Scaling Flashcards
Knut Schmidt - Neilsen
FOREVER CURIOUS. The title of one of his books, How Animals Work, captures the essence of biologist Knut Schmidt-Nielsen, who died in Durham, North Carolina, on 25 January at the age of 91. Considered the father of comparative physiology and integrative biology, the Duke University researcher endured the heat of the Sahara and the cold of the Arctic to learn how animals thrive in extreme climates. He discovered, for example, that moisture-conserving mucus in the nose—not water stored in its hump—helps protect camels against dehydration, and that special glands help seabirds and marine reptiles shed excess salt. His lab was a menagerie, including a misnamed 100-kilogram female ostrich called Pete who was a source for 1-kilo omelets. (Pete helped Schmidt-Nielsen and his colleagues learn how ostriches can run in the heat without sweating.) “Knut invoked in all of us a sense of curiosity about how animals function,” says Barbara Block of Stanford University in Palo Alto, California.
Size & Scale
“Scaling deals with the structural and functional consequences of changes in size or scale among otherwise similar organisms”
Size is measured in
Mass and linear dimensions
Symorphosis
If “animals were built reasonably”
Galileo
Galileo: animals of different sizes have different shaped bones. The cross-sectional area of the two thigh bones (pictured) is different compared to the weight of the animal and realized the strength of the bone is proportional to the cross-sectional area but the weight of the animal is dependent on the volume which is a cube (compared to cross-sectional area which is squared). 8 feet is the tallest a human can be and still stand Scaling based on allometry As the animal grows larger, the bone diameter has to grow disproportionately larger (by a 3:2 law).
Knut Schmidt-Nielsen (1916-2007)
Father of comparative physiology and integrative biology father of scaling Knut and his wife taught biology at case Studied how animals thrive in extreme climates Example: moisture-covering mucus in the nose (not water in the hump) helps protect camels against dehydration, special glands help seabirds and marine reptiles shed excess salt
Size and scale
“Scaling deals with the structural and functional consequences of changes in size or scale among otherwise similar organisms” Three parameters can be changed when size increases: Dimensions Materials Design Size measured in mass and linear dimensions
Isometric geometry
Isometric geometry Surface ∝ (length)^2 S ∝ L^2 Volume ∝ (length)^3 V ∝ L^3 Surface ∝ (volume)^2/3 S ∝ V^2/3
Linear scale vs log-log scale (linearizes the equation). Intercept becomes the constant and the slope of the line becomes the exponent.
Linear scale vs log-log scale (linearizes the equation). Intercept becomes the constant and the slope of the line becomes the exponent. S/V = kV0.67 → Slope of 0.67 S/V = kV(0.67 - 1.0) → Slope of -0.33
Allometric equation
y = axb ; or: log y = b log x + log a A is the constant; B is the slope
Allometry
Non-isometric scaling = “allometry” (allos = different)
Isometry
Similarity in triangles is linear proportional scaling = “isometry”
Blood Volume
A: Total blood volume increases in proportion to body size (slope = 1.0) y = 0.7 * mass1 Isometric Percent blood volume is the same but liters changes proportional to body size
Bone Mass
B: bone mass has to increase higher than proportional rate (slope = 1.08) Predict that as animals get larger, there must be some shape differences in animals
Overall oxygen consumption Rate/Metabolism
C: overall oxygen consumption/metabolism increases with body size (slope = 0.75) 0.75 is an observational number If you normalize the metabolic weight per g tissue, the larger the animal, the lower the metabolic rate gram tissue is. For the same organ (e.g., brain, muscle), a large animal has less oxygen consumption per gram of kidney (for example) than a small animal has.
Hematocrit
D: hematocrit is constant and does not scale with body size (slope = 0) Also: blood pressure, temperature (don’t scale)
HR
E: as body size increases, HR decreases (slope = -0.25) related to metabolism falling off
Kleibers law
is it universal and why does this make sense. Need to use it to relate mice studies to humans
West and brown
West and brown extedned the scale to 27 orders of magnitude
Metabolic rate
Met doesnt go up as fast as body mass Larger size met advantage bec cost per gram is less so u use less o2 and take less food in
Mouse to Elephant
“Mouse to elephant curve” Slope = 0.74 Pmet (Kcal/day) = 73.3 Mb0.74 Rounded to 70 Mb0.75 Max Kleiber (1932) y = axb; or log y = b log x + log a Specific - star normalized per gram using -.25
Lung and ventilation
As the animal gets larger, the lung gets larger proportionally (isometric) Tidal volume is structural (1.04) Vital capacity is structural (1.03) Ventilation rate is more related to metabolism (0.8) Compliance is physical and directly proportional (1.04) Elastic work per min is related to metabolism (0.78) Frequency of respiration (per min) (-0.26)
Tidal volume is structural
(1.04)
Vital capacity is
(1.03)
Ventilation rate
(0.8)
Compliance
(1.04)
Elastic work per min is
(0.78)
Frequency of respiration (per min)
(-0.26)
Vital capacity is
structural