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Module 1.2: Exchange and Transport

Explain, in terms of surface-area-to-volume ratio, why multicellular organisms need specialised
exchange surfaces and single celled organisms do not.

Multi cellular organisms need more nutrients and gases than a single celled organism and also the
substances need to travel a greater distance from the surface…

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cartilage Ciliated Goblet cells Smooth Elastic fibres
epithelium muscle

Trachea Lots of it yes yes yes yes

Bronchi Less than yes yes yes yes
trachea but
still there

bronchioles Large ones no no yes yes
yes, small
ones no.

alveoli No No No no no

Describe the functions of cartilage,…

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Vital capacity is the largest volume of air that can be moved into and out of the lungs in any one
breath. Approx 5 dm3 .

Describe how a spirometer can be used to measure vital capacity, tidal volume, breathing rate
and oxygen uptake.

A spirometer has a chamber filled…

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more food and nutrients to supply this energy. Mammals need to keep themselves warm so
need even more energy.

Explain the meaning of the terms single and double circulatory systems with reference to the
circulatory systems of fish and mammals.

A single circulatory system is like 1 loop. In a…

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Diastole: The heart fills with blood, the muscles in the heart are relaxed and the atrioventricular
valves are open with the semi lunar valves shut.

Atrial Systole: The atria contract, blood moves from atria to ventricles, the AV valves open and
the SL valves shut.

Ventricular systole: Ventricles contracts, blood…

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Open Circulatory system Close Circulatory system

Insects have open systems so the blood never Fish have a closed system. Blood stays inside
gets out of body cavity. Blood is not always vessels always. Tissue fluid bathes the blood in
held in vessels. The blood fluid bathes the nutrients that the…

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Tissue fluid doesn't contain most of the cells in blood or plasma proteins. It has to carry oxygen
and nutrients in the blood to cells and needs to carry carbon dioxide and wastes back to the

Lymph is what is formed when tissue fluid bathes the cells. Not all…

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Explain the significance of the different affinities for oxygen of fetal haemoglobin and adult

Fetal haemoglobin has a high affinity for oxygen than that of adult haemoglobin. In the placenta
the fetal haemoglobin absorbs the oxygen from the fluid in the mother's blood. This reduces the
oxygen tension within…

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In a multicellular plant organism the cells on the outside of the plant close to the environment
would gain all they need by simple diffusion but because there are many cells the cells inside the
plant would not receive enough water or nutrients to survive. In plants roots can obtain…

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Describe the structure and function of xylem vessels, sieve tube elements and companion cells.

Xylem vessels are long dead cells from end to end. They are hollow and are impregnated by
lignin which waterproofs the xylem as well as making it strong and preventing collapse. The lignin
forms patterns which…


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