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IMPROVISED RESPIROMETER
Dr. G. NAGARAJ
Zoology Section
Regional Institute of Education (NCERT)
Mysore – 570 006
India
gnriem@gmail.com
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Introduction
• Respirometer is an instrument/ setup/ device used to measure the
rate of respiration of a living organism by measuring its rate oxygen
uptake or CO2 release.
• Respirometers are designed to measure respiration either on the
level of a whole animal (or plant) or on the cellular level.
• The instrument consists of a sealed container with the living
specimen together with a substance to absorb the carbon dioxide
given off during respiration, such as soda lime pellets or cotton
wads soaked with potassium hydroxide.
• The oxygen uptake is detected by displacement of manometric
fluid in a thin glass U-tube connected to the container.
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Working Principle
• When the organism takes in oxygen it gives off an
equal volume of carbon dioxide.
• As this is absorbed by the KOH / soda lime, air is
sucked in from the U-tube to keep the pressure
constant, displacing the liquid.
• The rate of change gives a direct and reasonably
accurate reading for the organism's rate of
respiration.
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Precautions
• As changes in temperature or pressure can also
affect the displacement of the manometric fluid, a
second Respirometer identical to the first except with
a dead specimen (or something with same mass as
the specimen) is sometimes /if needed can be set up.
• Subtracting the displacement of the second
Respirometer from the first allows for control of these
factors.
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The above instrument is costlier and easily breakable. I improvised a simple
no-cost device from waste materials which also works on the same principle.
Regular Respirormeter
Pic-1. Regular Respirormeter
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Preparation of Improvised Respirometer
A. Materials Required
1. 500 ml water bottles – 1or 2
2. Rubber cork/ bottle cap/
thermo coal
3. Glass tube (5 mm dia.)
4. Transparent Nylon tube -2 feet
(5 mm dia.)
5. Card board, graph sheet &
pen
6. Needle and thread
7. A colour liquid like ink/ dye
8. Ink filler and vial
9. KOH pellets and cotton
10. The organism (cockroach,
cricket, germinating seeds)
Pic-2. Materials Required
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1. Make a single hole (5mm) in the rubber cork and insert apiece
of glass tube
2. Fix 2 feet transparent nylon tube on the top of the glass tube
and fix this cork in the mouth of water bottle tightly
3. Paste a graph sheet on a card board and fix the tube in ‘U’
shape (as shown in picture-3) with use of needle &thread
4. Mark 1-10 in the graph sheet near the ‘U’ tube
5. Tie the bottle also on the card board in such a way that it is
easily removable
6. Keep few pellets of KOH in a vial and plug the mouth with
cotton
7. Hang the vial inside the bottle with use of thread (Pic-3).
B. Assembling the device
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Procedure / Operation
1. Through a dropper add 5-10 ml of colour liquid in the ‘U’ tube
which functions as monometer
2. Remove the bottle and introduce cockroach/ honey bee/
germinating seed etc, fix the cork setup (monometer) and tie the
bottle again with card board
3. Note the initial time and liquid level in monometer
4. Leave the setup for 1 or 2 hrs and note the monometer level/
reading for every 10 minutes
5. Record the readings in observation table and calculate the
Respiratory Rater (RR).
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Project
• Take up small project to find out the effect of light, temperature,
sound, chemical, age of the animal, food (veg, non-veg/ protein,
carbohydrate, lipid) on RR of the animal.
Advantages of this Instrument
• The instrument is improvised from waste material hence, no
expenditure
• Simple experiments/ projects can be conducted at schools and
even at home
• Develops creative thinking, enquiry and experimentation attitude
• Learning by doing; so creates interest in learning.
