2010 June Unit 2

Question 1

Scientists’ analysis of blood proteins has indicated a lack of genetic diversity in populations of some organisms. Describe the processes that lead to a reduction in the genetic diversity of populations of organisms.(6 marks)

Answer 1

1) reduced variety/number of different alleles/DNA/reduced gene pool(in new population)
2) founder effect
3) a few individuals from population become isolated
4) genetic bottlenecks
5) significant fall in population
6) selective breeding
7) using organisms with particular alleles/traits

Question 2

Explain why an isotonic salt solution is used to dilute the blood sample.(3 marks)

Answer 2

Has same water potential;
No (net) water movement / osmosis; Cells will not swell/burst/change size;

Question 3

The structure of cellulose is related to its role in plant cell walls. Explain how.

Answer 3

Long/straight/unbranched chains (of glucose); (Joined by) hydrogen bonds;
Form (micro)fibrils/(macro)fibrils;
Provide rigidity/strength/support;

Question 4

The student wanted to calculate the rate of water uptake by the shoot in
cm3 per minute. What measurements did she need to make?(2 marks)

Answer 4

Distance and time;

Radius/diameter/area (of capillary tube);

Question 5

Suggest one advantage of using cytochrome c to determine relationships between
species.

Answer 5

present in all eukaryotes

Question 6

Heat from respiration helps mammals to maintain a constant body temperature.
Use this information to explain the relationship between the surface area to volume
ratio of mammals and the oxygen dissociation curves of their haemoglobins.

Answer 6

Smaller mammal has greater surface area to volume ratio;
Smaller mammal/larger SA:Vol ratio more heat lost (per unit
body mass);
Smaller mammal/larger SA:Vol ratio has greater rate of
respiration/metabolism;
Oxygen required for respiration;
(Haemoglobin) releases more oxygen / oxygen released more
readily / haemoglobin has lower affinity

Question 7

Use your knowledge of resistance to explain the results obtained with Norfloxacin and
drug X.

Answer 7

1. No/little resistance shown to drug X;
2. Mutation present (for antibiotic resistance);
3. Gene/allele for (antibiotic) resistance;
4. Bacteria with (antibiotic) resistance survive;
5. Vertical gene transmission;
6. Frequency of gene/allele (for resistance) increases;