Vertebrates

Chapter 34

Chordates

Bilateral symmetryNotochordJointed appendagesSegmentationBirds, reptiles, amphibians, fishes, & mammals

Chordates

Common features of chordatesPresent at some point in development1. Nerve cordHollowEctodermBeneath dorsal surfaceVertebrates (brain & spinal cord)

Chordates

2. NotochordDorsal side of primitive gut in embryoFluid filled cellsEnclosed in stiff fibrous tissuePersists in someSupportReduced to vertebral discs in others

Chordates

3. Pharyngeal slits: Connect pharynx & esophagus to outsideGills stay connect to outsidePharyngeal pouches:Slits do not connect to outsideTerrestrial vertebratesPresent in embryos4. Postanal tailAt least during embryo development

Chordates

HumansNerve cord staysNotochord is replaced by spinal column (discs)Pharyngeal pouches are lost Except one forms Eustachian tubeTail regresses tail bone

Chordates

Other featuresMuscles arranged in segmented blocksWork against internal skeletonHelps movement

Chordates

Phylum Chordata includes three subphyla, Vertebrates Two phyla of invertebratesUrochordates

Cephalochordates.

Fig. 34-2

Lobed fins

Legs

Amniotic egg

Milk

Jaws, mineralized skeleton

Lungs or lung derivatives

Vertebral column

Head

Notochord

Commonancestor ofchordates

ANCESTRALDEUTERO-STOME

Echinodermata(sister group to chordates)

Chondrichthyes(sharks, rays, chimaeras)

Cephalochordata(lancelets)

Urochordata(tunicates)

Myxini(hagfishes)

Petromyzontida(lampreys)

Mammalia(mammals)

Actinopterygii(ray-finned fishes)

Actinistia(coelacanths)

Amphibia (frogs,salamanders)

Dipnoi(lungfishes)

Reptilia(turtles, snakes,crocodiles, birds)

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Chordates

NonvertebratesNotocord but no backboneTunicates (urochordates)Marine, shallow watersSessileAdults no cavity or segmentationTadpole shows characteristics Tunic: sac of cellulose secreted by adultsSurrounds the animal

Chordates

Lancelets (cephalochordata)Shallow waters in oceanBuried in sand Anterior end sticking outPlanktonGill slitsClosest relative to vertebrate

Fig. 34.4

(b)(a)

Vertebrates

1. Vertebral column2. HeadBrain is enclosed in a bony skull or cranium Craniate chordates

Vertebrates

Other characteristics1. Neural crestCells that develop on crest of neural tube Form other structures (teeth, neurons, dermis)2. Internal organsLiver, kidney, endocrine glands3. EndoskeletonCartilage & bone helps with movement

Neural crest

Fig. 34-7

Migrating neuralcrest cellsNotochord

Dorsal edgesof neural plate

Neuralcrest

Neuraltube

Neural crest

Vertebrates

470 myaJawless fishJaw developedGave rise to Amphibians Were first vertebrate moved to landFirst reptiles 300 myaBirds (descendants of dinosaurs)Mammals 220 mya

Vertebrates

65 mya dinosaurs disappeared Gave rise to larger mammalsNine classes of vertebrae5 fish (2 are extinct)4 tetrapods (animals with 4 limbs)Amphibians, reptiles, birds, mammals

Fish

Marine & freshwater1. Vertebral column2. Jaws & paired appendagesHelps eat larger & active preyPaired fins help with swim

Fish

3. GillsExtract oxygen dissolved in waterVessels rich in bloodSupported by cartilage4. Single-loop blood circulationBlood pumped from heart to gillsOxygenated blood to body Returns to heart

Fish evolution

First fish jawless Internal skeleton made of cartilageSucked up small food particlesHagfish: Present day jawless fish

Fig. 34-10

Fish

Jaw 410 myaCartilage, supported gillsTeeth evolvedSpiny fish with scales had boneNo longer exist Bony & sharks developed nextSharks dominated for awhile

Fish

Skeleton cartilage with calcium carbonate Lighter skeletonShark teeth first to be developed Not firmly attached so fall out easilyReproduction advanced with internal fertilization Most females give birth to pups

Fish

Bony fishCartilage is replaced by bone OssificationEarly fish evolved in freshwater unlike sharkFirst bony fish were smallFins of thin scalesSymmetrical tails

Fish

Bony fish most dominant Swim bladderGas filled sac-keeps them floatingSharks have to keep moving or they sinkLateral line systemHelps fish detect movement of objectsHelps orient the fishGill cover

Fig. 34-16

Intestine

Adipose fin(characteristicof trout)

Cut edgeof operculum

Swimbladder Caudal

fin

Lateralline

UrinarybladderPelvic

fin

Anus

Dorsal finSpinal cord

Brain

Nostril

Gills

Kidney

Heart

Liver

Gonad

Anal fin

Stomach

Fig. 34-18

Fig. 34-19

Tetrapodlimbskeleton

Bonessupportinggills

Amphibians

First vertebrae to walk on landDescendants of fishSmallMore species than mammalsFrogs, salamanders & caccileansKey role in terrestrial food chains

Amphibians

Characteristics1. Legs4 legs helps movement (tetrapods)2. Cutaneous respirationRespiration occurs across their skinMoist skin3. LungsPair of lungs, poorly developedLower mouth-suck in air

Amphibians

4. Pulmonary veinsReturn aerated blood to heartRe-pumps to body5. Partially divided heartTwo chambers separatedPrevents un-aerated/aerated blood mixing

Amphibian evolution

Amphibia Greek “both lives”Evolved from lobe-finned fishAdaptations due to movement on land1. Legs2. Lungs3. Heart4. Reproduction5. Keep body from drying out

Amphibians

370 mya in GreenlandPresent day 3 ordersAnura Frogs & toadsFrogs smooth, moist skin, long hind legs Live in or near waterToads dry skin, short legsReproduce in water (tadpoles)Eggs fertilized externally

Amphibians

Urodela (Caudata)SalamandersLong tails, moist skinFertilization external, eggs in waterApodaTropical burrowing amphibiansResemble worms

Fig. 34-23

Reptiles

Reptiles

Characteristics1. Amniotic egg (Amniotes)Chorion: outer layer of eggBelow shell (gas exchange)Amnion: encases the embryo (cushions)Yolk sac: supplies food (blood supply)Allantois: surrounds a cavity in which wastes from the embryo goes

Fig. 34-26

Reptiles

2. Dry skinWatertight skinScales3. Thoracic breathingExpand & contract rib cagePulls air into lungs

Reptiles

Evolution 4 major groups of reptiles dominated for 250 million yearsDinosaursPresent day reptilesTurtles, lizards, snakes, & crocodiles

Fig. 34-27d

(d) Eastern box turtle (Terrapene carolina carolina)

Reptiles

Other characteristicsInternal fertilization4 chambered heartEctothermic: Body temperature determined by environmentRegulate temperature by behavior

Birds

Fig. 34-29

Airfoil wingwith contourfeathers

Toothed beak Wing claw

Long tail withmany vertebrae

Birds

Birds successful due to structure of the featherDerived from reptilian scalesBones are thinHollow

Birds

Bird’s anatomy modified to enhance flight.Reduce weightMissing of some organs.Females-only one ovary. Modern birds-toothless Grind food in a muscular gizzard Near stomach.

Birds

Descended from dinosaursAdaptations1. Efficient respiration2. Efficient circulation3. Endothermy Generate heat internally4. Amniotic egg

Mammals

Mammals

5300 living speciesSmallest # of species of vertebraeCharacteristics1. Mammary glandsNewborns nurseMilk is rich in fat, sugar, protein, vitamins & minerals

Mammals

2. HairConsists of proteinSensitive to touch (cat)Avoid colliding with objects3. EndothermyFat layer under skin4. PlacentaCarry & nourish babies

Mammals

5. TeethVariety of teeth to match diet6. Middle ear

Fig. 34-31

(b) In mammals, the articular and quadrate bones are incorporated into the middle ear.

(a) In Biarmosuchus, an early synapsid, the articular and quadrate bones formed the jaw joint.

Middle ear

Temporalfenestra

Jaw joint

Eardrum

Present-day reptile Present-day mammal

Malleus (articular)

Incus (quadrate)Sound

Stapes

Inner ear

Eardrum Middle ear

Sound

Inner earStapes

Key

Quadrate

Articular

Squamosal

Dentary

Mammals

1. Egg-layingMonotremes: duck-billed platypusFound in Australia2. Marsupials3. Placental mammals

Marsupials