2011 Unit 2 June

Question 1

Use your knowledge of osmosis to

suggest an advantage of using starch as a carbohydrate store.

Answer 1

• Insoluble;

* Does not affect water potential

Question 2

Use information in the diagram to explain what these adaptations are.

Answer 2

• Light sensitive eyespot / eyespot detects light;
• Flagellum enables movement towards light;
• Chloroplast/chlorophyll absorbs light/ for photosynthesis;

Question 3

Explain what is meant by genetic diversity.

Answer 3

• Difference in DNA

Question 4

Apart from genetic factors what other type of factor causes variation within a species?

Answer 4

• Environmental;

Question 5

Explain how this decrease may affect genetic diversity.

Answer 5

• Reduced (genetic diversity
• As fewer different/varied alleles
• (Genetic) bottleneck

Question 6

Explain how a change in the DNA base sequence for a protein may result in a change
in the structure of the protein.

Answer 6

• Change in amino acid/s /primary structure;
• Change in hydrogen/ionic/ disulfide bonds;
• Alters tertiary structure;

Question 7

Describe what happens in Metaphase

Answer 7

• Spindle formed / chromosome/centromere/chromatids attaches to spindle;
• Chromosomes/chromatids line up/move to middle/equator

Question 8

Describe what happens in Anaphase.

Answer 8

• Chromosome/centromere splits / chromatids/ ‘chromosomes’ separate/pulled apart
• To (opposite) sides/poles/centrioles (of cell);

Question 9

Explain the change in mass of untreated leaves in set A shown in the graph. 3 marks

Answer 9

• (Water) transpired/evaporates
/diffuses out;
• (Via) water potential gradient
/ leaf has higher water
potential;
• Stomata open;
• Water potential/diffusion
gradient reduces (during
investigation);
• Water not being replaced / no
water supply;
• Stomata close/closing

Question 10

Explain the advantage to the lugworm of having haemoglobin with a dissociation curve
in the position shown. Its to the .

Answer 10

• High(er) affinity for oxygen /
absorbs/loads more oxygen
• At lower partial pressure (of
oxygen) / lower pO2;

Question 11

In humans, substances move out of the capillaries to form tissue fluid. Describe how
this tissue fluid is returned to the circulatory system. 3 marks

Answer 11

• (Hydrostatic) pressure lower in
capillary/blood./higher in
tissues/tissue fluid;
• Water (returns)
• By osmosis
•  Water potential lower in blood/capillary
• Due to protein (in blood);
• (Returns) via lymph
(system/vessels

Question 12

Explain why biologists could use calls to investigate relationships between different
species of crane

Answer 12

• Allows recognition of same species
• Greater similarity in calls the closer
the relationship (between the
species);
• 
•
•

Question 13

Biologists can also use protein structure to investigate the relationship between
different species of crane. Explain why.

Answer 13

• More closely related (species)
have more similarities in primary structure
• In same protein 
• Amino acid sequence is related
to (DNA) base/triplet sequence

Question 14

There are over 12 000 species of plants in Costa Rica. Explain how this has resulted
in a high species diversity of animals.

Answer 14

• Greater variety / different foods;

* More habitats

Question 15

The number of species present is one way to measure biodiversity. Explain why an
index of diversity may be a more useful measure of biodiversity

Answer 15

• Also measures number of
individuals in a species
• Some species may be present
in low/high numbers

Question 16

It may be difficult to identify MRSA as the actual cause of death. Explain why

Answer 16

• Have other illness/weak

Question 17

Describe how gene transmission and selection have increased the difficulty of treating
bacterial infections with antibiotics.

Answer 17

• Antibiotic) resistant to gene
• Vertical (gene) transmission
• Horizontal (gene) transmission
• Resistant bacteria (survive and)
reproduce 
• Increase in frequency of
(resistant) allele
• Plasmid;
• Conjugation 
• Horizontal transmission/conjugation) can occur between bacteria of different species