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Human Bio > Chapter 12 - Trends in hominid evolution > Flashcards

Chapter 12 - Trends in hominid evolution Flashcards

1
Q

sources of evidence used to show how human characteristics evolved

A
  • Comparative anatomy
  • Comparative biochemistry (DNA and proteins)
  • Behaviour of living primates
  • Fossils of primates
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2
Q

What are the classification levels of humans within the primate order

A 
Order - Primates 
Superfamily - Hominoidea
Family - Hominidae
Subfamily - Homininae
Tribe - Hominini
Genus - Homo
Species - Sapiens
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3
Q

Body characteristics of primates

A

Not specialised for a particular environment

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4
Q

limb characteristics of primates

A

Generally unspecialised

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5
Q

hand/feet characteristics of primates

A
  • unspecialised in structure, allows for great diversity in use
  • Pentadactyl
  • Nails instead of claws
  • Grasping fingers and toes with friction ridges for gripping
  • First digit opposable
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6
Q

eye characteristics of primates

A
  • Forward facing for 3D (stereoscopic) vision

- Most are able to distinguish colour

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7
Q

smell characteristics of primates

A

very poor

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8
Q

teeth characteristics of primates

A

four incisors in both the upper and lower jaw

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9
Q

Brain characteristics of primates

A
  • Large and complex

- Cerebrum size increases as primates become more highly evolved

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10
Q

Reproduction characteristics of primates

A
  • Not restricted to a breeding season
  • Rhythmical sexual cycle
  • Usually only one offspring at a time
  • Long period of parental care for offspring
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11
Q

what are the primates classified as great apes

A

Humans, Chimpanzees, Orangutans and Gorillas

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12
Q

Arboreal

A

living in trees

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13
Q

opposable

A

the ability to use the thumb to tough the tips of each other digit

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14
Q

Hominidae

A

family including humans and the great apes (chimpanzees, gorillas, orangutans and bonobos)

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15
Q

Hominid

A

A member of the family hominidae

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16
Q

Hominin

A

A member of the tribe Hominini (humans past and present)

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17
Q

what are the characteristics of species in the hominidae family

A
  • A larger, more complex brain than other primates. Enables an increased cognitive ability
  • Five cusps in the molar teeth of the lower jaw
  • Arms that can freely rotate at the shoulder
  • Wide shallow chest cavity
  • No external tail
  • An appendix
  • Diurnal
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18
Q

what do the variations that reflect changes in the DNA nucleotide sequence during evolution of hominids relate to

A
  • Relative size of the cerebral cortex
  • Mobility of the digits
  • Locomotion (adaptations to bipedalism and qaudrupedalism
  • Prognathism and dentition
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19
Q

what is the most significant feature of primate evolution

A

The increase in size and complexity of the cerebrum

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20
Q

Cerebrum

A

The largest part of the brain, made up of left and right hemispheres

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21
Q

Cerebral cortex

A

The outer layer of the cerebrum, made up of grey matter. Region of brain concerned with higher functions (vision, memory, reasoning and manipulative ability)

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22
Q

what caused the brains of primates to increase in size

A

The pressure of natural selection in an arboreal environment would have favoured a more accurate visual and tactile perception along with better coordination between such sensory stimuli and any muscular response

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23
Q

Endocast

A

An impression of the inside of the brain case, either artificial or natural, made of rock or some other solid material

24
Q

Cranium capacity

A

The volume of that part of the skull that is occupied by the brain

25
Q

what is the average brain size of humans compared to other apes

A

1350cm^3 in adulthood compared to other apes which average between 400 and 500 cm^3

26
Q

which part of the brain has the greatest enlargement in surface area compared to apes

A

The frontal lobe. In humans making up 47% of the cortical surface, whereas in apes it only comprises 33%

27
Q

what are the benefits to an increase in size of the cerebral cortex

A
  • Enabled primates to move about and locate food
  • Develop social skills
  • Tool making (most highly developed in humans)
  • Greater variety of behavioural responses to meet a wide array of environmental problems
28
Q

cranium

A

The part of the skull that contains the brain

29
Q

Pentadactyl

A

Describes a limb with five fingers or toes

30
Q

prehensile

A

refers to the digits of a hand or foot that can grasp an object

31
Q

opposability

A

The ability to use the thumb to touch the tips of each of the other digits on the hand

32
Q

what is the evolutionary trend of the digits

A

Towards increasing ability to move the digits independently of one another

33
Q

precision grip

A

The grasping of an object between thumb tip and fingertip (eg holding pencil when writing)

34
Q

power grip

A

Force applied by the fingers and thumb towards the palm to transmit force to an object

35
Q

quadrapedalism

A

Walking on four legs

36
Q

bipedalism

A

walking on two legs

37
Q

foramen magnum

A

the opening beneath the cranium through which the spinal cord passes. During evolution has slowly moved forward to become more central, allowing skull to balance on top of the vertebral column so large neck muscles are not required

38
Q

curvature of spinal column

A

The smooth ‘C’ shaped curve seen in spines of apes has evolved to an ‘S’ shaped curve in humans. This improves body balance in the upright position and enables the head to balance on top of the neck

39
Q

lumbar

A

Describes the lower region of the spinal column, lumbar vertebrae support the lower back, achieving a double curvature

40
Q

Prognathism

A

having a protruding jaw. Reduction of prognathism in evolution is important in allowing the skull to balance on the top of the spine because the weight in front of the foramen magnum is approximately equal to the weight behind it.

41
Q

compare pelvis in humans and apes

A

The pelvis in humans is broader and shorter from top to bottom than in apes and bowl shaped

42
Q

importance of bowl shaped pelvis in humans

A

Supports abdominal organs when standing erect, proving greater stability for bipedal locomotion and supports developing foetus during pregnancy in females

43
Q

acetabulum

A

the socket of the pelvis in which the head of the thigh bone (femur) fits

44
Q

carrying angle

A

Because the pelvis is broad, the hip sockets are wide apart, but the femurs tend to converge towards the knees. This arrangement of the femurs forms an angle to the vertical, called the carrying angle

45
Q

adaptions of the knee for bipedalism

A

The wight of the body is transmitted down the outside of the femur to the knee. The knee joint is a two part hinge joint, with one hinge on either side of the ligaments in the middle of the joint. Because the weight is transmitted to the outer hinge, it is larger and stronger

46
Q

Longitudinal arch

A

The arch of the bones of the foot, running from front to back

47
Q

Transverse arch

A

The arch of the bones of the foot, running from side to side (humans have longitudinal and transverse arch, gorillas only have longitudinal)

48
Q

leg adaptations for bipedalism

A

Longer than arms, contributing to a low centre of gravity. carrying angle allows weight of body to be kept close to the central axis

49
Q

Muscle tone

A

Partial contraction of muscles to support the spine, hip, knee and ankle

50
Q

What are the evolutionary changes that allow bipedalism in humans

A
  • Central foramen magnum
  • ‘S’ shaped spine
  • Non protruding jaw
  • Broad pelvis
  • Carrying angle of the femur
  • Knee that is larger on the outside
  • Long legs
  • Longitudinal and transverse arches on the feet
  • Muscle tone
51
Q

why have the hominins lost the opposability of the big toe

A

the human foot has evolved into a weight bearing appendage rather than a grasping one

52
Q

Striding gait

A

A way of walking in which the hip and knee are fully extended

53
Q

advantages of bipedalism

A
  • More energy efficient
  • Leaves hands free to use tools and carry items
  • The upright stance achieves greater height and thus ability to see further
  • Upright stance means less of the body exposed to sunlight
  • Upright stance increases exposure to breezes, increasing cooling mechanisms
54
Q

dental formula

A

A formula that gives the number of each type of tooth in one quarter of the jaw

55
Q

Diastema

A

A gap in a row of teeth, usually refers to a gap next the the canine teeth in primates, with canine teeth that are much longer than the other teeth

56
Q

Dental arcade

A

The shape of the pattern made by the teeth as they are set in the jaw. ‘U’ pattern in apes, parabolic in humans

57
Q

Brow ridge

A

A ridge of bone above the eye sockets of the skull, as the size of the frontal lobe has increases, the brain occupies a larger volume, extending the cranium forward and reducing the brow ridges

Human Bio (17 decks)

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