Gas exchange

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  • Created by: Hindleyc
  • Created on: 01-06-18 11:21
What do single celled organisms like Amoeba have?
Large SA:Vol ratio
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What don't they have?
A specialised gas exchange surface as can accomplish all the exchange it needs by simple diffusion across its whole body surface
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Why is it rapid?
Diffusing distance involved are very small
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What does it require?
Concentration gradient that is established for both glucose and oxygen by using up internally and carbon dioxide that is produced internally
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What are CO2 and O2?
Small uncharged molecules that can pass easily through the pores in the membrane
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What is the exoskeleton of an insect?
Waterproof and gas-proof
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What did this mean?
had to evolve a separate gas exchange system
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What do they exchange?
Oxygen and Carbon dioxide between tissues and air
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What do they use a system of?
Air filled tubes called tracheae
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What do the tracheae do?
Open to the outside through small holes called spiracles along the side of body
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What do the spiracles do?
Lead to breathing tubes called tracheae that take air directly to respiring tissues
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What are the walls of the tracheal tubes stiffened with?
Bands of chitin
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What do the tracheae branch out/ lead to?
Network of tracheoles which are small and dense and pass close/in to respiring cells- penetrate into individual body cells- every part of body
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what is every cell in insects body close to/ adjacent to?
End of tracheal that is less than 1micrometre
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What is there a limit to?
Pressure they can withstand w/o collapsing - reason why insects small
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what else diffuses out of the spiracles along with CO2? what could this lead to?
Water vapour. dehydration in dry environments
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What are spiracles guarded by?
Valves that are controlled by muscles that enable the grasshopper to open and close them
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What happens when oxygen demand is low?
Partially close spiracles to prevent loss of water
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What else helps trap moisture reducing water loss?
Hairs that filter out dust as the air enters the spiracles
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What happens in smaller less active insects?
Gas exchange occurs through tracheal system by simple diffusion. spiracles opened when greater respiration needed by contracting muscles b/w each body segment so insect compress tracheae and pump gases in/out of body
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What do large active insects do?
Forcibly ventilate their tracheae. Contraction of muscles in abdomen compresses internal organs forcing air out of tracheae. Vol dec so pressure inc so air moves out
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What happens as muscles relax?
Abdomen springs back to normal volume and air drawn in- volume increases so pressure decreases so air moves in
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What do large air sacs attached to main tracheal tubes do?
Increase effectiveness of action
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further adaptations?
open and close spiracle valves in particular order possible for insect to such air into tracheal system and pass it out other end of body
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Why is important for insects to control gas exchange?
Small volume so greater desiccation
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What happens when asleep?
In response to changes in water potential water can leave the body cells and fill trachea thus reducing effective SA
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What happens when insect is most active?
Water leaves trachea again by osmosis producing max respiratory surface when required
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What happens at rest?
Water tends to accumulate in the tracheoles
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What happens when active?
Lactic acid accumulates in muscle cells from anaerobic resp. reducing water potential of cells- more negative. so water passes from the tracheoles into muscle cells by osmosis increasing SA and diffusion distance for gas exchange.
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Other cards in this set

Card 2

Front

What don't they have?

Back

A specialised gas exchange surface as can accomplish all the exchange it needs by simple diffusion across its whole body surface

Card 3

Front

Why is it rapid?

Back

Preview of the front of card 3

Card 4

Front

What does it require?

Back

Preview of the front of card 4

Card 5

Front

What are CO2 and O2?

Back

Preview of the front of card 5
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