Chapter 18 - Evolutionary Trends In Hominids

Question 1

Define bipedal locomotion

Answer 1

The ability to walk on two legs (limbs) with an upright position.

Question 2

Describe and name each level of classification in the binomial system.

Answer 2

Order - Primates
Tarsiers, lemurs, lorises, monkeys, apes and humans

Suborder - Haplorrhini
Tarsiers, monkeys, apes and humans

Infraorder - Simiilformes
Monkeys, apes and humans

Parvorder - Catarrhini
Old world monkeys, apes and humans

Super family - Hominoidea
Apes and humans

Family - Homindae
Orangutans, gorillas, chimpanzees and humans

Subfamily - Hominae
Chimpanzees and humans

Tribe - Hominini
All human ancestors

Genus - Homo
Some human ancestors

Species - Sapiens
Modern humans

Question 3

Describe how the position of the foramen magnum in humans aids bipedalism.

Answer 3

• Located centrally at the base of the cranium

- Reduces the need for neck muscles as the head is balanced

Question 4

Describe how the curvature of the spinal column in humans aids bipedalism.

Answer 4

• S shaped spine helps the body stay upright

- the lumbar vertebrae is wedge shaped and forms a jutting curve, allowing the head to balance on top of the neck

Question 5

Describe how the jaw in humans aids bipedalism.

Answer 5

• Small and less protruding, allowing the head to balance on top of the spinal column.

Question 6

Describe how pelvis in humans aids bipedalism.

Answer 6

• wide and broad shaped to hold the abdominal muscles and allow for large buttock muscles to keep the upper body erect
• Attachment of femurs is wide apart to contribute to the carrying angle
• The centre of gravity

Question 7

What is the purpose of the carrying angle?

Answer 7

The carrying angle ensures that weight distribution remains close to the central axis of the body when walking.

Question 8

Describe how the knee in humans aids bipedalism.

Answer 8

• Outer hinge larger and stronger, to take the weight of the body
• knees straighten for a striding gait
• ligaments prevent the knees for bending backwards and helps keep the body upright (no energy required)

Question 9

Describe how the foot in humans aids bipedalism.

Answer 9

• weight bearing limb
• weight is transferred from the back of the heel towards the front where the big toe acts as a pedestal for pushing off
• big toe is used for balance
• longitudinal and transverse arch to help with balance and bipedal locomotion and striding gate

Question 10

What are some other adaptions that help with bipedalism (posture and locomotion)

Answer 10

• Legs longer than arms to allow for striding gait

- legs lower the centre of gravity

Question 11

Define muscle tone.

Answer 11

Muscle tone is the partial contraction of skeletal muscles.

Question 12

Give an example of hour muscle tone works

Answer 12

The muscles in the back of the neck are partially contracted when a person is awake to keep the head erect.

Question 13

Define equilibrium

Answer 13

A state of physical balance

Question 14

Why do human arms swing when walking?

Answer 14

When walking, the trunk rotates around the pelvis. The arm naturally swings forward when the left leg is extended forward & vise versa.
If arms didn’t swing in this way, energy would be wasted in reversing the rotation of the body in each stride.

Question 15

What is the average size of a human brain?

Answer 15

1350cm3

Question 16

What is cranial capacity?

Answer 16

The volume inside of the cranium.

Question 17

What are endocasts, and what are their purpose?

Answer 17

Endocasts are impressions of the inside of the skull made from rock or some other solid material. They can occur naturally or made by using skulls that have been discovered.
They help to determine the shape of the brain surface, the gradual increase of the number of convolutions and the size of the frontal lobe.

Question 18

Define dental arcade

Answer 18

The dental arcade is the shape the rows of teeth in the upper jaw make.