Lecture 3: Biological Designs Flashcards
An animals ultimate design determined by nature must address what?
The physical demands it faces
Stress
Force applied to a material (gravity)
Strain
Deformation in a material caused by stress
Scaling effects
Consequences of size animal must deal with
Allometry
The change in an organism’s shape or proportions concomitant to a change in size
Scaling
The study of size and its consequences
Otogenic scaling
Scaling related to development
Phylogenic scaling
Scaling related to evolutionary relationships
Static Scaling
Looking at the organism as it is
How does enlargement of a body part affect an organism?
It places additional demands on the organism (often disproportionally)
- Mass increases stress on skeletal elements
- Increased oxygen and nutritional demands
Units for length
mm, cm, or m
Units for area
mm^2, cm^2, or m^2
Units for volume
mm^3, cm^3, or m^3
Given no change in an organism’s shape, how can even the smallest increments in length affect the area and volume of the body?
Area and volume will increase exponentially
How does an increase in volume affect the organism?
An increase in volume causes an increase in mass. This may lead to differences (disproportions) between the body and appendages.
Scaling independent features
A biologic feature independent of overall size and mass of the organism
What features are relatively independent of the effects of scaling?
- Size of red blood cells between organisms
- Muscle strength per square inch
- Biochemical properties of blood
- Body temperature
- Rate of muscle contraction
- The proportion of blood that is red blood cells and liquid plasma
Isometric
Two bodies (or two body parts) with the same proportions. Example: Legs
Allometric
Two bodies (or parts of bodies) with different proportions (that is, non-isometric), that changes in proportion to mathematical or natural rules
What does the allometric equation (Y=bx^a) represent?
Y = one of a paired measurement X = the second of a paired measurement, plotted on exponential axis b= constant (Y intercept) a = slope
If a~1, what is the allometric relationship?
Directly proportional –Body weight: heart weight –Body weight: lung weight –Body weight to blood volume (ml) –Body weight to skeletal mass
Negative allometries (a<1)
Relatively slower growing or becoming relatively smaller
–Body size (mass) : metabolic rate
Positive allometries (a>1)
Relatively faster growing or becoming relatively larger
–Beak length in shore birds: head size
Isometry
Body parts remain relatively constant as growth occurs or as species evolve
