bipedal vs quadrupedal

Question 1

what does it mean to be quadrupedal?

Answer 1

walking and using four legs
- ape

Question 2

what does it mean to be bipedal?

Answer 2

have and walk on only 2 legs
- human

Question 3

describe the foramen magnum for a quadrupedal

Answer 3

posterior position
- strong neck to support the weight of the head as it hands forward

Question 4

describe the foramen magnum for a bipedal

Answer 4

anterior/central position - has moved forward
skull balances on the vertebral column
transfers the weight down the spine minimizing energy to balance the head when upright

Question 5

what is the foramen magnum?

Answer 5

the opening in the skull through which the spinal cord passes to become the medulla oblongata.

Question 6

describe the shape of the spine of a quadrupedal

Answer 6

c shaped
acts as a spring and assists in the movment on all fours
enlarged cervical vertebrae for the attachment of large neck muscles which support the weight of the head (hangs forward)

Question 7

describe the shape of the spine of a bipedal

Answer 7

S-shaped spine
double curvature (lumbar and cervical curves)
Lumbar curve = improves balance in upright position bringing the weight above the feet.
Cervical curve = brings vertebral column directly under the center of gravity, improving stability when standing upright

Question 8

describe the center of gravity of a quadrupedal

Answer 8

Relatively higher = 1/3 of height is in legs
sits further forward, favoring locomotion on all fours

Question 9

describe the center of gravity of a bipedal

Answer 9

relatively lower =given that our legs are longer = in more weight in our legs
improves stability when upright
humans = their center of gravity is still very high,
makes it easier to start moving given that little energy is required to shift our weight forward

Question 10

describe the length of arms relative to legs of a quadrupedal

Answer 10

Arms are relatively long compared to their legs
makes arboreal locomotion much easier when swinging through trees
Longer arms also help hold upper body/head up higher when moving on all fours

Question 11

describe the length of arms relative to legs of a bipedal

Answer 11

long legs make it easier to cover a greater distance with each step making bipedal locomotion more efficient
lowers the relative center of gravity increasing stability when upright

Question 12

describe the shape of the pelvis of a quadrupedal

Answer 12

Longer thinner pelvis
Muscle attachment is dorsal = use their muscles to move their legs out to the side
Stronger abdominal muscles are needed to support internal organs since their weight is in front of their spinal column.

Question 13

describe the shape of the pelvis of a bipedal

Answer 13

short, broad, bowl-shaped pelvis
that supports the weight of the internal organs while upright
tilted forward
tilt aligns the pelvis with the spine
broader hip bone allows for attachment of larger glute muscles = and helps move legs with each stride.

Question 14

describe the carrying angle of a quadrupedal

Answer 14

No carrying angle
femurs perpendicular to pelvis = apes walk upright, they sway from side to side and are unable to place one foot in front of the other

Question 15

describe the carrying angle of a bipedal

Answer 15

have a carrying angle
hip sockets are far apart given the broad pelvis.
The femur’s angle inwards from the hip socket to the knees
ensures the weight distribution remains close to the central axis when walking = greater stability
Carrying angle = the striding gait in humans = humans can walk with one foot in front of the other = in more energy-efficient locomotion

Question 16

describe the arches of the foot of a quadrupedal

Answer 16

Single arch - longitudinal
not as efficient at absorbing impacts when walking
arch not as pronounced = flat foot when moving.

Question 17

describe the arches of the foot of a bipedal

Answer 17

Two arches - longitudinal and transverse arches
arches help transfer energy from heel to toe
act as shock absorbers and improve weight distribution when walking

Question 18

describe the structure of the foot of a quadrupedal

Answer 18

Big toe is opposable + other toes are curved = used for grasping and quadrupedal locomotion

Question 19

describe the structure of the foot of a bipedal

Answer 19

big toe = not opposable
in line with other toes + more robust
Other toes are shorter + no longer curved

Calcaneus (heel) bone = larger and robust

Question 20

describe the lower end of the femur of a quadrupedal

Answer 20

head of the femur = smaller and not as robust
does not have to support whole weight of the upper body alone

Question 21

describe the knee joint of a quadrupedal

Answer 21

Knee always stay slightly bent and cannot lock.
Bones of the knee joint are less robust

Question 22

describe the lower end of the femur of a bipedal

Answer 22

bottom of the femur (knee joint) has a buttress of bone = stops the sideways deflection of thigh muscles during walking
outer hinge of the femur is also larger and stronger to take the weight of the body.

Question 23

describe the knee joint of a bipedal

Answer 23

stronger lockable knee joint
means that no energy is required to support the body in a standing position
Larger stronger bones in the knee joint make them better suited to a weight-bearing role

Question 24

describe the rib cage of a quadrupedal

Answer 24

cone-shaped
to house the gut
provide a great range of motion around the shoulder to allow them to walk on all fours

Question 25

describe the rib cage of a bipedal

Answer 25

barrel-shaped
allowing arms to swing freely from side to side which is required to maintain balance when walking

Question 26

what are the advantages of bipedalism

Answer 26

more engery efficient means of moving
leaves the hands free to use tools + carry items
see futher = prey
less body is exposed to sunlight
increases SA exposed to breeze = increases cooling mecahnisms