Ch. 18 Evolutionary Trends of Hominids Flashcards

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1
Q

what is the ranks of primate tribe

A

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

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2
Q

define adaption

A

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

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3
Q

what are the 8 adaptions for erect posture

A

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

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4
Q

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

A

Humans
Located centrally underneath skull

apes= back

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5
Q

why did foreman magnum change position

A

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

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6
Q

what is the difference in neck muscles between humans and apes

A

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

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7
Q

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

A

o Apes: C shaped

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

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8
Q

what is a feature of the human spine, lumbar vertareb

A
  • Humans developed: Vertebrae in lower, lumbar, region (small of back) = wedged shaped from front to back= forming forward- jutting curve
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9
Q

what are three things that the lumbar curve provide

A

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

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10
Q

what is the difference in jaw between humans and apes

A
  • Apes= Protruding Jaw

- Human= flatter facial profile

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11
Q

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

A

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

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12
Q

what is the difference in pelvis between humans and apes

A
  • pelvis in humans= broader + shorter from top to bottom than in apes
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13
Q

what does the bowl shape pelvis allow

A

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

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14
Q

what does broad hip bones allow space for

A
  • Broad hip bones= space for attachment of large buttocks muscles= which move the legs and keep upper body erect
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15
Q

why does the femur converge inward

A

Because pelvis= broad= hip sockets wide apart

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16
Q

what does the carrying angle allow

A

♣ 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

17
Q

where does weight transmission fall along legs in humans

A

outside femur

18
Q

why is the outer hinge larger in humans

A

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

19
Q

explain the natural resistance of the knee

A
  • 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
20
Q

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

A

toe aligned, non opposable

21
Q

explain the two arches that enable bipedal locomotion

A
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
22
Q

define striding gait

A
  • Humans walk bipedally using striding gait- walking in such a way that hip and knee are fully extended
23
Q

what does humans having longer legs than apes cause

A

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

24
Q

why are human centre of gravity lower

A
  • 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
25
Q

where is muscle tone evident

A
  • Essential elements for maintaining upright stance= muscle tone
  • mostly evident in muscles that support body in upright position
26
Q

explain movement of apes (when compared to striding gait)

A

apes have bent knees and bodies bent forward at hips

27
Q

what is the movement process of striding gait

A

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

28
Q

what does swinging of arms allow

A
  • 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
29
Q

why do apes not have carrying angle

A

lack wide pelvis + carry angle // must sway

30
Q

difference in dental arcdade of humanoid and apes

A
humans= parabolic 
apes=  u
31
Q

why did brow ridge decrease

A
  • 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
32
Q

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

A

dna nucleotide sequences

33
Q

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

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