Environmental Engineering Reference
In-Depth Information
(a)
10
Homeotherms
Active
poikilotherms
1.0
Poikilotherms
0.1
0
10
20
30
40
Temperature (
°
C)
(b)
100
Homeotherms
10
Unicells
1
Poikilotherms
0.1
0.01
10
-16
10
-12
10
-8
10
-4
4
1
Body mass (kg)
(c)
1
Green = surface-water species
Purple = ground-water species
0.1
0.01
1
10
100
Body mass (mg wet mass)
FIGURE 3.2
Four primary determinants of metabolic rates of consumers. (a) Metabolic rates rise with rising
temperature and are higher for homeotherms than poikilotherms. (b) Metabolic rates (per unit mass) fall with ris-
ing body size.
((a) and (b) redrawn from
Peters 1983.)
(c) Metabolic rates may fall over evolutionary time in food-
poor habitats. (
Data from
Gourbault 1972.
)
where
e
is the base of natural logarithms,
E
i
is the activation energy of the average bio-
chemical reaction,
k
is Boltzmann's constant (a term from physics that relates the energy of
a molecule to its temperature), and
T
is the temperature (
K) (
Gillooly et al. 2001
).
Temperature dependence is also commonly expressed using Q
10
, the factor by which
