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Module 2: Exchange and Transport
1.2.2 Transport in Animals
(a) explain the need for transport systems in multicellular animals in terms of size, level of activity and surface
area: volume ratio

Singlecelled Animals Multicellular Animals
Example Paramecium Humans
Size Small (microscopic) Large
Diffusion Distances Small few layers of cells =…

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Module 2: Exchange and Transport
(d) describe, with the aid of diagrams and photographs, the external and internal structure of the mammalian


(e) explain, with the aid of diagrams the differences in the thickness of the walls of the different chambers of
the heart in terms of their…

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Module 2: Exchange and Transport
High pressure there is
moreresistance and friction due
to a greater blood flow

(f) describe the cardiac cycle, with reference to the action of the valves in the heart

Atrial Systole/ Ventricular Diastole:
1. Blood enters the atria and the pressure inside the atria increases…

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Module 2: Exchange and Transport
Calculating Heart Rate:
Heart Rate (beats per minute) = 60/Time taken for one cardiac cycle

(g) describe how heart action is coordinated with reference to the sinoatrial node (SAN), the atrioventricular
node (AVN) and the Purkyne tissue
1. The cardiac muscle is myogenic the heart…

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Module 2: Exchange and Transport

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Module 2: Exchange and Transport
Arteries Veins Capillaries
Function Carries blood away from the Carries blood to the heart They allow the exchange of
heart to the rest of the body materials between the blood
and cells of tissues
Transports All arteries carry oxygenated All veins carry deoxygenated Carries oxygenated…

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Module 2: Exchange and Transport

The pressure in the blood decreases as it moves away from the heart because the blood vessel branches into
more smaller vessels meaning they have a larger cross sectional area. Also there's more friction in the capillaries
therefore there is a lower pressure.

It's important…

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Module 2: Exchange and Transport

Feature Blood Tissue Fluid Lymph
Cells Erythrocytes, leucocytes Some phagocytic white Lymphocytes
and platelets blood cells
Proteins Hormones and plasma Some hormones, proteins Some proteins
proteins secreted by body cells
Fats Some transported as None More than in blood
lipoproteins (absorbed from lacteals in

Page 9

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Module 2: Exchange and Transport

(m) describe and explain the significance of the dissociation curves of adult oxyhaemoglobin at different carbon
dioxide levels (the Bohr effect)

Oxygen Dissociation Curve:
The first oxygen does not attach easily to the haem groups , due
to it being in the centre of the…


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