Biology Questions and Answers Unit 2

This was my last minute revision, but since it had my annotations about how I'd gone wrong, I had to anotate it and categorise everything. So here it is! It's from a collection of past papers so the question numbers are just there to separate everything.

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Biology Questions and Answers from past papers
Blood Vessels
Q: As the red blood cells pass through the capillary they bend as shown in
the diagram. Suggest one way in which this makes them better at carrying
out their function.
A: Faster diffusion (of oxygen) because more surface in contact with wall.
Figure 1
5a) Using information from Figure 1, explain two ways in which the blood
vessels in the body wall help the earthworm to absorb oxygen.
Many vessels/capillaries, or branching, or vessels in all parts of wall
give large surface area; (not just: 'large surface area')
narrow or thin vessels/walls give short diffusion distance;
(several) vessels to remove blood (rapidly) maintains diffusion
6ci) In the heart the blood pressure falls to zero while the ventricles are
filling. Use your knowledge of the structure of arteries to explain why the
minimum pressure in the artery of the arm stays well above zero.
Elastic fibres/tissue in arteries; (muscle ­ neutral)
recoil maintains pressure;
4 (b) The walls of arteries contain elastic tissue. Explain the function of the
elastic tissue.
Causes recoil / allows stretching;

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Using information in the table, explain what causes the rate of blood
flow to be slower in capillaries than in other vessels.…read more

Page 3

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Use the information to explain how the structures of the walls of
arteries, veins and capillaries are related to their functions.
1. thickest wall, enabling it to carry blood at high pressure / withstand
pressure surges;
2. most elastic tissue, which smoothes out flow / maintains pressure;
3. most muscle which maintains pressure;
4. muscle in wall to control blood flow;
5. thin wall does not have to withstand high pressure;
6. thin wall, allowing diffusion/exchange;
7.…read more

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5c) The blood of an earthworm contains haemoglobin.
Describe how haemoglobin helps the blood of the earthworm to transport
Forms oxyhaemoglobin / oxygen joins with haemoglobin;
high affinity (for oxygen) at high concentration;
low affinity/dissociates where oxygen concentration low;
enables more oxygen to be transported than water/plasma would;
5d) Explain the advantage to the lugworm of having the dissociation curve
to the left.…read more

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Explain the advantage of the curve for fetal haemoglobin being
different from the curve for adult haemoglobin.
fetal haemoglobin has higher affinity for oxygen / takes up oxygen
(becomes saturated) at lower partial pressure;
at partial pressures when adult haemoglobin dissociates fetal
haemoglobin takes up oxygen;
(b)ii The dissociation curve for adult haemoglobin changes during vigorous
Explain the advantage of this change in position.…read more

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Species A lives in water containing a low partial pressure of oxygen.
Species C lives in water with a high partial pressure of oxygen. The oxygen
haemoglobin dissociation curve for species A is to the left of the curve for
species C. Explain the advantage to species A of having haemoglobin with
a curve in this position.…read more

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In xylem;
evaporation / transpiration from leaves;
through stomata;
cohesion of water molecules;
leaf cells have more negative water potential, so water enters from
water drawn up as column/continuous stream;
adhesion of water to walls;
capillarity due to narrow lumen of xylem (vessels);
lignified walls keep xylem (vessels) open;
root pressure forces (some) water up;
Description includes rise and fall, with max at midday;
rise related to increasing temperature;
fall related to stomatal closure;
explanation in terms of rate of evaporation;
explanation of factor…read more

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The diagrams show a section through a typical leaf and a section
through a leaf from a xerophytic plant. The xerophytic leaf has a lower
transpiration rate than the typical leaf.…read more

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Explain why water moves from the apoplast pathway to the symplast
pathway when it reaches the endodermis layer.
(b) Casparian strip / suberin (accept casparien, not caspian);
impermeable / barrier to water movement (.idea. of waterproof, not
water enters cell along water potential/osmotic gradient / by
1(c) ATP is used at a high rate in the phloem tissue of roots. Explain what
ATP is used for in phloem tissue.…read more

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Describe how water is absorbed from the soil into a root and moves
towards the endodermis.
Osmosis/diffusion of water;
by/into root hairs;
down a water potential gradient / from high (less negative) to low
(more negative) water potential / towards a more negative water
potential / from a dilute to concentrated solution;
through symplast/vacuoles/plasmodesmata/cytoplasm;
through apoplast/along cell walls;
4(c) Some xerophytic plants have sunken stomata. Explain the advantage
of this adaptation.…read more


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