Biological Design Flashcards
Study of biological design is….
the study of basic physics
Animal morphology must obey….
the laws of physics
Scaling
- study of size and shape
- requires more than making a small structure large in the same proportion
- there is a disproportional change in different parts of the body as body size changes
Size
- physical forces that affect an animal are determined by its size
- general rule
General rule of size
- the larger the animal the more important gravity is
- the smaller the animal the more important are surface forces
i. frictional drag
ii. surface tension
Basic rule between length, surface area, and volume
If shape is held constant then the relationships between length, surface area, and volume and mass all change
Basic relationships between length, surface area and volume
- surface is proportional to length2
- volume is proportional to length3
- those relationships hold for any shape that we expand while maintaining shape
- examples
i. increase a sphere from marble to soccer ball size
ii. surface area increases 100 times
iii. volume increases 1000 times
Surface area
- directly affects the rate many events occur [what melts faster an equal mass of ice cubes or block of ice]
- biological functions
- absolute amount of O2 and food ingested increase with size
- as body size increases the O2 and food consumption per unit of body mass decreases
- in a homeothermic animal, the rate of heat loss is related to body size
i. due to surface to volume ratio
ii. smaller individuals have larger surface areas and loose heat faster
Surface area biological functions
- rate of oxygen consumption and heat loss
- importance of diffusion
- rate of digestion
- locomotive patterns
Volume and mass
- body mass is directly proportional to body volume
- Mass is proportional to length3
- in terrestrial organisms, with limbs, the mass is carried by the legs
i. cross sectional area of the limbs also increases disproportionally
ii. cross sectional area of the bones increases in proportion to mass and volume and not length
Shape
- maintain function
- allometry
- positive allometry occurs when the y variable grows faster than the x variable
- Negative allometry occurs when the y variable grows slower than the x variable
- isometry occurs when the proportions between two characteristics remain constant
- shape remains constant with increasing size
Shape’s maintain function:
- animal’s design has to be altered
2. because length, surface area and volume all change at different rates
Allometry
study of changes in shape
i. change in shape can be expressed in the form y=ax^b ii. equation describes how different body parts change relative to each other
biomechanics
application of engineering principles to biological design
principles of biomechanics
- basic quantities
i. length concept of distance
ii. time concept of flow of events
iii. force the effects of one body acting on another
iv. mass the property of matter
- weight is a measure of force operating on mass
- objects of different mass take different amounts of force to move - units are conventions, standard of measurement that are used to describe length, time and mass
- derived quantities which describe the motion of bodies
i. velocity
ii. acceleration
velocity
rate of change of an objects position, miles/hour
acceleration
rate of change of an objects velocity, miles/hour/hour
Basic Force Laws
- First Law of Inertia
- Second Law of Motion
- Third Law of Action and Reaction
First Law of Inertia
- tendency of a body to resist a change in its state of motion
- an object will continue in its state of rest or in a uniform path of motion until a new force acts on it to set it in motion or change the direction of its motion
- takes force to move something or change its direction
Second Law of Motion
- change in an objects motion is proportional to the force acting on it
- force=mass x acceleration F=ma
Third Law of Action and Reaction
for two objects in contact there is for each action an opposite and equal reaction
Free bodies and forces
- diagrams that show each isolated part of a system and the forces acting on each part
- permits the study of parts of a complex system
- can divide the mechanics into two conditions
i. static equilibrium
ii. dynamic equilibrium
static equilibrium
conditions when all forces acting on an object are balanced and equal
dynamic equilibrium
when forces acting on an object are not equal or unbalanced; motion is imparted
Torques and Levers
- skeletal and muscle systems of animals work together to generate movement
- muscles generate force; skeleton applies force
- study this using torques and levers
- parts of a lever system
i. lever arm-length is the distance from the weight to the furlerum
ii. fulcrum is the pivot point
iii. when a fulcrum is centered and weight on both lever arms is equal the system is balanced
iv. shorten one arm, more weight has to be added to that side to keep it balanced - torque
i. in-torque
ii. out-torque - to generate more force, shorten the out lever arm and lengthen the in lever arm
- to generate more speed, you shorten the in lever arm and lengthen the out lever arm
- examples
i. digger
ii. runner
iii. muscles can modify this basic pattern slightly
in-torque
torque of force generated by the lever arm that is closest to the fulcrum [origin of force]
out-torque
torque of force generated by lever arm that is furthest from the fulcrum
