Chapters 41– 45 Modern Biology

Chapters 41– 45 Modern Biology
Vertebrates

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

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

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

Vertebrates are a subphylum of the phylum Chordata
Not ALL chordates are vertebrates! Two groups of chordates, the urochordates and cephalochordates, never develop a hard internal skeleton (invertebrate)

Ancestral deuterostome
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

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

In most vertebrates, a more complex, jointed skeleton develops
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

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

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

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

Tunicates, subphylum Urochordata
Belong to the deepest-branching lineage of chordates Are marine suspension feeders commonly called sea squirts (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 Purple tunicate colony

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. Figure 34.4c

Lancelets, subphylum Cephalochordata
Known as lancelets, or amphioxus, (from the Greek for "both [ends] pointed"), they are small, eel-like, animals that spend much of their time buried in sand. In Asia, they are harvested commercially for food that is eaten by both humans and domesticated animals. Tentacle Mouth Pharyngeal slits Atrium Digestive tract Atriopore Segmental muscles Anus Notochord Dorsal, hollow nerve cord Tail 2 cm Figure 34.5

Tunicates and lancelets are marine suspension feeders
They retain the characteristics of the chordate body plan as adults Never really develop an endoskeleton True vertebrates did not come along until later Subphylum Vertebrata Classes: Agnatha – the jawless fish Chondrichthyes – the cartilaginous, jawed fish Osteichthyes – bony fish Amphibia Reptilia Aves Mammalia

During the Cambrian explosion, 530 million years ago
A skull, brain, eyes, and other sensory organs evolved 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 Vertebrates have an endoskeleton: Vertebrae enclosing a spinal cord An elaborate skull Cartilage and/or bone

Agnatha The least advanced vertebrate lineage that still survives
There are two groups of jawless fish (sometimes called cyclostomes), the lampreys and the hagfish, with about 100 species between them. In addition to the absence of jaws, Agnatha are characterized by absence of paired fins; the presence of a notochord both in larvae and adults; and seven or more paired gill pouches. Figure 34.9 Slime glands

Lampreys are jawless vertebrates
Inhabiting various marine and freshwater habitats Parasitize other fish Figure 34.10

The largest and most diverse subclass
Class Chondrichthyes The largest and most diverse subclass 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.

Chondrichthyans (Sharks, Rays, and Their Relatives)
Members of class Chondrichthyes Have a skeleton that is composed primarily of cartilage Jaws, with teeth

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.

Most sharks Have a streamlined body and are swift swimmers
Have acute senses Mako Nurse shark Hammerhead Whale shark – the largest fish in the sea

Ray-Finned Fishes and Lobe-Fins
The vast majority of vertebrates Belong to a group called Osteichthyes Are the vertebrates we informally call fishes Nearly all living osteichthyans Have a bony endoskeleton Jaws, teeth, flat overlapping scales Control their buoyancy with an air sac known as a swim bladder

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

Includes nearly all the familiar aquatic osteichthyans
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

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

Lobe-Fins Have muscular pelvic and pectoral fins
Include coelacanths, lungfishes, and tetrapods Figure 34.18

Evolution: Lungfish Modern lungfish in Africa, South America, and Australia are able to survive when their pools dry up by burrowing into the mud and sealing themselves within a mucous-lined burrow. During this time, they breathe air through their swim bladder instead of through their gills, and reduce their metabolic rate dramatically.

Evolution: “Walking” fish
Mudskippers: By using their highly modified pectoral (swimming) fins much like legs. And by flipping their bodies, they can "skip" across the mud (and water), which is a great way to avoid predators. They are poor swimmers, and will also use these fins to walk underwater Northern Snakehead: can breathe air, live outside of water for several days, where it might wriggle its way to other bodies of water. Considered invasive in places.

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

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

Amphibians Class Amphibia Most amphibians
Is represented by about 4,800 species of organisms Most amphibians Have moist, thin skin that complements the lungs in gas exchange Must lay eggs in water Young are very fish-like

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.

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

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

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

Evolution: More complete land-dwellers
“Amniotes” include reptiles, birds, and the mammals Requires a terrestrially adapted egg contains specialized membranes that protect the embryo Amniotes also have other terrestrial adaptations Such as relatively impermeable skin and the ability to use the rib cage to ventilate the lungs

Ornithischian dinosaurs
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

Extraembryonic membranes
The Amniote Egg 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

The reptile group includes
Reptiles The reptile group includes The tuatara, lizards, snakes, turtles, crocodilians, birds, and the extinct dinosaurs

Early Amniotes: the dinosaurs
The oldest reptilian fossils Date to about 300 million years ago Included large herbivores and eventually carnivorous predators Their ability to spend all their lives on land quickly led to their domination

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

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

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

lizards and snakes are lepidosaurs Lizards
Order Squamata lizards and snakes are lepidosaurs Lizards Are the most numerous and diverse reptiles, apart from birds Figure 34.27b (b) Australian thorny devil lizard (Moloch horridus)

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

Some turtles have adapted to deserts
Order Chelonia Turtles Are the most distinctive group of reptiles alive today Some turtles have adapted to deserts And others live entirely in ponds and rivers All turtles have a boxlike shell Made of upper and lower shields that are fused to the vertebrae, clavicles, and ribs

(d) Eastern box turtle (Terrapene carolina carolina)
Tortoises are generally turtles with high domed shells and elephantine legs. Totally terrestrial, they do not swim well and are likely to drown in deep water. Turtles are usually marine, with generally flattened, leathery, circular shells and flipper-feet for swimming. Some water turtles never leave that element. Terrapins are generally water turtles that frequent swampy areas and estuaries. Webbing between their toes, and spending time basking on land are characteristic. Figure 34.27d (d) Eastern box turtle (Terrapene carolina carolina)

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

The alligator’s head is somewhat broadened at the snout.
The crocodile’s head tends to run to a very narrow breadth from the eyes to the nostrils and the general color throughout the body and head is grayish. The crocodile is the only one of the three that is found mainly in salt water. The alligator’s head is somewhat broadened at the snout. The head of the caiman is more like that of the alligator but is not so broad. Alligators and caimans are greenish-black in general coloration. American alligator Nile crocodile caimen

Class Aves Birds probably descended from theropods, a group of small, carnivorous dinosaurs But almost every feature of their reptilian anatomy has undergone modification in their adaptation to flight 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

A bird’s most obvious adaptations for flight
Are its wings and feathers Also many hollow or fused bones Extra air sacs in lungs for breathing at altitude Figure 34.28a–c (a) wing (b) Bone structure Finger 1 (c) Feather structure Shaft Barb Barbule Hook Vane Forearm Wrist Palm Finger 3 Finger 2

Flightless Birds: “reverse evolution”?
On every continent Wings are reduced in size evolved in the absence of predators, on islands, and lost the power of flight because they had few enemies Or have claws on their feet/wings to use as a weapon against predators. Ostrich - Africa Penguin - Antarctica Rhea – S. America Emu. This ratite lives in Australia. Figure 34.30a

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.

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)

Mammals, class Mammalia
Are represented by more than 5,000 species 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

Living lineages of mammals originated in the Jurassic
most early mammals remained small and shrew-like throughout the Mesozoic Rapidly developed into larger more diverse forms following the Cretaceous-Tertiary extinction event 65 million years ago. What happened?

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

Marsupials Include opossums, kangaroos, and koalas

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).

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.

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

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

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.

The major eutherian orders (placental mammals)
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 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 Koala

The mammalian order Primates include
Lemurs, tarsiers, monkeys, and apes Humans are members of the ape group The Primates order is divided informally into three main groupings: prosimians, monkeys of the New World, and monkeys and apes of the Old World. The prosimians are species whose bodies most closely resemble that of the early proto-primates.

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

The most primitive group
Prosimians The most primitive group The lemurs of Madagascar and the lorises and pottos of tropical Africa and southern Asia Figure 34.37 The tarsiers of Southeast Asia

The fossil record indicates that monkeys
Anthropoid apes include monkeys and hominids worldwide 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)

Lemurs, lorises, and pottos
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 This is supported by DNA evidence

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.

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.

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

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 The study of human origins Is known as paleoanthropology

Chapters 41– 45 Modern Biology

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