animals: the vertebrates chapter 26. something old, something new every animal is a combination of...
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Something Old, Something Old, Something NewSomething New
Every animal is a combination of Every animal is a combination of traitstraits
Some traits are conserved from Some traits are conserved from remote ancestors remote ancestors
Other traits are unique to its branch Other traits are unique to its branch of the family treeof the family tree
Chordate FeaturesChordate Features
Deuterostomes Deuterostomes
All share four features:All share four features:
– Notochord supports bodyNotochord supports body
– Nervous system develops from dorsal Nervous system develops from dorsal nerve cordnerve cord
– Embryos have pharynx with slitsEmbryos have pharynx with slits
– Embryos have tail that extends past Embryos have tail that extends past anusanus
Chordate GroupsChordate Groups
Urochordata Urochordata
– Salps and tunicatesSalps and tunicates
Cephalochordata Cephalochordata
– Lancelets Lancelets
CraniatesCraniates
– Fishes, amphibians, reptiles, birds, Fishes, amphibians, reptiles, birds,
mammalsmammals
Tunicates (Urochordates)Tunicates (Urochordates) Larva is free-swimming Larva is free-swimming Adult is sessile and baglike with no coelomAdult is sessile and baglike with no coelom Both stages are filter feedersBoth stages are filter feeders Pharynx serves in both feeding and Pharynx serves in both feeding and
respirationrespiration
Tunicate Life Tunicate Life HistoryHistory
Larva Larva undergoes undergoes metamorphosimetamorphosis to adult forms to adult form
nerve cord notochord
gutTunicate larva
oral opening
atrial opening
pharynx with gill slits
Tunicate adult
pharynx
Figure 26.3Page 446
Lancelets Lancelets (Cephalochordates)(Cephalochordates)
Fish-shaped filter feedersFish-shaped filter feeders Simple brainSimple brain Segmented muscles Segmented muscles Chordate characteristics of adult:Chordate characteristics of adult:
– Notochord lies under dorsal nerve cordNotochord lies under dorsal nerve cord– Pharynx has gill slitsPharynx has gill slits– Tail extends past anusTail extends past anus
Lancelet Body PlanLancelet Body Plan
dorsal, tubular nerve cord
notochord
pharynx with gill slits tail extending past anus
anuspore of atrial cavity
hindgut
gonadaorta
midgut
segmented muscles
tentaclelike structures
around mouth
Figure Figure 26.4a26.4a
Page 447Page 447
Early CraniatesEarly Craniates
Reconstruction of one of the earliest known craniates
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• Brain inside Brain inside chamber of chamber of cartilage or bonecartilage or bone
• Arose before 530 Arose before 530 million years agomillion years ago
• Resemble Resemble lancelets, lamprey lancelets, lamprey larvalarva
Figure 26.4Page 447
Trends in the Evolution Trends in the Evolution of Vertebratesof Vertebrates
Shift from notochord to vertebral columnShift from notochord to vertebral column
Nerve cord expanded into brainNerve cord expanded into brain
Evolution of jawsEvolution of jaws
Paired fins evolved, gave rise to limbsPaired fins evolved, gave rise to limbs
Gills evolved, gave rise to lungsGills evolved, gave rise to lungs
Evolution of Evolution of JawsJaws
First fishes First fishes
lacked jaws lacked jaws
Jaws are Jaws are
modifications of modifications of
anterior gill anterior gill
supportssupportsFigure 26.5Page 448
supporting structures
gill slit
jaw
spiracle jaw support
jaw
Early jawless
fish(agnathan)
Early jawed fish
(placoderm)
Modern jawed fish
(shark)
Existing Jawless FishesExisting Jawless Fishes
Cylindrical bodyCylindrical body
Cartilaginous Cartilaginous
skeletonskeleton
No paired finsNo paired fins
gill openings (seven pairs)Lamprey
Hagfish
tentacles gill slits (twelve pairs) mucous glands
Jawed FishesJawed Fishes
Most diverse and numerous group Most diverse and numerous group
of vertebratesof vertebrates
Two classes:Two classes:
– Chondrichthyes (cartilaginous fishes)Chondrichthyes (cartilaginous fishes)
– Osteichthyes (bony fishes)Osteichthyes (bony fishes)
Cartilaginous Fishes: Cartilaginous Fishes: Class ChondrichthyesClass Chondrichthyes Most are marine Most are marine
predatorspredators
Cartilaginous skeletonCartilaginous skeleton
Main groups:Main groups:
– Skates and raysSkates and rays
– SharksSharks
– Chimaeras (ratfishes)Chimaeras (ratfishes)
Bony Fishes: Bony Fishes: Class OsteichthyesClass Osteichthyes
Includes 96 percent of Includes 96 percent of
living fish speciesliving fish species
Three subclasses:Three subclasses:
– Ray-finned fishesRay-finned fishes
– Lobe-finned fishesLobe-finned fishes
– Lung fishesLung fishes
Body Plan of a Bony Body Plan of a Bony FishFish
muscle segments
fin supports
brain
olfactory bulb
heart
liver
gallbladderstomach
intestineswim bladderkidney
anus
urinary bladder
Figure 26.9bPage 451
Lobe-Finned FishesLobe-Finned Fishes
CoelocanthsCoelocanths
Lunglike sacs do not Lunglike sacs do not function in gas exchangefunction in gas exchange
LungfishesLungfishes
Have gills and one lung or a pair Have gills and one lung or a pair
Must surface to gulp air Must surface to gulp air
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Figure 26.9fPage 451
Early AmphibiansEarly Amphibians
Fishlike skull Fishlike skull
and tail and tail
Four limbs Four limbs
with digitswith digits
Short neck Short neck Acanthostega
Ichthyostega
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Figure 26.10aPage 452
Modern AmphibiansModern Amphibians
All require water at some stage in All require water at some stage in
the life cycle; most lay eggs in waterthe life cycle; most lay eggs in water
Lungs are less efficient than those of Lungs are less efficient than those of
other vertebratesother vertebrates
Skin serves as respiratory organSkin serves as respiratory organ
From Fins to LimbsFrom Fins to Limbs
Genetic enhancer controls genes Genetic enhancer controls genes involved in formation of digits on involved in formation of digits on limb boneslimb bones
Change in a single master gene can Change in a single master gene can drastically alter morphologydrastically alter morphology
Living Amphibian Groups Living Amphibian Groups
Frogs and toadsFrogs and toads
SalamandersSalamanders
CaeciliansCaecilians
Rise of AmniotesRise of Amniotes
Arose during CarboniferousArose during Carboniferous
Adaptations to life on landAdaptations to life on land
– Tough, scaly skinTough, scaly skin
– Internal fertilizationInternal fertilization
– Amniote eggsAmniote eggs
– Water-conserving kidneysWater-conserving kidneys
Adaptive RadiationAdaptive Radiation
Produced numerous lineagesProduced numerous lineages
Extinct groups include:Extinct groups include:
– Therapsids (ancestors of Therapsids (ancestors of
mammals)mammals)
– Marine plesiosaurs & ichthyosaursMarine plesiosaurs & ichthyosaurs
– Dinosaurs and pterosaursDinosaurs and pterosaurs
Living ReptilesLiving Reptiles
Not a monophyletic groupNot a monophyletic group
CrocodiliansCrocodilians
TurtlesTurtles
TuatarasTuataras
Snakes and lizardsSnakes and lizards
Evolutionary History of Evolutionary History of AmniotesAmniotes
lizards
snakes
tuataras
birds
archosaurs
dinosaurs
pterosaurs
crocodilians
ichthyosaurs
plesiosaurs
turtles
synapsids
therapsidsanapsids
(mammals)
stem reptiles
Paleozoic era Mesozoic eraCarboniferous Permian Triassic Jurassic Cretaceous
Figure 26.14Page 455
Crocodile Body PlanCrocodile Body Plan
Figure Figure 26.13c26.13c
Page 454Page 454
snout
olfactory lobe
spinal cord
vertebral column
gonad
kidney
cloaca
intestine
stomach
liver
heart
esophagus
hindbrain, midbrain, forebrain
Turtles Turtles
Armorlike shell Armorlike shell Horny plates instead of Horny plates instead of
teethteeth Lay eggs on landLay eggs on land
Figure 26.15Page 456
Lizards and SnakesLizards and Snakes
Largest order (95 Largest order (95 percent of living reptiles)percent of living reptiles)
Most lizards are Most lizards are insectivores with small insectivores with small peglike teeth peglike teeth
All snakes are carnivores All snakes are carnivores with highly movable with highly movable jawsjaws
hollow fang
venom gland
Figure 26.15dPage 457
TuatarasTuataras
Only two living speciesOnly two living species
Live on islands off coast of New Live on islands off coast of New
ZealandZealand
Look like lizards, but resemble Look like lizards, but resemble
amphibians in some aspects of amphibians in some aspects of
their brain and in their way of their brain and in their way of
walkingwalking
Birds Birds
Diverged from small theropod Diverged from small theropod
dinosaurs during the Mesozoicdinosaurs during the Mesozoic
Feathers are a unique traitFeathers are a unique trait
– Derived from reptilian scalesDerived from reptilian scales
– Serve in insulation and flightServe in insulation and flight
Amniote EggAmniote Egg
yolk sac embryo
chorion
amnion
albumin
hardened shell
allantois
Figure 26.16aPage 458
Adapted for FlightAdapted for Flight
Four-chambered Four-chambered heartheart
Highly efficient Highly efficient respiratory systemrespiratory system
Lightweight bones Lightweight bones with air spaceswith air spaces
Powerful muscles Powerful muscles attach to the keel attach to the keel
Figure 26.17Page 458
Mammals: Phylum Mammals: Phylum MammaliaMammalia
HairHair Mammary Mammary
glandsglands Distinctive teethDistinctive teeth Highly Highly
developed braindeveloped brain Extended care Extended care
for the youngfor the youngFigure 26.19c
Page 460
Mammal Origins & RadiationMammal Origins & Radiation
During Triassic, synapsids gave rise to During Triassic, synapsids gave rise to therapsids (ancestors of mammals)therapsids (ancestors of mammals)
By Jurassic, mouselike therians had By Jurassic, mouselike therians had evolved evolved
Therians coexisted with dinosaurs Therians coexisted with dinosaurs through Cretaceousthrough Cretaceous
Radiated after dinosaur extinction Radiated after dinosaur extinction
Three Mammalian LineagesThree Mammalian Lineages
MonotremesMonotremes– Egg-laying mammals Egg-laying mammals
MarsupialsMarsupials– Pouched mammalsPouched mammals
EutheriansEutherians– Placental mammalsPlacental mammals
Role of Geologic ChangeRole of Geologic Change
Monotremes and marsupials evolved Monotremes and marsupials evolved while Pangea was intactwhile Pangea was intact
Placental mammals evolved after Placental mammals evolved after what would become Australia had what would become Australia had split offsplit off
No placental mammals in AustraliaNo placental mammals in Australia Elsewhere, placental mammals Elsewhere, placental mammals
replaced most marsupials replaced most marsupials
Living MonotremesLiving Monotremes
Three speciesThree species
– Duck-billed platypus Duck-billed platypus
– Two kinds of spiny Two kinds of spiny
anteater anteater
All lay eggsAll lay eggs
Living MarsupialsLiving Marsupials
Most of the 260 species are native Most of the 260 species are native to Australia and nearby islandsto Australia and nearby islands
Only the opossums are found in Only the opossums are found in North AmericaNorth America
Young are born in an undeveloped Young are born in an undeveloped state and complete development state and complete development in a permanent pouch on mother in a permanent pouch on mother
Living Placental MammalsLiving Placental Mammals
Most diverse mammalian groupMost diverse mammalian group Young develop in mother’s uterusYoung develop in mother’s uterus Placenta composed of maternal and fetal Placenta composed of maternal and fetal
tissues; nourishes fetus, delivers oxygen, tissues; nourishes fetus, delivers oxygen, and removes wastesand removes wastes
Placental mammals develop more quickly Placental mammals develop more quickly than marsupials than marsupials
Earliest PrimatesEarliest Primates
Primates evolved more than 60 million Primates evolved more than 60 million
years ago during the Paleoceneyears ago during the Paleocene
First primates resembled tree shrewsFirst primates resembled tree shrews
– Long snoutsLong snouts
– Poor daytime visionPoor daytime vision
From Primates to HumansFrom Primates to Humans
““Uniquely” human traits Uniquely” human traits
evolved through evolved through
modification of traits that modification of traits that
evolved earlier, evolved earlier,
in ancestral formsin ancestral forms
HominoidsHominoids
Apes, humans, and extinct species of Apes, humans, and extinct species of their lineagestheir lineages
In biochemistry and body form, humans In biochemistry and body form, humans are closer to apes than to monkeysare closer to apes than to monkeys
HominidsHominids– Subgroup that includes humans and Subgroup that includes humans and
extinct humanlike speciesextinct humanlike species
Trends in Lineage Trends in Lineage Leading to HumansLeading to Humans
Less reliance on smell, more on visionLess reliance on smell, more on vision
Skeletal changes to allow bipedalismSkeletal changes to allow bipedalism
Modifications of hand allow fine Modifications of hand allow fine
movementsmovements
Bow-shaped jaw and smaller teethBow-shaped jaw and smaller teeth
Longer lifespan and period of dependency Longer lifespan and period of dependency
Adaptations to anAdaptations to anArboreal LifestyleArboreal Lifestyle
Better daytime visionBetter daytime vision
Shorter snoutShorter snout
Larger brain Larger brain
Forward-directed eyesForward-directed eyes
Capacity for grasping Capacity for grasping
motionsmotions
The First HominoidsThe First Hominoids
Appeared during MioceneAppeared during Miocene
Arose in Central AfricaArose in Central Africa
Spread through Africa, Asia, EuropeSpread through Africa, Asia, Europe
Climate was changing, becoming Climate was changing, becoming
cooler and driercooler and drier
The First HominidsThe First Hominids
Sahelanthropus tchadensis Sahelanthropus tchadensis arose 6-7 million years agoarose 6-7 million years ago Bipedal australopiths evolved during Miocene into PlioceneBipedal australopiths evolved during Miocene into Pliocene
Exact relationships are not knownExact relationships are not known
A. anamensisA. afarensis A. africanus
A. garhiA. boisei A. robustus
Homo HabilisHomo Habilis 1.9-1.6 million years ago1.9-1.6 million years ago
May have been May have been
the first member the first member
of genusof genus
Lived in Lived in
woodlands of woodlands of
eastern and eastern and
southern Africasouthern AfricaH. habilis
Figure 26.31Page 468
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Homo erectusHomo erectus22 million-53,000? years agomillion-53,000? years ago
Evolved in Africa Evolved in Africa
Migrated into Europe and Asia Migrated into Europe and Asia
Larger brain than Larger brain than H. habilisH. habilis
Creative toolmakerCreative toolmaker
Built fires and used furs for Built fires and used furs for
clothingclothing
Homo sapiensHomo sapiens
Modern man evolved by 100,000 Modern man evolved by 100,000 years agoyears ago
Compared to Compared to Homo erectus:Homo erectus:– Smaller teeth and jawsSmaller teeth and jaws– ChinChin– Smaller facial bonesSmaller facial bones– Larger-volume brain caseLarger-volume brain case
NeanderthalsNeanderthals
Early humans that lived in Europe and Early humans that lived in Europe and Near EastNear East
Massively built, with large brainsMassively built, with large brains Disappeared when Disappeared when H. sapiensH. sapiens
appearedappeared DNA evidence suggests that they did DNA evidence suggests that they did
not contribute to modern European not contribute to modern European populationspopulations
Earliest Fossils Are African Earliest Fossils Are African
Africa appears to be the cradle of Africa appears to be the cradle of
human evolutionhuman evolution
No human fossils older than 2 million No human fossils older than 2 million
years exist anywhere but Africayears exist anywhere but Africa
Homo erectusHomo erectus left Africa in waves left Africa in waves
from 2 million to 500,000 years agofrom 2 million to 500,000 years ago
Where Did Where Did H. sapiensH. sapiens Arise? Arise?
Two hypotheses:Two hypotheses:
– Multiregional modelMultiregional model
– African emergence modelAfrican emergence model
Both attempt to address Both attempt to address
biochemical and fossil evidencebiochemical and fossil evidence
Multiregional ModelMultiregional Model
Argues that Argues that H. erectusH. erectus migrated to many migrated to many locations by about 1 million years agolocations by about 1 million years ago
Geographically separated populations Geographically separated populations gave rise to phenotypically different gave rise to phenotypically different races of races of H. sapiensH. sapiens in different locations in different locations
Gene flow prevented races from Gene flow prevented races from becoming speciesbecoming species
African Emergence ModelAfrican Emergence Model
Argues that Argues that H. sapiensH. sapiens arose in sub- arose in sub-Saharan AfricaSaharan Africa
H. sapiensH. sapiens migrated out of Africa and migrated out of Africa and into regions where into regions where H. erectusH. erectus had had preceded thempreceded them
Only after leaving Africa did Only after leaving Africa did phenotypic differences arisephenotypic differences arise