2016

Question 1

Explain what is meant by a phylogenetic group

[1 mark]

Answer 1

(Grouped according to) evolutionary links/history/relationships / common ancestry;

Question 2

Explain what is meant by species. [2 marks]

Answer 2

1. Able to reproduce;
2. Accept: smallest taxonomic group/groups of organisms with same genes/ chromosomes/same number of chromosomes
3. Accept: Breed for ‘reproduce’
4. To produce fertile offspring;

Question 3

What term is used to describe the structure of a protein made of two or more
polypeptides?
[1 mark]

Answer 3

Quaternary (structure);

Question 4

Describe the role of haemoglobin in supplying oxygen to the tissues of the body.
[2 marks]

Answer 4

1. Oxyhaemoglobin formed/ haemoglobin is loaded/ uptakes/associates/binds with oxygen in area of higher ppO2 / in gas exchange surface/lungs/gills;
2. (oxygen) unloaded/dissociates from/released (in area of lower ppO2 / in capillaries/to cells/tissues);

Question 5

Explain the advantage to a person with anaemia of the change shown in the oxygen
dissociation curve.
[3 marks]

Answer 5

1. (Anaemia curve shifted to right) haemoglobin has lower affinity for oxygen / binds less tightly;
2. releases more oxygen / oxygen is released quicker / oxygen dissociates/ unloads more readily to muscles/tissues/cells;
3. (For) respiration;

Question 6

What is meant by species diversity?[1 mark]

Answer 6

Number of species in a community;

Question 7

Give two pieces of information needed to calculate an index of diversity for a
community.
[2 marks]

Answer 7

1. Number of (organisms of) each species;

2. Total number of organisms (of all species) / Total number of species;

Question 8

A scientist investigated the effect sewage entering a river had on the distribution of
organisms living in the river. Where sewage entered the river, he found a high density of
organisms but a low index of diversity.
Suggest how sewage entering the river could explain the scientist’s findings.
[2 marks]

Answer 8

1. Described effect of sewage (eg oxygen depletion/is toxic/kills);
2. Prevents some/many species colonising/ reproducing/remaining;
3. Sewage is food source for (individuals of) some/a few/species;
4. (So) increase only in their numbers;

Question 9

A second scientist repeated the investigation of the first scientist at the same place. The
second scientist obtained a high index of diversity.
Explain how the second set of results affects the ability of the scientists to make any
conclusions about the effect of sewage on the index of diversity.
[2 marks]

Answer 9

1. Results are not repeatable / are not representative / unreliable / conflict / contradict;
2. Can’t make any conclusions;

Question 10

Suggest the additional steps that should be taken by the scientists before they are able
to make any conclusions about the effect of sewage entering this river.
[1 mark]

Answer 10

Do repeats to find a pattern/distribution/mean (of index of diversity);

Question 11

Name the structure through which gases enter and leave the body of an insect.
[1 mark]

Answer 11

Spiracle;

Question 12

Name the small tubes that carry gases directly to and from the cells of an insect.
[1 mark]

Answer 12

Tracheole/trachea;

Question 13

Explain the movement of oxygen into the gas exchange system of an insect when it is at
rest.
[3 marks]

Answer 13

1. Oxygen used in (aerobic) respiration;
2. (so) oxygen (concentration) gradient (established);
3. (so) oxygen diffuses in;

Question 14

Abdominal pumping takes place during vigorous activity in insects. This causes regular
squeezing of the tubes of the gas exchange system.
A scientist investigated the effect of abdominal pumping on the pressure in the tubes
and the volume of carbon dioxide released by the insect.Describe and explain these results.
[3 marks]

Answer 14

1. Abdominal pumping/pressure in tubes linked to carbon dioxide release;
2. (Abdominal) pumping raises pressure in body;
3. Air/carbon dioxide pushed out of body /air/carbon dioxide moves down pressure gradient (to atmosphere);

Question 15

Describe and explain the appearance of chromosome K in cell C.
[2 marks]

Answer 15

1. (Chromosomes consist of) two chromatids connected at centromere;
2. (Because) DNA has replicated;
   OR
3. K is on equator of spindle;
4. (because) attached at centromere;

Question 16

Explain what is happening at point J in cell B.

[2 marks]

Answer 16

1. Crossing over / exchange of alleles /lengths of DNA / recombination;
2. Between (chromatids of) homologous chromosomes;

Question 17

Use information from all three cells in Figure 4 to explain how the number of
chromosomes in cell D was produced.
[1 mark]

Answer 17

1. Separation/segregation of pairs/homologous chromosomes;

Question 18

Figure 5 shows the mass of DNA present in cells of a population of healthy cells where
mitosis is occurring.Explain why some cells contain a mass of DNA between 1 and 2 arbitrary units.
[1 mark]

Answer 18

(DNA) replication taking place/not finished;

Question 19

A scientist examined the structure of mustard plant leaves. He viewed temporary
mounts of leaf tissues with an optical microscope. Figure 6 shows a drawing of typical
results.Describe how temporary mounts are made.
[2 marks]

Answer 19

1. Thin slice/section;
2. Put on slide in water / solution / stain;
3. Add cover slip;

Question 20

Describe how the scientist could have used the temporary mounts of leaves to
determine the mean number of chloroplasts in mesophyll cells of a leaf.
[3 marks]

Answer 20

1. Select large number of cells / select cells at random;
2. Count number of chloroplasts;
3. Divide number of chloroplasts by number of cells;

Question 21

There are many different types of cell in a leaf, each with its own function.
What term is used to describe a structure such as a leaf?
[1 mark]

Answer 21

Organ;

Question 22

What is the name of a position of a gene on a chromosome?

[1 mark]

Answer 22

Locus;

Question 23

What is meant by genetic diversity?

[1 mark]

Answer 23

Differences in DNA / differences in base sequence of DNA;

Question 24

Miniature terriers were first bred from bull terriers in the 19th century.
Suggest one explanation for the observed difference in genetic diversity between
miniature terriers and bull terriers.
[2 marks]

Answer 24

1. (Bull terrier) breeding has included a genetic bottleneck/ small population/more inbreeding/ greater selection (pressure);
2. Reduced number of different alleles/size of gene pool;
   Or
3. Miniature (terrier) breeding has included more outbreeding/less selection (pressure);
4. Increased number of different alleles/larger gene pool/more variety of alleles;

Question 25

Suggest the advantage of the change in blood flow in the mesenteric artery during exercise. [3 marks]

Answer 25

1. More blood flows to (skeletal) muscles (during exercise); 2. (supplying) more oxygen / glucose / removing more carbon dioxide/ lactic acid/ heat; 3. For high (rate of) respiration / to meet increased demand for energy/ATP; OR Prevents anaerobic respiration/lactic acid build up;

Question 26

The sport scientists concluded people should not do vigorous exercise after a meal. Does the information from Table 5 and Figure 7 support this conclusion? [4 marks]

Answer 26

Immediate effect of exercise after meal 1. Meal increases blood flow in (mesenteric) artery AND exercise decreases blood flow in (mesenteric) artery; Overall effect on blood circulation 2. Insufficient blood (flow to small intestines / muscles); Effect on blood flow of type of meal 3. Carbohydrate meal quick(er) / during exercise; OR Protein/fat meal slow(er) / after exercise; Effect of reduced blood flow on cells 4. (More) anaerobic (respiration) / lactic acid produced; OR less aerobic respiration; Consequence for person of changed blood flow 5. Less absorption (of digested food) / faeces contains digested food; 6. Cramp / indigestion / discomfort / fatigue;

Question 27

Blood leaving the kidney eventually returns to the kidney. Describe the pattern of blood circulation in a mammal that causes blood to return to the kidney. [6 marks]

Answer 27

1. (blood flows from kidney along) renal vein to vena cava; 2. (along) vena cava to right atrium/side of heart; 3. (along) pulmonary artery to lungs; 4. (along) capillaries to pulmonary vein; 5. (along) pulmonary vein to left atrium/side of heart; 6. (along) aorta to renal artery (to kidney); 7. Blood may pass through several complete circuits before returning to kidney;

Question 28

Suggest and explain one reason for the observed differences in percentage of neomycin-resistant E. coli in turkeys and chickens. [2 marks]

Answer 28

1. Large(r) percentage of resistant bacteria in turkeys/low(er) percentage of resistant bacteria in chickens; 2. Large(r) percentage of resistant bacteria in turkey farmers/low(er) percentage of resistant bacteria in chicken farmers;

Question 29

The scientists followed strict safety guidelines when collecting samples of faeces. Apart from the risk of contamination from E. coli this was especially important when collecting samples from humans. Explain why. [1 mark]

Answer 29

(Human) faeces contain pathogens;

Question 30

Use the information provided to identify and explain one way in which the scientists increased the reliability of their method. [2 marks]

Answer 30

1. Large number of farms / farmers (surveyed) / 46; | 2. so results are (likely to be) representative / can identify anomalous results;

Question 31

Suggest how the scientists could use DNA to investigate whether the neomycin-resistant bacteria in farmers were identical to the strain of bacteria in the birds they kept. [2 marks]

Answer 31

1. (DNA) hybridisation (of gene for resistance in bacteria taken from bird and farmer); 2. (Identical) strands separate at high(est) temperature; OR 3. Compare base/nucleotide sequence (of gene for resistance in bacteria taken from bird and farmer); 4. (Identical strains) have identical/same base sequence

Question 32

At one time, most animal feeds contained antibiotics that increased the rate of animal growth. In the UK, fewer animal feeds now contain antibiotics. Suggest reasons why. [4 marks]

Answer 32

1. (Antibiotic use has) increased cases of bacterial resistance; 2. Transfer/horizontal transmission of (resistance) gene to pathogens/harmful bacteria; 3. (Antibiotic) resistant bacteria cause harm / medical treatments less effective; 4. Avoids side effects on animals; 5. Increased demand for organic food; 6. Antibiotic/resistant bacteria could be present in human food; 7. High cost of antibiotics; 8. Legislation has controlled antibiotic use;