Ch. 18 Evolutionary Trends of Hominids

Question 1

what is the ranks of primate tribe

Answer 1

Hominidae (Hominids) (humans, orang, gorillas, chimps) >
Homininae (Hominines)(gorillas, chimps, humans) >
Hominini (hominins) (humans)

Question 2

define adaption

Answer 2

any characteristic that helps an organism survive and reproduce in its natural environment

Question 3

what are the 8 adaptions for erect posture

Answer 3

o Position of foramen magnum, curvature of spinal column, jaw, the pelvis, the carrying angle, the knee, the foot, center of gravity

Question 4

what is the difference in position of foramen magnum between humans and apes

Answer 4

Humans
Located centrally underneath skull

apes= back

Question 5

why did foreman magnum change position

Answer 5

(During evolution) FM gradually moved forward until skull is able to balance on top of vertebral column

Question 6

what is the difference in neck muscles between humans and apes

Answer 6

Humans- Weight of skull is borne by vertebral column so large neck muscles not required

apes- Needs large neck muscles to hold head in position

Question 7

what is the difference in curvature of spine between humans and apes

Answer 7

o Apes: C shaped

o Humans: Double curvature= S shape (contributes to upright stance)

Question 8

what is a feature of the human spine, lumbar vertareb

Answer 8

• Humans developed: Vertebrae in lower, lumbar, region (small of back) = wedged shaped from front to back= forming forward- jutting curve

Question 9

what are three things that the lumbar curve provide

Answer 9

o improves body balance in upright position
o enables head to balance on top of neck
o cervical curve in neck= brings vertebral column directly under center of gravity of skull

Question 10

what is the difference in jaw between humans and apes

Answer 10

• Apes= Protruding Jaw

- Human= flatter facial profile

Question 11

why did jaw reduce and become flatter (what did it allow)

Answer 11

o Change Important in allowing skull to balance on top of spine, because weight in front of foramen magnum is approx.. equal to weight behind
o // balance achieved with minimum muscular effort

Question 12

what is the difference in pelvis between humans and apes

Answer 12

• pelvis in humans= broader + shorter from top to bottom than in apes

Question 13

what does the bowl shape pelvis allow

Answer 13

supports abdominal organs while standing erect + females to support developing fetus during pregnancy

Question 14

what does broad hip bones allow space for

Answer 14

• Broad hip bones= space for attachment of large buttocks muscles= which move the legs and keep upper body erect

Question 15

why does the femur converge inward

Answer 15

Because pelvis= broad= hip sockets wide apart

Question 16

what does the carrying angle allow

Answer 16

♣ Ensures weight distribution remains close to central axis of body when walking
♣ Allows for greater stability when walking as enables the body to be rotated about the lower leg and foot, and each footstep to follow more-or-less straight line
♣ Enables humans to have a striding gait instead of swaying side to side (as gorillas) when walking on two legs

Question 17

where does weight transmission fall along legs in humans

Answer 17

outside femur

Question 18

why is the outer hinge larger in humans

Answer 18

o Because weight transmitted to outer hinge= its larger + stronger than inner one

Question 19

explain the natural resistance of the knee

Answer 19

• Although weight of body transmitted down outside of each leg, center of gravity tends to fall through a line just in front of knees
  ♣ = force that tries to bend knee backward but is resisted by ligaments making up knee joint
  ♣ This natural resistance produces knee joint that requires no energy to support standing body position

Question 20

what is best evidence to show humans loss of prehensility in foot

Answer 20

toe aligned, non opposable

Question 21

explain the two arches that enable bipedal locomotion

Answer 21

o	Enabled humans perfect bipedal locomotion 
a.	Longitudinal arch 
♣	Running from front to back
b.	Transverse arch 
♣	Running from side to side 
♣	Unique to humans

Question 22

define striding gait

Answer 22

• Humans walk bipedally using striding gait- walking in such a way that hip and knee are fully extended

Question 23

what does humans having longer legs than apes cause

Answer 23

o Increase length of stride when walking

o Serve to lower center of gravity of body, the point at which all weight of body appears to be concentrated

Question 24

why are human centre of gravity lower

Answer 24

• In contrast to humans (where almost half of total height= in leg length) ape only about one third of total height taken up in leg length
  o Results in center of gravity being further up body
  o Apes Centre of gravity at chest/ humans= level of pelvis
  ♣ Humans lower COGravity= contributes to stability when moving bipedally or standing erect

Question 25

where is muscle tone evident

Answer 25

• Essential elements for maintaining upright stance= muscle tone
• mostly evident in muscles that support body in upright position

Question 26

explain movement of apes (when compared to striding gait)

Answer 26

apes have bent knees and bodies bent forward at hips

Question 27

what is the movement process of striding gait

Answer 27

foot hits ground, weight= transmitted from heel along outside of foot as far as ball, crosses ball (via transverse arch) and finally borne by big toe > whole weight of body propelled by big toe

Question 28

what does swinging of arms allow

Answer 28

• When walking, trunk rotates about the pelvis
• Forward swinging of arms compensates for natural rotation;
  o right arm naturally swings forward as left is extended and vice versa
• Swinging of arms=
  ♣ keep shoulders at right angles to the direction of travel
  ♣ reduces amount of energy expended
  o If arms did not move as they do, energy wasted in reversing rotation of body after each stride

Question 29

why do apes not have carrying angle

Answer 29

lack wide pelvis + carry angle // must sway

Question 30

difference in dental arcdade of humanoid and apes

Answer 30

humans= parabolic 
apes=  u

Question 31

why did brow ridge decrease

Answer 31

• Gradual enlargement of cranial portion of skull to accommodate increasing size of frontal region of brain= more distant forehead + reduction in size of brow ridge

Question 32

SCASA: what are species within the great ape family differentiated by

Answer 32

dna nucleotide sequences

Question 33

SCASA: what has the differences in dna nucleotide sequences resulted in differences of:

Answer 33

• relative size of the cerebral cortex
• mobility of digits
• locomotion (adaptations)
• prognathism and dentition