chapter 12

Question 1

Family Hominidae: chimps, bonobos, gorilla, orangutans, humans – members are hominids

Answer 1

chimps, bonobos, gorilla, orangutans, humans – members are hominids

Question 2

great apes
7 characteristics

Answer 2

Larger, more complex brain than other primates.
Enables ↑ cognitive ability –

5 cusps in the molar teeth of the lower jaw

Arms that can freely rotate at the shoulder

A wide, shallow chest cavity

NO external tail

An appendix

Diurnal – active during the day

Question 3

Variations to Family Hominidae Characteristics

Answer 3

Relative size of cerebral cortex
Mobility of the digits
Locomotion – adaptations to bipedalism (2 legs) and quadrupedalism (4 limbs)
Prognathism and dentition

Question 4

Cerebral Cortex - change in relative size

Answer 4

Large & complex brain for body size – greater information processing

Human brain:↑ in size (volume) Av size 1350cm3
Frontal lobe: 47% of total surface area (cf 33% apes) – thinking, problem solving, planning, processing, motor functions,memory
↑ in convolutions (folds) = ↑surface area = ↑in cerebral cortex size
Effects on primate way of life: ……

Question 5

Endocast

Answer 5

an impression of the inside of the brain case, to determine volume/ size/ cranial capacity = 1350 cm3
(Can determine cc + no. of convolutions +
frontal lobe size / development from endocast)

Question 6

Mobility of Digit

Answer 6

Primates have unspecialised pentadactyl (5 digits) limbs

Grasping or prehensile digits (to climb, swing in the trees, arboreal lifestyle.

Opposable thumbs and big toes (except humans – lost when foot became weightbearing.

Manual dexterity: ability to coordinate hand, finger movements to grasp + manipulate objects
Human hand is short and broad, with short straight fingers, long + strong thumb
Precision grip: able to grasp objects with precision eg writing pen, needle when sewing versus power grip.

Question 7

Nails

Answer 7

– flattened out to protect tip of finger, better grip, no claws (claws limit grasping)

Question 8

Friction ridges (fingerprints)

Answer 8

to allow better grip between digits + object.
Ridges in skin = increase grip
Patterns unique to individual

Question 9

9 adaptions for bipedalism -Locomotion

Answer 9

Position of foramen magnum
Curvature of spinal column
The jaw
The pelvis
The knee
The foot
Centre of gravity
Muscle tone
Striding gait

Question 10

Position of foramen magnum

Answer 10

opening beneath the cranium through which the spinal cord passes.

This allows the skull to balance on top of the vertebral column

Question 11

Curvature of the spinal cord

Answer 11

Smooth C’ shape curve ----- S’ shaped
Human: double curvature achieved by lower vertebrae in lumbar region
Cervical curve – brings vertebral column directly under centre of gravity of the skull

Question 12

The Jaw

Answer 12

size + protrusion of jaw reduced.
Apes – show prognathism - protruding jaw. Humans flatter facial profile
mainly due to softer food, large jaw for chewing tough plant material not
needed.
Change allows skull to balance on top of spine because, weight in front = weight behind.
Balance achieved with minimal muscular effort

Question 13

The Pelvis

Answer 13

Broader + shorter from top to bottom
Bowl-shaped – (i) supports the abdominal organs when standing,
(ii) provides greater stability for bipedal walking (iii) supports developing foetus during pregnancy
F (broader than M) —à passage of infant at birth
Broad hip bone —-àattachment for large buttock muscles import. in leg movement and keeping upper body erect

Question 14

The Carrying Angle

Answer 14

Hip joint is directly under trunk + head —– weight of body transferred from pelvis to legs

Large head of femur – fits into the acetabulum.

Pelvis broad-hip sockets far apart, but femurs tend to converge towards the knee

Femur forms angle= carrying angle
Ensures weight distribution remains close to the central axis of the body when walking.

Allows for greater stability in upright posture
When walking: body rotates about the lower leg + foot + each footstep follows a straight-line.
Striding gait – a way of walking in which the hip + knee are fully extended.

Question 15

6) The Knee

Answer 15

bipedal species: weight of body transferred down the outside of the femur to the knee.
Knee joint = 2-part hinge joint, with 1 hinge on either side of the cruciate ligaments in the middle of the joint. Weight is transmitted to outer hinge – (of femur + tibia) it is larger + stronger than the inner one.

Question 16

7) The foot

Answer 16

From knee – most of body weight(BW) transmitted through tibia to ankle
(Tibia larger + stronger than fibula
Big toe – large + aligned with others
Foot has 2 arches: longitudinal - runs front to back, transverse - runs side to side (this one unique to humans)
Arches absorb energy as the foot comes down, which enables the foot to be pushed back up again like a spring recoil \

Non-opposable big toe for weight bearing

Question 17

Centre of Gravity (CofG)

Answer 17

Humans: legs longer than arms, this ↑ the length of stride when walking
This also ↓ centre of gravity

The lower the CofG =more stability

Question 18

) Muscle tone

Answer 18

Muscle tone - the partial contraction of skeletal muscles to ensure the body is kept in an upright position/stance.

Question 19

Striding gait –

Answer 19

walking upright in such a way that the hip and knee are fully straightened.

When a step is taken weight is transferred from (1) heel — along (2) outside of the foot to (3) ball of foot — across ball of foot (via transverse arch) to (4) big toe then, big toe thrusts off.

Question 20

Advantages of bipedalism 6

Answer 20

A more energy efficient means of moving

Leaves the hands free to use tools

Leaves the hands free to carry items

Upright stance achieves greater height – can see further

Upright stance means – less of the body exposed to sunlight

Upright stance - ↑ exposure to breezes, increasing body cooling mechanisms

Question 21

diastema

Answer 21

– have a gap

Question 22

Molar teeth evolved from

Answer 22

3-cusps (early mammals) —– 4-cusps upper molars (+) —- 5-cusps lower molars (Y)

Evolved from mainly fruit diet of the ap

Question 23

During Evolution of primates the (4)

Answer 23

Diastema has been lost
The number of teeth and prognathism has ↓
The number of cusps on the molars has ↑
The jaw has become more parabolic in shape

Question 24

The Laetoli footprints

Answer 24

The Laetoli footprints are evidence that early hominins existed over 3 million years ago. Although there have been a number of interpretations of these footprints, with different numbers and sexes for the individuals who made them, most scientists agree that they were made by Australopithecus afarensis (a separate species of australopithecines) 3.56 million years ago. The footprints indicate a bipedal form of locomotion.

Question 25

‘Lucy

Answer 25

‘Lucy’ is a female skeleton that was 40% complete. ‘Lucy’ has been classified as Australopithecus afarensis based on evidence gained from the dental arcades, the size of the canines and the prominence of the cusps on the cheek teeth.