Animal Metabolism Biology Lab Report Template Page 2
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3Measurement of oxygen consumption in a homeotherm
Procedure B. Mouse metabolism at ambient and cold temperatures
Mice are homeothermic endotherms. They maintain relatively constant body temperature
In this procedure we will measure the oxygen consumption of the common laboratory
(T
) throughout the day. Thus, it should be expected that mice would increase their
mouse (Mus musculus) at two temperatures, room or ambient (T
) and a reduced
b
a
metabolic rate to maintain constant body temperature if the ambient temperature (T
)
temperature near 1 °C. The procedure is illustrated in Figure 5. NOTE: Each group will
a
begins to fall.
run one mouse at only one temperature. The mice will be placed in a respirometer
containing soda lime (a CO
absorbent and drying agent) and equilibrated at temperature
2
for 10 minutes. At this time, the respirometer is sealed and 10 cc of room air is added.
The time for the manometer to return to the initial level is recorded. The respirometer is
opened to room air for 1 minute to allow fresh air into the chamber, and then the
determination is made again. Three determinations of oxygen consumption will be made
at each temperature. Raw data should be recorded on the data sheet shown in Table 2.
Mouse weight and respirometer temperature must be recorded at the beginning and end
of a temperature session.
The computation of oxygen consumption is a straightforward algebraic manipulation of
the raw numbers. Weight specific metabolic rate (MR) should be expressed as mL
O
/gm/hr. This may be calculated as for each run:
2
Figure 3. Typical Endothermic Metabolic Response to Ambient
10
cc
60
sec
60
min
1
=
(2)
MR
x
x
x
t
min
hr
wt
In Figure 3 you can see the temperature-related metabolic response seen in most
endotherms. TNZ refers to the thermoneutral zone, or the range of temperatures over
where 10cc is the volume injected into the respirometer, t is the time in seconds to return
which the animal's metabolic rate remains fairly constant. At these temperatures, the
to the initial manometer reading after the 10 cc injection and wt is the weight of the
animal's metabolic rate is as low as it can be during the waking state. The lower critical
mouse in grams. You should set up an Excel spreadsheet to complete your calculations.
temperature (LCT) is the point where metabolic rate increases to assist in maintaining
You should calculate MR for each determination.
body temperature in the face of the decreasing temperature. UCT, or upper critical
temperature, is the point where energy is utilized to loose excess heat. The slope of the
You must now convert your gas volumes to standard pressure and temperature, for dry
oxygen consumption rates above and below the critical temperatures, and the width of
air (STPD: 0 °C, 760 mm Hg). The soda lime dried the air in the chamber, so you won't
the TNZ are related to the type of animal, its size and its evolutionary history. For
need to deal with water vapor pressure.
However, you will need to apply the
instance, the arctic fox, an animal well adapted for the life at cold temperatures, has UCT
temperature-modified form of Boyle's law to adjust the volumes to STP:
of only 0 °C. Even more startling is their TNZ, which extends far below -10 °C. Humans,
on the other hand, evolved in a warm climate, witnessed by their narrow TNZ, high critical
P
V
P
V
temperatures (Figure 4).
=
(3)
1
1
2
2
T
T
1
2
Where P
is the room barometric pressure (in mm Hg), V
is the gas volume (i.e. the
B
1
MR), T
is the temperature of the respirometer in °K, P
is standard pressure (760 mm
1
2
Hg), T
is 273 °K, and V
is the adjusted volume (STP).
2
2
Raw data for all mice at all temperatures will be available on the class website. Using all
of the data, please construct a graph similar to Figure 3, with metabolic rate (in mLs
O
/gm/hr, STPD) plotted against ambient temperature.
2
Figure 4. Thermoneutral Zones of Humans and Arctic
BIO 3A Lab: Animal Metabolism
Page 3 of 6
BIO 3A Lab: Animal Metabolism
Page 4 of 6
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(03/09
(03/09
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