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Chapter 6

Textbook Chapter 6 Notes

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University of Toronto Mississauga
Heather Miller

Notes From Reading CHAPTER 6:A N OVERVIEW OF THEP RIMATES (PGS.115-144) Learning Objectives  Describe the characteristics that set primates apart from other mammals  Explain how humans are anatomically and behaviorally connected to the other primates  Explain the differences between the major grouping of nonhuman primates, such as apes and monkeys  Describe some of the many challenges facing free-ranging nonhuman primates today Introduction  Primates – members of the mammalian order Primates, which included lemurs, lorises, tarsiers, monkeys, apes and humans  One way to understand any organism is to compare its anatomy and behavior with that of other, closely related species  This comparative approach helps explain how and why physiological and behavioral systems evolved as adaptive responses to various selective pressures  Good starting point to compare ourselves with our closet living relatives of nonhuman primates (lemurs, lorises, tarsiers, monkeys and apes)  Evolution is not a goal-directed process  Anthropoids – members of a suborder of Primates, the infraorder Anthrpoidea. Traditionally, the suborder includes monkeys, apes and humans  Each lineage or species has come to possess unique qualities that make it better suited to a particular habitat and lifestyle  The only species that represent final evolutionary stages of particular lineages are the ones that become extinct Primate Characteristics  Some basic mammalian traits are body hair, a relatively long gestation period followed by live birth, mammary glands, different types of teeth, the ability to maintain a constant internal body temperature through physiological means or endothermy, increase brain size and a considerable capacity for learning and behavioral flexibility  Primatologists have drawn attention to a group of characteristics that, when taken together, more or less characterize the entire primate order  While some traits are unique to primates, many other are retained ancestral mammalian characteristics shared with other mammals Limbs and Locomotion  A tendency toward an erect posture (especially in the upper body) o All primates show this tendency to some deree o Variously associated with sitting, leading, standing and occasionally, bipedal walking  A flexible, generalized limb structure, which allows most primates to practice various locomotor behaviors o Primates have retained some bones (ie. collarbones) and certain abilities that have been lost in more specialized mammals such as horses o By maintaining a generalized locomotor anatomy, primates aren’t restricted to one form of movement, like many other mammals o Primates also use their limbd for many activities besides locomotion  Prehensile hands (and sometimes feet) o Many can manipulate objects, but not as skillfully as primates o All primates use their hands and frequently their feet, to grasp and manipulate objects o Retention of five digits on the hands and feet  varies somewhat throughout the order, with some species having reduced thumbs or second digits (first fingers) o An opposable thumb and, in most species, a divergent and partially opposable big toe  most primates are capable of moving the thumb so that it one in contact with the second digit or the palm of the hand Notes From Reading CHAPTER 6:A NO VERVIEW OF THP RIMATES (PGS.115-144) o Nails instead of claws  characteristic is seen in all primates except some highly derived New World monkeys o Tactile pads enriched with sensory nerve fibres at the end of the digits  this characteristic enhances the sense of touch Diet and Teeth  Lack of dietary specialization o This is typical of most primate, who tend to eat a wide assortment of food items o Primate are generally omnivorous  A generalized dentition o Primate teeth aren’t specialized for processing only one type of food, a trait related to a general lack of dietary specialization The Senses and the Brain  Diurnal – active during the day  Diurnal primates rely heavily on vision and less of the sense of smell, especially compared to other mammals o Reflected in evolutionary changes in the skill, eyes and brain  Color vision o This is a characteristic of all diurnal primates o Nocturnal (active during the night) primates don’t have color vision  Depth perception o Primates have stereoscopic vision or the ability to perceive objects in three dimensions o Eyes placed toward the front of the face (not the sides)  provides for overlapping visual fields or binocular vision o Visual information from each eye transmitted to visual enters in both hemispheres of the brain  in primates, about 40% of the fibers remain on the same side, so that both hemispheres receive much of the same information o Visual information organized into three-dimensional images by specialized structures in the brain itself  capacity for stereoscopic vision depends on each hemisphere of the brain receiving visual information from both eyes and from over lapping visual fields  Decreased reliance on the sense of smell o Some species have large muzzles but isn’t related to olfaction (the sense of smell) o It is for the need to accommodate large canine teeth  Expansion and increased complexity of the brain o General trend among placental mammals and especially true for primates o In primates, the expansion is most evident in visual and association areas of the neocortex o Neocortex – more recently evolved portion of the brain that is involved in higher mental functions and composed of areas that integrate incoming information from different sensory organs o Sensory Modalities – different forms of sensation Maturation, Learning and Behavior  A more efficient means of fetal nourishment, longer periods of gestation, reduced numbers of offspring (with single births the norm), delayed maturation, and extension of the entire life span  A greater dependence on flexible, learned behavior o Correlated with delayed maturation and longer periods of infant and child dependency on at least one parent o Parental investment in offspring is increased  The tendency to live in social groups and the permanent association of adult males with the group o Except for nocturnal species, primates tend to associate with other individuals  The tendency toward diurnal activity patterns Notes From Reading CHAPTER 6:A N OVERVIEW OF THE PRIMATES (PGS.115-144) o Seen in most primates o Lorises, tarsiers, one monkey species and some lemurs are nocturnal o All other monkeys, apes and humans are diurnal Primate Adaptations  “Environmental circumstance” refer to several interrelated variables o Including climate, diet, habitat and predation Evolutionary Factors  Arboreal – tree-living; adapted to life in the trees  Adaptive Niche – an organism’s entire way of life: where it lives, what it eats, how it gets food, how it avoids predators and so on  Throughout the course of evolution, primates increasingly found food (leaves, seeds, fruits, nuts, insects and small mammals) in the trees themselves  Their dietary shift enhanced a general trend towards omnivory  Increased reliance on vision, coupled with grasping hands and feet, are also a complex, three-dimensional environment with uncertain footholds, acute color vision with depth perception is extremely beneficial  Forward-facing eyes (binocular vision), grasping hands and feet, and the presence of nails instead of claws may not have come about solely as adaptive advantages in a purely arboreal setting  Sussman argued that because visual predation isn’t common among primates, forward- facing eyes, grasping hands and feet, omnivory and color vision may have arisen in response to the demand for fine visual and tactile discrimination Geographical Distribution and Habitats  Nonhuman primates are found in tropical or semitropical areas of the New and Old Worlds  In the New World, these areas include southern Mexico, Central America and parts of South America  Old World primates are found in Africa, India, Southeast Asia and Japan  Some Old World monkeys (ie. baboons) spend much of the day on the ground  All nonhuman primates spend some time in the trees, especially when sleeping Diet and Teeth  Most primates eat a combination of fruits, nuts, seeds, leaves, other plant materials and insects  Many get animal protein from birds, amphibians and small mammals including other primates  Others have become more specialized and mostly eat leaves  Dental Formula – numerical device that indicates the number of each type of tooth in each side of the upper and lower jaws  Dental formula for a generalized placental mammal is (3 incliners, 1 canine, 4 premolars, 3 molars)  The number of each kind of tooth varies between lineages  Humans, apes and all Old World monkeys share the same dental formula:  Most primates have premolars and molars with low, round cusps, a pattern that enables them to process most types of food Locomotion  Quadrupedal – using all four limbs to support the body during locomotion; the basic mammalian (and primate) form of locomotion  The limbs of terrestrial quadrupeds are approximately the same length  In arboreal quadrupeds, forelimbs are somewhat shorter  Vertical clinging and leaping is another form of locomotion (characteristic of some lemurs and tarsiers) o Support themselves vertically by grapsing onto trunks of trees or other large plants while their knees and ankle are tightly flexed  Brachiation – arm swinging, a form of locoation used by some primates Notes From Reading CHAPTER 6:A N OVERVIEW OF THE PRIMATES (PGS.115-144) o Involves hanging from a branch and moving by alternately swinging from one arm to the other  Because of anatomical modifications at the shoulder joint, apes and humans are capable of true brachiation  Brachiation is seen in species with arms longer then legs, a short stable lower back, long curved fingers, shortened thumbs  Some New World monkeys, such as spider monkeys, are called semibrachiators, since they practice a combination of leaping with some arm swining  Some New World monkeys enhance arm swinging by using a prehensile tail which in effect serves as an extra hand Primate Classification  The order Primates includes all primates  The suborder, primates are divided into two smaller categories: o Strepsirhini – lemurs and lorises o Haplorhini – tarsiers, monkeys, apes and humans  There is a biological statement that all the lemurs and lorises are more closely related to one another then they are to any of the other primates  Likewise, humans, apes, monkeys and tarsiers are more closely related to one another than they are to the lorises and lemurs  Comparisons of the genomes of different species are important because they reveal such difference in DNA as the number of nucleotide substitutions and.or deletions that have occurred isnce related species last shared a common ancestor  There are more variation in noncoding DNA segments and portions that have been inserted deleted, or duplicated  The most important discovery of all is that humans have much more non-protein-coding DNA than do the other primates  Geneticistis are beginning to understand some of the functions of non-protien-coding DNA, and they hope to explain why humans have so much of it and how it makes us different from our close relatives A Survey of the Living Primates Lemurs and Lorises  The suborder Strepsirhini includes the lemurs and lorises, the most nonderived or primitive, living primates  Their greater olfactory capabilities (compared with other primates) are reflected in the presence of a relatively long snout and a moist, fleshy pad, or rhinarium, at the end of the nose  Rhinarium – the moist, hairless pad at the end of the nose seen in most mammalian species. The rhinarium enhances an animal’s ability to smell  Other characteristics distinguishing lemurs and lorises from other prima
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