Comprehension

Question 1

3 marks

Black bears can hibernate for up to 7 months without food or water
Suggest and explain how.

Fat stores in their body

Answer 1

1. Fat store used in respiration/metabolism
2. Less energy store is required due to low respiration
3. Gluconeogenesis
4. Low surface area to volume reduces heat loss
5. Long loop of Henle so less water lost
6. Water provided from respiration;
7. Reduced/no urination
8. Less evaporation

Question 2

4 marks

During hibernation, the heart rate and the metabolic rate of black bears decrease
Use your knowledge of the nervous control of heart rate to describe how these are linked.

Answer 2

1. Low metabolism so less Co2 in blood
2. Detected by chemoreceptors
3. Located in carotid and aorta
4. Fewer impulses to medulla oblongata
5. More impulses along parasympathetic pathway
   Fewer impulses along sympathetic pathway
6. To SAN

Question 3

2 marks

Suggest two reasons why people had the drug injected into the cerebrospinal fluid rather than taking a pill containing the drug.

Answer 3

1. Drug will directly/quickly reach brain
   2.Drug not destroyed by acid/ Drug not digested by enzymes

Question 4

3 marks

People with red-green colour blindness are unable to distinguish between red and green, and also between other colours. They have green-sensitive cones but the photoreceptive pigment they contain does not function. Explain why.

Answer 4

1. Green sensitive cones non functional
2. 3 different types of cone cells= blue/green/red light sensitive cone cells
3. Other colours seens due to stimulation o fmore than 1 cone cell

Question 5

2 marks

Suggest and explain two reasons why a poor supply of phosphate ions results in poor growth of plants

Answer 5

1. Required to make ATP, so less respiration / less energy for growth
2. Required to make nucleotides, so less DNA for cell division
3. Required to make RuBP / NADP, so less CO2 fixed / reduced into sugar
4. Required to make phospholipids for membranes

Question 6

2 marks

Suggest how defensive enzymes produced by plants destroy bacteria

Answer 6

1. Hydrolyse
2. Murein in cell wall

Question 7

2 marks

Suggest and explain the advantage to tomato plants of transmitting signal proteins through mycorrhizal networks, rather than releasing them into the air

Answer 7

1. Direct plant-to-plant transmission
2. So localised/ faster response