- Metabolisms
- Growth and shape
- Survival
- Impact of predation and competition
- Population density and growth
- Territory area
- Food acquisition
- Species diversity
- Reproduction
Some key aspects to consider:
- There are general scaling rules that apply across organisms
- Scaling relationships can be inter-related producing counterintuitive insights.
Power functions
Y= Yom^b
log(Y) = log(Yo)+ b*log(m)
m=mass
b= predictive of slope.
Log transformations allow a better appreciation of the slope of the function.
b = 1.0 means it is isometric, which indicates that the process/pattern to mass ratio is 1:1. (This is rare)
b ≠ 1.0 means it is allometric
b = 0 means there is a scale invariance
Scaling can also be geometric, this means shape doesn't change with body size:
b = 1/3 means the scaling process is in relation to length
b = 2/3 means the scaling process is in relation to area
Types of scaling:
- Within organisms
- Tree cross-sectional area
- Geometric scaling with area M^0.66
- M^0.75 gives a greater slope. Extra scaling gives tree an advantage against buckling and fractures in high flow forces
- Mammalian heart rate
- M^-0.25
- Number of heart beats per lifetime does not vary with body size
- Among individuals
- Standard metabolic rate
- Energy expenditure at rest; Kleiber's rule (1932)
- MR = M^0.75
- Scaling at population-community levels
- Scaling of body mass and population density of mammalian herbivores
- (Population density)(Metabolic rate) = M^0 = scale invariance
- Energetic Equivalence Rule (EER) = population energy flux of individuals is invariant with body size
- Species of different body sizes use approximately equal amounts of energy
- Plants: Population density related to mass; M^-0.75
- Metabolic resource use in plants; M^0.75
- EER applies to marine and terrestrial plants
Types of size-density relationships
- Global size-density relations
- Local size-density relations
- All population data taken from a single region
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