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Date November 2020 Marks available 2 Reference code 20N.3.SL.TZ0.2
Level Standard level Paper Paper 3 Time zone TZ0 / no time zone
Command term State Question number 2 Adapted from N/A

Question

In an investigation to compare the elasticity of arteries and veins, rings of the same diameter (20 mm) of artery and vein tissue were cut from blood vessels obtained from a mammal.

[Source: © International Baccalaureate Organization 2020.]

Each ring was attached to a clamp. Multiple masses of 10 g were added and removed. The vertical diameter of the artery and the vein was measured, both with the mass and once the mass had been removed.

The results are shown in the table.

State the independent and dependent variables in this experiment.

Independent: 

Dependent: 

[2]
a.

State one feature of the rings that has to be kept constant apart from their initial diameter.

[1]
b.

Explain the differences between the results shown for vein and artery.

[3]
c.

Markscheme

a. Independent: mass;

b. Dependent: (vertical) diameter/length;

Do not accept elasticity

a.

a. width/section depth/slice of the ring;

b. same animal/age/freshness/temperature;

Don’t accept thickness or diameter.

b.

a. veins have thinner walls (than arteries);

b. veins sustain lower (blood) pressure (than arteries);

c. when stretched, veins become longer (than arteries);

d. veins have less muscle/elastic (fibre in their) walls (than arteries);

e. veins have lower elasticity/recover less/remain more stretched (than arteries after weights removed);

Accept inverse for arteries in all cases.

Do not accept a listing of numerical values without explanation.

c.

Examiners report

The experiment described an investigation to compare the elasticity of arteries and veins. In (a) the most common error was to reverse the correct responses of mass and diameter.

a.

In part (b) many candidates suggested that the samples should be of the same thickness.

b.

In part (b) many candidates suggested that the samples should be of the same thickness.

c.

Syllabus sections

Core » Topic 6: Human physiology » 6.2 The blood system
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