Lecture 4

Question 1

List 5 facts of the axial skeleton

Answer 1

Dorsal, Segmented disks separated by mobile joints, Bone or cartilage, Houses the spinal cord,
Develops around the notochord

Question 2

True or false: Notochords are synapomorphic in chordates

Answer 2

true

Question 3

Do hagfish and lamprey have nodules resembling centrum?

Answer 3

No, resembling vertebral arches, no body (centrum)

Question 4

2 pieces of vertebrae evolution

Answer 4

Arches on notochord, Centra (body of the vertebrae)

Question 5

What is aspondyly?

Answer 5

Vertebrae that lack centra (like the hagfish / fossil gnathostomes)

Question 6

What is it called when a centra is a single bone fused to other vertebral elements compared to being formed of multiple bones?

Answer 6

Monospondyly vs. diplospondyly or polysplondyly

Question 7

What are the two fates of the notochord?

Answer 7

the notochord remains intact with the centra surrounding it, In other species the centra is fully ossified and the remnants of the notochord form the gel-like centre of the intervertebral disks

Question 8

Structure and function of acoelous

Answer 8

Flat ends , Receive and distribute compressive forces

Question 9

Structure and function of amphicoelous

Answer 9

All surfaces are concave, Allows limited motion in most direction

Question 10

Structure and function of procoelus

Answer 10

Ball and socket, Extensive motion in all directions without stretching the nerve

Question 11

Structure and function of hetercoelus

Answer 11

Saddle-shaped at both ends, Extends but doesn’t twist (ex. Bird necks)

Question 12

What are apophyses?

Answer 12

are processes that extend from the centra or the arches and articulate with other structures

Question 13

Function of zygopophyses

Answer 13

allow vertebrae to interlock with one another, dictate the strength and flexibility of the vertebral column

Question 14

Function of Diapophysis and Parapophysis

Answer 14

processes that allow vertebrae to articulate with the ribs

Question 15

What is regional specialization?

Answer 15

vertebrae in different regions of the vertebral column have different functions and therefore have different forms

Question 16

What do ribs do? (2)

Answer 16

provide a secure site for muscle attachment, form the thoracic cavity

Question 17

What does the hemal arch do?

Answer 17

Protects the caudal artery and vein (blood vessels of the tail)

Question 18

What do extinct sarcopterygians show

Answer 18

Show the same basic trunk vs caudal specialization as other aquatic gnathostomes

Question 19

What did extant sarcopterygians evolve?

Answer 19

Secondarily evolved very simplified vertebrae with a simple ring around the notochord and supporting neural and hemal arches

Question 20

Do agnathans have appendages?

Answer 20

they have a tail but no pelvic or pectoral fins

Question 21

What do paired pectoral fins do?

Answer 21

stabilize the head

Question 22

How is pectoral girdle fused to the skull?

Answer 22

in ray-finned and cartilaginous fishes (balance)

Question 23

What can paired appendages help with?

Answer 23

Buoyancy

Question 24

What do cartilaginous and bony fishes do to achieve natural buoyancy

Answer 24

Density - fats, gases. Dynamic lift - pectoral fins, rostrum

Question 25

What is a swim bladder?

Answer 25

a gas filled sack that help them achieve neutral buoyancy

Question 26

Can ray-fins be used for propulsion on land? Can tails be used for propulsion on land?

Answer 26

Not very effectively, yes but it is difficult

Question 27

How are digits made by appendages?

Answer 27

During embryonic development, all the radial bones move up and polarize over & become the digits of the appendages, Slight change in the genetic program

Question 28

True or false: almost all amniotes are quadadactyl

Answer 28

False. Pentadactyl

Question 29

What allows tetrapods to walk without dragging their bellies or tails on the ground

Answer 29

Quadrupedal gait

Question 30

What is a bi pedal gait

Answer 30

walking on two legs

Question 31

What posture do early tetrapods have

Answer 31

sprawling posture

Question 32

What does an upright posture do

Answer 32

allows large animals to support their body weight on land more efficiently

Question 33

Does bone density in marine mammals increase or decrease, why?

Answer 33

Increases to offset the buoyancy of the lungs

Question 34

What bone density do larger land animals require?

Answer 34

stronger (larger and more dense) limb and girdle bones to support their body weight against gravity

Question 35

What happens to bone density in space

Answer 35

lose bone density in space as they no longer need to support their body weight against gravity

Question 36

Why do bones degrade in space?

Answer 36

Osteocytes are not getting gravity signal - stop building extracellular matrix - skeletons don’t need to support bodies anymore

Question 37

Tell me about the bone density in amphibious fishes

Answer 37

increased bone density in pectoral girdles

Question 38

What does vertebral structure do to prevent sagging

Answer 38

balance between flexibility and support

Question 39

What does zygapophyses do to prevent sagging

Answer 39

interlocking processes provide structural support for the vertebral column, Prevent sag and twisting

Question 40

What does the atlas and axis do in amniotes

Answer 40

the first 2 cervical vertebrae in amniotes allow the head to move independently of the vertebral column

Question 41

Why don’t fish need to turn their head?

Answer 41

Fish have non-cranial sensory organs

Question 41

What do necks allow for in tetrapods

Answer 41

allow separation of the skull and pectoral girdle

Question 42

Why do thoracic ribs fuse ventrally with a sternum?

Answer 42

Protection, Pectoral muscle attachment, Support for pectoral girdle

Question 43

How do snakes prevent sagging in the vertebral column

Answer 43

their vertebrae have extra processes