Body Size Flashcards
Do larger animals have greater or less gravitational forces?
Greater
What is allometry?
Study of differential growth
What are the different types of allometry?
Ontogenic = body proportions change with development
Isometric = body proportions stay the same with development
Static = body proportions differ between individuals of same sex and age in a species
Evolutionary = body proportions differ between species
What is an example of ontogenic allometry?
Foals have proportionally longer legs that adults
Foetus head is larger compared to the body
What is an example of isometric allometry?
Frog growing from froglet to an adult
What is an example of static allometry?
Often seen is sexually selected traits
Male horn beetle horn size
What is an example of evolutionary allometry?
Insect wing size between species
What is the equation of allometry?
y = ax^b
y = body part size
x = measure of whole body size
a = size of y when x=1 (initial growth index)
b = scaling exponent
What happens when b = 0
No allometric relationship
Size of body part stays the same as the body grows
What happens when b = 1
Isometric relationship
y grows at the same linear rate as x
What happens when b < 1
It is negative allometry
Increases slowly compared to body size so y<x
Not linear so sits below isometric line
What happens when b > 1?
Positive allometry
Body part increases at a faster rate than body size
Not linear
How to linearise allometric relationships?
Using log scales
log y = log a + blog x
Isometric would lie on 1 to 1 relationship line
What are the allometries of male and female beetle mandibles?
Female mandibles grow isometrically as under natural selection
Male mandibles grow under positive allometry as under sexual selection so can vary in size
What is the equation of metabolic rates?
Metabolic rate = body weight ^0.75
