Spec 2018

Question 1

2.2. At each site the scientists used traps to collect the ants. They used a large number of traps placed at random.
Explain the importance of using a large number of traps at each site. (1)

Answer 1

(1) produces a more reliable mean / makes sure sample is representative

Question 2

2.3. Explain the importance of placing the traps at random (1)

Answer 2

(1) prevents bias

Question 3

3.4. Describe how oxygen in air in the alveoli enters the blood in capillaries (2)

Answer 3

(1) diffusion
(2) across (alveolar) epithelium / (capillary) endothelium

Question 4

4.3. In the enzyme RoR exp, describe a suitable control for this investigation. Explain the purpose of this control (IV=substrate conc, DV=RoR)
(2)

Answer 4

(1) using no enzyme / denatured enzyme
(2) to ensure that the change is from an enzyme only

Question 5

6.2. They measured the initial length of each cylinder then placed the cylinders into test tubes containing diff. conc. of sucrose solution. Stoppers were placed in the tubes & the tubes were left overnight. Explain why the stoppers were placed in the tubes. (2)

Answer 5

(1) to prevent evaporation
(2) changing the conc. / WP (of solution)

Question 6

7.3. The data in table 3 are mean values. Explain how standard deviations of these mean values would help you interpret the data in table 3. (Table not needed) (2)

Answer 6

(1) SD gives a measure of spread / variation
(2) more SDs overlap, the less likely it is that differences are real/significant

Question 7

8.3. Suggest what stimulates the spiracles to open. Provide evidence from the graph to justify your answer. (Not needed) (2)

Answer 7

(1) increasing CO2 conc.
(2) as the conc. of oxygen at that point remains constant

Question 8

8.5. Abdominal pumping increases the efficiency of gas exchange between the tracheoles and muscle tissue of an insect. Explain why. (2)

Answer 8

(1) more oxygen enters / oxygen enters quickly
(2) so it maintains conc. gradient

Question 9

9.1. What is the name of the bond between the 2 monosaccharides that make up lactose? (1)

Answer 9

Glycosidic

Question 10

9.3. Describe and explain how you would expect the height to breadth ratio of an epithelial cell from a lung alveolus to differ from the height to breadth ratio of a milk-producing cell. (2)

Answer 10

(1) ratio would be less / smaller
(2) cell is thin/ has large SA / adapted for diffusion

Question 11

9.6. The lactose-containing vesicles increase in diameter as they move towards the plasma membrane of the milk-producing cell. Use your knowledge of WP to explain why. (2)

Answer 11

(1) WP inside vesicle = more negative/ lower
(2) water moves into vesicle by osmosis / diffusion

Question 12

9.7. Suggest one advantage of milk producing cells containing large numbers of mitochondria (2)

Answer 12

(1) supply energy / ATP
(2) for active transport / synthesis / exocytosis