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Gas Exchange in Single-Celled Organisms and Insects (Gas Exchange in…
Gas Exchange in Single-Celled Organisms and Insects
Gas Exchange in Single-Celled Organisms
Small t/f large SA:V
Respiration:
O2 absorbed by diff. across body surf., covered by cell - surface membrane
CO2 diff. out of body surface
Cell wall of living cell, no barrier to diff.
Respiratory Gases Move in + out of Tracheal Sys.:
Along diff. grad.
When cells respire O2 is used up t/f conc. toward end of tracheoles fall = diff. grad. + causes O2 to diff. from tubes to cells. CO2 produced by cell res. = diff. grad. in opposite direction, from cells to tubes.
Diff. in air, much more rapid than in H2O, t/f respiratory gases r exchanged more rapidly
Mass Transport
Contraction of mucles = insects can squeeze trachea enabling mass movements of air in + out
Further speeds up ex. of respiratory gases
Ends of Tracheoles, Filled with H2O
Muscle cells, around tracheoles anaerobically respire, produces lactate, soluble + lowers water potential
H2O moves to cells from tracheoles by OSMOSIS, water @ ends decreases vol. + t/f draws further air in2 them t/f final diff. path. is in gas rather then liquid phase + t/f diff is more rapid
Inc. rate @ which air is moved in the tracheoles but leads to greater H2O evap.
Gas Exchange in Insects
Insects conserve water
Gas ex. SA required conflicts with conserving water b/c H2O will evap.
For gas ex. insects use TRACHEAE
Supported by strengthened rings that prevent collapse
Divide into smaller dead-end tubes, TRACHEOLES
Extend throughout boddy tissue
Atmospheric air with O2 is brought directly to respiring tissues b/c, short diff. path. from tracheal to any body cell
Gas Exchange in Insects 2
Gases enter + leave trough SPIRACLES, on body surface
May be open/closed by a valve
When open, H2O vapour can evap.
Periodically open to allow gas ex.
Most of time spiracles are closed, prevent water loss
Tracheole System
Efficient method of transport
Limitations
Relies on diff. 2 ex. gases b/w environment and cells
For diff to be effective...
Diff. path. needs to be shot = insects are small
Length of diff. path. limits size of insects