Chapter 34

Chapter 34

Chapter 34 Vertebrates PowerPoint Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Overview: Half a Billion Years of Backbones Early in the Cambrian period, about 530 million years ago, an astonishing variety of animals inhabited Earths oceans.

One type of animal gave rise to vertebrates, one of the most successful groups of animals. The animals called vertebrates get their name from vertebrae, the series of bones that make up the backbone. There are about 52,000 species of vertebrates, including the largest organisms ever to live on the Earth. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Are humans among the descendants of this ancient organism? Concept 34.1: Chordates have a notochord and a dorsal, hollow nerve cord Vertebrates are a subphylum within 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 other invertebrates. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Phylogeny of living chordates Echinodermata (sister group to chordates) Chordates

Cephalochordata (lancelets) ANCESTRAL DEUTEROSTOME Urochordata (tunicates) Notochord Head Vertebral column Actinopterygii (ray-finned fishes)

Jaws, mineralized skeleton Lungs or lung derivatives Lobe-fins Actinistia (coelacanths) Dipnoi (lungfishes) Lobed fins Amniotic egg Reptilia

(turtles, snakes, crocodiles, birds) Mammalia Milk (mammals) Amniotes Legs Tetrapods Amphibia (frogs, salamanders) Gnathostomes Osteichthyans

Chondrichthyes (sharks, rays, chimaeras) Vertebrates Petromyzontida (lampreys) Craniates Myxini (hagfishes) Common ancestor of

chordates Derived Characters of Chordates All chordates share a set of derived characters. Some species have some of these traits only during embryonic development. Four key characters of chordates: Notochord Dorsal, hollow nerve cord Pharyngeal slits or clefts Muscular, post-anal tail Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Chordate characteristics Dorsal, hollow

nerve cord Muscle segments Notochord Mouth Muscular, post-anal tail Anus Pharyngeal slits or clefts Notochord

The notochord is a longitudinal, flexible rod between the digestive tube and nerve cord. It 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. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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. The nerve cord develops into the central nervous system: the brain and the spinal cord.

Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 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. Functions of pharyngeal slits: Suspension-feeding structures in many invertebrate chordates Gas exchange in vertebrates (except vertebrates with limbs, the tetrapods) Develop into parts of the ear, head, and neck in tetrapods. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Muscular, Post-Anal Tail Chordates have a tail posterior to the anus. In many species, the tail is greatly reduced during embryonic development. The tail contains skeletal elements and muscles. It provides propelling force in many aquatic species. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Lancelets are named for their bladelike shape. They are marine suspension feeders. Adults retain characteristics of chordate body plan. Cirri 2 cm

Mouth Pharyngeal slits Atrium Notochord Digestive tract Atriopore Dorsal, hollow nerve cord Segmental muscles Anus Tail

Tunicates (Urochordata) are more closely related to other chordates than are lancelets. They are marine suspension feeders commonly called sea squirts. As an adult, a tunicate draws in water through an incurrent siphon, filtering food particles. Juveniles, not adults, have a notochord. Incurrent siphon to mouth Water flow Notochord Dorsal, hollow nerve cord Excurrent

siphon Atrium Pharynx with slits Tunic Excurrent siphon Tail Muscle segments Incurrent siphon

Intestine Anus Intestine Esophagus Stomach An adult tunicate Excurrent siphon Stomach Atrium Pharynx with slits A tunicate larva

Fossil of an early Chordate 5 mm Segmented muscles Pharyngeal slits Hagfishes have a cartilaginous skull and axial rod of cartilage derived from the notochord, but lack jaws and vertebrae Slime glands Derived Characters of Vertebrates

During the Cambrian period, a lineage of craniates evolved into vertebrates. Vertebrates became more efficient at capturing food and avoiding being eaten. Vertebrates have the following derived characters: Vertebrae enclosing a spinal cord An elaborate skull Fin rays, in the aquatic forms. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Lampreys represent the oldest living lineage of vertebrates. They are jawless vertebrates inhabiting various marine and freshwater habitats. Origins of Bone and Teeth

Mineralization appears to have originated with vertebrate mouthparts. The vertebrate endoskeleton became fully mineralized much later. Today, jawed vertebrates, or gnathostomes, outnumber jawless vertebrates. Gnathostomes jaws might have evolved from skeletal supports of the pharyngeal slits. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Hypothesis for the evolution of vertebrate jaws Gill slits Cranium

Mouth Skeletal rods Other characters common to gnathostomes: An additional duplication of Hox genes An enlarged forebrain associated with enhanced smell and vision In aquatic gnathostomes, the lateral line system, which is sensitive to vibrations. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Chondrichthyans (Sharks, Rays, and Their Relatives) Chondrichthyans (Chondrichthyes) have a

skeleton composed primarily of cartilage. The cartilaginous skeleton evolved secondarily from an ancestral mineralized skeleton. The largest and most diverse group of chondrichthyans includes the sharks, rays, and skates. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Chondrichthyans Pectoral fins Pelvic fins (a) Blacktip reef shark (Carcharhinus

melanopterus) (b) Southern stingray (Dasyatis americana) (c) Spotted ratfish (Hydrolagus colliei) Most sharks Have a streamlined body and are swift swimmers Are carnivores Have a short digestive tract; a ridge called the spiral valve increases the digestive surface area Have acute senses. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Shark eggs are fertilized internally but embryos can develop in different ways: Oviparous: eggs hatch outside the mothers body. Ovoviviparous: the embryo develops within the uterus and is nourished by the egg yolk. Viviparous: the embryo develops within the uterus and is nourished through a yolk sac placenta from the mothers blood. The reproductive tract, excretory system, and digestive tract empty into a common cloaca. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The vast majority of vertebrates belong to a clade of gnathostomes called Osteichthyes. Osteichthyes includes the bony fish and tetrapods.

They have a bony endoskeleton. Aquatic osteichthyans are the vertebrates we informally call fishes. Most fishes breathe by drawing water over gills protected by an operculum. Fishes control their buoyancy with an air sac known as a swim bladder. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Anatomy of a trout - bony fish - Osteichthyes Spinal cord Swim bladder

Dorsal fin Brain Adipose fin (characteristic of trout) Nostril Anal fin Cut edge of operculum Liver

Gills Heart Kidney Stomach Intestine Gonad Lateral line Anus Pelvic fin

Urinary bladder Caudal fin Derived Characters of Tetrapods Tetrapods have some specific adaptations: Four limbs, and feet with digits Ears for detecting airborne sounds. In one lineage of lobe-fins, the fins became progressively more limb-like while the rest of the body retained adaptations for aquatic life. For example, Acanthostega lived in Greenland 365 million years ago.

Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings A Devonian era relative of tetrapods Bones supporting gills Tetrapod limb skeleton Origin of Tetrapods Ray-finned fishes

Coelacanths Lungfishes Eusthenopteron Panderichthys Tiktaalik Elginerpeton Metaxygnathus Acanthostega Ichthyostega Hynerpeton Greerpeton Amphibians Amniotes PALEOZOIC Silurian

430 415 Devonian 400 Permian Carboniferous 385 370 355 340 325 310 Time (millions of years ago) 295

280 265 0 Amphibians Amphibians (class Amphibia) are represented by about 6,150 species of organisms in three orders. Amphibian means both ways of life, referring to the metamorphosis of an aquatic larva into a terrestrial adult. Most amphibians have moist skin that complements the lungs in gas exchange. Fertilization is external in most species, and the eggs

require a moist environment. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Amphibians (a) Order Urodela (b) Order Anura (c) Order Apoda The dual life of a frog (a) Tadpole (b) During

metamorphosis (c) Mating adults 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 mammals. Amniotes are named for the major derived character of the clade, the amniotic egg, which contains membranes that protect the embryo. The extraembryonic membranes are the amnion, chorion, yolk sac, and allantois. Amniotes have other terrestrial adaptations, such as relatively impermeable skin and the ability to use the

rib cage to ventilate the lungs. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The amniotic egg Chorion Amnion Allantois Yolk sac Embryo Amniotic cavity with amniotic

fluid Shell Yolk (nutrients) Albumen Reptiles - lay shelled eggs on land The reptile clade includes the tuataras, lizards, snakes, turtles, crocodilians, birds, and the extinct dinosaurs. Reptiles have scales that create a waterproof barrier. 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. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Hatching reptiles Dinosaurs diversified into a vast range of shapes and sizes. They included bipedal carnivores called theropods. Paleontologists have discovered signs of parental care among dinosaurs. Dinosaurs, with the exception of birds, became extinct by the end of the Cretaceous. Their extinction may have been partly caused by an asteroid.

Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Extant reptiles (other than birds). (a) Tuatara (Sphenodon punctatus) (b) Australian thorny devil lizard (Moloch horridus) (c) Waglers pit viper (Tropidolaemus wagleri)

(d) Eastern box turtle (Terrapene carolina carolina) (e) American alligator (Alligator mississippiensis) Birds - reptilian anatomy modified for Flight Derived Characters of Birds: Many characters of birds are adaptations that facilitate flight The major adaptation is wings with keratin feathers Other adaptations include lack of a urinary bladder, females with only one ovary, small gonads, and loss of teeth. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Form fits function: the avian wing and feather Finger 1 (b) Bone structure Palm Finger 2 (a) Wing Forearm Shaft Vane Finger 3 Wrist Shaft

Barb Barbule Hook (c) Feather structure Flight enhances hunting and scavenging, escape from terrestrial predators, and migration. Flight requires a great expenditure of energy, acute vision, and fine muscle control. Birds probably descended from small theropods, a group of carnivorous dinosaurs. By 150 million years ago, feathered theropods had evolved into birds. Archaeopteryx remains the oldest bird known. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Archaeopteryx, the earliest known bird Toothed beak Airfoil wing with contour feathers Wing claw Long tail with many vertebrae Diversity

among living birds (a) Emu - flightless (b) Mallards - web feet (c) Laysan albatrosses (d) Barn swallows Derived Characters of Mammals Mammals, class Mammalia, are represented by more than 5,300 species. Mammals have Mammary glands, which produce milk Hair

A larger brain than other vertebrates of equivalent size Differentiated teeth. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings evolution of the mammalian ear bones Key Articular Temporal fenestra Quadrate Dentary Squamosal

Jaw joint (a) In Biarmosuchus, an early synapsid, the articular and quadrate bones formed the jaw joint. Middle ear Stapes Eardrum Eardrum Inner ear Middle ear Inner ear Stapes

Sound Sound Incus (quadrate) Malleus (articular) Present-day reptile Present-day mammal (b) In mammals, the articular and quadrate bones are incorporated into the middle ear. By the early Cretaceous, the three living lineages of mammals emerged: monotremes,

marsupials, and eutherians. Monotremes are a small group of egg-laying mammals consisting of echidnas and the platypus. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings an Australian monotreme Marsupials Marsupials include opossums, kangaroos, and koalas. The embryo develops within a placenta in the mothers uterus. A marsupial is born very early in its development. It completes its embryonic

development while nursing in a maternal pouch called a marsupium. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Australian marsupials (a) A young brushtail possum (b) Long-nosed bandicoot Evolutionary convergence of marsupials and placental mammals Marsupial mammals Plantigale

Eutherian mammals Deer mouse Marsupial mole Marsupial mammals Wombat Woodchuck Mole Tasmanian devil

Sugar glider Eutherian mammals Wolverine Flying squirrel Kangaroo Patagonian cavy Eutherians - Placental Mammals Compared with marsupials, eutherians = placental mammals have a longer period of pregnancy.

Young complete their embryonic development within a uterus, joined to the mother by the placenta. Molecular and morphological data give conflicting dates on the diversification of eutherians. In Australia, convergent evolution has resulted in a diversity of marsupials that resemble the eutherians in other parts of the world. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Monotremata Marsupials (324 species) ANCESTRAL

MAMMAL Monotremes (5 species) Mammalian Diversity Marsupialia Eutherians (5,010 species) Proboscidea Sirenia Tubulidentata

Hyracoidea Afrosoricida (golden moles and tenrecs) Macroscelidea (elephant shrews) Xenarthra Rodentia Lagomorpha Primates Dermoptera (flying lemurs) Scandentia (tree shrews) Carnivora Cetartiodactyla Perissodactyla Chiroptera

Eulipotyphla Pholidota (pangolins) Mammalian diversity Primates The mammalian order Primates includes lemurs, tarsiers, monkeys, and apes. There are three main groups of living primates: Lemurs, lorises, and pottos Tarsiers Anthropoids (monkeys and apes) Humans are members of the ape group. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

Lemurs Derived Characters of Primates Most primates have hands and feet adapted for grasping. Other derived characters of primates: A large brain and short jaws Forward-looking eyes close together on the face, providing depth perception Complex social behavior and parental care A fully opposable thumb (in monkeys and apes). Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings A phylogenetic tree of primates

Lemurs, lorises, and pottos Tarsiers ANCESTRAL PRIMATE Old World monkeys Gibbons Orangutans Gorillas Chimpanzees and bonobos Humans 60

50 40 30 20 Time (millions of years ago) 10 0 Anthropoids

New World monkeys The first monkeys evolved in the Old World (Africa and Asia). In the New World (South America), monkeys first appeared roughly 25 million years ago. New World and Old World monkeys underwent separate adaptive radiations during their many millions of years of separation. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings New World monkeys and Old World monkeys (a) New World monkey

(b) Old World monkey Nonhuman apes (a) Gibbon (b) Orangutan (c) Gorilla (d) Chimpanzees (e) Bonobos Concept 34.8: Humans are mammals that have a large brain and bipedal locomotion The species Homo sapiens is about 200,000 years old, which is very young, considering that life has

existed on Earth for at least 3.5 billion years. The study of human origins is known as paleoanthropology. Hominins (formerly called hominids) are more closely related to humans than to chimpanzees. Paleoanthropologists have discovered fossils of about 20 species of extinct hominins. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Derived Characters of Humans A number of characters distinguish humans from other apes: Upright posture and bipedal locomotion Larger brains Language capabilities and symbolic thought

The manufacture and use of complex tools Shortened jaw Shorter digestive tract. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings A timeline for some selected hominin species 0 Paranthropus robustus Homo ergaster Paranthropus boisei

0.5 Homo Homo neanderthalensis sapiens ? 1.0 Australopithecus africanus Millions of years ago 1.5 2.0

2.5 Kenyanthropus platyops Australopithecus garhi Australo3.0 pithecus anamensis 3.5 Homo rudolfensis 4.0 4.5

5.0 Ardipithecus ramidus Australopithecus afarensis 5.5 6.0 6.5 7.0 Homo erectus

Orrorin tugenensis Sahelanthropus tchadensis Homo habilis Hominins originated in Africa about 67 million years ago Early hominins had a small brain but probably walked upright. Two common misconceptions about early hominins: Thinking of them as chimpanzees Imagining human evolution as a ladder leading directly to Homo sapiens.

Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Australopiths Australopiths are a paraphyletic assemblage of hominins living between 4 and 2 million years ago. Some species walked fully erect. Robust australopiths had sturdy skulls and powerful jaws. Gracile australopiths were more slender and had lighter jaws. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Upright posture predates an

enlarged brain in human evolution (a) Australopithecus afarensis skeleton (b) The Laetoli footprints (c) An artists reconstruction of what A. afarensis may have looked like Bipedalism & Tool Use Hominins began to walk long distances on two legs about 1.9 million years ago. The oldest evidence of tool use, cut marks on animal

bones, is 2.5 million years old. The earliest fossils placed in our genus Homo are those of 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. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Homo erectus originated in Africa by 1.8 million years ago It was the first hominin to leave Africa. Neanderthals, Homo neanderthalensis, lived in Europe and the Near East from 200,000 to 28,000 years ago.

They were thick-boned with a larger brain, they buried their dead, and they made hunting tools. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Homo Sapiens Homo sapiens appeared in Africa by 195,000 years ago. All living humans are descended from these African ancestors. The oldest fossils of Homo sapiens outside Africa date back about 115,000 years and are from the Middle East. Humans first arrived in the New World sometime before 15,000 years ago.

Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 160,000-year-old fossil of Homo sapiens Rapid expansion of our species may have been preceded by changes to the brain that made cognitive innovations possible. For example, the FOXP2 gene is essential for human language, and underwent intense natural selection during the last 200,000 years. Homo sapiens were the first group to show evidence of symbolic and sophisticated thought. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

You should now be able to: 1. List the derived traits for: chordates, craniates, vertebrates, gnathostomes, tetrapods, amniotes, birds, mammals, primates, humans. 2. Describe the trends in mineralized structures in early vertebrates. 3. Describe and distinguish between Chondrichthyes and Osteichthyes. 4. Describe an amniotic egg and explain its significance in the evolution of reptiles and mammals. 5. Explain why the reptile clade includes birds. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 6. Distinguish among monotreme, marsupial, and eutherian mammals. 7. Define the term hominin.

8. Describe the evolution of Homo sapiens from australopith ancestors, and clarify the order in which distinctive human traits arose. 9. Explain the significance of the FOXP2 gene. Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

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