THE PRIMATES

Year 13 Biology

Achievement standard 3.7

Terms Arboreal – Tree-dwelling Binocular Vision – ability to see 3D, depth

perception and colour Prehensile – ability to grasp (hands, feet, tail) Quadrapedalism – walking on all four limbs Brachiation – use of arms to suspend body during

feeding and to move the body by arm-swinging Bipedalism – walking on two legs (habitual) Hominid – Humans and their ancestors Hominoid – Group containing humans and apes

Primate Groups Prosimians

Arboreal or tree living Grasping hands and feet Long, mobile limbs Quadrapedal Binocular vision Upright sitting position Nails instead of claws Use scent marking to

communicate – wet nose

Primate Groups New World Monkeys

(Americas) Prehensile or grasping tail – used

as a 5th limb Quadrapedal Arboreal or tree living Nostrils wide apart E.g. spider monkey

Primate Groups Old world monkeys (Africa

and Asia) Tail not prehensile Quadrapedal Some are ground living Nostrils close together – reduced

sense of smell E.g. Baboon

Primate Groups Great Apes

Some brachiating Mostly ground dwelling Quadrapedal Flattened nose Bony eye ridges E.g. Gibbon, Gorilla, chimp,

Orangutan

Primate Groups Hominids

Bipedal Reduced canines and outer teeth Large cerebral cortex (forebrain) Eye ridges reduced, chin and nose

protrude Very sensitive skin Reduced body hair Very complex social behaviour

Evolution of Apes and Human (Hominoids)

Primate Skull Features

Sagittal Crest Cranial Vault

Brow Ridge

Heavy Malar

Diastema

Protruding Muzzle

Large CaninesMassive Molars

Massive Jaw

Foramen Magnum

Zygomatic Arch

Nuchal Crest

General Ape Characteristics

No tail Y-5 Pattern on teeth.

Quadrupedal Semi or fully-erect posture Arms long in comparison with hind limbs Rib cage flattened from front to back Larger brains Upper lip free from gums Powerful canine teeth and large incisors

Differences between Humans and Apes Main physical differences between

quadrupedalism and bipedalism The Skull Teeth and Jaw The legs The feet The chest

Physical differences between Apes and Humans

Physical differences between Apes and Humans – The Skull

HUMANS APES

Occipital Condyle forward Occipital Condyle far back

Foramen Magnum positioned underneath skull

Foramen Magnum positioned towards the back

Area of attachment for neck (nuchal) muscles is small

Area for attachment for neck (nuchal) muscles is large. Apes also have large sagittal crest for attachment on heavy chewing muscles

Large Brains – 1400 cm3 Smaller Brains – 400 – 500cm3

Modern human has chin and nose that sticks out

Apes have no chin and a flat nose

Face is flat with forehead rising up from the eyes. Some early human had wide cheek bones called Zygomatic Arch.

Forehead slopes back from the eyes, large brow ridges. Apes are prognathic – lower face and jaw project in front of upper parts of face.

Physical differences between Apes and Humans – The Skull

Physical differences between Apes and Humans – The Skull

Physical differences between Apes and Humans – The teeth and jaw.

HUMANS APES

Both males and females have small incisors and canines that do not project further than any of the other teeth

Apes have large incisors and canines.

Both premolars have 2 cusps First premolar has one cusp and second has 2 cusps.

No Diastema Diastema in lower jaw where canines fit.

Palate is arched and teeth shaped like a rounded ‘V’

Palate is flat and teeth shaped like a ‘U’ with parallel sides

Physical differences between Apes and Humans – The teeth and jaw.

Physical differences between Apes and Humans – The pelvis and backbone

HUMANS APES

Backbone is S shaped Backbone is arched

Pelvis is broad, shallow from top to bottom and bowl-shaped

Pelvis is narrow and elongated

Centre of gravity is just behind the lower back above the legs

Centre of gravity is in the middle of the spine.

Have large gluteus maximus muscles to support femur and pelvis

Small gluteus maximus and support body with arms instead.

Physical differences between Apes and Humans – The pelvis and backbone

Physical differences between Apes and Humans – The legs

HUMANS APES

Head of femur is far apart and knee ends close together forming an angle (valgus angle)

Head of femur and knee ends in a vertical line – no angle

Outer condyle is larger than inner one in the knee joint

Inner condyle is larger than outer one in the knee joint.

Legs are longer than arms

Arms are longer than legs

Physical differences between Apes and Humans – The feet

HUMANS APES

Foot has short toes. The big toe is longer and lies close alongside the other toes.

Gap between the big toe and the rest and the big toe is shorter than the rest

Weight is taken on the outside of the foot. Inner side is elevated into an arch.

Apes have flat feet.

Physical differences between Apes and Humans – The chest

HUMANS APES

Chest is broard and narrow, flattened from front to back

Chest is flattened at the sides

Collar bone is long Collar bone is shorter than in humans

Shoulder blades lie on back Shoulder blades sit along the sides of the chest.

Bipedalism V’s Quadrupedalism

Advantages and disadvantages of bipedal (upright) walking

Advantages DisadvantagesCan see further

Free hands

Can carry babies etc

Can throw stones and wield sticks

Can keep cooler by less sun falling on the body and more wind off the ground

Look larger and more menacing

Greater display of sexual organs to members of opposite sex

Back-aches

Painful birth

Takes a long time to learn to walk

Varicose veins

Why walk upright?

In Early Africa, Apes lived in a continuous forest and as a result were adapted for an arboreal life.

Climate changed (drier) and forest retreated leaving large areas of grassland.

Divergent evolution occurred – some remaining in the trees and some developing bipedalism as an adaptation for moving between the patches of forest.