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9 Cards in this Set

  • Front
  • Back

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

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

What are spiracles?

Tiny pores on insect body surface=gases enter/leave trachae (opened/closed by valve)

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

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

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

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

Why are spiracles not constantly open?

- spiracles open=water evaporates from insect

- majority of time spiracles closed=prevent water loss

- periodically open=gas exchange

How are insects adapted to minimise water loss from their bodies?

- Small SA:Vol

- Ability to close spiracles

- Waterproof outer cuticle