6.2- Gas exchange in single-celled organisms and insects

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  • Created by: Megan2413
  • Created on: 03-02-17 17:02
What is a terrestrial organism?
An organism that lives on land
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How do single celled organism exchange gases?
By simple diffusion through their skin
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What stops water from easily diffusing from the surfaces of insects?
They have a waterproof covering
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What is an insects spiracle?
Tiny pores on their surface for gas exchange
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How can spiracles avoid too much water loss by evaporation?
They have a valve that controls it if it is open or closed
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What are two limitations to gas exchange via spiracles?
- Transport is limited to diffusion - Insects must have a large surface area to volume ratio for diffusion so they can only grow so big
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What is tracheae?
It is an internal network of tubes for gas exchange
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What strengthens the structure of tracheae?
It is supported by strengthened rings
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What are the smaller dead-end tubes that tracheae branch off into called?
Tracheoles
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Where are the tracheaoles found?
Extended throughout all the body tissues of the insect
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How does this make diffusion more effective?
Atmospheric air, with the oxygen it contains, is brought directly to the respiring tissues, as there is a short diffusion pathway from a tracheole to any body cell
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What are the three ways in which gases move in and out of the tracheal system?
- Along a diffusion gradient - Mass transport - The ends of the tracheoles are filled with water
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How are gases moved along a diffusion gradient in an insect?
When cells are respiring, oxygen is being used up, reducing the concentration in the body cells compared to the high concentration in the trachea and tracheoles, hence creating a diffusion gradient
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What is mass transport?
When muscle contractions in insects can squeeze the trachea, enabling mass movements in and out
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How do the tracheoles containing water at the ends help diffusion of gases?
When muscle cells respire anaerobically, this produces lactate in the cells, which when mixed with water, reduces the water potential inside the cells, drawing water in by osmosis. As water is moved in the cells, this decreases the volume of the -->
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tracheoles, hence drawing in more air further into the trachea
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Now try the green box question on page 134 of the text book
... Get on with it then.
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Other cards in this set

Card 2

Front

How do single celled organism exchange gases?

Back

By simple diffusion through their skin

Card 3

Front

What stops water from easily diffusing from the surfaces of insects?

Back

Preview of the front of card 3

Card 4

Front

What is an insects spiracle?

Back

Preview of the front of card 4

Card 5

Front

How can spiracles avoid too much water loss by evaporation?

Back

Preview of the front of card 5
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