Embed Size (px)
Citation preview
11
IMPROVISED RESPIROMETER
Dr. G. NAGARAJ
Zoology Section
Regional Institute of Education (NCERT)
Mysore – 570 006
22
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.
33
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.
44
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.
55
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
66
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
& pen6. Needle and thread7. A colour liquid like ink/
dye 8. Ink filler and vial9. KOH pellets and cotton10. The organism
(cockroach, cricket, germinating seeds)
Pic-2. Materials Required
77
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
88
Improvised Respirometer
Bottle Monometer
Cockroach
KOH
Cork
Nylon tube
Pic.3. Improvised Respirometer
99
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).
1010
Observation Table
SNTime (min)
Monometer Reading (cm) Net
Rise (cm)
RRInitial Final
1 10
2 20
3 30
4 40
5 50
6 60
1111
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.
1212
Thank you
