Jun 2014 Unit 2

Question 1

What is meant by hierarchy?

Answer 1

1. Groups within groups;

2. No overlap

Question 2

Explain the role of independent segregation in meiosis.

Answer 2

1. (To provide) genetic variation

3. (To produce) haploid cells

Question 3

A zeedonk is the offspring produced from breeding a mountain zebra with a donkey.
he body cells of a mountain zebra contain 32 chromosomes.
The body cells of a donkey contain 62 chromosomes.
Use this information to suggest why zeedonks are usually infertile.

Answer 3

because they will have 47 chromosomes

Chromosomes cannot pair because it is an odd number

Question 4

What is selective breeding?

Answer 4

(Humans breed) organisms with

certain/chosen characteristics

Question 5

Explain one potential problem that can be caused by selective breeding.

Answer 5

1. Inbreeding / breed closely related
   organisms;
2. (So higher probability of) mutations
   being passed on

3. Reduced genetic variation/diversity
/ smaller gene pool / less variety of
alleles;
4. (So) can be killed by/susceptible to
the same/a disease / reduces ability
to adapt

Question 6

If a dog breeder wishes to use selective breeding for one of these features, which one
should he choose? Use information in Table 1 to explain your answer.

Answer 6

1. Select tracking/(Large)
Munsterlander;
2. (As) high (heritability) value/0.8/
closer to 1/ mainly due to genetic
factors;

Question 7

What do the standard deviations suggest about the differences in heritability values for
searching between the two breeds of hunting dog?

Answer 7

1. (SDs) overlap / values shared;
2. (So difference between means) is
   not significant/is due to chance;

Question 8

The oxygen dissociation curve for haemoglobin shifts to the right during vigorous
exercise. Explain the advantage of this shift.

Answer 8

1. Lower affinity for oxygen / releases more
   oxygen / oxygen is released quicker /
   oxygen dissociates/unloads more readily;
2. (To) muscles/tissues/cells;
3. (For) high/rapid respiration;

Question 9

Explain how the body shape of a Weddell seal is an adaptation to living in a cold
environment.

Answer 9

1. Small SA:VOL;
2. (So) reduces heat loss / (more) heat
   retained

Question 10

Describe and explain the changes in the rate of blood flow to the different organs
during a long dive

Answer 10

1. Brain is the same, others fall;
2. Brain controls other organs/remains active/
   needs constant supply of oxygen;
3. Lungs not used/are used less / seal is not
   breathing

Question 11

Describe and explain how the countercurrent system leads to efficient gas exchange
across the gills of a fish.

Answer 11

1. Water and blood flow in opposite directions;
2. Maintains concentration
3. Along whole gill

Question 12

Amoebic gill disease (AGD) is caused by a parasite that lives on the gills of some
species of fish. The disease causes the lamellae to become thicker and to fuse
together.
AGD reduces the efficiency of gas exchange in fish. Give two reasons why

Answer 12

1. (Thicker lamellae so) greater/longer
   diffusion distance/pathway;
2. (Lamellae fuse so) reduced surface area;

Question 13

The volume of water passing over the gills increases if the temperature of the water
increases. Suggest why.

Answer 13

1. Increased metabolism/respiration/enzyme
   activity;
2. Less oxygen

Question 14

The antibiotic tetracycline binds to ribosomes in bacterial cells.
Explain how this causes the death of bacterial cells.

Answer 14

1.Prevents protein synthesis;
2. (So) enzymes not produced / any named
process involving proteins/enzymes is
inhibited;

Question 15

Suggest how a change in the amino acid sequence of this protein could make a
bacterium resistant to tetracycline.

Answer 15

1. Different tertiary structure/tertiary shape;
2. (So tetracycline) does not fit/bind/ is not
   complementary / does not enter

Question 16

All primates produce a species-specific type of haemoglobin. An antibody against
human haemoglobin could be used to compare the evolutionary relationships between
different primates. Describe and explain how.

Answer 16

1. Antibody and haemoglobin/blood (of
 different primates) 
2. complex/
3. Amount of precipitate/complex/ thickness of
 band shows relationship

Question 17

These data suggest that gibbons are the most distantly related to humans. Explain
how.

Answer 17

(Largest decrease in separation temperature) –
no mark
1. (So) few(er) hydrogen/H bonds;
2. (So) few(er) complementary bases/ few(er)
base pairs;

Question 18

There were differences in separation temperature of DNA formed from
single-stranded DNA of the same species of primate. Suggest why

Answer 18

(Same species) have different alleles

Question 19

Some fields acted as controls. They were sprayed with a solution that did not contain the herbicide. Explain the purpose of these control fields.

Answer 19

1. (Shows) results are due to the herbicide/
   are not due to another factor;
2. (To) compare the effect of using and not
   using the herbicide

Question 20

Suggest an explanation for the relationship between the concentration of herbicide
and the mean crop yield.

Answer 20

1. (More) weeds killed so more crops/plants
   survive/higher yield/less competition;
2. High concentrations (of herbicide)

Question 21

Explain the relationship between the concentration of herbicide and the mean index of diversity of insects.

Answer 21

1. Reduced plant diversity / fewer plant
   species / fewer varieties of plant;
2. Fewer habitats/niches;
3. Fewer food sources/varieties of food;

Question 22

Explain how the structure of DNA is related to its functions.

Answer 22

1. Sugar-phosphate (backbone)/double
   stranded/helix so provides strength/stability
   /protects bases/protects hydrogen bonds;
2. Long/large molecule so can store lots of
   information;
3. Helix/coiled so compact;
4. Base sequence allows information to be
   stored/ base sequence codes for amino
   acids/protein;
5. Double stranded so replication can occur
   semi-conservatively/ strands can act as
   templates;
6. Complementary base pairing / A-T and G-C
   so accurate replication/identical copies can
   be made;
7. (Weak) hydrogen bonds for replication/
   unzipping/strand separation;
8. Many hydrogen bonds so stable/strong;

Question 23

What do these data suggest about the relative importance of the mutant alleles of
genes C, D and E on increasing the risk of developing lung cancer? Explain your
answer.

Answer 23

1. (Mutation) in E produces highest risk/1.78;
2. (Mutation) in D produces next highest
   risk/1.45;
3. (Mutation) in C produces least risk/1.30;

Question 24

Describe similarities and differences in the response of healthy cells and cancer cells
to the drug between times F and G.

Answer 24

(Similarities):

1. Same/similar pattern / both decrease, stay the same then increase;
2. Number of cells stays the same for same length of time;

(Differences):
(Per unit volume of blood)
3. Greater/faster decrease in number of
healthy cells / more healthy cells killed /
healthy cells killed faster;
4. Greater/faster increase in number of
healthy cells / more healthy cells
replaced/divide / healthy cells
replaced/divide faster

Question 25

More cancer cells could be destroyed if the drug was given more frequently.
Suggest why the drug was not given more frequently

Answer 25

1. More/too many healthy cells killed;
2. (So) will take time to replace/increase in
   number;
3. Person may die/have side effects;

Question 26

In this investigation, neither the volunteers nor the scientists knew if a particular
volunteer was receiving the vaccine or a placebo.
Suggest two reasons why this made the scientists’ results more reliable.

Answer 26

1. (Scientists) can’t show bias

2. (Volunteers ‘placebo effect’

Question 27

The scientists measured the concentration of nicotine in the blood of two volunteers who smoked the same number of cigarettes per day.
Suggest two reasons why the concentration of nicotine in the blood of these smokers might be different.

Answer 27

1. Amount of nicotine in cigarettes;

2. Amount inhaled

Question 28

Suggest how this vaccine could help people to stop smoking

Answer 28

1. Antibodies to nicotine produced / antibodies bind to nicotine;
2. (So) nicotine does not bind to protein/does not reach the brain;
3. (So) cigarettes/smoking does not satisfy addiction/reward smokers/ release (reward) chemicals

Question 29

Some people have suggested that this vaccine should not be given free to smokers
on the National Health Service (NHS). Evaluate this suggestion.

Answer 29

1. People choose to smoke
2. Should spend this money on
   education/preventing people from
   starting to smoke/treating other
   health problems/ vaccines are
   expensive;
   (Disagree):
3. Unethical not to treat;
4. Less money needed to

Question 30

A journalist reported that this vaccine is a major breakthrough in helping people to
stop smoking. Do these data support this statement? Explain your answer.

Answer 30

1.High antibody responders have a high % to stop smoking/are more likely to stop
smoking;
2. Only a few may be high antibody
responders/ no numbers on how many are
high/medium/low antibody responders;
3. Percentage who stopped smoking is similar
for placebo group and low/medium
responders / some/% of placebo group (still)
stopped smoking / placebo has the lowest
value/% to stop smoking;
4. Large sample size/double blind so
reliable/representative;
5. Antibody levels peak at/drop after 5 months /
boosters may be needed at/after 5 months;
6. May start smoking again after 5/6 months /
do not know the percentage who stopped
smoking after 5/6 months;
7. Nicotine is not the only factor responsible for
making people smoke