BI2CV1 Week 4 Lecture 7 - The Scaling of Vertebrate Life PDF

Hi, I’m Jacob! T. rex, Museum of the Rockies Hell Creek Formation (~66 Mya) Week 4 lectures Lecture 7: The Scaling of Vertebrate Life How and why animals get big Properties of scaling Energetics and metabolism Evolutionary trends with size Lecture 8: The Movement of Ve...

Hi, I’m Jacob! T. rex, Museum of the Rockies Hell Creek Formation (~66 Mya) Week 4 lectures Lecture 7: The Scaling of Vertebrate Life How and why animals get big Properties of scaling Energetics and metabolism Evolutionary trends with size Lecture 8: The Movement of Vertebrates How and why animals move differently Biomechanics Posture and stance Convergent evolution  The Scaling of Vertebrate Life Emily Willoughby (2022) BI2CV1: Comparative Vertebrate Biology Lecture 7 Dr Jacob Gardner [email protected]  Diversity across scales Diversity of life is dominated by differences in size Size dictates ecology (e.g., behaviour, prey-predator relationships, number of offspring, food-energy budget, migratory patterns, etc.) Size determines habitat suitability Bee hummingbird, smallest bird Patagotitan (sauropod dinosaur), AMNH  Functional change with size Eukaryotic cells: 10-100 um in diameter (carry organelles) At the cellular level, size determines function Nutrient transport: red blood cells (6-8 um wide) Sperm (2-3 um wide) are much smaller than an ovum (100 um)  Scaling factor (recap) Expected scaling relationships while maintaining isometry Area: A ∝ L2 or L ∝ A1/2 Volume: V ∝ L3 or L ∝ V1/3 Greater surface area to volume ratio at smaller sizes ×2 Length L 2L ×k V ∝ L3 A ∝ L2 ×4 A2 = 6(2L)2 Area A = 6L2 Value = 24L2 ×k2 V A ×8 Volume V = L3 V2 = (2L)3 ×k3 = 8L3 L where k is some scaling factor  Scaling factor (recap) Life scales with mass Log10-scale: change in 10x scale Deals with linear relationships rather than exponential ones Linear relationship between a measure of interest and body mass Log- scale  Expected scaling relationships (recap) Isometry: Positive Isomet allometr Two measures scale in proportion to y ry each other under theoretical expectations. Allometry: One measure scales disproportionately to another compared to theoretical expectations. Negative Positive allometry: allometr y More than expected Negative allometry: Less than expected  Scaling in biology (recap) Scaling relationships in biology are often allometric Ontogeny: individual growth Differences among species (evolution) Slope >1 Positive allometry Slopes