What two features of a terrestrial organism helps to reduce water loss?
Waterproof covering eg: Insects have a rigid outer skeleton covered with a waterproof cuticle. Small surface area to minimsise the area over which water is lost.
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What gas exchange system have insects developed?
An internal network of tubes called trachae divided into tracheoles. They extend throughout all the body tissues so oxygen gets directly to respiring tissues.
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What are two ways gases are moved in and out of the tracheal system?
Along a diffusion gradient and by ventilation.
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How is a diffusion gradient maintained?
Cells use up oxygen when respiring so concentration falls so oxygen diffuses in from the atmosphere. CO2 is released from cells which creates a diffusion gradient in the opposite direction.
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How does ventilation speed up gas exchange?
Movements of muscles create mass movement of air in and out of the trachae.
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How can the spiracles be opened?
By valves.
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What happens when the spiracles open and what are they for?
Water can evaporate from the insect and they open the spiracles to allow gas exchange.
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Explain why water is always lost from the gas exchange surfaces of terrestrial organisms.
Gas exchange surfaces are permeable, higher concentration of water molecules inside animal than out(Water potential gradient), water diffuses outwards.
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Why is rate of water loss very low in most insects?
Spiracles can close and limits exposure of respiratory surface. Trachea cuticle lined so water is only lost through tracheoles. Trachea is inside, limiting exposure of respirotary surface.
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Other cards in this set
Card 2
Front
What gas exchange system have insects developed?
Back
An internal network of tubes called trachae divided into tracheoles. They extend throughout all the body tissues so oxygen gets directly to respiring tissues.
Card 3
Front
What are two ways gases are moved in and out of the tracheal system?
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