Today Calculate metabolic rate using different methods – indirect calorimetry and respirometry. Examine the effects of size on metabolic rate Examine the effects of temperature on metabolic rate.

MW of glucose = 182

A Roach Ate Chicago ? We hear a lot these days about gene cloning and adding growth genes to breed larger cattle and larger rats. What would happen if growth genes were applied of all animals / What are the limits of size ? How would body shape have to change ?

Isometry = body dimensions scale exactly i. e Isometry = body dimensions scale exactly i.e. as the height doubles the arm length doubles. Note that the surface to volume ratio changes, however. 96(16x) Surface:volume 6:1 3:1 2:1 1.5:1

With allometric change the proportions vary With allometric change the proportions vary. Note the size of the head and eyes.

If the large roach ( 8 inches)were 4 x as long as the small one (2 inches) its surface area would be 42 times greater and its volume would be 43 time greater. The small roach would have a surface to volume ratio of 4:1 and the large roach 2:1 . The small roach would have a much more efficient absorbtive surface for digestion and respiration. If there were isometric scaling of the body, legs of the large roach would have a cross sectional area 16x greater but a volume or density 64x greater. Legs would be carrying 4 x as much weight.

Metabolic Rate = a Mb (1) where a is the log/log intercept, M is mass and b is the rate of change of metabolic rate with mass. For Mass specific rate MR/M = aM b /M = aM b-1(2) Expressing these equations as logs gives a straight line where b= the slope. For (1) log MR = log a + b(log M) For (2) log MR/M = log a +( b-1) log M

In general large animals live slower than small animals In general large animals live slower than small animals. Chicken heart rate = 300 beats/minute. Elephant heart rate = 30 beats/minute. Elephant mass = 10,000 chicken mass. Warm blooded animals die after 1-2 billion heart beats so elephant lives longer.

For metabolic rate b = .75

For surface area b = .63

For a single species (I.e. small range) b = .67

Rubner rule: Metabolic rate varies with mass 2/3 If length = l 1; then area is proportional to l2 and volume is proportional to l3 ; so the surface to volume ratio is l2:l3 or l 2/3 Problems : shouldn’t there be differences between ectotherms and endotherms ? Between plants and animals ? Kleibner’s Rule == Metabolic rate = mass 3/4