Terrestrial and aquatic locomotion in frogs

Question 1

What do frogs need to do to meet their functional demand?

Answer 1

Maximise jump distance
Given that:
- jump force = mass x acceleration
- takeoff speed = acceleration x duration

Question 2

How do frogs maximise jump distance?

Answer 2

1. Produce more force for a faster accleration (i.e more acceleration)
2. Accelerate for longer - higher takeoff speed as an increase in speed with constant acceleration increases the duration of the movement

Question 3

What do fossil records show in regards to structural modifications in frogs?

Answer 3

Structural modifications have developed to meet functional demand

1. fusion of the lower limb bones - increase in speed = mass x increased acceleration
2. elongation of legs over evolution - increase in speed = acceleration x increased duration
   - structure/function relationship

Question 4

How are frogs pelvic bones and musculature modified?

Answer 4

1. elongation of ilium bones
2. fusion of sacral bones
3. apperence of urostyle
4. modified muscles
   - related theory = frogs have modified pelvic bones and musculature to align force with frog body
   - assumed to be true but untested

Question 5

How do we test this theory?

Answer 5

Digital 3D reconstruction, computer stimulation, anatomical reconstruction
Rotational acceleration helps control takeoff angle
Convergent evolution: many different species independently developed this hinge mechanism
Frogs also have long-stretchy tendons which allow catapult-like jumping - increased power for jumping, functional demand = absorb impact force without tissue damage
- fused radius-ulna to withstand higher forces
- supra-scapula cartilage acts as a shock absorber

Question 6

What are the functional demands met by a skeletal system?

Answer 6

1. produce stride length
2. produce thrust & weight support
   - salamanders have spinal flexibility
   - frogs have an evolutionary trade - off - stiff spine is good for jumping but bad for running

Question 7

How do walker-runners walk efficiently?

Answer 7

1. modified limb lengths

2. modified limb posture

Question 8

How are frogs adapted to swim?

Answer 8

Functional demand = generate fluid thrust with feet
Modifications =
1. Reduced arm length
2. Webbed feet
3. Small body area
- ratio of webbed feet area/body area, greatest in q
aquatic species

Question 9

What are recurring concepts of structure-function relationships?

Answer 9

1. Loss of skeletal mobility (fusion) - stability + strength
2. Gain of skeletal mobility (new joints) - locomotor flexibility
3. Expansion of bone - increased area for muscle attachment
4. Thickening of bone girth - withstand greater loads