UNIT 3- Exchange end of unit test

Question 1

The pieces of leaf tissue were very thin

explain why this was important (2)

Answer 1

1. Single/few layer(s) of cells;

Accept: more/too many/overlapping.
‛Single layer’ without reference to cells/tissue should not be
credited.

2. So light can pass through;

Question 2

Investigated number of stomata

Suggest appropriate units the student should use to compare the distribution of stomata on leaves?

Answer 2

Stomata per mm 2 or cm 2

OR
Number per mm 2 or cm 2 ;
Accept: mm −2 or cm −2 .

Question 3

2 reasons why its important that the student counted the number of stomata in serval parts of each piece of the leaf tissue (2)

Answer 3

1. Distribution may not be uniform

OR
So it is a representative sample;
Accept: more/fewer stomata in different areas.
Ignore: anomalies/random/bias.
2. To obtain a (reliable) mean;
Accept: ‘average’.

Question 4

One of the 2 plant species used by the student in this investigation was Xerophyte

Other than the distribution of stomata , suggest and explain two xerophytic features the leaves of this plant might have (2)

Answer 4

(d) 1. Hairs so ‘trap’ water vapour and water potential gradient decreased;

2. Stomata in pits/grooves so ‘trap’ water vapour and water
   potential gradient decreased;
3. Thick (cuticle/waxy) layer so increases diffusion distance;
4. Waxy layer/cuticle so reduces evaporation/transpiration.
5. Rolled/folded/curled leaves so ‘trap’ water vapour and water
   potential gradient decreased;
6. Spines/needles so reduces surface area to volume ratio;

Question 5

The student then compared the rate of transpiration (evaporation of water) from the two species of plant . She did this by measuring the rate of water uptake by each plant species

suggest 2 reasons why the rate of water uptake by a plant might not be the same as the rate of transpiration (2)

Answer 5

1. Water used for support/turgidity;
2. Water used in photosynthesis;
3. Water used in hydrolysis;
4. Water produced during respiration;

Question 6

Water potential of blood plasma is more negative at venule end explain why (3)

Answer 6

1. Water has left the capillary;
2. Proteins (in blood) too large to leave capillary;
3. Increasing / giving higher concentration of blood proteins (and thus wp).

Question 7

What other info is needed to calculate the mean rate of movement of the 14c down the trun
k? (1)

Answer 7

Length of trunk (between top and bottom).

Question 8

Describe what happens to the diaphragm between times P and Q (down) to bring about change in its change (1)

Answer 8

(a) 1.Flatten / moves down;
1. Ignore: additional information about rib movements
2. (Diaphragm muscle) contracts;

Question 9

Air moves into the lungs between times P and Q . Explain how the diaphragm causes this (3)

Answer 9

1.Diaphragm contracts / moves down / flattens;

Ignore refs to rib movement

2. Increases volume (of thorax) and decrease in pressure;
3. Accept pressure lower than atmospheric pressure
4. Air moves from high to lower pressure / down pressure gradient;
5. Reject: by diffusion

Question 10

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

Answer 10

1.Diffusion;

Accept down diffusion gradient

2. Across (alveoli) epithelium / (capillary) endothelium;
3. Accept: capillary epithelium / squamous cell

Question 11

HPFH is a condition in which production of fetal haemoglobin continues into adulthood. Adult Haemoglobin is also produced

People with HPFH do not usually show symptoms suggest why (1)

Answer 11

Enough adult Hb produced / enough oxygen released / idea that curves / affinities /
Hb are similar / more red blood cells produced;

Question 12

Two precautions the students should have taken when setting up the potometer to obtain reliable measurements of water uptake by the plant shoot (2)

Answer 12

1.Seal joints / ensure airtight / ensure watertight;

Answer must refer to precautions when setting up the apparatus
Ignore: references to keeping other factors constant

2. Cut shoot under water;
3. Cut shoot at a slant;
4. Dry off leaves;
5. Insert into apparatus under water;
6. Ensure no air bubbles are present;
7. Shut tap;
8. Note where bubble is at start / move bubble to the start position;

Question 13

A potometer meaused rate of water uptake rather than the rate of transpirstions. Does not truly measure the rate of transpiraion why 2 reasons? (2)

Answer 13

1.Water used for support / turgidity;

Accept: water used in (the cell’s) hydrolysis or condensation
(reactions) for one mark. Allow a named example of these
reactions

2. Water used in photosynthesis;
3. Water produced in respiration;
4. Apparatus not sealed / ‘leaks’;

Question 14

Relationship between the number of leaves removed from the plant shoot and the mean rate of water uptake (3)

Answer 14

1. Less surface area / fewer stomata;
2. Less evaporation / transpiration;
3. Less cohesion / tension / pulling (force);

Question 15

How is pressure in the ventricle related to blood flow into the aorta (2)

Answer 15

1.Ventricle pressure rises then blood starts to flow into aorta because pressure causes

(aortic / semilunar) valve to open;

Accept times, eg ventricle pressure rises at 0.3 (25)
seconds, followed by blood flow into aorta at 0.35 / 0.4 seconds
Idea of sequence is essential
Accept times

2.Ventricle pressure starts to fall so blood flow falls;

Idea of sequence is essential

Question 16

How is pressure in the ventricle related to the thickness of the ventricle wall (2)

Answer 16

1.Thickness of wall increases because ventricle (wall) contracts;
Must be idea that increase in thickness is linked to contraction
Accept muscle for ventricle and systole for muscle contraction

2.Contraction causes the increase in pressure;

Accept thickening of wall