34_VERTEBRATE Zoology Lecture Note_ppt (1).pptx

This is an excellent material for teaching vertebrate zoology course

1. Chapter 34 Vertebrates

2. Overview: Half a Billion Years of Backbones By the end of the Cambrian period, some 540 million years ago An astonishing variety of animals inhabited Earth’s oceans One of these types of animals Gave rise to vertebrates, one of the most successful groups of animals

3. The animals called vertebrates Get their name from vertebrae, the series of bones that make up the backbone Figure 34.1

4. There are approximately 52,000 species of vertebrates Which include the largest organisms ever to live on the Earth

5. Concept 34.1: Chordates have a notochord and a dorsal, hollow nerve cord Vertebrates are a subphylum of the phylum Chordata Chordates are bilaterian animals That belong to the clade of animals known as Deuterostomia Two groups of invertebrate deuterostomes , the urochordates and cephalochordates Are more closely related to vertebrates than to invertebrates

6. A hypothetical phylogeny of chordates Chordates Craniates Vertebrates Gnathostomes Osteichthyans Lobe-fins Tetrapods Amniotes Milk Amniotic egg Legs Lobed fins Lungs or lung derivatives Jaws, mineralized skeleton Vertebral column Head Brain Notochord Ancestral deuterostome Echinodermata (sister group to chordates) Urochordata (tunicates) Cephalochordata (lancelets) Myxini (hagfishes) Cephalaspidomorphi (lampreys) Chondrichthyes (sharks, rays, chimaeras) Actinopterygii (ray-finned fishes) Actinistia (coelacanths) Dipnoi (lungfishes) Amphibia (frogs, salamanders) Reptilia (turtles, snakes, crocodiles, birds) Mammalia (mammals) Figure 34.2

7. Derived Characters of Chordates All chordates share a set of derived characters Although some species possess some of these traits only during embryonic development Muscle segments Brain Mouth Anus Dorsal, hollow nerve cord Notochord Muscular, post-anal tail Pharyngeal slits or clefts Figure 34.3

8. Notochord The notochord Is a longitudinal, flexible rod located between the digestive tube and the nerve cord Provides skeletal support throughout most of the length of a chordate In most vertebrates, a more complex, jointed skeleton develops And the adult retains only remnants of the embryonic notochord

9. Dorsal, Hollow Nerve Cord The nerve cord of a chordate embryo Develops from a plate of ectoderm that rolls into a tube dorsal to the notochord Develops into the central nervous system: the brain and the spinal cord

10. Pharyngeal Slits or Clefts In most chordates, grooves in the pharynx called pharyngeal clefts Develop into slits that open to the outside of the body These pharyngeal slits Function as suspension-feeding structures in many invertebrate chordates Are modified for gas exchange in aquatic vertebrates Develop into parts of the ear, head, and neck in terrestrial vertebrates

11. Muscular, Post-Anal Tail Chordates have a tail extending posterior to the anus Although in many species it is lost during embryonic development The chordate tail contains skeletal elements and muscles And it provides much of the propelling force in many aquatic species

12. Tunicates Tunicates, subphylum Urochordata Belong to the deepest-branching lineage of chordates Are marine suspension feeders commonly called sea squirts

13. Figure 34.4c Tunicates most resemble chordates during their larval stage Which may be as brief as a few minutes Pharynx with slits Notochord Tail Dorsal, hollow nerve cord Atrium Stomach Intestine Excurrent siphon Incurrent siphon Muscle segments (c) A tunicate larva is a free-swimming but nonfeeding “tadpole” in which all four chief characters of chordates are evident.

14. As an adult A tunicate draws in water through an incurrent siphon, filtering food particles (a) An adult tunicate, or sea squirt, is a sessile animal (photo is approximately life-sized). (b) In the adult, prominent pharyngeal slits function in suspension feeding, but other chordate characters are not obvious. Tunic Pharynx with numerous slits Atrium Excurrent siphon Incurrent siphon to mouth Stomach Esophagus Intestine Anus Excurrent siphon Figure 34.4a, b

15. Lancelets Lancelets, subphylum Cephalochordata Are named for their bladelike shape Tentacle Mouth Pharyngeal slits Atrium Digestive tract Atriopore Segmental muscles Anus Notochord Dorsal, hollow nerve cord Tail 2 cm Figure 34.5

16. Lancelets are marine suspension feeders That retain the characteristics of the chordate body plan as adults

17. Early Chordate Evolution The current life history of tunicates Probably does not reflect that of the ancestral chordate

18. Gene expression in lancelets Holds clues to the evolution of the vertebrate form BF1 BF1 Otx Otx Hox3 Hox3 Forebrain Midbrain Hindbrain Nerve cord of lancelet embryo Brain of vertebrate embryo (shown straightened) Figure 34.6

19. Concept 34.2: Craniates are chordates that have a head The origin of a head Opened up a completely new way of feeding for chordates: active predation Craniates share some common characteristics A skull, brain, eyes, and other sensory organs

20. Derived Characters of Craniates One feature unique to craniates Is the neural crest, a collection of cells that appears near the dorsal margins of the closing neural tube in an embryo Notochord (a) The neural crest consists of bilateral bands of cells near the margins of the embryonic folds that form the neural tube. (b) Neural crest cells migrate to distant sites in the embryo. Migrating neural crest cells Ectoderm Ectoderm Dorsal edges of neural plate Neural crest Neural tube Figure 34.7a, b

21. Neural crest cells Give rise to a variety of structures, including some of the bones and cartilage of the skull (c) The cells give rise to some of the anatomical structures unique to vertebrates, including some of the bones and cartilage of the skull. Figure 34.7c

22. The Origin of Craniates Craniates evolved at least 530 million years ago During the Cambrian explosion

23. The most primitive of the fossils Are those of the 3-cm-long Haikouella Figure 34.8a (a) Haikouella . Discovered in 1999 in southern China, Haikouella had eyes and a brain but lacked a skull, a derived trait of craniates.

24. In other Cambrian rocks Paleontologists have found fossils of even more advanced chordates, such as Haikouichthys Figure 34.8b (b) Haikouichthys . Haikouichthys had a skull and thus is considered a true craniate . 5 mm

25. Hagfishes The least derived craniate lineage that still survives Is class Myxini , the hagfishes Figure 34.9 Slime glands

26. Hagfishes are jawless marine craniates That have a cartilaginous skull and axial rod of cartilage derived from the notochord That lack vertebrae

27. Concept 34.3: Vertebrates are craniates that have a backbone During the Cambrian period A lineage of craniates evolved into vertebrates

28. Derived Characters of Vertebrates Vertebrates have Vertebrae enclosing a spinal cord An elaborate skull Fin rays, in aquatic forms

29. Lampreys Lampreys, class Cephalaspidomorphi Represent the oldest living lineage of vertebrates Have cartilaginous segments surrounding the notochord and arching partly over the nerve cord

30. Lampreys are jawless vertebrates Inhabiting various marine and freshwater habitats Figure 34.10

31. Fossils of Early Vertebrates Conodonts were the first vertebrates With mineralized skeletal elements in their mouth and pharynx Dorsal view of head Dental elements Figure 34.11

32. Armored, jawless vertebrates called ostracoderms Had defensive plates of bone on their skin Pteraspis Pharyngolepis Figure 34.12

33. Origins of Bone and Teeth Mineralization Appears to have originated with vertebrate mouthparts The vertebrate endoskeleton Became fully mineralized much later

34. Concept 34.4: Gnathostomes are vertebrates that have jaws Today, jawless vertebrates Are far outnumbered by those with jaws

35. Derived Characters of Gnathostomes Gnathostomes have jaws That evolved from skeletal supports of the pharyngeal slits Mouth Gill slits Cranium Skeletal rods Figure 34.13

36. Other characters common to gnathostomes include Enhanced sensory systems, including the lateral line system An extensively mineralized endoskeleton Paired appendages

37. Fossil Gnathostomes The earliest gnathostomes in the fossil record Are an extinct lineage of armored vertebrates called placoderms Figure 34.14a (a) Coccosteus , a placoderm

38. Another group of jawed vertebrates called acanthodians Radiated during the Devonian period Were closely related to the ancestors of osteichthyans Figure 34.14b (b) Climatius , an acanthodian

39. Chondrichthyans (Sharks, Rays, and Their Relatives) Members of class Chondrichthyes Have a skeleton that is composed primarily of cartilage The cartilaginous skeleton Evolved secondarily from an ancestral mineralized skeleton

40. The largest and most diverse subclass of Chondrichthyes Includes the sharks and rays Figure 34.15a, b Pectoral fins Pelvic fins (a) Blacktip reef shark ( Carcharhinus melanopterus ) . Fast swimmers with acute senses, sharks have paired pectoral and pelvic fins. (b) Southern stingray ( Dasyatis americana ) . Most rays are flattened bottom-dwellers that crush molluscs and crustaceans for food. Some rays cruise in open water and scoop food into their gaping mouth.

41. A second subclass Is composed of a few dozen species of ratfishes Figure 34.15c (c) Spotted ratfish ( Hydrolagus colliei ) . Ratfishes , or chimaeras, typically live at depths greater than 80 m and feed on shrimps, molluscs , and sea urchins. Some species have a poisonous spine at the front of their dorsal fin.

42. Most sharks Have a streamlined body and are swift swimmers Have acute senses

43. Ray-Finned Fishes and Lobe-Fins The vast majority of vertebrates Belong to a clade of gnathostomes called Osteichthyes

44. Nearly all living osteichthyans Have a bony endoskeleton Aquatic osteichthyans Are the vertebrates we informally call fishes Control their buoyancy with an air sac known as a swim bladder

45. Fishes breathe by drawing water over four or five pairs of gills Located in chambers covered by a protective bony flap called the operculum Nostril Brain Spinal cord Swim bladder Dorsal fin Adipose fin (characteristic of trout) Caudal fin Cut edge of operculum Gills Heart Liver Kidney Stomach Intestine Gonad Anus Urinary bladder Lateral line Anal fin Pelvic fin Figure 34.16

46. Ray-Finned Fishes Class Actinopterygii , the ray-finned fishes Includes nearly all the familiar aquatic osteichthyans (a) Yellowfin tuna ( Thunnus albacares ), a fast-swimming, schooling fish that is an important commercial fish worldwide (b) Clownfish ( Amphiprion ocellaris ), a mutualistic symbiont of sea anemones (c) Sea horse (Hippocampus ramulosus ), unusual in the animal kingdom in that the male carries the young during their embryonic development (d) Fine-spotted moray eel ( Gymnothorax dovii ), a predator that ambushes prey from crevices in its coral reef habitat Figure 34.17a–d

47. The fins, supported mainly by long, flexible rays Are modified for maneuvering, defense, and other functions

48. Lobe-Fins The lobe-fins, class Sarcopterygii Have muscular and pectoral fins Include coelacanths, lungfishes, and tetrapods Figure 34.18

49. Concept 34.5: Tetrapods are gnathostomes that have limbs and feet One of the most significant events in vertebrate history Was when the fins of some lobe-fins evolved into the limbs and feet of tetrapods

50. Derived Characters of Tetrapods Tetrapods have some specific adaptations Four limbs and feet with digits Ears for detecting airborne sounds

51. The Origin of Tetrapods In one lineage of lobe-fins The fins became progressively more limb-like while the rest of the body retained adaptations for aquatic life Tetrapod limb skeleton Bones supporting gills Figure 34.19

52. Extraordinary fossil discoveries over the past 20 years Have allowed paleontologists to reconstruct the origin of tetrapods Figure 34.20 Amniotes Amphibians Greerpeton Hynerpeton lchthyostega Acanthostega Metaxygnathus Elginerpeton Eusthenopteron Panderichthys Lungfishes Coelacanths Ray-finned fishes Paleozoic Silurian Devonian Carboniferous Permian To present 420 415 400 385 370 355 340 325 310 295 280 265 Millions of years ago

53. Amphibians Class Amphibia Is represented by about 4,800 species of organisms Most amphibians Have moist skin that complements the lungs in gas exchange

54. Order Urodela Includes salamanders, which have tails Figure 34.21a (a) Order Urodela . Urodeles (salamanders) retain their tail as adults.

55. Order Anura Includes frogs and toads, which lack tails Figure 34.21b (b) Order Anura . Anurans, such as this poison arrow frog, lack a tail as adults.

56. Order Apoda Includes caecilians, which are legless and resemble worms Figure 34.21c (c) Order Apoda . Apodans , or caecilians, are legless, mainly burrowing amphibians.

57. Amphibian means “two lives” A reference to the metamorphosis of an aquatic larva into a terrestrial adult Figure 34.22a–c (a) The male grasps the female, stimulating her to release eggs. The eggs are laid and fertilized in water. They have a jelly coat but lack a shell and would desiccate in air. (b) The tadpole is an aquatic herbivore with a fishlike tail and internal gills. (c) During metamorphosis, the gills and tail are resorbed , and walking legs develop.

58. Concept 34.6: Amniotes are tetrapods that have a terrestrially adapted egg Amniotes are a group of tetrapods Whose living members are the reptiles, including birds, and the mammals

59. A phylogeny of amniotes Figure 34.23 Synapsids Ancestral amniote Reptiles Diapsids Archosaurs Saurischians Lepidosaurs Dinosaurs Parareptiles Turtles Crocodilians Pterosaurs Ornithischian dinosaurs Saurischian dinosaurs other than birds Birds Plesiosaurs Ichthyosaurs Tuatara Squamates Mammals

60. Derived Characters of Amniotes Amniotes are named for the major derived character of the clade , the amniotic egg Which contains specialized membranes that protect the embryo

61. The extraembryonic membranes Have various functions Figure 34.24 Shell Albumen Yolk (nutrients) Amniotic cavity with amniotic fluid Embryo Yolk sac. The yolk sac contains the yolk, a stockpile of nutrients. Blood vessels in the yolk sac membrane transport nutrients from the yolk into the embryo. Other nutrients are stored in the albumen (“egg white”). Allantois . The allantois is a disposal sac for certain metabolic wastes pro- duced by the embryo. The membrane of the allantois also functions with the chorion as a respiratory organ. Amnion. The amnion protects the embryo in a fluid-filled cavity that cushions against mechanical shock. Chorion . The chorion and the membrane of the allantois exchange gases between the embryo and the air. Oxygen and carbon dioxide diffuse freely across the shell. Extraembryonic membranes

62. Amniotes also have other terrestrial adaptations Such as relatively impermeable skin and the ability to use the rib cage to ventilate the lungs

63. Early Amniotes Early amniotes Appeared in the Carboniferous period Included large herbivores and predators

64. Reptiles The reptile clade includes The tuatara, lizards, snakes, turtles, crocodilians, birds, and the extinct dinosaurs

65. Reptiles Have scales that create a waterproof barrier Lay shelled eggs on land Figure 34.25

66. Most reptiles are ectothermic Absorbing external heat as the main source of body heat Birds are endothermic Capable of keeping the body warm through metabolism

67. The Origin and Evolutionary Radiation of Reptiles The oldest reptilian fossils Date to about 300 million years ago The first major group of reptiles to emerge Were the parareptiles , which were mostly large, stocky herbivores

68. As parareptiles were dwindling The diapsids were diversifying The diapsids are composed of two main lineages The lepidosaurs and the archosaurs

69. The dinosaurs Diversified into a vast range of shapes and sizes Included the long-necked giants called the theropods

70. Figure 34.26 Traditionally, dinosaurs were considered slow, sluggish creatures But fossil discoveries and research have led to the conclusion that dinosaurs were agile and fast moving Paleontologists have also discovered signs of parental care among dinosaurs

71. Lepidosaurs One surviving lineage of lepidosaurs Is represented by two species of lizard-like reptiles called tuatara Figure 34.27a (a) Tuatara ( Sphenodon punctatus )

72. Figure 34.27b (b) Australian thorny devil lizard (Moloch horridus ) The other major living lineage of lepidosaurs Are the squamates , the lizards and snakes Lizards Are the most numerous and diverse reptiles, apart from birds

73. Snakes are legless lepidosaurs That evolved from lizards Figure 34.27c (c) Wagler’s pit viper ( Tropidolaemus wagleri ), a snake

74. Turtles Turtles Are the most distinctive group of reptiles alive today Some turtles have adapted to deserts And others live entirely in ponds and rivers

75. All turtles have a boxlike shell Made of upper and lower shields that are fused to the vertebrae, clavicles, and ribs Figure 34.27d (d) Eastern box turtle ( Terrapene carolina carolina )

76. Alligators and Crocodiles Crocodilians Belong to an archosaur lineage that dates back to the late Triassic Figure 34.27e (e) American alligator (Alligator mississipiensis )

77. Birds Birds are archosaurs But almost every feature of their reptilian anatomy has undergone modification in their adaptation to flight

78. Derived Characters of Birds Many of the characters of birds Are adaptations that facilitate flight

79. A bird’s most obvious adaptations for flight Are its wings and feathers Figure 34.28a–c (a) wing (b) Bone structure Finger 1 (c) Feather structure Shaft Barb Barbule Hook Vane Shaft Forearm Wrist Palm Finger 3 Finger 2

80. The Origin of Birds Birds probably descended from theropods A group of small, carnivorous dinosaurs

81. By 150 million years ago Feathered theropods had evolved into birds Archaeopteryx Remains the oldest bird known Figure 34.29 Toothed beak Airfoil wing with contour feathers Long tail with many vertebrae Wing claw

82. Living Birds The ratites, order Struthioniformes Are all flightless Figure 34.30a (a) Emu . This ratite lives in Australia.

83. The demands of flight Have rendered the general body form of many flying birds similar to one another Figure 34.30b–d (b) Mallards. Like many bird species, the mallard exhibits pronounced color differences between the sexes. (c) Laysan albatrosses. Like most birds, Laysan albatrosses have specific mating behaviors, such as this courtship ritual. (d) Barn swallows. The barn swallow is a member of the order Passeriformes . Species in this order are called perching birds because the toes of their feet can lock around a branch or wire, enabling the bird to rest in place for long periods.

84. Foot structure in bird feet Shows considerable variation Figure 34.31 Grasping bird (such as a woodpecker) Perching bird (such as a cardinal) Raptor (such as a bald eagle) Swimming bird (such as a duck)

85. Concept 34.7: Mammals are amniotes that have hair and produce milk Mammals, class Mammalia Are represented by more than 5,000 species

86. Derived Characters of Mammals Mammary glands, which produce milk Are a distinctively mammalian character Hair is another mammalian characteristic Mammals generally have a larger brain Than other vertebrates of equivalent size

87. Early Evolution of Mammals Mammals evolved from synapsids In the late Triassic period

88. The jaw was remodeled during the evolution of mammals from nonmammalian synapsids And two of the bones that formerly made of the jaw joint were incorporated into the mammalian middle ear Sound Sound Jaw joint Jaw joint Key Dentary Angular Squamosal Articular Quadrate Dimetrodon Morganucodon Dimetrodon Morganucodon Eardrum Eardrum Middle ear Middle ear Stapes Inner ear Inner ear Stapes Incus (evolved from quadrate) Malleus (evolved from articular ) (b) During the evolutionary remodeling of the mammalian skull, the quadrate and articular bones became incorporated into the middle ear as two of the three bones that transmit sound from the eardrum to the inner ear. The steps in this evolutionary remodeling are evident in a succession of fossils. (a) The lower jaw of Dimetrodon is composed of several fused bones; two small bones, the quadrate and articular , form part of the jaw joint. In Morganucodon , the lower jaw is reduced to a single bone, the dentary , and the location of the jaw joint has shifted. Figure 34.32a, b

89. Living lineages of mammals originated in the Jurassic But did not undergo a significant adaptive radiation until after the Cretaceous

90. Monotremes Monotremes Are a small group of egg-laying mammals consisting of echidnas and the platypus Figure 34.33

91. Marsupials Marsupials Include opossums, kangaroos, and koalas

92. A marsupial is born very early in its development And completes its embryonic development while nursing within a maternal pouch called a marsupium Figure 34.34a (a) A young brushtail possum. The young of marsupials are born very early in their development. They finish their growth while nursing from a nipple (in their mother’s pouch in most species).

93. In some species of marsupials, such as the bandicoot The marsupium opens to the rear of the mother’s body as opposed to the front, as in other marsupials Figure 34.34b (b) Long-nosed bandicoot. Most bandicoots are diggers and burrowers that eat mainly insects but also some small vertebrates and plant material. Their rear-opening pouch helps protect the young from dirt as the mother digs. Other marsupials, such as kangaroos, have a pouch that opens to the front.

94. In Australia, convergent evolution Has resulted in a diversity of marsupials that resemble eutherians in other parts of the world Figure 34.35 Marsupial mammals Eutherian mammals Plantigale Marsupial mole Sugar glider Wombat Tasmanian devil Kangaroo Deer mouse Mole Woodchuck Flying squirrel Wolverine Patagonian cavy

95. Eutherians (Placental Mammals) Compared to marsupials Eutherians have a longer period of pregnancy Young eutherians Complete their embryonic development within a uterus, joined to the mother by the placenta

96. Phylogenetic relationships of mammals Figure 34.36 Ancestral mammal Monotremes Marsupials Eutherians Monotremata Marsupialia Xenarthra Proboscidea Sirenia Tubulidentata Hyracoidea Afrosoricida (golden moles and tenrecs ) Macroscelidea (elephant shrews) Rodentia Lagomorpha Primates Dermoptera (flying lemurs) Scandentia (tree shrews) Carnivora Cetartiodactyla Perissodactyla Chiroptera Eulipotyphla Pholidota (pangolins) Possible phylogenetic tree of mammals. All 20 extant orders of mammals are listed at the top of the tree. Boldfaced orders are explored on the facing page. This diverse clade includes terrestrial and marine mammals as well as bats, the only flying mammals. A growing body of evidence, including Eocene fossils of whales with feet, supports putting whales in the same order ( Cetartiodactyla ) as pigs, cows, and hippos. This is the largest eutherian clade . It includes the rodents, which make up the largest mammalian order by far, with about 1,770 species. Humans belong to the order Primates. All members of this clade , which underwent an adaptive radiation in South America, belong to the order Xenarthra . One species, the nine-banded armadillo, is found in the southern United States. This clade of eutherians evolved in Africa when the continent was isolated from other landmasses. It includes Earth’s largest living land animal (the African elephant), as well as species that weigh less than 10 g.

97. The major eutherian orders Figure 34.36 ORDERS AND EXAMPLES MAIN CHARACTERISTICS Monotremata Platypuses, echidnas Proboscidea Elephants Sirenia Manatees, dugongs Cetartiodactyla Artiodactyls Sheep, pigs cattle, deer, giraffes Lagomorpha Rabbits, hares, picas Carnivora Dogs, wolves, bears, cats, weasels, otters, seals, walruses Xenarthra Sloths , anteaters, armadillos Cetaceans Whales, dolphins, porpoises Echidna African elephant Manatee Tamandua Jackrabbit Coyote Bighorn sheep Pacific white- sided porpoise Lay eggs; no nipples; young suck milk from fur of mother Long, muscular trunk; thick, loose skin; upper incisors elongated as tusks Aquatic; finlike forelimbs and no hind limbs; herbivorous Reduced teeth or no teeth; herbivorous ( sloths ) or carnivorous (anteaters, armadillos) Chisel-like incisors; hind legs longer than forelegs and adapted for running and jumping Sharp, pointed canine teeth and molars for shearing; carnivorous Hooves with an even number of toes on each foot; herbivorous Aquatic; streamlined body; paddle-like forelimbs and no hind limbs; thick layer of insulating blubber; carnivorous Diet consists mainly of insects and other small invertebrates Adapted for flight; broad skinfold that extends from elongated fingers to body and legs; carnivorous or herbivorous Hooves with an odd number of toes on each foot; herbivorous Opposable thumbs; forward-facing eyes; well-developed cerebral cortex; omnivorous Chisel-like, continuously growing incisors worn down by gnawing; herbivorous Short legs; stumpy tail; herbivorous; complex, multichambered stomach Teeth consisting of many thin tubes cemented together; eats ants and termites Embryo completes development in pouch on mother ORDERS AND EXAMPLES MAIN CHARACTERISTICS Marsupialia Kangaroos, opossums, koalas Tubulidentata Aardvark Hyracoidea Hyraxes Chiroptera Bats Primates Lemurs, monkeys, apes, humans Perissodactyla Horses, zebras, tapirs, rhinoceroses Rodentia Squirrels, beavers, rats, porcupines, mice   Eulipotyphla “Core insecti - vores ”: some moles, some shrews Star-nosed mole Frog-eating bat Indian rhinoceros Golden lion tamarin Red squirrel Rock hyrax Aardvark Koala

98. Primates The mammalian order Primates include Lemurs, tarsiers, monkeys, and apes Humans are members of the ape group

99. Derived Characters of Primates Most primates Have hands and feet adapted for grasping Primates also have A large brain and short jaws Forward-looking eyes close together on the face, providing depth perception Well-developed parental care and complex social behavior A fully opposable thumb

100. Living Primates There are three main groups of living primates The lemurs of Madagascar and the lorises and pottos of tropical Africa and southern Asia Figure 34.37

101. The tarsiers of Southeast Asia The anthropoids, which include monkeys and hominids worldwide

102. The oldest known anthropoid fossils, about 45 million years old Indicate that tarsiers are more closely related to anthropoids Figure 34.38 60 50 40 30 20 10 Millions of years ago Ancestral primate Lemurs, lorises , and pottos Tarsiers New World monkeys Old World monkeys Gibbons Orangutans Gorillas Chim - panzees Humans Anthropoids

103. The fossil record indicates that monkeys First appeared in the New World (South America) during the Oligocene The first monkeys Evolved in the Old World (Africa and Asia)

104. New World and Old World monkeys Underwent separate adaptive radiations during their many millions of years of separation Figure 34.39a, b (a) New World monkeys, such as spider monkeys (shown here), squirrel monkeys, and capuchins, have a prehensile tail and nostrils that open to the sides. (b) Old World monkeys lack a prehensile tail, and their nostrils open downward. This group includes macaques (shown here), mandrills, baboons, and rhesus monkeys.

105. The other group of anthropoids, the hominoids Consists of primates informally called apes Figure 34.40a–e (a) Gibbons, such as this Muller's gibbon, are found only in southeastern Asia. Their very long arms and fingers are adaptations for brachiation . (b) Orangutans are shy, solitary apes that live in the rain forests of Sumatra and Borneo. They spend most of their time in trees; note the foot adapted for grasping and the opposable thumb. (c) Gorillas are the largest apes: some males are almost 2 m tall and weigh about 200 kg. Found only in Africa, these herbivores usually live in groups of up to about 20 individuals. (d) Chimpanzees live in tropical Africa. They feed and sleep in trees but also spend a great deal of time on the ground. Chimpanzees are intelligent, communicative, and social. (e) Bonobos are closely related to chimpanzees but are smaller. They survive today only in the African nation of Congo.

106. Hominoids Diverged from Old World monkeys about 20–25 million years ago

107. Concept 34.8: Humans are bipedal hominoids with a large brain Homo sapiens is about 160,000 years old Which is very young considering that life has existed on Earth for at least 3.5 billion years

108. Derived Characters of Hominids A number of characters distinguish humans from other hominoids Upright posture and bipedal locomotion Larger brains Language capabilities Symbolic thought The manufacture and use of complex tools Shortened jaw

109. The Earliest Humans The study of human origins Is known as paleoanthropology

110. Paleoanthropologists have discovered fossils of approximately 20 species of extinct hominoids That are more closely related to humans than to chimpanzees

111. These species are known as hominids Figure 34.41 Homo sapiens Homo neanderthalensis Homo ergaster ? Homo erectus Homo habilis Homo rudolfensis Paranthropus robustus Paranthropus boisei Australopithecus garhi Australopithecus africanus Australopithecus afarensis Kenyanthropus platyops Australopithecus anamensis Ardipithecus ramidus Orrorin tugenensis Sahelanthropus tchadensis 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 Millions of years ago

112. Hominids originated in Africa Approximately 6–7 million years ago Early hominids Had a small brain, but probably walked upright, exhibiting mosaic evolution

113. Two common misconceptions of early hominids include Thinking of them as chimpanzees Imagining human evolution as a ladder leading directly to Homo sapiens

114. Australopiths Australopiths are a paraphyletic assemblage of hominids That lived between 4 and 2 million years ago

115. Some species walked fully erect And had human-like hands and teeth Figure 34.42a–c (a) Lucy, a 3.24-million-year-old skeleton, represents the hominid species Australopithecus afarensis . (b) The Laetoli footprints, more than 3.5 million years old, confirm that upright posture evolved quite early in hominid history. (c) An artist’s reconstruction of what A. afarensis may have looked like.

116. Bipedalism Hominids began to walk long distances on two legs About 1.9 million years ago

117. Tool Use The oldest evidence of tool use—cut marks on animal bones Is 2.5 million years old

118. Early Homo The earliest fossils that paleoanthropologists place in our genus Homo Are those of the species Homo habilis , ranging in age from about 2.4 to 1.6 million years Stone tools have been found with H. habilis Giving this species its name, which means “handy man”

119. Homo ergaster Was the first fully bipedal, large-brained hominid Existed between 1.9 and 1.6 million years Figure 34.43

120. Homo erectus Originated in Africa approximately 1.8 million years ago Was the first hominid to leave Africa

121. Neanderthals Neanderthals, Homo neanderthalensis Lived in Europe and the Near East from 200,000 to 30,000 years ago Were large, thick-browed hominids Became extinct a few thousand years after the arrival of Homo sapiens in Europe

122. Homo sapiens Homo sapiens Appeared in Africa at least 160,000 years ago Figure 34.44

123. The oldest fossils of Homo sapiens outside Africa Date back about 50,000 years ago

124. The rapid expansion of our species May have been preceded by changes to the brain that made symbolic thought and other cognitive innovations possible Figure 34.45