animal evolution the chordates - del mar college ::...
TRANSCRIPT
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Animal Evolution – The Chordates
Chapter 26 Part 1
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Impacts, Issues
Transitions Written in Stone
Fossils such as Archaeopteryx, an ancient
winged dinosaur with feathers, are evolutionary
evidence of transitions between species
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26.1 The Chordate Heritage
Chordates
• Most diverse lineage of deuterostomes
• Some are invertebrates; most are vertebrates
• Bilateral and coelomate
• Cephalized and segmented
• Complete digestive system
• Closed circulatory system
• Classified by embryonic characteristics
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Modern Chordate Groups
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Embryonic Chordate Characteristics
Four characteristics of chordate embryos may
not persist in adults
• Notochord of stiff connective tissue that extends
the length of the body and supports it
• Dorsal, hollow nerve cord parallels the notochord
• Gill slits across the wall of the pharynx
• Tail that extends beyond the anus
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Invertebrate Chordates
Lancelets are the only group of chordates that
retains all chordate characteristics as adults
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Fig. 26-2b, p. 434
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Fig. 26-2b, p. 434
a Dorsal, hollow
nerve cord
b Notochord c Pharynx
with gill slits
d Tail extends
beyond anus
eyespot
tentacle-like
structures
around mouth
segmented
muscles
(myomeres)
midgut hindgut
aorta gonad pore of atrial
cavity anusepidermis
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Invertebrate Chordates
Tunicates have typical chordate larvae, but
adults retain only the pharynx with gill slits
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Fig. 26-3a, p. 435
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Fig. 26-3a, p. 435
nerve
cord notochord
gut
pharynx with gill slits
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Fig. 26-3b, p. 435
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Fig. 26-3c, p. 435
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Fig. 26-3c, p. 435
pharynx
with gill
slits
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Fig. 26-3d, p. 435
1 cm
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Craniates
Craniates have a braincase of cartilage or bone
(cranium) that encases the brain, paired eyes,
and other sensory structures on the head
Craniates includes fishes, amphibians, reptiles,
birds, and mammals
Hagfishes are the only modern craniates that
are not vertebrates
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Hagfishes
Soft bodied, boneless fishes
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Fig. 26-4a, p. 435
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Fig. 26-4a, p. 435
tentacles gill slits (twelve pairs) mucous glands
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Fig. 26-4b, p. 435
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Fig. 26-4c, p. 435
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26.1 Key Concepts
Characteristics of Chordates
Four traits characterizes the chordates:
• A supporting rod (notochord)
• A hollow, dorsal nerve cord
• A pharynx with gill slits in the wall
• A tail extending past an anus
Certain invertebrates and all vertebrates belong
to this group
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26.2 Vertebrate Traits and Trends
Vertebrates are chordates with an internal
skeleton (endoskeleton) of cartilage or bone
with a supportive backbone (vertebral column)
made up of individual vertebrae
Modern vertebrates (except lampreys) have
jaws derived from gill-supporting structures
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Gill-Supporting Structures
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Fig. 26-6a, p. 437
supporting
structure
for gill slits
gill slits
A In early jawless fishes, supporting
elements reinforced a series of gill slits
on both sides of the body.
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Fig. 26-6b, p. 437
jaw, derived
from support
structure
B In early jawed fishes (e.g., placoderms), the
first elements were modified and served as
jaws. Cartilage reinforced the mouth’s rim.
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Fig. 26-6c, p. 437
location of spiracle
(modified gill slit)
jaw support
jaw
C Sharks and other modern jawed
fishes have strong jaw supports.
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Evolution of Internal Skeleton
Fishes evolved appendages (fins) for swimming
Pelvic and pectoral fins gave rise to paired limbs in amphibians, which began the move to land
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Evolution of Other Systems
Living in water (fish)
• Blood moves in a single circuit from heart to gills
(respiratory organs that function in water)
Moving to land
• Modification of the respiratory system (lungs)
and circulatory system (two circuits)
• Efficient kidneys to conserve water, and a
system of internal fertilization
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Chordate Family Tree
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Fig. 26-5, p. 436
lancelets
tunicates
hagfishes
lampreyscartilaginous
fishes
ray-finned
fisheslobe-finned
fishes
lungfishes
amphibians
―reptiles‖
birds mammals
amniotes
tetrapods
swim bladder
or lungs
jawed
vertebratesvertebrates
craniates
ancestral chordates
Origin
of the
first
jawless
fishes.
Jawed
fishes,
including
the placo-
derms
and
sharks,
evolve.
Adaptive
radiation
of fishes,
and the
first
amphibians
move
onto land.
Diversification
of fishes and
amphibians.
Armored
fishes go
extinct.
Reptiles
arise and
start to
diversify.
Early
amphibians
in decline.
Dinosaurs
and marine
reptiles
evolve.
Birds,
mammals,
and modern
amphibians
arise.
Dinosaurs
dominate.
Dinosaur
diversity
peaks, then
extinction
by period’s
end.
Adaptive
radiation
of
mammals.
Ordovician Carboniferous Jurassic Tertiary
488 443 416 359 299 251 200 146 66
Silurian Devonian Permian Triassic Cretaceous
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26.2 Key Concepts
Trends Among Vertebrates
In vertebrate lineages, a backbone replaced the
notochord
Jaws and fins evolved in water
Fleshy fins with skeletal supports evolved into
limbs that allowed vertebrates to walk onto land
On land, lungs replaced gills and circulation
changed in concert
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26.3 The Jawless Lampreys
Lampreys have no jaws or paired fins; they
undergo metamorphosis, and many are
parasites of other fishes
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26.4 The Jawed Fishes
Jawed fishes typically have paired fins and a
body covered with scales
Cartilaginous fishes (Chondrichthyes) have a
cartilage skeleton, gill slits, and teeth that shed
• Sharks and rays
Bony fishes (Osteichthyes) have a bony
skeleton, gill covers, and a swim bladder
• Ray-finned fishes, lungfishes, coelacanth
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Ray-Finned Bony Fishes
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Fig. 26-9a, p. 439
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Fig. 26-9a, p. 439
swim bladder kidney
ovary nerve cord
brain
cloaca intestine stomach liver heart gills
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Fig. 26-9b, p. 439
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Fig. 26-9c, p. 439
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Fig. 26-9d, p. 439
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Lungfish
Lungfishes have gills and lunglike sacs for
breathing air
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Coelacanth
The only modern lobe-finned fish; closely related
to amphibians
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26.5 Amphibians—
First Tetrapods on Land
Tetrapods (four-legged walkers)
• Branched from lobe-finned fishes in Devonian
Amphibians
• Land-dwelling vertebrates that return to water to
breed, undergo metamorphosis, and have a
three-chambered heart
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Adapting to Life on Land
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Fig. 26-12a, p. 440
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Fig. 26-12b, p. 440
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Fig. 26-12c, p. 440
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Fig. 26-12d, p. 440
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Modern Amphibians
Salamanders and newts
• Body form most like early tetrapods, side-to-side
walking motion
Caecilians
• Includes many limbless, blind burrowers
Frogs and toads
• Tailless adults with long, muscular hind legs
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Salamander and Caecilian
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Frog
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26.6 Vanishing Acts
Amphibians depend on standing water to breed
and have a thin skin unprotected by scales
These features make them vulnerable to habitat
loss, disease, and pollution – causing
deformities and threatening species
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Frog Deformity
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26.3-26.6 Key Concepts
Transition from Water to Land
Vertebrates evolved in the seas, where
cartilaginous and bony fishes still live
Of all vertebrates, modern bony fishes are most
diverse
One group gave rise to aquatic tetrapods (four-
legged walkers), the descendants of which
moved onto dry land
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26.7 The Rise of Amniotes
Amniotes are animals with embryos that
develop inside a waterproof egg; their
waterproof skin and highly efficient kidneys
make them well adapted to dry habitats
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Amniotes
Four branches of amniotes lead to synapsids
(mammals), anapsids (turtles), lizards and
snakes, and crocodiles and birds
Reptiles are an artificial group referring to
amniotes other than bird or mammals
Dinosaurs are extinct amniotes; birds are their
descendents
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The Ruling Reptiles
For 125 million years, dinosaurs dominated the
land and sea (Example: Ichthyosaurs)
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Amniote Phylogeny
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Fig. 26-16c, p. 442
snakes
lizards
―stem‖
reptiles tuataras
ichthyosaurs
plesiosaurs
birds
therapod
dinosaurs
other
dinosaurs
pterosaursarchosaurs
crocodilians
turtles
therapsidsanapsids
synapsids mammals
PALEOZOIC ERA MESOZOIC ERA
TERTIARY
TO
PRESENT
CARBONIFEROUS PERMIAN TRIASSIC JURASSIC CRETACEOUS
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26.8 So Long, Dinosaurs
K-T asteroid impact hypothesis
• Asteroid impacts changed life on Earth, defining
the Cretaceous-Tertiary (K-T) boundary
• Most dinosaurs became extinct
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26.9 Diversity of Modern Reptiles
Reptile characteristics
• Scale-covered body
• Cloaca for waste disposal
• Four approximately equal limbs (except snakes)
• Internal fertilization
• Body temperature determined by surroundings
(ectotherms)
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Crocodile Body Plan
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Fig. 26-18, p. 444
kidney (control
of water, solute
levels in internal
environment)
olfactory
lobe (sense
of smell)
hindbrain,
midbrain,
forebrainspinal
cord
vertebral column
gonad
snout
unmatched
rows of teeth
on upper and
lower jawsesophagus
lung
heart
liver
stomach
intestine cloaca
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Turtles and Tortoises
Turtles and tortoises have a bony, scale-
covered shell attached to the backbone
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Fig. 26-19b, p. 445
hard shell vertebral column
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Lizards
Lizards, the most diverse reptiles, have many
interesting defenses
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Tuataras
The two remaining species of tuataras have a
third eye under the skin of the forehead
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Snakes
Snakes are legless, but some have bony
remnants of hindlimbs
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Fig. 26-19f (1), p. 445
venom
gland
hollow
fang
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Crocodilians
Crocodilians, close relatives of birds, are the
only reptiles with a four-chambered heart