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9 Cards in this Set
- Front
- Back
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How does gas exchange occur in single-celled organisms? |
- small=large SA:Vol - Absorb O2/Expels CO2: diffusion across body surface (cell surface membrane) - cell wall=no additional barrier to diffusion of gases |
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How does gas exchange occur in insects? |
- exchange respiratory gases directly with the air - air channeled into trachae (internal tube network)=supported by strengthening rings to prevent collapse - divide into small dead end tubes (tracheoles)=extend through all body tissues |
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What are spiracles? |
Tiny pores on insect body surface=gases enter/leave trachae (opened/closed by valve) |
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What are the three reasons why respiratory gases move in and out of the tracheal system? |
- Across the diffusion gradient - Mass transport - End of tracheoles have water |
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How does the diffusion gradient allow respiratory gases to move in/out the tracheal system? |
- respiring cells use O2=lower conc. to tracheoles=diffusion gradient;atmosphere to tracheoles to cells - respiring cells produce CO2=higher conc. to tracheoles=diffusion gradient: cells to tracheoles to atmosphere |
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How does mass transport allow respiratory gases to move in/out the tracheal system? |
- contracting muscles=squeeze trachea=mass movement of air in/out=speeds respiratory gas exchange |
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How do the end of tracheoles containing water allow respiratory gases to move in/out the tracheal system? |
- Major activity: muscle cells around tracheoles anaerobic respire=lactate (soluble/lower water potential of muscle cells)=water moves (osmosis) from tracheoles to cells = vol water in tracheole lower, draw air in =rapid diffusion=greater water evaporation |
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Why are spiracles not constantly open? |
- spiracles open=water evaporates from insect - majority of time spiracles closed=prevent water loss - periodically open=gas exchange |
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How are insects adapted to minimise water loss from their bodies? |
- Small SA:Vol - Ability to close spiracles - Waterproof outer cuticle |
