1 - Metabolic Rate Flashcards
(18 cards)
What is metabolic rate
The rate at which an organism consumes energy
How is metabolism measured
Using respirometry, which measures O₂ consumption or CO₂ production – useful for calculating basal metabolic rate or response to exercise
How is metabolic rate measured in the field
By injecting labelled water isotopes into an animal to track energy expenditure under natural conditions
Do larger organisms have higher or lower absolute metabolic rates
Higher absolute metabolic rates – they consume more energy overall
What is mass-specific metabolic rate, and how does it relate to body size
It’s the energy use per unit of body mass.
Smaller organisms have higher mass-specific metabolic rates than larger ones
Why do bigger animals have higher absolute energy demands
Because they need more energy for basic functions like breathing, digestion, circulation, and locomotion (due to more resistance from air and water)
What is allometric scaling in relation to metabolic rate
t refers to how metabolic rate (Y) scales with body mass (M) using the equation Y = aM^b, where b ≈ 0.75
What are the implications of allometric scaling
Smaller animals have faster metabolisms per gram
Drug dosages must be adjusted for larger animals due to lower mass-specific metabolic rates
What are endotherms and give examples
Animals like mammals and birds that internally regulate body temperature
What are the advantages of endothermy
Can stay active in cold environments
Better predator avoidance
What are the disadvantages of endothermy
High energy cost
Requires frequent feeding
What are ectotherms and give examples
Animals like reptiles, fish, and amphibians that rely on external heat sources to regulate body temperature
What are the advantages of ectothermy
Lower energy demands
More energy available for growth and reproduction
What are the disadvantages of ectothermy
Activity depends on environmental temperature
Reduced mobility in the cold
How do metabolic rates differ between large and small organisms in terms of life history
Large organisms: slower metabolism, longer lifespan, slower reproduction
Small organisms: faster metabolism, shorter lifespan, faster reproduction
What is the Surface Area to Volume Hypothesis in relation to metabolism
Larger animals have less surface area per unit volume, making it harder to dissipate heat, contributing to slower metabolism
What does the Adaptive View suggest about metabolic rate in large animals
That natural selection favours lower metabolic rates in larger animals to help them conserve energy over time
Metabolic Rate Equation
Y = Y0 Mb
Y = metabolic rate
Y0 = ‘normalisation constant’
M = mass
b = ‘allometric exponent’ (0.75 for multicellular eukaryotes)
