Gas Exchange in single-celled organisms and insects

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  • Created by: Molly
  • Created on: 24-04-13 13:01
How is gas exchanged in single-celled organisms?
Oxygen is absorbed by diffusion across their body surface. Carbon dioxice from respiration diffuses out across their body surface.
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What is a terrestrial insect?
An insect that lives on land.
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What is the problem for terrestrial organisms?
Water easily evaporates from the surface of their bodies and they can become dehydrated. As a result they need to conserve water.
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How do terrestrial organisms conserve water?
They have waterproof coverings - in the form of a rigid outer skeleton in insects. They also have a small surface area to volume ratio which minimises the area over which water is lost.
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What is an issue with having a rigid outerskeleton?
Insects cannot use their body surface to diffuse respiratory gases.
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What are the trachea?
An internal network of tubes that are supported by strengthened rings to prevent them from collapsing.
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What are the smaller tubes of trachea called?
Tracheoles
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how is oxygen moved in and out of the tracheal system along a diffusion gradient?
Along a diffusion gradient - In respiration oxygen is used and so the conc decreases at the tracheoles. This causes a diffusion gradient ans so gaseous oxygen diffuses from the atmosphere in to the trachea and in to cells.
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how does CO2 move in and out of the tracheal system along a diffusion gradient?
CO2 is produced during respiration which creates a diffusion gradient in the opposite direction and so CO2 diffuses from the cells to the atmosphere.
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What is ventilation?
The movement of muscles in insects that creates mass movements of air in and out of the trachea.
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How do gases enter and leave the trachea?
Through tiny pores called spiracles on the body surface. These spiracles are opened and closed by a valve.
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What can leave the insect when the spiracles are open?
Water.
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Why do insects keep their spiracles closed for the majority of the time?
So that water does not escape.
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What is a limitation of the tracheal system for gas exchange?
Relies mostly on diffusion to exchange gases between the environment and the cells. Diffusion pathways have to be short and so the insect is very small.
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Explain why there is a conflict between the need for gas exchange and the need to conserve water in terrestrial insects?
Because both water and gas escape through the spiracles.
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Card 2

Front

What is a terrestrial insect?

Back

An insect that lives on land.

Card 3

Front

What is the problem for terrestrial organisms?

Back

Preview of the front of card 3

Card 4

Front

How do terrestrial organisms conserve water?

Back

Preview of the front of card 4

Card 5

Front

What is an issue with having a rigid outerskeleton?

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