2014 Unit 2

Question 1

What is meant by a hierarchy?

Answer 1

• Groups within groups

* No overlap between groups

Question 2

Explain the role of independent segregation in meiosis.

Answer 2

• To provide genetic variation
• Allows different combinations of maternal and paternal chromosomes
• To produce haploid cells
• Allows homologus pairs to arrange randomly at equator/separate

Question 3

A zeedonk is the offspring produced from breeding a mountain zebra with a donkey.
• The 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

• Zeedonk has an uneven number of chromosomes

* Chromosomes cannot pair/ are not homologus/ meiosis cannot occur/haploid cells not produced

Question 4

What is selective breeding

Answer 4

• Human breed organisms with certain characteristics/alleles

Question 5

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

Answer 5

• Lower affinity of oxygen/releases more oxygen/ oxygen dissociates more readily
• To muscles/tissues/cells
• For rapid/high respiration

Question 6

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

Answer 6

• Small surface:volume ratio

* So reduces heat loss

Question 7

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

Answer 7

• Brain controls other organs/needs constant supply of oxygen
• Heart rate decreases
• Blood diverted to muscles
• Oxygen is conserved

Question 8

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

Answer 8

• Water and blood flow in opposite directions
• Maintains concentration
• Along whole length of gill/lamellae

Question 9

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

Answer 9

• Increased metabolism/respiration/enzyme activity

* Less oxygen dissolved in water

Question 10

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

Answer 10

• Prevents protein synthesis

* So enzymes not produced

Question 11

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

Answer 11

• Different tertiary structure

* So tetracycline is not complementary

Question 12

Evolutionary relationships between different primates can be found by comparing their
proteins and DNA.
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 12

• Antibody and haemglobin mixed
• Precipitate/ complex/ formed
• Amount of precipitate/complex thickness of band shows relationship in protein DNA

Question 13

What two measurements are needed to calculate an index of diversity

Answer 13

• Number of each species
• Total number of individuals / number of
species

Question 14

Explain how the structure of DNA is related to its functions

Answer 14

• Sugar phosphate backbone/double stranded/helix so provides strength/stability/protect bases/protect hydrogen bonds
• Long/large molecule so can store lots of information
• Helix/coiled so compact
• Base sequence allows information to be
stored/ base sequence codes for amino
acids/protein
• Double stranded so replication can occur
semi-conservatively/ strands can act as
templates
• Complementary base pairing so accurate replication

Question 15

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

Answer 15

• Too many healthy cells killed
• So will take time to replace
• Person may die/side effects

Question 16

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 16

• Amount of nicotine in cigarettes
• (Different) blood volumes
• Some volunteers received the
vaccine/placebo
• Rate of binding (of
nicotine) to protein