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Human Bio Year 12 > Primate evolution > Flashcards

Primate evolution Flashcards

1
Q

What are the features that all primate have

A

Body: not specialised, generally erect posture

limbs: unspecialised, flexible=more movement

hands/feet: pentadactyl (5xfingers/toes), nails (no claws), grasping fingers/toes w/friction ridges for gripping, first digit opposable

eyes: fwd facing=stereoscopic vision (increase depth perception), able to distinguish colour

sense of smell: poor

teeth: 4xincisors in upper/lower jaw

brain: large and complex, cerebrum size increases as primate becomes more evolved

reproduction: rhythmical sexual cycle, usually one offspring at time, long period of parental care

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2
Q

Describe how humans are classified as primates

A

Humans as primates are great apes. Part of the same family (Hominids).The species vary within this family due to change in DNA sequences

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2
Q

How do you differentiate between great apes and other primates

A

-larger, more complex brain than other primates (enables increased cognitive ability)
-five cusps in molar teeth of the lower jaw
-arms that can freely rotate at shoulder
-wide shallow chest cavity
-no external tail
-an appendix
-diurnal (active during the day)

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3
Q

How does variation in hominids come about

A

Via change to:
-relative size of cerebral cortex
-mobility of digits
-locomotion-adaptation to bipedalism/quadrupedalism
-prognathism and dentition

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4
Q

What is the evolutionary trend for the cerebral cortex

A

-47% of cortical surface is frontal lobe for humans while 33% is frontal for apes (higher functioning area of brain)
-increase brain size=increased depth+number of convolutions of cerebral cortex=increase SA
-anew ability of creating, not just using tools
-larger brain=increase cranium capacity-more skull used by humans to house brain
-humans lack a prominent brow ridge
-shortened snout=flat face with more prominent nose

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5
Q

Describe the evolutionary trend for mobility of digits

A

-increased mobility + independent digit movements
-first digit opposability+relatively longer than other digits
-claws give way to nails, thus human have no claws
-humans lack big toe opposability due to weight bearing bipedalism
-more mobility allows for manipulation of objects with great skill and precision grip

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6
Q

Describe the evolutionary trend for locomotion

A

Change overtime from quadrupedalism to bipedalism acted as a selective pressure during natural selection, allowing human ancestors to survive.

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7
Q

What are the adaptations for erect posture

A

-position of foramen magnum (centre vs back)
-curvature of spinal column (S vs C)
-centre of gravity
-jaw, pelvis, carrying angle, knee, foot

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8
Q

Describe the evolutionary trend of the foramen magnum

A

Hole where brain joins spinal cord
-position has gradually moved forward to become more central
-for humans: centre=no large neck muscles and skull balance on top of spine
-for gorillas: towards back=large neck muscles to hold head)

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9
Q

Describe the evolutionary trend for curvature of the spinal cord

A

-humans: double curvature (s-shaped) allowing upright position
-lumbar vertebrae wedge shaped
-improved balance, head on top of neck

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10
Q

Describe the evolutionary trend for the jaw

A

-change to flatter profile
-apes had protruding jaw=prognathism
-due to gradual reduction, skull balances better on top of spine
-less muscular effort to hold head

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11
Q

Describe the evolutionary trend for the pelvis

A

-broader/shorter in humans (wide)
-long/narrow in apes
-wider in females to allow infant passage during birth
-the gradual widening of pelvis allows attachment of muscles to move legs bipedally and keep erect posture
-support abdominal organs=less strain on abdominal muscles to hold in place

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12
Q

Describe the evolutionary trend for the carrying angle

A

-increases in femur
-pelvis shape (broad/short) allows hip joint to be directly under trunk and head
-wide pelvis allows femur (w/larger head) to converge twds knee (femur angled twds knee forms carrying angle)

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13
Q

Describe the evolutionary trend for the knee

A

-weight distribution remains close to central axis (centre of gravity falls in front of knee) and outside of knee
-good stability for walking (body can rotate about lower leg, footsteps follow straight line, creates striding gait)
-ligaments create resistance to knee bending bwds+outer ligament larger+stronger
-joints therefore need no energy to support standing position

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14
Q

Describe the evolutionary trend for the foot

A

-weight transferred from knee-tibia-ankle
-no prehensility
-big toe=larger inline with other digits
-metatarsals shaped to form 2x arches: longitudinal arch (front to back) and transverse (side to side)
-perfect bipedal locomotion

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15
Q

Describe the evolutionary trend for centre of gravity

A

point at which weight of body concentrated
-humans have longer legs than arms (increase stride length + lowers centre of gravity)
-lower centre of gravity creates stability during bipedal locomotion and standing erect

16
Q

Describe the evolutionary trend for muscle tone

A

partial contraction of skeletal muscles
-supports upright position in hips, knees, ankle, abdominal and spine

17
Q

Describe the evolutionary trend for striding gait

A

-full extension of hip and knee into straight position
-hominins are only animals w/this locomotion
-foot evolved to be weight bearing

18
Q

How does striding gait occur

A
  1. Foot hits ground
  2. Weight transmitted form heel along outside of foot
  3. Weight crosses ball of foot
  4. Then to big toe
    -trunk rotates about pelvis
    -right arm swings fwd as left leg extends
19
Q

Describe some advantages of bipedalism

A

-energy efficient means of moving
-hands free to use tools and carry items
-upright stance achieves height=ability to see further, less of body exposed to sunlight, increased exposure to breeze=cooling mechanism

20
Q

Describe the evolutionary trend for number and shape of teeth (dentition)

A

-gradual decline in tooth size (canines especially)
-parabolic dental arcade
-decrease in number of teeth (due to reduction in jaw/face size)
-no diastema

21
Q

Describe the evolutionary trend for prognathism and brow ridges

A

-fwd jutting jaw has decreased to flat face
-decrease in brow ridge size
-more prominent nose
-flatter face=central weight position=skull can balance during upright stance
-as size of frontal lobe increases, brain occupies more=reduced brow ridge

22
Q

Define brachiation
What are it’s adaptations?

A

Arboreal locomotion. Movement accomplished by swinging from one hold to another by arms.
-longer arms than legs and flexible shoulder joints
-long, strong finger for grasping and holding body weight

Human Bio Year 12 (17 decks)

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