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 Nuchal Crest Brow Ridge Heavy Malar Zygomatic Arch Diastema Foramen Magnum Protruding Muzzle Massive Jaw Massive Molars Large Canines 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 Foramen Magnum positioned towards underneath skull the back Area of attachment for neck (nuchal) Area for attachment for neck (nuchal) muscles is small 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 Apes have no chin and a flat nose sticks out Face is flat with forehead rising up Forehead slopes back from the eyes, from the eyes. Some early human had large brow ridges. Apes are wide cheek bones called Zygomatic prognathic – lower face and jaw Arch. 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 Apes have large incisors and incisors and canines that do not canines. project further than any of the other teeth 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 Palate is flat and teeth shaped like a like a rounded ‘V’ ‘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 Pelvis is narrow and elongated bottom and bowl-shaped Centre of gravity is just behind the Centre of gravity is in the middle of lower back above the legs the spine. Have large gluteus maximus Small gluteus maximus and support muscles to support femur and pelvis 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 Head of femur and far apart and knee knee ends in a ends close vertical line – no together forming angle an angle (valgus angle) Outer condyle is Inner condyle is larger than inner larger than outer one in the knee one in the knee joint joint. Legs are longer Arms are longer than arms than legs Physical differences between Apes and Humans – The feet HUMANS APES Foot has short toes. The big toe is Gap between the big toe and the longer and lies close alongside the rest and the big toe is shorter than other toes. the rest Weight is taken on the outside of the Apes have flat feet. foot. Inner side is elevated into an arch. Physical differences between Apes and Humans – The chest HUMANS APES Chest is broard and narrow, Chest is flattened at the sides flattened from front to back 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 Disadvantages Can see further Back-aches Free hands Painful birth Can carry babies etc Takes a long time to learn to walk Can throw stones and wield Varicose veins 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 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.
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