Chapter 18

Question 1

What’s an adaptation?

Answer 1

Any characteristic that helps an organism survive/reproduce in its natural habitat.

Question 2

Adaptations for an erect posture: position of foramen magnum

Answer 2

Hole in skull where brain joins spinal cord
Humans - centrally in the base of skull, balancing on top of vertebrae -> not requiring large muscle groups for stability
Apes - towards back of skull, requires large muscles to hold head in position

Question 3

Evolutionary trends within primates: curvature of spinal cord

Answer 3

Humans - S-shaped, contributes to upright stance (skull/vertebral column both fall in line of centre of gravity)
Apes - C-shaped, non-weight bearing

Question 4

Evolutionary trends within primates: the jaw

Answer 4

Humans - flatter face, due to jaw size reduction overtime (protrusion).
Allows skull to balance more efficiently -> also has a parabolic shape

Apes - protruding jaw, u-shaped, no chin

Question 5

Evolutionary trends within primates: the pelvis

Answer 5

Humans - short, wide, broad and bowed shaped -> wide hip bones provide SA for attachment of the muscles required for an upright stance

Apes - narrow, long and there is an absent of a carrying angle

Question 6

Evolutionary trends within primates: carrying angle

Answer 6

Humans - varies, greater carrying angle -> ensures weight distribution around central axis around outside of femur = increasing stability (striding gait)

Apes - narrow pelvis, non-existent carrying angle (swaying gait), weight distribution around inside of femur

Question 7

Evolutionary trends within primates: knee

Answer 7

Human - knees close, force that tries to bend knees backwards is resisted -> requiring no energy to support the body in standing

Apes - far apart

Question 8

Evolutionary trends within primates: foot

Answer 8

Humans - presence of transverse/longitudinal arch, big toe in line with other toes, large calcaneus (heel)

Apes - longitudinal arch, prehensile capabilities due to location of big toe

Question 9

Evolutionary trends within primates: centre of gravity

Answer 9

Humans - lower, in pelvis -> presence of longer legs than arms
Increases the length of strid

Apes - higher, chest level -> due to shorter legs than arms and a heavy rib cage (where your weight is distributed)

Question 10

Evolutionary trends within primates: stance and locomotion

Answer 10

Muscle tone - partial contraction of skeletal muscle

Humans - Striding gait - walking where hips/knees are fully extended When walking, the trunk rotates around pelvis -> compensates by forward swinging of arms opposite to leg
Apes - swaying gait

Question 11

Evolutionary trends within primates: relative size of cerebral cortex

Answer 11

Humans - increased brain size from apes -> determined by endocasts (impressions of the inside of the skull)

Increased brain size formed a flatter profile (face) due to growth of frontal lobe

Question 12

Evolutionary trends within primates: prognathism and dentition

Answer 12

Reduction of prognathism occurs overtime as the face becomes flatter

Humans - parabolic shape, smaller molars, deceased robustness of teeth and non-protruding canines

Apes - u-shaped,

Question 13

What advantages does walking bipedally have?

Answer 13

• for food hunting/gathering
• avoid predators, able to see further and run faster
• better to walk longer distances
• hands free for carrying and using tools

Question 14

Disadvantages for bipedal walking?

Answer 14

Can’t escape from predators into a tree.
Can’t run as fast than a quadrupedal.
Difficult to maintain body temp in cold environments.