2012 Unit 2 June

Question 1

What is an organ?

Answer 1

• A group of tissues;

Question 2

Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside
the leaf.

Answer 2

• (Carbon dioxide enters) via stomata;
• (Stomata opened by) guard cells;
• Diffuses through air spaces;
• Down diffusion gradient

Question 3

Suggest how the faster rate of growth may increase profit for a farmer

Answer 3

• Beet/ harvested earlier;

Question 4

Describe and explain how selection will have affected the genetic diversity of sugar
beet.

Answer 4

• (Diversity) reduced / smaller gene
pool
• As alleles have been chosen/
rejected;

Question 5

Name the monomers that form a cellulose molecule

Answer 5

• Beta glucose

Question 6

Explain one way in which the structure of cellulose is linked to its function

Answer 6

• H-bonds / micro/macro fibrils /fibres;

* Strength / rigidity / inelasticity;

Question 7

Mitosis is important in the life of an organism. Give two reasons why

Answer 7

• Growth
• Replace cells
• Genetically identical cells;
• .Asexual reproduction /cloning

Question 8

DNA is a polymer. What is the evidence from the diagram that DNA is a polymer?

Answer 8

• .Repeating nucleotides / monomer

/molecules;

Question 9

The gene for this polypeptide contains more than this number of bases.
Explain why

Answer 9

• Some regions of the gene are non-coding

/ introns / start/stop code

Question 10

Name one other taxonomic group to which all members of the Apodiformes belong.

Answer 10

• Kingdom / phylum / class;

Question 11

Name the taxonomic group between order and genus

Answer 11

• Family;

Question 12

Explain how the standard deviation helps in the interpretation of these data

Answer 12

• Shows the spread of the data / how
data varies
• Low SD means results more reliable /
repeatable

Question 13

Use your knowledge of transpiration to explain the changes in the rate of flow in the
xylem shown in the graph.

Answer 13

• Stomata open;
• Transpiration highest around midday;
• Middle of day warmer / lighter;
• (Increased) tension/water potential gradient
• Cohesion (between water molecules);

Question 14

Explain why the values for the pressure in the xylem are negative.

Answer 14

• (Inside xylem) lower than atmospheric

pressure / (water is under) tension

Question 15

Explain the difference in thickness between the pulmonary artery and the pulmonary
vein.

Answer 15

• High pressure / smoothes out blood
flow
• Artery wall contains more
collagen

Question 16

The thickness of the aorta wall changes all the time during each cardiac cycle.
Explain why

Answer 16

• (Aorta wall) stretches;
• Because ventricle/heart contracts /
systole / pressure increases;
• (Aorta wall) recoils;
• Because ventricle relaxes / heart relaxes
• Maintain smooth flow / pressure

Question 17

Which of the three blood vessels shows the greatest variation in wall thickness?
Explain your answer.

Answer 17

• Aorta

* Largest Standard deviation

Question 18

Describe how tissue fluid is formed and how it is returned to the circulatory system.

Answer 18

Formation
• High blood / hydrostatic pressure /
pressure filtration;
• Forces water / fluid out
• Large proteins remain in capillary
Return
• Low water potential in capillary /
blood;
• Due to (plasma) proteins;
• Water enters capillary / blood;
• (By) osmosis;

Question 19

The flasks were incubated at 35 oC. Suggest why they were incubated at this
temperature.

Answer 19

• Fastest rate of growth
• Optimum
temperature for enzymes

Question 20

The scientist put the same volume of bacterial culture into each flask. Explain why.

Answer 20

• Same amount of bacteria

Question 21

What was the purpose of the control flask?

Answer 21

• To show that only the antibiotic has an

effect

Question 22

Give two ways in which a bacterium could become resistant to an antibiotic.

Answer 22

• Mutation

* Horizontal transmission

Question 23

The people chosen to be included in the survey were all of a similar age. Suggest why

Answer 23

• Age affects immune system

Question 24

Some dentists recommend a course of antibiotics when someone has a tooth
extracted. Does the information in parts (b), (c) and (d) support this recommendation?
Explain your answer.

Answer 24

• Antibiotic reduces number of bacteria
• (Survivors have) resistant gene/
• (Resistant bacteria) reproduce