Evolution - Chapter 12 Flashcards
Order (classification)
Primates - tarsiers, lemurs, lorises, monkeys, apes and humans
Suborder (classification)
Haplorrhini - tarsiers, monkeys, apes and humans
Infraorder (classification)
Simiiformes - monkeys, apes and humans
Parvorder (classification)
Catarrhini - old world monkeys, apes and humans
Superfamily (classification)
Hominoidea - apes and humans
Family (classification)
Hominidae - Humans and great apes
Subfamily (classification)
Homininae - all modern humans and extinct chimpanzees, gorillas and humans
Genus (classification)
Homo - extinct humans and modern humans
Species (classification)
Sapiens - modern humans
Cerebrum size in lemurs vs humans
In primates, the cerebrum has progressively increased in size, lemurs = 24cm^3 and humans = 1350cm^3
Frontal lobe in humans vs apes
In humans the frontal lobe makes up 47% of the total cortical surface vs apes it makes up 33%.
frontal lobe - higher functions of thinking, reasoning, planning and processing take place
Convolutions in brains of hominids
have strong patterns of convolutions which enable surface area of brain to increase. they have results in a 50% increase in SA of human brain compared to without them.
- has effects on how primates live, e.g, tool making involves a predetermined image of what the completed tool should look like.
How is cranial capacity found?
determined by measuring the volume inside the cranium using an enbocast.
Pentadactyl
have 5 digits on each limb.
- highly mobile, which is a feature related to the arboreal way of life of primate ancestors.
Prehensile
(grasping) refers to the digits of a hand or foot that can grasp an object - essential for climbing.
Evolutionary trends towards increasing mobility
- thumb and big toe and highly developed in this respect
- they’re independent and opposable
Opposability
the ability to use the thumb to touch the tips of each of the other digits on the hand.
- degree of opposability varies and depends on the length of the first digit compared with the other four.
- opposability was lost in the big toe when the human foot became a weight bearing rather than a grasping.
- having highly mobile digits has enabled humans to manipulate objects with great skill.
Precision grip
the grasping of an object between thumb and fingertip, e.g, holding a pen when writing.
Power grip
force applied by the fingers and thumb towards the palm to transmit force to an object.
Adaptations to locomotion
- position of the foramen magnum
- curvature of the spinal column
- the jaw
- the pelvis
- the knee
- the foot
- centre of gravity
- muscle tone
- striding gate
- advantages of bipedalism
Position of the foramen magnum
The opening between the cranium through which the spinal cord passes.
- moved forward to become more central
- this allows the skull to balance on top of the vertebral column
- ape/gorilla - needs large neck muscles to hold head up
- in humans, the weight of the skull is borne by the vertebral column - so no large neck muscles necessary
Curvature of the spinal cord
- curvature has changed to allow upright posture
- smooth ‘c-shaped’ curve has evolved to a ‘s-shaped’ curve in humans
- this improved body balance and enables head to balance on top of spine/neck
- humans have double curvature achieved by the lower vertebrae in lumbar region
- cervical curvature - brings vertebral column directly under centre of gravity of skull
The jaw
- from ape-like ancestor, size and protrusion of jaw is reduced
- apes show prognathism (protruding jaw). humans have 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 of foramen magnum is equal to the weight behind.
The pelvis
gorilla = taller, narrower pelvis and is a long shape
human = broader and shorter pelvis (from top to bottom.
- bowl shaped supports abdominal organs when standing, provides greater stability for bipedal walking and supports developing foetus during pregnancy.
- broad hip bone provides an attachment for large buttock muscles, important in leg movement and keeping upper body erect.
The knee
- in bipedal species: weight of body transferred down the outside of the femur to the knee
- ## knee joint = 2 part hinge joint, with one hinge on either side of the cruciate ligaments in the middle of the joint. weight is transmitted to outer hinge
