Appendicular Skeleton

Question 1

What happened to the digits over time?

Answer 1

-reduction of digits
- early tetrapods had 6+ digits
- have been reductions & fusions
- phalanges can be lost, but not easily gained

Question 2

How many digits do birds, horses, and humans have?

Answer 2

birds = 4
horses = 1
humans = 5

Question 3

What is an example of a digit trying to be gained?

Answer 3

an extra digit that is actually a sesamoid bone

Question 4

Sesamoid bone

Answer 4

• bone within tendon
• prevents wear on tendon
• fulcrum point for limb (patella)
• areas of high stress
• can be found in foot or hand (not everybody)

Question 5

What is a fabella?

Answer 5

sesamoid bone opposite side of patella in 20% of people

Question 6

Why is it so hard to re-gain 6+ digits?

Answer 6

1. pleiotropic (one gene affecting multiple traits) developmental effects
2. hand-food-genital syndrome

Question 7

What is hand-food-genital syndrome?

Answer 7

• changes in hand/foot development
• leads to problems with reproduction tract

Question 8

What advantage do diggers have?

Answer 8

mechanical advantage - lots of power - less speed

Question 9

What advantage do runners have?

Answer 9

velocity advantage - lots of speed - less power

Question 10

What is an example of an animal that has both force and speed and why?

Answer 10

a deer because it has many muscles with many insertion points on bone and therefore different fulcrum points (input levers differ due to differing muscle attachments)

Question 11

What are the muscles of deer that give it, its dual advantage?

Answer 11

1. contraction of gluteus medius - high velocity
2. contraction of semimembranous - mechanical advantage

Question 12

Example of flexion & extion

Answer 12

• limited to 1 plane
• lateral & medial malleolus grip ankle bone like wrench on bolt

Question 13

Example of elastic recoil

Answer 13

achilles tendon
- rubber-band recoil in camels is energy saving