Chapter 29 presentation

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Chapter 29Vertebrates

Figure 29.1

• Examples of critically endangered vertebrate species include (a) the Siberian tiger (Panthera tigris), (b) the mountain gorilla (Gorilla beringei), and (c) the Philippine eagle (Pithecophega jefferyi). (credit a: modification of work by Dave Pape; credit b: modification of work by Dave Proffer; credit c: modification of work by “cuatrok77”/Flickr)

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Phylum Chordata• Chordates are deuterostome coelomates• Nearest relatives are echinoderms (the only other

deuterostomes)• Fishes, amphibians, reptiles, birds, and mammals

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Protostomes

SpiraliaEcdysozoa

Platyzoa Lophotrochozoa

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Deuter-ostomes

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4 Features

1. Dorsal nerve cord (not ventral like other animal phyla)

2. Notochord3. Pharyngeal slits4. Postanal tail


Hollow dorsal nerve cord

Pharyngeal pouches

Notochord

Postanal tail

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• All chordates have all four of these characteristics at some time in their lives

• Other characteristics also distinguish chordates

• Chordate muscles are arranged in segmented blocks called somites

• Most chordates have an internal skeleton against which the muscles work


500 µm© Eric N. Olson, Ph.D./The University of Texas MD Anderson Cancer Center

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Nonvertebrate Chordates

• Lancelets are scaleless chordates• Notochord persists throughout animal’s life• Spend most of their time partly buried• Have no distinguishable head• Feed on plankton using cilia-generated currents• Closest relatives to vertebrates

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Oral hood with tentacles

Notochord

Dorsal nerve cord

Muscle blocks

Postanal tail

Pharynx

Pharyngeal slits

IntestineAnus

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History of the Fishes

• The first fishes had mouths with no jaws • “Agnathans” are “jawless fish”• Includes lampreys and hagfish

• Jawed fishes soon became dominant• “Gnathostomes”

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lampreys cartilaginous fish

ray-finned fish

lobe-finned fish

Amphibia(amphibians)

Mammalia(mammals)

Mammary glands, hair, synapsid skull

Legs with digitsLobed finsInternal bony skeleton

Rayed fins

JawsVertebral column

Cranium

hagfish birds

Feathers

DiapsidskullAmniotic egg

Reptilia

turtles snakes crocodiles

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Subphylum Vertebrata• Vertebrates are chordates with a spinal column• Vertebrates make up only about 5% of the animal kingdom• Distinguished from non-vertebrates by

• Vertebral column which encloses and protects the dorsal nerve cord• Head with cranium and sensory organs

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Fishes• Most diverse vertebrate group• Over half of all vertebrates are fish• Provided the evolutionary base for invasion of land by amphibians

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• Fishes have the following characteristics1. Vertebral column

• Hagfish do not2. Jaws and paired appendages

• Hagfish and lamprey do not3. Internal gills4. Single-loop blood circulation5. Nutritional deficiencies

• Cannot synthesize the amino acids phenylalanine, tryptophan, or tyrosine

• This inability has been inherited by all their descendants (including humans!)

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Evolution of the JawCopyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Anterior gill arch

Gill slit

Skull

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Class Chondrichthyes

• The “cartilaginous fish”• Sharks, skates, rays• Cartilage skeleton “calcified” with granules of calcium

carbonate• Light, strong skeleton


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• Sharks were among the first vertebrates to develop teeth

• Evolved from rough scales on mouth’s skin• Easily lost but continuously replaced

• Sharks (and bony fishes) have a fully developed lateral line system

• Series of sensory organs under the skin that detects changes in pressure waves

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Bony fishes

• Evolved at the same time as sharks about 400 MYA• However, they adopted a heavy internal skeleton made

completely of bone

• Bony fishes are the most species-rich group of all vertebrates (> 30,000 living species)

• Significant adaptations include swim bladder and gill cover


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• Gases are taken from the blood, and the gas gland secretes the gases into the swim bladder; gas is released from the bladder by a muscular valve, the “oval body”


Dorsal aorta

To heart

Swim bladder

Gills

Gill cover(operculum)

Gas gland

Oval body

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Two Major Groups of Bony Fishes• Ray-finned fishes (class Actinopterygii)

• Parallel bony rays support and stiffen each fin• There are no muscles within the fins

• Lobe-finned fishes (class Sarcopterygii)• Have paired fins that consist of a long fleshy muscular lobe• Supported by central core of bones with fully articulated joints• Almost certainly the ancestors of ambhibians

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Rays

a.

Shouldergirdle

Ray-finned (class Actinopterygii)

a:© Federico Cabello/SuperStock; b: © Raymond Tercafs/Bruce Coleman Inc./Photoshot

Rays

b.

Shouldergirdle

Lobe-finned (class Sarcopterygii)

Central core ofbones in fleshylobe

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Class Amphibia• First vertebrates to walk on land • Direct descendants of fishes


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Ichthyostega

• Amphibians evolved from lobe-finned fish• Ichthyostega was one of the first amphibians• Sturdy forelegs, flipper-shaped hindlimbs

• Moved like a seal

• Long, broad, overlapping ribs form solid cage for lungs and heart

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Tiktaalik• In 2006, a transitional fossil was found

that connects the evolution between fish and Ichthyostega

• Had gills and scales like a fish, but a neck like an amphibian

• Shoulder, forearm, and wrist bones were like those of amphibians, but at the end of the limb was a lobed fin, rather than the toes of an amphibian

• Sometimes called a “fishapod”

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Lobe-finned Fish

Tibia

Femur

Pelvis

Fibula

Humerus

Shoulder

Radius

Ulna

a.

Tibia

FemurPelvis

Fibula

Humerus

Shoulder

Radius

c.

Early Amphibian

Ulna

Humerus

Shoulder

RadiusUlna

b.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.


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5 features that distinguish amphibians from fish:1. Legs2. Lungs3. Cutaneous respiration – gas exchange across moist skin4. Pulmonary veins – establishes a “pulmonary circuit”5. Partially divided heart – improves separation of

pulmonary and systemic circuits

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3 Modern Amphibian groups

• Frogs, toads, salamanders, caecilians• Must lay eggs in water


b.a. c.

Order Anura Order Caudata Order Apoda

a: © Digital Vision/Getty Images RF; b: © Suzanne L. Collins & Joseph T. Collins/Photo Researchers, Inc.; c: © Jany Sauvanet/Photo Researchers, Inc.

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• Reptiles, birds, and mammals are amniotes• The amniotic egg has four membranes

• Chorion• Outermost layer, allows gas exchange

• Amnion• Encases embryo in fluid-filled cavity

• Yolk sac• Provides food

• Allantois • Contains excreted wastes from embryo

Amniotes

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Leathery shell Embryo Amnion

Chorion Yolk sac Allantois

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Class Reptilia

• All living reptiles exhibit three key features1. Amniotic eggs, which are watertight 2. Dry skin, which covers body and prevents water loss3. Thoracic breathing, which increases lung capacity


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• Reptiles dominated earth for 250 million years• Reptiles are distinguished by the number of holes on

side of the skull behind eye orbit• 0 (anapsids), 1 (synapsids), 2 (diapsids)


Anapsid Skull Synapsid SkullOrbit

Orbit

Lateral temporalopening

Diapsid Skull

Orbit

Lateral temporalopening

Dorsal temporalopening

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Most Reptiles

Lung capillaries

Fish

Gill capillaries

Right atrium

Ventricle

Atrium

Other capillaries Other capillaries

a. b.

2 atria and 2 ventricles delivers oxygenated blood to the systemic circuit with higher pressure

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• Turtles, tortoises, tuataras, lizards, snakes, crocodiles, and alligators

• Most living reptiles are ectothermic• Regulate body temperature by moving in and out of

sunlight

• Reptiles occur worldwide except in the coldest regions, where it is impossible for ectotherms to survive

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Class Aves• Birds are the most diverse of all terrestrial vertebrates

• 28 orders, 166 families, about 8,600 species

• Success lies in unique structure – feather

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• Birds still retain many reptilian traits• Amniotic eggs and scales on legs• Lack teeth and tails of reptiles

• Two major distinguishing traits• Feathers

• Modified scales of keratin• Provide lift for flight and conserve heat

• Flight anatomy and physiology• Bones are thin and hollow• Many are fused for rigidity – anchor strong flight muscles

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• Feathers developed from reptile scales• Linked structures provide continuous surface and a

sturdy but flexible shape

Shaft

Quill

Barbule

Hooks

Barb


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• Archaeopteryx is the first known bird• Had skull with teeth, long reptilian tail• Feathers on wings and tail

• Feather probably evolved for insulation

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• Most paleontologists agree that birds are the direct descendants of theropod dinosaurs


Sinosauropteryx Velociraptor Caudipteryx Archaeopteryx Modern Birds

This theropod dinosaur had short arms and ran along the ground. Its body was covered with filaments that may have been used for insulation and that are the first evidence of feathers.

Recently discovered fossils of this theropod indicate that it is intermediate between dinosaurs and birds. This small, very fast runner was covered with primitive (symmetrical and therefore flightless) feathers.

This oldest known bird had asymmetrical feathers, with a narrower leading edge and streamlined trailing edge. It could probably fly short distances.

Birds

Dinosaurs

This larger, carni- vorous theropod possessed a swiveling wrist bone, a type of joint that is also found in birds and is necessary for flight.

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• Physiological adaptations for flight1. Efficient respiration

• Air passes all the way through lungs in a single direction

2. Efficient circulation• 4-chambered heart so muscles receive fully

oxygenated blood• Rapid heartbeat

3. Endothermy• Body temperature (40–42oC) permits higher

metabolic rate

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Class Mammalia• There are about 4,500 species of mammals

• 3,200 species are either rodents, bats, shrews, or moles


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• 2 fundamentally mammalian traits1. Hair

• Structure: Long, keratin-rich filaments that extend from hair follicles

• Function: Insulation, camouflage, sensory structure2. Mammary glands

• Females possess mammary glands that secrete milk

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• Other notable features of mammals• Endothermy depends on higher metabolic rate

• 4-chambered heart• Respiration using diaphragm

• Placenta in most mammals• Specialized organ that brings fetal and maternal blood into close

contact

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Uterus

Chorion

Umbilicalcord

PlacentaYolk sac

Amnion

Fetus

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• The mammalian lineage also gave rise to several adaptations in some groups

1. Specialized teeth • Different types of teeth are highly specialized to match

particular eating habits• Contrast carnivore teeth to herbivore teeth

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Dog

Deer Beaver

Elephant Human

Grinding teeth

Ripping teeth

Chiseling teeth

Incisors Canine Premolars and molars

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2. Digestion of plants • Herbivorous mammals rely on mutualistic partnerships

with bacteria for cellulose breakdown

3. Development of hooves and horns• Hooves are specialized keratin pads • Horns are bone surrounded by keratin• Antlers are made of bone, not keratin

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4. Flying mammals: Bats • Only mammals capable of powered flight• Wing is a leathery membrane of skin and muscle stretched

over 4 finger bones• Navigate in the dark by echolocation

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History of Mammals• Mammals have been around since the time of the

dinosaurs, about 220 mya• Tiny, shrewlike, insect-eating, tree-dwelling creatures• May have been nocturnal – large eye sockets

• Mammals reached their maximum diversity after the mass extinction of dinosaurs (65 mya)

• There has been a decline in the total number of mammalian species over last 15 million years

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Monotremes• Lay shelled eggs• Lack well-developed nipples• Only three living species

• Duck-billed platypus• 2 echidna species

a.


(top): © Dave Watts/Alamy; (bottom): © B.J Alcock/Visuals Unlimited

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Marsupials• Major difference is pattern of embryonic

development• Short-lived placenta• After birth, it crawls into marsupial pouch,

latches onto nipple, and continues to develop

• Kangaroo – Australia• Opossum – the only North American

marsupial

b.


(top): © W. Perry Conway/Corbis; (bottom): © Volume 6/Corbis RF

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Placental Mammals• Produce a true placenta that nourishes

embryo throughout its development• Forms from both fetal and maternal

tissues• Young undergo a considerable period of

development before they are born

• Includes most living mammals

c.


© Juergen & Christine Sohns/Animals Animals - Earth Scenes

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Evolution of Primates• Primates are the mammals that gave rise to our own species• Evolved two features that allowed them to succeed in an arboreal

environment1. Grasping fingers and toes

• First digit (thumb) is opposable in many2. Binocular vision

• Eyes are shifted toward the front of the face• Lets brain judge distances precisely

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• About 40 MYA, the earliest primates split into two groups

1. Prosimians• Only a few survive today• Lemurs, lorises and tarsiers• Large eyes with increased visual

acuity• Most are nocturnal

2. Anthropoids

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• Anthropoids• Include monkeys, apes, and humans• Expanded brain• Live in groups with complex social interactions

• Care for young for extended period• Long period of learning and brain development

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• 30 MYA• New World monkeys migrated to South America

• All arboreal; many have prehensile tail• Old World monkeys and hominoids remained in Africa

• No prehensile tails


New World Monkeys Old World Monkeys Hominoids

a. b. c.a: © J & C Sohns/agefotostock; b: © PhotoDisc/Getty Images RF; c (left): © Dynamic Graphics Group/IT Stock Free/Alamy RF; c (right): © Joe McDonald/Visuals Unlimited

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• Hominoids include• Apes

• Apes are not monkeys!• Gibbon, orangutan, gorilla, and chimpanzee• Larger brains than monkeys and lack tails

• Hominids• Humans • Soon after the gorilla lineage diverged, the common ancestor of all

hominids split off from the chimpanzee line to begin the evolutionary journey leading to humans

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Lem

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Anthropoids

Hominoids

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Tars

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Prosimians

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Apes vs. Hominids• The common ancestor of apes and hominids is thought to have been

an arboreal climber• Hominids became bipedal, walking upright• Apes evolved knuckle-walking

• Differences related to bipedal locomotion• Human vertebral column is more curved• Spinal cord exits from bottom of skull• Humans carry much of the body’s weight on the lower limbs

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77.5 6.5 6 5.5 5 1.54.5 14 0.5 03.5 23 2.5Millions of Years Ago (MYA)

Homo sapiens sapiens

Homo floresiensis

Homo erectus

Homo habilis

Australopithecus africanus

Australopithecus afarensis

Australopithecus robustus

Ardipithecus ramidus Australopithecus boisei

Australopithecus anamensis

Sahelanthropus tchadensis

Homo ergaster

Homo heidelbergensis

Homo neanderthalensisHomo habilis Homo floresiensisAustralopithecus

afarensisAustralopithecus

robustusHomo sapiens

sapiens

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Genus Australopithecus• Our knowledge is based on hundreds of fossils found in Africa

• Characteristics• Weighed about 18 kg• About 1 m tall• Hominid dentition• Brains no larger than those of apes• Walked upright

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Modern Humans – Genus Homo

• Modern humans first appeared in Africa about 600,000 years ago• Three species are thought to have evolved

• Homo heidelbergensis (oldest)• Coexisted with H. erectus

• Homo neanderthalensis• Shorter and stockier than modern humans

• Homo sapiens (“wise man”)

• Some lump all 3 into H. sapiens

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Homo sapiens• Only surviving hominid• Progressive increase in brain size

• Effective making and use of tools• Refined and extended conceptual thought• Use of symbolic language

• Extensive cultural experience• We change and mold our world rather than change

evolutionarily in response to the environment• We record history

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• Groupings based on overall genetic similarity are different from those based on skin color or other visual features


Genetic Similarity Skin Pigmentation

a. b.

Education

Chapter 29 presentation