Skeletal Adaptations to Ecological Niche

Quick Quiz 1.What type of lever is your elbow/forearm? (5 pts) 2.What does mechanical advantage tell you about the lever? (2.5 pts) 3.What is the approximate MA of your elbow extending? (2.5 pts)

Just a Note This is NOT about physics It’s about WHY bones are they way they are Bones-joint ARE levers Math/physics is just a TOOL to help describe the way they work

Before We’re Done Look at skeletons and draw conclusions about their purposes Describe limbs have changed in adaptation to different niches Tremendous diversity from a common platform

Homology

This unit is exploratory. I provide essential background; you do the critical thinking!

Bones as levers

Lever Fulcrum Resistance Effort

Fulcrum in the ‘middle’ Resistance in ‘middle’ Effort in ‘middle’

FREFRE

Class 3 Class 1

Class 3 Class 1

Class 2

Power vs.

Speed

Mechanical advantage = D effort / D resistance

It’s only a model…

Model Effort Arm Resistance Arm Force needed to hold 50 g Distance Effort moved Distance resistance moved

Class 3

Effort Fulcrum Resistance Fulcrum is the stand Effort is the spring scale Resistance is the weight

Effort Fulcrum Resistance Measure distance from elbow to where biceps attaches and place spring at this distance Measure distance from elbow to middle of palm and place weight at this distance

Class 3

Effort Fulcrum Resistance Lift mass so it is parallel to table and record FORCE to hold if parallel How far did the effort MOVE? The resistance MOVE? Fill in table

Effort Fulcrum Resistance Move effort toward resistance and measure again Two more times What do your data indicate? Ratio? Pattern?