Fi aure 2 A. 

 where c 



R, 

 C. 



Energy intake (I) 

 < C£ (see text). 

 As^in A, but where Ci 



and cost (0) as functions of individual biomass (W) 



W *. = optimum size, E $ = 1-0, 



as in colony qrowth. 



°R, 



Enemy surplus (E s ) as a function of W where Ci : C2> Habitats 

 increase in food availability or decrease in physiological cost. 



Hj, H2, H- 



D. As in C but where c^ = C2, M = maximum size (non-asymptotic), set by non- 

 energetic causal factor such as size-dependent mortality. 



E 



E, 



A 



B 



w 



w 



Growth 

 metabolic 

 Extrinsic 

 potential 

 getic cos 

 example, 

 dators in 

 behavior) 



the diffe 

 to reprod 



GROWTH RATES AMD SIZE ASYMPTOTES 



rates depend on intrinsic factors such as the all 

 activity and to reproduction, or genetically dete 

 factors that influence growth include local food 

 energy intake) and the physical nature of the hab 

 t). Intertidal habitats with high temperature or 

 generally increase metabolism integrated over time 

 a particular habitat can affect their prey's ener 

 and intake (time available for foraging). Growth 



Ci c 



rence between energy intake (kiW ) and cost U2W 

 uction (g(W)) (Sebens 1979, 1982) 



ocation of energy to 

 rmined limits to size, 

 availability (determining 

 itat (determining ener- 

 desiccation stress, for 

 The frequency of pre- 

 gy loss (e.g. , escape 

 rate (dW/dt) depends on 



) minus the allocation 



dW/dt 



kjW 



■1 



k 2 W 



g(W) 



assuming a simple power function relationship between intake or cost and body mass 

 (W) (Fig. 2). Under most conditions, reproductive output (g(W)) (and thus offspring 

 number = fitness) will be maximized when W is chosen such that when dW/dt = 



(growth ceases), k^W * - k2W ^ is at its greatest. In other words, this hypo- 

 thetical organism should stop growing at some asymptotic size W Qpt where W opt = 



(C2k 2 /c 1 k 1 ) 1/(c l" c 2 ) . The parameter Co equals 0.7-1.0 and cj £0.7 for a variety of 

 organisms, thus producing the predicted size asymptote because energy intake scales 

 at a lower power of mass than does cost. Colonial organisms need not conform to 



11 



