BI2CV1 Scaling of Vertebrate Life Lecture 7 PDF

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...

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