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…

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maintains blood pressure or to allow smoother / more constant
blood
pressure / prevents rupture (physical damage);




1b) Using information in the table, explain what causes the rate of blood
flow to be slower in capillaries than in other vessels.

small diameter/ lumen / small mean cross sectional area /…

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6. narrow lumen, reduces flow rate giving more time for diffusion;

7. red blood cells in contact with wall/ pass singly, gives short diffusion

distance / more time for diffusion;

7e) Use the information to explain how the structures of the walls of
arteries, veins and capillaries are related to…

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Haemoglobin

5c) The blood of an earthworm contains haemoglobin.

Describe how haemoglobin helps the blood of the earthworm to transport
oxygen.

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;…

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carbon dioxide dissolves in blood;
forming acid;
increases hydrogen ion concentration;
anaerobic respiration produces lactate;

4a(ii) 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;…

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7a) 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…

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the leaves.

In xylem;
evaporation / transpiration from leaves;
through stomata;
cohesion of water molecules;
leaf cells have more negative water potential, so water enters from
xylem;
water drawn up as column/continuous stream;
adhesion of water to walls;
capillarity due to narrow lumen of xylem (vessels);
lignified walls keep xylem…

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increased water potential;
reduced diffusion gradient / water potential gradient;
slower rate of water loss / less evaporation;




2b) 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.…

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6b(ii) explain why the diameter of the branch decreased during the first 12
hours.

(increase transpiration) produce a higher tension / reduces the
pressure in the xylem reducing the diameter;
adhesive forces between xylem and water;

1b) Explain why water moves from the apoplast pathway to the symplast
pathway when…

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3 (a) 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…

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