Evolution: Biological Evolution Flashcards
Cranium/Brain Case
The part of the skull that encloses the brain and protects it from injury.
What is the “Brow Ridge”? What is it’s purpose?
Well developed body ridges above and around the eyes protect the eyes from the powerful forces generated by chewing, biting, impact during conflict.
Purpose of the “canines”
The canines are large pointed teeth used for holding and biting prey as well as displays of agression/dominance.
What is the “Zygomatic Arch”?
The arch of bone that extends along the front side of the skull. Important chewing muscles pass through here, the “cheekbone”.
-Enhanced bite/grind forces
-enhance shape and strength of face & protect eye socket
What is the “Nuchal Crest”?
Cranial attachment point for large neck muscles involved in the movement, and stabilisation of the head and vertebrae.
Allows for better support and stabalisation of heat and maintain upright posture.
What is the “Sagittal Crest”?
A ridge of bone running lengthwise along the midline of the top of the skull.
Purpose: to provide large SA to anchor/attatche strong temporalis muscles (jaw muscles)
-Stronger Bite force (chew more fibourous plants/bones)
-More effective chewing
Purpose of the molars and premolars
Large flat teeth that shear, crush, and grind tough fiborous food while chewing.
What is a “Diastema”?
Space between teeth for large canine teeth to fit into so teeth can come back together.
What is a “Prognathism”?
When the lower portion of the face projects forwards.
What is the difference between a “hominin” and “living hominid”?
Hominin: subfamily of hominids including all living and fossil species belonging to the human lineage
Hominid: The family of primates
2 Adaptive Advantages of Bipedalism? (energy and thermoregulatory)
- Energy efficient locomotion:
Favours low speed endurance locomotion (long distances)
(walking 2 legs LESS ENERGY than 4)
-longer, more rewarding journeys (F+H)
-more energy to reproduce
-reduce competition, overpopulation, predation
- Thermoregulation: decreased exposure to direct sunlight
(Absorbing less heat, keeping body cool in hot, exposed environments)
-Remain in sun for longer w/o taking breaks (follow prey)
-Increased air flow around body (higher from ground - stronger air currents)
2 Adaptive Advantages of Bipedalism? (hands and height)
- Hands Free: carrying objects
-making tools, shelter, clothing - increased hand dexterity and chance of survival
-food carried back to safe place & shared - Height
-enhanced visual field – see over tall grass (predators/food/competitors/environmental change) w/out expending large amounts of energy)
-look larger, more threatening to a predator
2 Problems caused by Bipedalism (birth & back pain)
- Challenges during childbirth:
Changes in pelvic shape (biped - bowl shape) Babies born with larger skulls
Narrower birth canal
Increased risk of complications during labour
- Back Pain:
Biped (S-shaped spine) & (bowl shaped pelvis) Spine required to support weight of upper body causing stress on lower back and spine.
Increase susceptibility to injury
2 Problems caused by Bipedalism (feet & circulation)
- Decreased stability and balance (feet)
Body rests on just 2 limbs
Arches on feet may collapse (flat feet)
^ distorted bones - decreased stability & balance
- Varicose Veins
Upright posture allows blood to collect in leg veins
Blood must overcome 1.2m of gravitational pressure to return to the heart - poor circulation
Skeletal Change (spine)
Quadruped: (C-shaped)
- Support’s abdomen
- Absorbs forces from locomotion.
- Counterbalances downward force
(organs & chest)
Biped: (S-shaped spine)
- Aligns center of gravity over pelvis
- Absorbs locomotive forces
- Supports upright posture, reducing muscle effort.
