1)

(ii) Outline how this structure is held together.

...........................................................................................................................

........................................................................................................................... (2)

(iii) Region A inserts into the membrane. Deduce, with a reason, the nature of the amino acids that

would be expected to be found in this region.

...........................................................................................................................

........................................................................................................................... (2)

(Total 20 marks)

Answer: (a) 50 – 12 = 38 (mm2); Accept 12–50 = –38

(38 ÷ 50) x 100 = (–)76%; (ECF) 2

(b) Sesamia (was most successfully controlled);

in control plants Sesamia caused most damage;

all types of Bt/genetically modified maize/A–I show (significant) decrease

in damage by Sesamia;

mark for correct numerical comparison;

Sesamia caused no damage to type E/ in one instance;

Busseola not controlled/affected by Bt/genetically modified maize/

caused largest amount of damage in types A–I/increased damage in

some varieties;

Eldana controlled by some types of maize / B/C/D but not others /

Eldana caused least damage in control and not much difference in

many maize types; 3 max

(c) males: (440 – 325 =) 115 g; (Accept answers in range 105–125 g)

females: (268 – 215 =) 53 g; (Accept answers in range 51–57 g)

Units required, no workings required. 2

(d) (promotes) highest rate of growth at start of study / tapering off later in

the study;

Bt maize appears to cause less growth/mass gain than rat

food / vice versa;

more pronounced difference in females;

no difference in growth/mass gain between Bt and non-Bt maize; 2 max

(e) (Bt) maize may not be as good as the (commercially prepared) rat food;

Bt maize appears to be as good a food source as non-Bt maize;

Bt maize an acceptable/safe food source;

Answers require a judgement about Bt maize as a food source rather

than a description. 1 max

(f) decomposers / recycle nutrients / cause decay / nitrification/nitrogen

fixation / denitrification 1


66

(g) (for both groups) overall biomasses were higher during flowering than

harvest / vice versa

the microbial biomass for the Bt crop was (slightly) lower than for the

non-Bt crops at flower time;

the microbial biomass for the Bt crop was (slightly) higher than for

the non-Bt crops at harvest time; 2 max

(h) data does not support the hypothesis as there is little difference between

biomass found in the soil (surrounding) roots (of the Bt and non-Bt) at

either time;

data does not support the hypothesis as there is a slightly positive effect

at harvest;

data supports hypothesis as there is a slightly negative effect at flowering; 2 max

(i) (i) α helix / alpha helix 1

(ii) hydrogen bonds;

between the turns of the helix (rather than between R-groups);

bonds between carboxyl and NH groups/C-O---H-N; 2 max

(iii) non-polar amino acids/R-groups;

(inner part of phospholipid) bilayer is hydrophobic/non-polar; 2 [20]


67

Topic 7: DNA and Proteins (Cambridge University Press)

1 The following statements are false. Rewrite each statement so that it is correct. There may be more than one

mistake in each statement. (7)

a Genes are small sections of DNA that code for individual nucleic acids.

b DNA bases are paired as follows: guanine with thymine and cytosine with adenine.

c Chromosomes are short and made of protein.

d A nucleosome consists of RNA wrapped around two histone proteins.

2 a In the diagram below, label the following: (5)

deoxyribose, phosphate, pyrimidines, purines, 3' end, 5' end

b Explain what the term ‗antiparallel‘ means. (1)

c In which direction does DNA replication occur? (To which end of the molecule are DNA nucleotides added?)

(1)

3 Arrange these statements, which describe DNA replication, in the correct order. (7)

A DNA replication takes place in the nucleus during interphase.

B DNA polymerase checks the new strands and corrects mistakes so the two new strands are identical to the

original strand.

C Nucleotides bond to their complementary bases with hydrogen bonds.

D Sugar and phosphate groups are joined together by DNA polymerase.


68

E The DNA double helix is unwound by the enzyme helicase.

F Two new strands rewind to form two new double helices.

G Both strands act as a template: nucleotides with the correct complementary bases pair up with bases of the

exposed strands.

4 Complete the following table, which describes the roles of the enzymes involved in DNA replication. (5)

Enzyme Function in DNA replication

helicase

synthesises RNA primers

DNA polymerase III

removes RNA primer and replaces it with DNA

DNA ligase

5 During transcription, DNA is opened up by RNA polymerase. One strand is used to form mRNA. Which of the

following statements are true and which are false?

a The sense strand has the same base sequence as the new mRNA. (1)

b The antisense strand is the template for transcription. (1)

c The 3' end of a free RNA nucleotide is added to the 5' end of the RNA molecule that is already synthesized.

(1)

d The new mRNA has a base sequence that is complementary to the antisense strand. (1)

e Eukaryotic DNA is different from prokaryotic DNA because it contains stretches of DNA that are non-

coding. (1)

f Introns are removed from mRNA after it is produced in eukaryotes. (1)

6 Enzyme activity may be affected by competitive or non-competitive inhibitors.

a Identify which of the diagrams below represents each type of inhibition. (4)

b Explain the shapes of the two graphs, which show rate of reaction plotted against substrate concentration.

(2)


69

Answers

1 a Genes are small sections of DNA that code for polypeptides. (1)

b DNA bases are paired as follows: guanine with cytosine and thymine withadenine. (1)

c Chromosomes are long and made of DNA and histone proteins. (2)

d A nucleosome consists of DNA wrapped around eight histone proteins and held in place by two further

histones. (3)

2 a (5)

b Antiparallel means that the two DNA strands run in opposite directions to one another. (1)

c During replication, the 5' end of a nucleotide is added to the 3' end of the chain of nucleotides that is being

made. (1)


70

3 A, E, G, C, D, F, B (7)

4 (5)

Enzyme Function in DNA replication

helicase unwinds the double helix

RNA primase synthesises RNA primers

DNA polymerase III synthesises new DNA strand by adding nucleotides

DNA polymerase I removes RNA primer and replaces it with DNA

DNA ligase joins the ends of Okazaki fragments

5 c is false; all other statements are true. (6)

6 a Diagram A and graph C represent competitive inhibition. Diagram B and graph D

represent non-competitive inhibition. (4)

b In graph C, the effect of the inhibitor is reduced as the concentration of the substrate increases.

In graph D, as the concentration of substrate is increased, the rate of reaction increases but does not reach the same level as without an

inhibitor. The inhibitor does not compete for active sites


71

Topic 8 :Respiration and Photosynthesis(Cambrige University Press)

1 The diagram below shows processes taking place in two plant organelles, A and B.

a Name the organelles A and B. (2)

b Name the substances X and Y. (2)

c What are ATP and reduced NADP used for in the light-independent reaction? (2)

d State where in the cell glycolysis and the Krebs cycle occur. (2)

2 Complete the following table, which compares the production of ATP in mitochondria and in chloroplasts. Write

‗true‘ or ‗false‘ in the boxes to indicate which statements correctly describe processes that occur in each organelle.

(10)

Process Mitochondrion Chloroplast

photons excite electrons

electrons pass through carrier molecules

oxidative phosphorylation occurs

ATP is produced from ADP and Pi

takes place in both light and darkness

3 The graph below shows the uptake and release of carbon dioxide by a green plant at different light intensities.


72

a The point P is known as the compensation point. Using the information on the graph, explain what is

happening at this point. (2)

b Describe the shape of the graph at point Q and explain what is happening in the cells. (2)

c What are the products of the light-dependent reactions? (2)

d Why does the uptake of CO2 slow down at higher light intensities? (1)

4 a Why do plants need an effective root system in order to photosynthesize? (1)

b Copy and complete the following paragraph, which describes part of the process of photosynthesis, by

inserting the correct words in the spaces. (8)

Chlorophyll a and chlorophyll b are both found in chloroplasts. Chlorophylls absorb mainly

_______________ and _______________ wavelengths of light. In the process of cyclic

photophosphorylation, light displaces an electron from a chlorophyll molecule. This electron is returned to

the chlorophyll via a series of _______________ _______________, each of which is at a lower energy

level. _______________ is synthesised as the electrons flow. _______________ is used in the light-

independent reactions, which occur in the _______________ of the chloroplast. In the process of non-cyclic

photophosphorylation,the electrons are combined with_______________ _______________, which are

produced from the photolysis of _______________.

Answers

1 a A = chloroplast, B = mitochondrion (2)

b X = oxygen, Y = carbon dioxide (2)


73

c ATP is used to regenerate RuBP. Reduced NADP (NADPH + H+) supplies hydrogen ions for the production

of triose phosphate. (2)

d Glycolysis occurs in the cytoplasm; the Krebs cycle occurs in the matrix of the mitochondrion. (2)

2 (10)

Process Mitochondrion Chloroplast

photons excite electrons false true

electrons pass through carrier molecules true true

oxidative phosphorylation occurs true false

ATP is produced from ADP and Pi true true

takes place in both light and darkness true false

3 a At the compensation point, uptake and release of carbon dioxide are equal, therefore the rate of

photosynthesis and rate of respiration are equal. (2)

b Up until point Q, the rate at which carbon dioxide uptake increases with light intensity is at its greatest,

indicating that the rate at which photosynthesis increases with light intensity is also at its greatest up to this

point. Beyond point Q, the rate of increase starts to drop (the graph becomes less steep and begins to plateau).

(2)

c ATP and reduced NADP (NADPH + H+) (2)

d This indicates that another factor, other than light intensity, is now limiting the rate of photosynthesis (for

example, temperature). (1)

4 a Water is required for photosynthesis and this enters the plant through its roots. (1)

b Chlorophyll a and chlorophyll b are both found in chloroplasts. Chlorophylls absorb mainly blue and red

wavelengths of light. In the process of cyclic photophosphorylation, light displaces an electron from a

chlorophyll molecule. This electron is returned to the chlorophyll via a series of electron carriers, each of

which is at a lower energy level. ATP is synthesised as the electrons flow. ATP is used in the light-

independent reactions, which occur in the grana of the chloroplast. In the process of non-cyclic

photophosphorylation,the electrons are combined withhydrogen ions, which are produced from the

photolysis of water. (8)

5 (5 – 1 mark for each correctly filled box)

Photosynthesis Respiration

Place where H+

ions accumulate

in thylakoid space in grana between inner and outer membranes of mitochondria

Source of H+ ions photolysis of water molecules hydrogen acceptors such as NADH + H

+

Source of energy light from the Sun glucose

Use of ATP used in the stroma to reduce CO2 in used in metabolic reactions in


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formed light-independent reactions cytoplasm


75

Topic 9 : Plant Physiology

1. The diagram below shows a cross section of a stem. What is the structure labelled Y and one of its functions?

Structure Y Function

A. phloem storage of water and starch

B. xylem mechanical support

C. phloem gas exchange

D. xylem transport of sugars

(Total 1 mark)

B [1]

2. Plants develop brightly coloured flowers to attract animals. Which process is directly assisted by this adaptation?

A. Seed dispersal

B. Pollination

C. Fertilization

D. Germination (Total 1 mark)

B [1]


(a) Outline the various stages of the cell cycle.

(4)


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(b) Describe the differences in the structures of dicotyledonous plants and monocotyledonous plants.

(5)

(c) Define the term transpiration and explain the factors that can affect transpiration in a typical terrestrial

plant.

(9)

(Total 20 marks)

(a) G1 the cell grows/duplication of organelles;

S is synthesis stage when DNA is synthesized/replicated;

G2 the chromosomes begin condensing/preparation for cell division;

G1, S and G2 make up interphase;

during mitosis nuclear division occurs/all four stages listed;

during cytokinesis cytoplasm/cell divides/daughter cells formed; 4 max

(b) monocotyledon seeds contain one cotyledon/seed leaf;

dicotyledon seeds contain two cotyledons/seed leaves;

monocotyledons have parallel veins;

dicotyledons have net-like veins;

monocotyledon stems have scattered vascular bundles;

dicotyledon stems have vascular bundles around edge;

monocotyledon roots are adventitious/fibrous;

dicotyledon roots are from radicle/tap root/branched;

monocotyledon flower parts/petals are (usually) in threes;

dicotyledon flower parts/petals are (usually) in fours or fives; 5 max

(c) (transpiration is) loss of water vapour from the leaves/

stomata (and stems) of plants;

temperature, humidity, light (intensity) and wind all affect

transpiration;

high temperatures increase evaporation rate of water/transpiration;

(accept converse)

high humidity lowers the rate of water evaporation/transpiration;

(accept converse)

air currents/wind increase water evaporation/transpiration; (accept converse)

high light (intensity)/sunlight (usually) increases photosynthesis/

water evaporation through the stomata/transpiration;

stomata open to allow gaseous exchange/entry of CO2;

abscisic acid stimulates closing of stomata;

guard cells open/close the stomata;

adaptations of (xerophyte) plant structures reduce water loss/

transpiration;

)physiology C4 / CAM / formlow growth

y /mata in da close sto stomata /reduced/sunken/spines

leavesrolled/area surface reduced/cuticle leaf thicker(

example; one


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second example; (of above) 9 max

Award [8 max] if definition is missing.

(Plus up to [2]for quality)

[20]

4. How do mineral ions in the soil move to the root through the soil?

A. Osmosis

B. Mass flow of water

C. Translocation

D. Through phloem (Total 1 mark)

B [1]

5. How are fluids transported in the xylem and the phloem?

Xylem Phloem

A. away from the root only towards the root only

B. towards the root only away from the root only

C. away from and towards the root towards the root only

D. away from the root only away from and towards the root

(Total 1 mark)

D [1

6. (a) The photograph below shows the flowers of Campanula persicifolia. Label structures I, II and III.


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[Source: photograph provided by IB examiner]

(3)

(b) (i) Using the external features shown in the photograph, state the phylum to which this plant

belongs.

...........................................................................................................................

........................................................................................................................... (1)

(ii) Comment on the hypothesis that the plant shown in the photograph could be pollinated by an

animal.

...........................................................................................................................

........................................................................................................................... (2)

(c) Outline the use of the binomial system of nomenclature in Campanula persicifolia.

......................................................................................................................................

...................................................................................................................................... (2)

(Total 8 marks)

(a) I. sepal;

II. ovary / receptacle;

III. petal; 3

(b) (i) Angiospermophyta / Angiospermophytes / Angiosperms

Do not accept flowering plants. 1


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(ii) confirms the hypothesis; must be qualified

stigma/anther inside the flower/ring of petals so as visiting animal

enters it brushes past them;

colourful petals (provide contrast) so that flowers can be seen

by animals;

(slightly) cone-shaped flowers so animals come in; 2 max

(c) first name/Campanula for genus / second name/persicifolia for species;

(all) members of Campanula persicifolia share special/unique features;

two names make a unique combination to designate species / worldwide

recognized nomenclature; 2 max [8]

7. (a) Draw a labelled diagram of the structure of a chloroplast as seen with an electron microscope. (4)

(b) Describe how water is carried by the transpiration stream.

(7)

(c) Explain how flowering is controlled in long-day and short-day plants. (7)

(Total 18 marks)

(a) Award [1] for each of the following clearly drawn and correctly labelled.

Label lines must be unambiguous in terms of what they are indicating.

double/inner and outer membrane/envelope—shown as two concentric

continuous lines close together;

granum/grana —shown as a stack of several disc-shaped subunits;

(intergranal) lamella — shown continuous with thylakoid membrane;

thylakoid — one of the flattened sacs;

stroma;

(70S) ribosomes/(circular) DNA / lipid globules / starch granules /

thylakoid space; 4 max

(b) transpiration is water loss (from plant) by evaporation;

flow of water through xylem from roots to leaves is the transpiration stream;

evaporation from spongy mesophyll cells;

replaced by osmosis from the xylem;

(diffusion of water vapour) through stomata;

water lost replaced from xylem / clear diagram showing movement of

water from xylem through cell(s) (walls) to air space;

water pulled out of xylem creates suction/low pressure/tension;

transpiration pull results;

water molecules stick together/are cohesive;

due to hydrogen bonding/polarity of water molecules;

xylem vessels are thin (hollow) tubes;

adhesion between water and xylem due to polarity of water molecules;

creates continuous column/transpiration stream; 7 max


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(c) flowering affected by light;

phytochrome;

exists in two (interconvertible) forms/Pfr and Pr;

Pr (red absorbing/660 nm) converted to Pfr (far-red/730 nm absorbing) in

red or day light;

sunlight contains more red than far red-light so Pfr predominates

during the day;

gradual reversion of Pfr to Pr occurs in darkness;

Pfr is active form / Pr is inactive form;

in long-day plants, flowering induced by dark periods shorter than

a critical length / occurs when day is longer than a critical length;

enough Pfr remains in long-day plants at end of short nights to stimulate

flowering;

Pfr acts as promoter of flowering in long-day plants;

short-day plants induced to flower by dark periods longer than a

critical length/days shorter than a critical value;

at end of long nights enough Pfr has been converted to Pr to allow

flowering to occur;

Pfr acts as inhibitor of flowering in short-day plants; 7 max



(a) Draw a labelled diagram showing the tissues present in a dicotyledonous leaf. (4)

(b) Outline the light-dependent reactions of photosynthesis. (6)

(c) Explain the effect of light intensity and temperature on the rate of photosynthesis. (8)

(Total 20 marks)

(a) Award [1] for each structure clearly drawn and correctly labelled. Accept

a plan diagram without individual cells.

upper and lower epidermis;

palisade mesophyll under upper epidermis to of leaf thickness;

spongy mesophyll/layer in lower half of leaf;

vein showing separate areas of xylem above phloem;

stoma/stomata labelled in (lower) epidermis;

two guard cells; (at least one must be labelled for mark) 4 max

(b) (chlorophyll/antenna) in photosystem II absorbs light;

absorbing light/photoactivation produces an excited/high energy/

free electron;

electron passed along a series of carriers;

reduction of NADP+ / generates NADPH + H

+;

3

1

2

1


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absorption of light in photosystem II provides electron for photosystem I;

photolysis of water produces H+ / O2;

called non-cyclic photophosphorylation;

in cyclic photophosphorylation electron returns to chlorophyll;

generates ATP by H+ pumped across thylakoid membrane / by

chemiosmosis / through ATP synthetase/synthase; 6 max

(c) both light and temperature can be limiting factors;

other factors can be limiting;

graph showing increase and plateau with increasing light / description

of this;

graph showing increase and decrease with increasing temperature /

description of this;

light:

affects the light-dependent stage;

at low intensities insufficient ATP;

and insufficient NADPHH + H+

produced;

this stops the Calvin cycle operating (at maximum rate);

temperature:

affects light-independent stage / Calvin cycle;

temperature affects enzyme activity;

less active at low temperatures / maximum rate at high temperatures;

but will then be denatured (as temperature rises further);

Award [5 max] if only one condition is discussed. 8 max


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Topic 10 :Genetics ( Cambridge University Press)

1. The table below shows some processes associated with mitosis or meiosis or both. For each process, complete the table

using a tick () in the appropriate box if it applies to mitosis, meiosis I or meiosis II, and a cross () if it does not. (5)

Process Mitosis Meiosis I Meiosis II

takes place during the formation of gametes

DNA replicates before prophase

chromosomes form pairs before prophase

chiasmata form

random assortment of chromatids occurs during anaphase

2 a Define ‗polygenic inheritance‘. (1)

b If a polygenic characteristic is controlled by two genes, each of which has two alleles, how many different

genotypes are possible for the characteristic? Give the possible genotypes. (2)

3 In a dihybrid cross, the genotypes of a variety of plant were TtHh, Tthh, ttHh, tthh where T = tall and H = hairy.

Which of the following crosses would produce offspring giving a ratio of 1 : 1 : 1 : 1 in the phenotype?

(1)

A TtHhTtHh

B TtHhTthh

C TtHhttHh

D TtHhtthh

E TTHHtthh

4 In a species of tropical bird, red plumage is dominant to white and the crested form is dominant to non-crested.

When two heterozygous birds were crossed, a ratio of 3 red, crested birds : 1 white, non-crested bird was obtained.

Explain how this has occurred, using a Punnett grid. (4)

ANSWER:

1. (5 – 1 mark for each correct row)

Process Mitosis Meiosis I Meiosis II

takes place during the formation of gametes

DNA replicates before prophase

chromosomes form pairs before prophase

chiasmata form

random assortment of chromatids occurs during anaphase


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2 a Polygenic inheritance is the inheritance of phenotypes that are determined by the combined effect of several

genes. (1)

b 9 possible genotypes. If the alleles are a and A, and b and B, possible genotypes are aabb, Aabb, aaBb,

AAbb, AbBb, aaBB, AaBB, AABb and AABB. (2)

3 D (1)

4 The genes are linked. If the alleles are R = red and P = crested, then the heterozygotes are RrPp. The gametes are

shown as R Pand r p, because of the linkage. (2)

So in a Punnett grid:

R P r p

R P red, crested red, crested

r p red, crested white, non-

crested

(2)


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Topic 11: Animal Physiology

Which of the cells labelled in the diagram below provides nourishment for developing sperm cells?

[Source: Freeman & Bracegirdle, An Atlas of Histology, (Heinemann: 1976) p. 91, Copyright holder unknown.]

(Total 1 mark)

ANSWER:

C [1]


(a) Draw a labelled diagram of the adult female reproductive system. (4)

(b) Outline the roles of progesterone and estrogen in the human menstrual cycle. (6)

(c) Explain the function and structure of the placenta. (8)

(Total 20 marks

Answer:

(a) Award [1] for each structure clearly drawn and correctly labelled.

ovary — shown adjacent to but not joined to oviduct/fallopian tube;

oviduct/fallopian tube — shown as a tube leading into a uterus;

uterus —shown with a thicker wall than oviduct/fallopian tube;

vagina — shown leading from the uterus, connected to the cervix;


85

cervix —shown as a constriction between the vagina and uterus;

endometrium — shown as inner lining of uterus; 4 max

(b) follicles secrete estrogen / FSH stimulates secretion of estrogen;

(rapid) increase in estrogen stimulates FSH/LH production;

estrogen also stimulates repair/thickening of endometrium/uterus lining;

LH causes follicle to produce less estrogen/more progesterone;

corpus luteum secretes more estrogen/progesterone;

progesterone maintains/stimulates thickening of endometrium/uterus lining;

estrogen/progesterone inhibit FSH/LH secretion;

estrogen/progesterone levels fall after day 21–24 if no embryo/fertilization;

lower concentration of estrogen/progesterone allows disintegration of endometrium/uterus lining /

menstruation occurs;

Award [4 max] if only one hormone is explained. 6 max

(c) transfer of foods/nutrients/glucose from mother to fetus;

fetal gas exchange/transfer of oxygen from mother to fetus;

transfer of excretory products/CO2 from fetus to mother;

transfer of antibodies/hormones from mother to fetus;

secretion of estrogen/progesterone;

from approximately 12 weeks / when ovary/corpus luteum stops secretion;

disc shaped structure;

connected to the fetus by an umbilical cord;

embryonic tissue invades/grows into the uterine wall;

placental villi increase the surface area (for exchange);

fetal capillaries in placenta/placental villi;

inter-villous spaces/sinuses through which mother‘s blood flows;

small distance between fetal and mother‘s blood/narrow placental barrier;

Allow reference to embryo instead of fetus throughout. 8 max

(Plus up to [2] for quality) [20]

3. What structure within muscle tissue is surrounded by membrane and has multiple nuclei?

A. Muscle bundle

B. Muscle fibre

C. Myofibril

D. Sarcomere (Total 1 mark)

Answer:

B [1]


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4. Which cells activate helper T-cells by antigen presentation?

A. B-cells

B. Bacteria

C. Macrophages

D. Plasma cells (Total 1 mark)

Answer:

C

5. The Bowman‘s capsule is a cup-shaped structure that is part of the nephron. What is the source of glucose in the

fluid in the Bowman‘s capsule?

A. Blood in the glomerulus

B. Urine in the renal pelvis

C. Filtrate in the distal convoluted tubule

D. Interstitial fluid in the medulla (Total 1 mark)

Answer:

A

6. The diagram below shows a human egg.

What are the structures labelled I, II and III?

I II III

A. acrosomes zona pellucida follicle cells

B. acrosomes cell wall sperm

C. cortical granules cell wall sperm

D. cortical granules zona pellucida follicle cells

(Total 1 mark)


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Answer:

D


(a) Outline how antibiotic resistance in bacteria can arise in response to environmental change. (5)

(b) Outline the principle of immunity. (6)

(c) Discuss the benefits and dangers of vaccination. (7)

(Total 20 marks)

Answer:

(a) antibiotic resistance can be inherited;

alleles for resistance can be passed from one cell to another by exchange

of plasmids/conjugation;

some varieties are more resistant than others;

bacteria reproduce very rapidly and have high mutation rate;

evolution can occur rapidly;

increased exposure to antibiotics is the environmental change that

selects for resistant varieties;

for example, in hospitals / animal feed / inappropriate prescriptions /

not finishing prescriptions;

bacteria without resistance die / resistant bacteria survive and pass on

genes to next generation;

results in change in genetic makeup of population; 5 max

(b) immunity is the ability of an organism to resist infection;

due to presence of (specific) antibodies;

immunity can be active or passive;

passive due to receiving antibodies from external sources/across

placenta/from breast milk/injection;

active results from facing an infection directly/through vaccination;

pathogen/foreign cell invades body;

leads to clonal selection/formation of B memory cells;

B-cells produce specific antibodies;

if same pathogen enters body again memory cells activated/stimulated

to divide;

antibodies produced faster and in greater amounts; 6 max

(c) Benefits: [4 max]

immunity results

can limit pandemics/epidemics/spread of (infectious) diseases;

diseases can be eradicated/smallpox eliminated;

reduces mortality/deaths due to disease;

can protect vulnerable groups/young/old/with other conditions;


88

decrease crippling effects of diseases (such as polio);

decreased health care costs;

Dangers: [4 max]

may produce (mild) symptoms of the disease;

human error in preparation/storage/administration of vaccine;

individual may react badly to vaccine / defective immune system /

hypersensitive/allergic reaction;

immunity may not be life-long/booster required;

possible toxic effects of mercury-based preservatives/thimerosal; 7 max


8. Which structure is acted upon by ADH (vasopressin)?

A. Proximal convoluted tubule

B. Bowman‘s capsule

C. Loop of Henle

D. Collecting duct (Total 1 mark)

Answer:

D [1

9. What is the difference between spermatogenesis and oogenesis?

Spermatogenesis Oogenesis

A. final cells are a similar size final cells are not all the same size

B. cells produced are undifferentiated cells produced are differentiated

C. spermatogenesis begins in a boy at birth oogenesis begins in a girl before she is born

D. one germinal epithelium cell produces

four sperm cells in a testis

one germinal epithelium cell produces one

oocyte in the ovary

(Total 1 mark)

Answer:

A [1]

10. What are the names of the two structures labelled I and II in the arm joint diagram below?


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I II

A. biceps radius

B. biceps humerus

C. triceps humerus

D. triceps ulna

(Total 2 mark)

Answer:

D [1]


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Option C

1.(a) Define gross production.

..................................................................................................................................... (1)

(b) Outline the characteristics of a desert biome.

.....................................................................................................................................

..................................................................................................................................... (3)

(Total 4 marks)

ANSWER:

(a) (gross production =) net production + respiration;

(gross production is) the total amount of organic matter produced by

plants in an ecosystem; 1 max

(b) temperature is high during daytime and low during night time;

solar radiation during day is high / heat loss during night is high;

moisture is less than 500 mm rainfall per annum;

vegetation is sparse;

fauna is specialized; 3 max [4]

2. Which group of organisms in the carbon cycle converts carbon into a form that is available to primary

consumers?

A. Decomposers

B. Detritus feeders

C. Producers

D. Secondary consumers (Total 1 mark)

ANSWER:

C

3. (a) Outline the temperature, moisture and vegetation characteristics of any one biome.

.....................................................................................................................................

.....................................................................................................................................


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(3)

(b) Discuss ecological arguments for the preservation of biodiversity.

.....................................................................................................................................

..................................................................................................................................... (4)

(Total 7 marks)

ANSWER: (a) correctly named biome eg temperate deciduous forest;

level of precipitation eg moderate precipitation / 75–150 cm throughout

the year;

temperature range eg 15–18C / warm summers and 3–7C / cold winters /

significant annual temperature variation;

dominant plant eg dominant plants are broad leaf trees (that lose leaves

annually) / ecosystem characteristics eg significant diversity of understory

plants; 3 max

(b) species within an ecosystem are interdependent;

loss of one species affects a network of other species;

organism that expands to fill unoccupied niche might disrupt balance;

species impact abiotic factors;

example of impact on abiotic factor such as: increased erosion / decrease soil

fertility / microclimate changes etc;

human cultures / indigenous populations ability to live sustainably within

ecosystem might be affected; 4 max [7]

4. Which diagram shows the flow of energy through a community with three trophic levels?

(Total 1 mark)

ANSWER:

D

5. (a) Outline the major differences in temperature and moisture that are characteristic of two named biomes.

......................................................................................................................................

A. B.

C. D.


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...................................................................................................................................... (2)

(b) Explain, using a named example, the cause and consequence of biomagnification.

......................................................................................................................................

...................................................................................................................................... (3)

(Total 5 marks)

ANSWER:

(a)

named biome temperature moisture

desert high temperature/thermal

amplitude in day and cold

at night

dry / average rainfall less

than 25 cm year–1

;

tropical rainforest hot damp / wet / average rainfall

225 cm year–1

;

tundra cold / –6°C to –12°C dry / average rainfall 25 cm

year–1

;

Both temperature and moisture are required for mark to be awarded.

Accept other correct biomes. 2 max

(b) named example;

definition of biomagnification;

cause;

consequence;

e.g.

name: DDT / pesticide to control mosquitoes of malaria;

definition of biomagnification: chemicals accumulate along

the food chain;

cause: as fat soluble, it accumulates in fatty tissue;

consequence: becoming more concentrated at each trophic level /

increasingly more toxic / ultimately leading to death of organism up in food chain;3 max [5]

6. (a) (i) State one example of a deliberate release of an alien species, including the name of the organism and

where it was released.

...........................................................................................................................

........................................................................................................................... (1)

(ii) Using the example from (a)(i), outline the reason for its release and the impact it had on the

environment.


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...........................................................................................................................

........................................................................................................................... (2)

(b) Explain, using a named example, the cause and consequence of biomagnification.

......................................................................................................................................

...................................................................................................................................... (3)

(Total 6 marks)

ANSWER:

(a) (i) named example and location where it was released

e.g. beaver/castor liberated in Tierra del Fuego

Answers need a named example and a location. 1

(ii) reason for release;

impact on environment;

e.g. for hunting/fur;

but built dams which altered river courses; 2

(b) named example;

definition of biomagnification;

cause;

consequence;

e.g.

name: DDT / pesticide to control mosquitoes of malaria;

definition of biomagnification: chemicals accumulate along the

food chain;

cause: as fat soluble, it accumulates in fatty tissue;

consequence: becoming more concentrated at each trophic level /

increasingly more toxic / ultimately leading to death of organism up in food chain;3 max [6]

7. Population growth, as shown by the curve below, is the result of changes in mortality, natality, immigration and

emigration. Which of the following statements about population growth is correct?


94

A. In phase I there is no mortality.

B. In phase II mortality equals natality and immigration equals emigration.

C. In phase II mortality and emigration are less than natality and immigration.

D. In phase III mortality and emigration are less than natality and immigration. (Total 1 mark)

Answer: C

8. Why do food chains in an ecosystem rarely contain more than five organisms?

A. Nutrients are recycled by the decomposers back to the producers.

B. Nutrients are lost from the ecosystem when organisms die.

C. The conversion of food into growth by an organism is not very efficient.

D. Energy is recycled by the decomposers back to the producers. (Total 1 mark)

Answer: C

9. This question is about the food web below

What is the energy transfer level from the kangaroo rat to the weasel shown in the food web above?

A. Three times greater than the energy transfer from the roadrunner to the bobcat

B. Half the energy transfer from chaparral plants to the meadow mouse

C. A quarter of the energy transfer from the quail to the bobcat

D. Approximately the same as the energy transfer from the meadow mouse to the opossum


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Answer: D [1]

10. Describe the distribution of tundra in the world today.

................................................................................................................................................

................................................................................................................................................ (Total 3 marks)

Answer: tundra is found in the Northern hemisphere only;

at latitudes of around 60°;

size of tundra is changing due to global warming; 2 max [3]


96

Option C (Cambridge University press)

1 Copy and complete this table to summarize the types of bond found in protein structure. (4)

Level of protein structure Types of bond

primary

secondary

tertiary

quaternary

2 An allosteric, non-competitive inhibitor may combine with an enzyme and cause the shape of the active site to

change so that the substrate cannot bind to it. Such inhibitors, if they bind reversibly, can act in end-product

inhibition of metabolic reactions. End-product inhibition is an example of negative feedback.

a Explain the meanings of these terms:

i allosteric site

ii non-competitive

iii active site

iv end-product inhibition

v negative feedback. (5)

b Why do most enzymes work only with one substrate? (2)

3 The diagram below shows part of the light-independent reactions of photosynthesis.

a Identify substances X, Y and Z. (3)

b State where in the chloroplast this reaction occurs. (1)

c State what GP is used for, apart from the production of glucose. (1)

d What reaction occurs during the formation of starch from glucose? (1)


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4 Comment on the following statements.

a Protein and amino acids are respired if an organism is starving. (3)

b In the desert, a camel stores and respires fat rather than carbohydrate. (3)

c Reactions of the Krebs cycle may stop the process of glycolysis. (2)

5 Draw a suitable chart to summarize the reactions of respiration. (7)

6 a Draw and label a chloroplast to show the main features seen using an electron microscope. (3)

b Annotate your diagram with the functions of the important structures. (3)

7 Summarize the importance of photosynthesis

Answer

1 (4 – 1 mark per correctly filled box)

Level of protein structure Types of bond

primary peptide linkages

secondary hydrogen bonds

tertiary hydrogen bonds, disulfide bridges, ionic bonds, van der Waals forces

quaternary two or more proteins held together by a non-protein group (for example, an iron atom in hemoglobin)

2 a i The allosteric site of an enzyme is the site (not the active site) to which a regulator molecule binds.

(1)

ii A non-competitive inhibitor binds to an enzyme molecule at a site away from the active site. (1)

iii The active site is the site at which the substrate molecule(s) binds. (1)

iv End-product inhibition occurs when rising levels of a product of a metabolic reaction affect an enzyme

earlier in the pathway and turn off the pathway. (1)

v Rising levels of a product cause the reaction to be ‗switched off‘, so that the product is no longer

formed. As levels of the product fall, the reaction is ‗switched on‘ again, and production resumes.

(1)

b The shape and bonding between enzyme and substrate are specific. If the substrate is not the correct shape

and does not have appropriate charges on its molecule, it will not bind to the active site and the reaction will

not proceed. (2)

3 a X = carbon dioxide, Y and Z = ADP and NADP (can be either way round) (3)

b in the stroma (1)


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c to regenerate RuBP (1)

d a condensation reaction (1)

4 a If an organism is starving, protein can be used as a source of energy. Protein is split into amino acids, which

are then deaminated (the NH2 group is removed). The remainder of the molecule enters the respiratory

process. Some amino acids are converted to pyruvate, others enter the Krebs cycle. In either case, ATP is

synthesised in the usual way. This only occurs during starvation because the protein comes from the

organism‘s tissues and leads to loss of body mass. Protein may also be respired if an excess is taken in the

diet.

(3)

b When fat is used as a source of energy, it yields more than 1 g of water for each 1 g of fat converted, making

it ideal for a camel in very dry conditions.

Fat is split into fatty acids and glycerol. Glycerol is phosphorylated and converted to pyruvate and enters the

Krebs cycle. Fatty acids are converted to acetyl CoA in a series of steps that remove two-carbon units. The

same series of reactions is repeated several times until the whole carbon chain is broken down, transferring a

lot of energy for ATP synthesis. These reactions occur in the liver and excess acetyl CoA produced there is

released and taken to other tissues. The liver can supply the needs of the whole body. (3)

c Glycolysis can be ‗switched off‘ by end-product inhibition. The rate of respiration is controlled by the

amount of ATP produced. If ATP production has been rapid it accumulates in cells and inhibits one of the

enzymes that catalyses the phosphorylation of sugar in glycolysis. The enzyme involved is allosteric and the

shape of its active site is determined by the ratio of ATP to ADP. This mechanism controls the rate of

respiration.

(2)

5 (7)


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6 a and b (6)

7 Photosynthesis captures light energy from the Sun, which is the source of energy for the majority of food chains.

(1)

Photosynthesis produces oxygen and has created the Earth‘s atmosphere. It also regulates the concentration of

carbon dioxide it contains. (2)

Photosynthesis is an important part of the carbon cycle and has stored the energy in fossil fuels that are used

today


100

Option H

Paper 1

1. Is the blood in the aorta, left ventricle and pulmonary artery oxygenated or deoxygenated?

Aorta Left ventricle Pulmonary artery

A. oxygenated deoxygenated deoxygenated

B. deoxygenated oxygenated oxygenated

C. oxygenated oxygenated deoxygenated

D. oxygenated oxygenated oxygenated

(Total 1 mark)

Answer: C [1]

2. What normally prevents the membranes of the alveoli from sticking together during expiration?

A. The thickness of the single-cell layer of alveoli membranes

B. The secretion of fluids in the inner surface of the alveoli

C. The pressure within the thoracic cavity

D. The dense net of capillaries covering the alveoli (Total 1 mark)

B [1]

3. This question refers to the following diagram of the digestive system.


101

Which organs are associated with the transformation of glucose into glycogen?

A. 1 and 4

B. 2 and 3

C. 2 and 4

D. 1 and 3 (Total 1 mark)

Answer: A

4. Which of the following is correct for lipase?

Substrate Source pH optimum

A. triglycerides pancreas pH = 8

B. fatty acids small intestine pH = 7

C. triglycerides small intestine pH = 9

D. fatty acids pancreas pH = 9

(Total 1 mark)

Answer: A

5. What causes air to be breathed out by the lungs?

A. The diaphragm relaxes and the ribs fall.

B. The ribs rise and the external intercostal muscles relax.

C. The internal intercostal muscles contract and the ribs rise.

D. The diaphragm contracts and internal intercostal muscles contract. (Total 1 mark)

Answer: A

6. (a) State the missing source, optimum pH requirement, substrate and product of the human enzymes in the table

below.


Amylase Salivary gland 7

Lipase Lipids Fatty acids and glycerol

(2)


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(b) Explain the need for enzymes in digestion.

......................................................................................................................................

...................................................................................................................................... (2)

(c) Draw a labelled diagram to show the interconnections between the gall bladder, pancreas and small

intestine.

(2)

Answer: (a) Award [1] for every two correct.


Amylase Salivary

gland

7 starch/amylose/

glycogen;

maltose/short

polysaccharides

/disaccharides

/dextrin;

Lipase Pancreas; Allow any pH in

range 7–9

Lipids Fatty acids and

glycerol

2 max

(b) rate of digestion at body temperature would be too slow / enzymes

increase the rate of digestion;

enzymes break large molecules down into small/soluble molecules;

for absorption/diffusion into blood; 2 max

(c) labelled sac-shaped gall bladder with a duct;

tubule/(bile) duct shown connecting gall bladder directly to small

intestine/duodenum / tubule/(bile) duct merging with the pancreatic

duct before entering small intestine; Alternative answers are

accepted because of variations in human anatomy.

pancreas drawn with pancreatic duct connected to small intestine

and pancreas labelled; 2

A duct is preferred to a line, but since this is a diagram, both are acceptable. [6]

Paper 2

1. Researchers extracted an enzyme from the human digestive system and tested its activity at different pH values

on proteins extracted from the blood of cows. The results are shown in the graph below.


103

(a) Deduce from where in the human digestive system this enzyme was extracted.

...................................................................................................................................... (1)

(b) Outline the need for enzymes in the digestive system.

......................................................................................................................................

...................................................................................................................................... (2)

(c) State one function of the large intestine.

...................................................................................................................................... (1)

(d) Explain how the structure of the villus is adapted for absorption.

......................................................................................................................................

......................................................................................................................................

...................................................................................................................................... (3)

(Total 7 marks)

Answer: (a) stomach 1

(b) enzymes speed up the digestive processes;

(chemical) break down of food/food particles/large molecules;

make soluble products/molecules small enough to be absorbed; 2 max

(c) to (re)absorb water/vitamins(s) (e.g. K and B12) / temporary storage of feces 1

(d) N.B.for each marking point, function should accompany structure.

shape of villus has large surface area to improve absorption / microvilli

increase surface area to improve absorption;

thin walls/epithelium to allow fast diffusion;

capillaries/rich blood supply (nearby) to absorb digested food products/

maintain concentration gradient;


104

lacteal in villus to absorb fatty acids/fats (and carry them away from

small intestine);

protein pumps in membrane to carry on active transport / channel

proteins in membrane to facilitate diffusion;

large number of mitochondria provide ATP for active transport; 3 max [7]

2. The electron micrograph below shows cells from the intestine.

[Source: C Candalh, Inserm, magnification ×10 000]

(a) In the electron micrograph above, state the name of the

(i) structure labelled X.

........................................................................................................................... (1)

(ii) type of cells labelled Y.

...........................................................................................................................


105

(1)

(b) Define hormone.

...................................................................................................................................... (2)

(c) Outline the circulation of blood through liver tissue.

......................................................................................................................................

...................................................................................................................................... (3)

(Total 7 marks)

Answer: (a) (i) microvilli/microvillus 1

(ii) epithelial cell/enterocyte 1

(b) chemical (messengers) secreted by (endocrine) glands;

into the blood / transported by the blood;

act on target organs/cells; 2 max

(c) hepatic artery carries oxygenated blood;

hepatic portal vein carries blood from gut/deoxygenated blood;

blood from hepatic portal vein and hepatic artery mix;

flows through sinusoids;

hepatic vein carries blood away from liver; 3 max [7]


(a) Blood is a liquid tissue containing glucose, urea, plasma proteins and other components.

List the other components of blood. (5)

(b) Outline how the human body prevents blood glucose concentration from rising excessively. (5)

(c) Blood plasma, glomerular filtrate and urine have different concentrations of solutes, such as glucose,

protein and urea. Explain the processes occurring in the kidney that cause differences in the

concentrations of these solutes between blood plasma, glomerular filtrate and urine. (8)

(Total 20 marks)

Answer: (a) plasma/water;

dissolved gases / CO2 / O2;

erythrocytes / red blood cells;

leucocytes / white blood cells;

lymphocytes and phagocytes;

platelets;

hormones / named hormone(s);


106

amino acids / albumin / antibodies;

salts / minerals / ions other named solute in plasma apart from

glucose, urea and plasma proteins; 5 max

(b) blood glucose concentration monitored by pancreas/islets/beta cells;

(more) insulin secreted in response to high blood glucose / glucose

above threshold level;

insulin stimulates cells to absorb glucose;

glucose used in cell respiration (rather than lipids);

glucose converted to glycogen;

by liver/muscle cells;

glucose converted to fatty acids / triglycerides / fat;

negative feedback process;

Accept these points if clearly made in an annotated diagram. 5 max

(c) (filtrate formed by) ultrafiltration;

glucose / amino acids / soluble components enter Bowman‘s capsule;

proteins in blood plasma but not in filtrate / proteins not filtered

out (of blood);

glucose not in urine (normally);

(selective) reabsorption (of glucose);

in the proximal convoluted tubule;

by active transport / microvilli increase the surface area;

little/no urea reabsorbed

concentration increases / urea more concentrated in urine than in

blood plasma;

water reabsorbed from filtrate;

by osmosis;

in descending limb of nephron / in proximal convoluted tubule;

salts actively transported into the medulla (from filtrate);

creating concentration gradient/hypertonic medulla;

collecting duct permeability altered depending on blood solute

concentration; 8 max


Paper 3

Tufted ducks (Aythya fuligula) are found in lakes and lagoons throughout Europe. They eat molluscs, insects and

plants, sometimes from the surface but mostly by diving under the water. The graph shows how the heart rate

of a tufted duck changes when diving under the water.


107

[R Stephenson, P J Butler and A J Woakes. 1986. ―Diving behaviour and heart rate in tufted ducks (Aythya fuligula).” J Exp Biol.

Vol 126. Pp 341–359.]

(a) State the length of time the tufted duck was under the water.

...................................................................................................................................... (1)

(b) Outline the changes in the heart rate during the dive.

......................................................................................................................................

...................................................................................................................................... (2)

(c) Suggest, with a reason, the type of respiration used by the tufted duck during the dive.

......................................................................................................................................

...................................................................................................................................... (1)

When swimming on the surface, the blood supply to different parts of the body of the tufted duck varies

according to whether it is swimming at normal speed or maximum speed.


108

[Source: Butler, PJ, Turner, DL, Al-Wassia, A & Bevan, RM. 1988. ―Regional distribution of blood flow during swimming in the

tufted duck (Aythya fuligula).‖ J Exp Biol. Vol 135. Pp 461–472.]

(d) Calculate the percentage increase in blood flow to the leg muscles when the tufted duck changes from

swimming at normal speed to swimming at maximum speed.

...................................................................................................................................... (1)

(e) Compare the blood flow to the heart muscles with the blood flow to the flight muscles when changing

from swimming at normal speed to swimming at maximum speed.

......................................................................................................................................

...................................................................................................................................... (2)

(f) Explain the changes in blood flow that occur when swimming at maximum speed.

......................................................................................................................................

...................................................................................................................................... (2)

(g) Predict, with reference to both graphs, what would happen to the blood flow to the heart muscles when

the tufted duck is diving.

......................................................................................................................................

......................................................................................................................................

......................................................................................................................................


109

...................................................................................................................................... (2)

(h) State the hormone that affects heart rate.

......................................................................................................................................

...................................................................................................................................... (1)

(Total 12 marks)

Answer:

(a) 40 s/seconds (units required) 1

(b) initially the heart rate decreases rapidly;

heart rate increases over the next seconds;

heart rate falls to its lowest level / reaches lowest level after

55 s/seconds / 35 s/seconds after start of dive;

in the last seconds before the dive ends, the heart rate increases; 2 max

(c) anaerobic respiration because the tufted duck cannot breathe/

ventilate under water / replace oxygen that has been used;

aerobic respiration because the tufted duck uses stored oxygen;

both aerobic (at the beginning) and anaerobic (at the end) because

oxygen was used up during the dive; 1 max

To award [1], reason must be given.

(d) 200 (%) 1

(e)

Heart muscles Flight muscles

swimming at maximum speed

causes increase in blood flow to

heart muscles

swimming at maximum speed causes

decrease in blood flow to flight

muscles;

swimming at normal speed, less

blood flow to heart muscles (20 ml

min–1

) / swimming at maximum

speed, more blood flow to heart

muscles (24 ml min–1

)

swimming at normal speed, greater

blood flow to flight muscles (39 ml

min–1

) / swimming at maximum

speed, less blood flow to flight

muscles (18 ml min–1

);

small change in blood flow to heart

muscles when changing speed (4 ml

min–1

more)

big change/almost half amount of

blood flow to flight muscles when

changing speed (22 ml min–1

less);

Award [1] for each correct row. Answers do not need to be shown

in a table format, but must be comparative statements. 2 max

(f) legs/leg muscles need more energy/ATP for fast swimming;

legs/leg muscles need more blood to provide oxygen/glucose for energy;

(the legs need more blood) to remove carbon dioxide;

the heart needs more blood to pump faster;


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intestines/kidneys/flight muscles have less blood to allow for

increased flow to heart/legs; 2 max

(g) blood flow decreases;

as heart rate is seen to decrease in the first graph;

as lower heart rate means less requirement for oxygen/nutrients/

blood/removal of waste; 2 max

(h) adrenaline / epinephrine / noradrenaline / norepinephrine 1 [12]

With warm wishes

Mariam Ohanyan

Have a good luck

students guied( ohanyan)

Science