Ecological Implications of Body size

1. Ecological Implications of Body size

2. Body Size and Mortality

3. Production vs. Body Size

4. Prey Size Spectrum

5. Synthesis of Body Size Relationships

6. Energetic Equivalence Hypothesis Assume a group of animals all feeding on the same food source The group of animals all have different body sizes Is the energy used by each group of animals related to body size?

7. Energetic Equivalence Hypothesis

8. What happens when animals are eating each other? Now they�re no longer using the same energy source We have to keep track of the ratio of predator to prey body sizes, and the efficiency of energy transfer

9. Brown and Gillooly Hypothesis Assume 10% transfer efficiency between trophic levels Assume a ratio of Predator : Prey body mass = 10 4 You can then calculate the energy available as a function of body size

10. Brown and Gillooly Hypothesis

11. Brown and Gillooly Hypothesis

12. How is this used? If you can measure the Predator-Prey size ratio, you can determine how abundance scales with body size Jennings and Mackinson sought to determine this Used ratios of 15N/14N to determine trophic position of animals in the North Sea food web d15N = the per mil deviation of ratio compared to a standard source This usually increases by about 3.4 per trophic level

13. Determining predator-prey size ratios Plot trophic level vs. body size

14. Biomass Size Spectra: An ecological Indicator? Biomass size spectra is the relationship between body size and total biomass take all organisms w/in a body size range count up all of the biomass of those organisms repeat for different ranges of body size The relationship between body size and biomass (the slope) might be used as an ecological indicator Certainly indicates fisheries impacts, but that�s probably due to the size-selectivity of the fishery