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2.2 Adaptations for gas exchange
1. Living things need to obtain materials such as carbon dioxide and oxygen from the environment and
remove waste from their cells to the environment.
Organisms are differently adapted so gas exchange can take place whether it be in
water or on land. In particular…

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be thin so diffusion paths are short
moist to allow a medium for gasses dissolve in before diffusion
maintain a concentration gradient so diffusion will take place.

9. The large moist area for gaseous exchange is a region of potential water loss.

10. Earthworms are multicellular, terrestrial animals restricted to…

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Fish can be further classified into two groups according to the material that makes up their
Cartilaginous fish:
Skeletons are made entirely of cartilage.
Normally live in the sea e.g. shark
Characterised by five gill clefts that
open at five gill slits.
Gas exchange involves parallel flow.
Therefore blood…

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13. The gills have an extensive network of blood capillaries to allow efficient diffusion and
haemoglobin for oxygen carriage.

14. Compared with parallel flow, counter current flow increases efficiency because the
diffusion gradient between the adjacent flows is maintained over the whole surface.

Blood flows between the gill plates under…

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20. The human respiratory system includes epiglottis, trachea, bronchi, bronchioles, alveoli,
pleural membranes, ribs, intercostal muscles, diaphragm. These are involved in two
functions: ventilation andexchange of gases.

Lungs are enclosed within the Thorax , an air tight cavity
At the base of the thorax is a sheet of muscles, the…

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They are thin and moist providing a short diffusion path and a medium for
gasses to dissolve into.
Intercostal muscle contract and relax to move the ribcage up and down.
two pleural membranes surround the pleural cavity membranes will secrete
pleural fluid which acts as a lubricant , reducing friction…

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the spiracles lead to a system of branched chitin lined air tubes called tracheae.
spiracles act as valves , reducing water loss
when not flying insects rely on diffusion for gas exchange
during flight movements of the abdomen ventilate the tracheae
tracheal branches out into tracheoles.

24. Plants rely entirely…

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Palisade cells are arranged so that the light energy has few cell walls to pass through.
In dim light the chloroplasts will move to the top of the cells to maximise the light

28. Light can pass through to the spongy mesophyll. The spaces between mesophyll cells
allow carbon…

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37. Xerophytes may open stomata at night instead of during the day in order to conserve water, whilst
other plants may close stomata during the day or night under drought conditions.
Xerophytes are plants which have adapted to live under conditions of low water
availability. An example is marram grass…


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