2012 January

Question 1

Name X and Y.

2 marks

Answer 1

1.Granum/grana/thylakoid2. Stroma;

Question 2

Describe the function of a chloroplast.(2 marks)

Answer 2

1. Absorbs/traps/uses light;
2. For photosynthesis;
3. Produces carbohydrates/sugars/ lipids/protein;

Question 3

Name this stage.

1 mark

Answer 3

Anaphase

Question 4

Describe what happens during this stage that results in the production of two
genetically identical cells.(2 marks)

Answer 4

1. Sister/identical chromatids/ identical chromosomes;

2. To (opposite) poles/ends/sides;

Question 5

A sample of epithelial tissue from the small intestine of an animal was analysed.
Some of the cells had 8.4 units of DNA, others had only 4.2 units.
Use your knowledge of the cell cycle to explain why some cells had 8.4 units of DNA
and others had only 4.2 units.(2 marks)

Answer 5

1. 8.4/cells with twice DNA content = replicated DNA / late interphase / prophase / metaphase / anaphase;
2. 4.2 = DNA not replicated / (early) interphase / telophase / cell

Question 6

How many different genera are shown in this diagram?(1 mark)

Answer 6

5;

Question 7

A scientist carried out breeding experiments with catfish from different populations.
Describe how the results could show that the catfish belong to the same species.
(1 mark)

Answer 7

Fertile offspring produced;

Question 8

The variety of colours displayed by catfish is important in courtship. Give two ways in
which courtship increases the probability of successful mating.(2 marks)

Answer 8

1. Attracts/recognises same species;
2. Attracts/recognises mate/opposite sex;
3. Indication of sexual maturity/ fertility / synchronises mating;
4. Stimulates release of gametes;
5. Form pair bond;

Question 9

What is the maximum number of amino acids for which this base sequence could code?(1 mark)

Answer 9

4;

Question 10

Explain how this mutation leads to the formation of non-functioning PAH.(3 marks)

Answer 10

1. Change in amino acid/(sequence of) amino acids/primary structure;
2. Change in hydrogen/ionic/ disulphide bonds;
3. Alters tertiary structure/active site (of enzyme);
4. Substrate not complementary/cannot bind (to enzyme/active site) / no enzyme-substrate complexes form;

Question 11

Use the information in the diagram to give two symptoms you might expect to be
visible in a person who produces non-functioning PAH.(2 marks)

Answer 11

1. Lack of skin pigment / pale/light skin / albino;

2. Lack of coordination / muscles action affected;

Question 12

One mutation causing phenylketonuria was originally only found in one population in
central Asia. It is now found in many different populations across Asia. Suggest how
the spread of this mutation may have occurred.(1 mark)

Answer 12

Founder effect / colonies split off / migration / interbreeding;

Question 13

Use information in the diagram to explain why vancomycin does not affect human cells.(1 mark)

Answer 13

Human cells) don’t have a cell wall;

Question 14

Use information in the diagram to explain how tetracycline prevents bacterial growth.(1 mark)

Answer 14

Affects) protein synthesis;

Question 15

Frequent treatment with vancomycin can result in resistant strains of bacteria. Explain how.(3 marks)

Answer 15

1. Mutation present/occurs;
2. Resistance gene/allele;
3. Resistant bacteria (survive and) reproduce;
4. Vertical (gene) transmission / Horizontal (gene) transmission / conjugation;

Question 16

The gene for resistance to vancomycin is very common in the bacterium Enterococcus
faecalis. The same gene has now been found in the bacterium Staphylococcus
aureus.
Use your knowledge of gene transmission to explain how the gene was passed from
one species of bacterium to another.(3 marks)

Answer 16

1. Horizontal (gene) transmission;
2. Via conjugation/pilus;
3. Plasmid/Gene/DNA replicated/copied;
4. Plasmid transferred (to S.aureus);

Question 17

Scientists can use protein structure to investigate the evolutionary relationships
between different species. Explain why.(2 marks)

Answer 17

1. Amino acid sequences / primary structure;
2. Closer the (amino acid) sequence the closer the relationship;
3. (Protein structure) related to
   (DNA) base/triplet sequence;

Question 18

Comparing the base sequence of genes provides more evolutionary information than
comparing the structure of proteins. Explain why.(2 marks)

Answer 18

1. Reference to base triplets/triplet code / more bases than amino acids / longer base sequence than amino acid sequence;
2. Introns / non-coding DNA;
3. Degeneracy of code / more than one code for each amino acid;

Question 19

Explain the importance of taking a large number of samples at each site.(1 mark)

Answer 19

Produces a more reliable mean/average / makes sure sample was representative / reduce effect of extreme values / identify anomalies;

Question 20

Explain the importance of taking samples at random.(1 mark)

Answer 20

Removes bias;

Question 21

Explain the effect of developing this golf course on the index of diversity of insects.(3 marks)

Answer 21

1. Increase in variety of
plants/shrubs/grass;
2. More habitats/niches;
3. Greater variety of food sources /
more food sources;

Question 22

Root pressure moves water through the xylem. Describe what causes root pressure.(3 marks)

Answer 22

1. Active transport by endodermis;
2. ions/salts into xylem;
3. Lowers water potential (in xylem);
4. (Water enters) by osmosis;

Question 23

The rate of water movement in the upper branches was different from the rate of water
movement in the trunk. Describe how.(2 marks)

Answer 23

1. Maximum/overall rate is higher (in branches);
2. Reaches maximum/peak earlier (in the day) (in branches);
3. Starts higher / ends lower (in branches)

Question 24

The results of this investigation support the cohesion tension theory. Explain how.(2 marks)

Answer 24

1. Maximum/overall rate is higher (in branches);
2. Reaches maximum/peak earlier (in the day) (in branches);
3. Starts higher / ends lower (in branches)

Question 25

Explain how oxygen is loaded, transported and unloaded in the blood.(6 marks)

Answer 25

1. Haemoglobin carries oxygen / has a high affinity for oxygen / oxyhaemoglobin;
2. In red blood cells;
3. Loading/uptake/association in lungs;
4. at high p.O2;
5. Unloads/ dissociates / releases to respiring cells/tissues;
6. at low p.O2;
7. Unloading linked to higher carbon dioxide (concentration);

Question 26

The larvae in this investigation were kept at a temperature of 17 oC. Why was it
important that the larvae of both species were kept at the same temperature?(2 marks)

Answer 26

1. Allows comparison;
2. (Different temperature) affects enzymes;
3. (Different temperature) affects respiration/metabolism;
4. (Different temperature) affects amount of dissolved oxygen;

Question 27

Describe the difference in the way carbon dioxide is lost from the body of an Australian
lungfish and an African lungfish.(1 mark)

Answer 27

More (than in African) lost via gills in
Australian lungfish / less (than
African) lost via lungs in Australian
lungfish;

Question 28

African lungfish are likely to survive for longer than Australian lungfish when living in
pools that dry up. Explain why.(2 mark)

Answer 28

1. More/most exchange is via lungs
   (in African lungfish);
2. Gills will not function/function less
   efficiently (in air);

Question 29

Apart from age, suggest two factors that the scientists should have considered when
selecting volunteers for this trial.(2 mark)

Answer 29

1. Sex;
2. Lifestyle;
3. Body mass;
4. Health;
5. Ethnicity;
6. Genetic factors / family history;

Question 30

In analysing the results of this investigation, the scientists took into account the age of
the volunteers. Suggest why.(1 mark)

Answer 30

Age affects risk of cancer;

Question 31

Tea and coffee contain caffeine. A newspaper reported the results of this investigation
under the headline ‘Caffeine helps cut cancer risk’. Explain why scientists could not
support this view solely on the basis of this investigation.(4 mark)

Answer 31

1. Correlation does not mean causal relationship;
2. Tea/coffee contains other substances;
3. Contain different amounts of caffeine;
4. Estimated intake (of tea/coffee);
5. No control group;
6. Only one type of cancer studied;
7. Further studies required / only one investigation/study/group;

Question 32

Another group of scientists investigated the effect of caffeine on blood flow to certain
parts of the brain. Volunteers were given different concentrations of caffeine solution
to drink. A control group was also set up. Describe how the control group should have been treated.(2 mark)

Answer 32

1. Treated the same;

2. No caffeine;

Question 33

Volunteers who drank the same concentration of caffeine solution often had different
concentrations of caffeine in their blood. Suggest one reason for the difference in
concentration of caffeine in the blood of volunteers.(1 mark)

Answer 33

1. Absorb different amounts;
2. Broken down by enzymes/digested;
3. Different blood volumes;
4. Differences in metabolism;
5. Caffeine from a different source;

Question 34

The investigation showed that caffeine reduces the blood flow to certain parts of the
brain. Suggest one way in which this could lead to a reduced risk of brain cancers(2 mark)

Answer 34

1. Absorb different amounts;
2. Broken down by enzymes/digested;
3. Different blood volumes;
4. Differences in metabolism;
5. Caffeine from a different source;