Biology Paper 2

Question 1

Water lilies have stomata on the upper surface of the leaves.
Explain why water lilies have no stomata on the lower surface of the leaves.

Answer 1

• lower surface of leaf is not in contact with air
• so gas exchange cannot occur

Question 2

Describe how this sugar is transported from the leaves to the flowers of the
water lily

Answer 2

• in the phloem
• dissolved in water
• by translocation
• using active transport

Question 3

One water lily plant was brought from America 10 years ago and planted in the
lake shown in Figure 2.
Explain why this non-indigenous plant now covers the whole surface of the lake.

Answer 3

• because conditions allowed adaption to the conditions
• it outcompeted the natural plants
• therefore it reproduces

Question 4

Describe how starch is broken down into glucose.

Answer 4

• enzymes like amalyse
• starch fits into the active site
• bonds between glucose molecules in starch broken

Question 5

The food is mashed before the trypsin is added.
Explain the advantage of mashing the food before adding the trypsin.

Answer 5

• to increase the surface area
  of the food
• so trypsin will break down
  more protein

Question 6

Explain how one structure of a vein helps the blood return to the heart.

Answer 6

• veins contain valves
• which prevent the backflow
  of blood

Question 7

The stroke volume for person B before exercising was 61ml per beat.
Calculate the cardiac output for person B before exercising.
Give your answer in litres per minute.

Answer 7

• 65 x 61 = 3965
• 3965 / 1000 = 3.965 litres

Question 8

The cardiac output for person A during exercise was 5.5 litres per minute.
Explain why the heart rate for person A needed to be higher than the heart rate
for person B during exercise.

Answer 8

• person A had a lower stroke volume
• pumps less blood out per beat
• so needed to have a higher heart rate to get a similar cardiac output