BBS2062 Allometry
Index:
BBS2062 Allometry .................................................................................................................................. 1
Case 1 How large was Pegasus? .............................................................................................................. 2
Case 2 Are mice big enough? .................................................................................................................. 7
Case 3 Shopping with kids ..................................................................................................................... 16
Case 4 Of mice and men ........................................................................................................................ 25
Case 5 Matters of the heart .................................................................................................................. 33
Lectures BBS2062 .................................................................................................................................. 36
Lecture 1: Introduction lecture ............................................................................................................. 36
Lecture 2: Animal research and tissue engineering .............................................................................. 40
Lecture 3: Pharmacokinetics/pharmacodynamics ................................................................................ 46
Lecture 4: Thermoregulation................................................................................................................. 53
Lecture 5: Paediatrics Lecturer: tba ...................................................................................................... 62
,Case 1 How large was Pegasus?
Learning goals:
1. What is allometry?
- describe positive allometry , negative allometry, isometry using the
allometric equation
Allometry describes how the characteristics of living creatures change with size. The term originally
referred to the scaling relationship between the size of a body part and the size of the body as a
whole, as both grow during development. However, more recently the meaning of the term
allometry has been modified and expanded to refer to biological scaling relationships in general.
The allometric equation
Scaling exponent b defines the type of scaling relationship:
- If b=1 then isometry, no differential growth, the relative size of y
to x is the same for all values of x.
- If b<1 then negative allometry, as x increases, y becomes
relatively smaller.
- If b>1 then positive allometry, as x increases, y becomes
relatively bigger.
- THIS IS ONLY TRUE WHEN COMPARING LIKE DIMENSIONS. (e.g.
length to length or mass to mass)
When comparing different parameters however you look at isometry for different dimensions:
,Log transformation:
Can have a difference in intercept and slope:
- Pos: wings grow disproportionally larger as body size increases.
- Neg: wings grow disproportionally smaller as body size increases.
- Iso: Wings grow proportionally with body size.
Primary and secondary signal
Primary signal of allometry relation: Intercept and slope of the allometric relation.
Secondary signal of allometry relation: Deviation from the expected allometric relation.
Allometric equations express convenient and valuable generalizations. However, there are important
limits where they can and can't be used, the following points should be remembered;
- Allometric equations are descriptive; they are not biological laws.
- Allometric equations are useful for showing how a variable quantity is related to body size,
all other things being equal (which most certainly they are not).
, - Allometric equations are valuable tools because they may reveal principles and connections
that otherwise remain obscure.
- Allometric equations are useful as a basis for comparisons and can reveal deviations from a
general pattern. May be due to "noise" or may reveal a significant secondary signal.
- Allometric equations are useful for estimating an expected magnitude for some variable, an
organ or a function, for a given body size.
- Allometric equations cannot be used for extrapolations beyond the range of the data on
which they are based.
2. Describe the different parameters often used in allometry (e.g. length of leg
bones, the weight of organs such as the liver and heart, the heart and
ventilation rate not too much depth)
- How do various parameters in normal mammals and birds scale with body size? What about the
length of leg bones, the weight of organs such as the liver and heart, the heart and ventilation
rate? Do larger animals consist of larger cells? In flying vertebrates, what about wing length, area
and stroke frequency?
- which really need to be taken into account? most important?
Metabolic rate changes with body size
- Metabolic rate increases when size of an animal increases.
- Energy increases by 25% when an animal doubles in size, meaning that 1 g of material in
a large animal shows less consuming of energy per unit of time than a smaller animal.
- Thus b would be 0.75 in an allometric equation.
- Mammals:
-
- Birds:
Longevity changes with body size
- As animal size increases the life expectancy also increases.
- Life expectancy dependent on amount of times your heart beats.
Locomotion changes with body size
- Locomotion in swimming animals
Index:
BBS2062 Allometry .................................................................................................................................. 1
Case 1 How large was Pegasus? .............................................................................................................. 2
Case 2 Are mice big enough? .................................................................................................................. 7
Case 3 Shopping with kids ..................................................................................................................... 16
Case 4 Of mice and men ........................................................................................................................ 25
Case 5 Matters of the heart .................................................................................................................. 33
Lectures BBS2062 .................................................................................................................................. 36
Lecture 1: Introduction lecture ............................................................................................................. 36
Lecture 2: Animal research and tissue engineering .............................................................................. 40
Lecture 3: Pharmacokinetics/pharmacodynamics ................................................................................ 46
Lecture 4: Thermoregulation................................................................................................................. 53
Lecture 5: Paediatrics Lecturer: tba ...................................................................................................... 62
,Case 1 How large was Pegasus?
Learning goals:
1. What is allometry?
- describe positive allometry , negative allometry, isometry using the
allometric equation
Allometry describes how the characteristics of living creatures change with size. The term originally
referred to the scaling relationship between the size of a body part and the size of the body as a
whole, as both grow during development. However, more recently the meaning of the term
allometry has been modified and expanded to refer to biological scaling relationships in general.
The allometric equation
Scaling exponent b defines the type of scaling relationship:
- If b=1 then isometry, no differential growth, the relative size of y
to x is the same for all values of x.
- If b<1 then negative allometry, as x increases, y becomes
relatively smaller.
- If b>1 then positive allometry, as x increases, y becomes
relatively bigger.
- THIS IS ONLY TRUE WHEN COMPARING LIKE DIMENSIONS. (e.g.
length to length or mass to mass)
When comparing different parameters however you look at isometry for different dimensions:
,Log transformation:
Can have a difference in intercept and slope:
- Pos: wings grow disproportionally larger as body size increases.
- Neg: wings grow disproportionally smaller as body size increases.
- Iso: Wings grow proportionally with body size.
Primary and secondary signal
Primary signal of allometry relation: Intercept and slope of the allometric relation.
Secondary signal of allometry relation: Deviation from the expected allometric relation.
Allometric equations express convenient and valuable generalizations. However, there are important
limits where they can and can't be used, the following points should be remembered;
- Allometric equations are descriptive; they are not biological laws.
- Allometric equations are useful for showing how a variable quantity is related to body size,
all other things being equal (which most certainly they are not).
, - Allometric equations are valuable tools because they may reveal principles and connections
that otherwise remain obscure.
- Allometric equations are useful as a basis for comparisons and can reveal deviations from a
general pattern. May be due to "noise" or may reveal a significant secondary signal.
- Allometric equations are useful for estimating an expected magnitude for some variable, an
organ or a function, for a given body size.
- Allometric equations cannot be used for extrapolations beyond the range of the data on
which they are based.
2. Describe the different parameters often used in allometry (e.g. length of leg
bones, the weight of organs such as the liver and heart, the heart and
ventilation rate not too much depth)
- How do various parameters in normal mammals and birds scale with body size? What about the
length of leg bones, the weight of organs such as the liver and heart, the heart and ventilation
rate? Do larger animals consist of larger cells? In flying vertebrates, what about wing length, area
and stroke frequency?
- which really need to be taken into account? most important?
Metabolic rate changes with body size
- Metabolic rate increases when size of an animal increases.
- Energy increases by 25% when an animal doubles in size, meaning that 1 g of material in
a large animal shows less consuming of energy per unit of time than a smaller animal.
- Thus b would be 0.75 in an allometric equation.
- Mammals:
-
- Birds:
Longevity changes with body size
- As animal size increases the life expectancy also increases.
- Life expectancy dependent on amount of times your heart beats.
Locomotion changes with body size
- Locomotion in swimming animals
