081 ESTIMATION OF RATE OF RESPIRATION IN COCKROACH

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EXPERIMENTAL SET UP
Take a test tube, place 3-5 KOH pellets and cover
with cotton
Place a cockroach in the tube
Fit a U shaped manometer to the test tube through
one holed rubber cork
Place coloured water in the manometer
Attach a graph paper piece to the manometer
A small glass bottle empty ball pen refill can
be used to improvise the set up.
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After arranging the setup, mark the initial level
of water on manometer
Observe and note down changes in the level of
water at regular intervals, say one minute
After 5-6 such readings open the cork to allow
fresh air into test-tube
Tabulate readings in the table
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CALCULATIONS

• Amount of air used (oxygen consumed)
• Volume of water displaced in
  monometer / min.
• p r² h.
• r radius of manometer tube,
• h change in level.
• Rate of respiration ml / min

You can also try experiments with grasshoppers
for comparison or by increasing the temperature
by keeping test tube in warm water or decreasing
temperature by keeping the tube in ice.