Vertebrates

Transcription

Vertebrates

Chapter 34
Phylum Chordata and relatives
PHYLUM
HEMICHORDATA
P. CHORDATA
SUBP. CRANIATA
VERTEBRATA
SUBP. UROCHORDATA
& CEPHALOCHORDATA
GNATHOSTOMATA
Myxini Cephalaspidomorphi
Vertebrates
Jaws, etc.
9. Vertebral elements
10. Median fins
11. Better Organs, etc.
5. Cranium: brain & skeletal protection
6. Duplicate HOX genes
7. Neural crest
8. Organs & Organ systems
PowerPoint Lectures for
Biology, Seventh Edition
3. Notochord
4. Post-anal tail
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
1. 
Hollow, dorsal nerve cord
2. 
Pharyngeal slits or clefts
Phylum Chordata
P. Chordata, Subphylum Craniata, Vertebrata
•  Half a Billion Years of Backbones
•  The animals called vertebrates
•  By the end of the Cambrian period, some 540
million years ago
–  Get their name from vertebrae, the series of
bones that make up the backbone
–  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
Figure 34.1
•  There are approximately 52,000 species of
vertebrates
•  Chordates are deuterostome, bilaterian
animals
–  Which include the largest animals ever to live
on the Earth
•  Chordates have a:
–  Notochord
–  Post-anal tail
–  Pharyngeal slits or clefts
–  Dorsal, hollow nerve cord
1
Phylogeny of the Chordata
Chordates
Craniates
•  P. Chordata includes two invertebrate groups:
Vertebrates
Gnathostomes
Lobe-fins
Mammalia
(mammals)
Amphibia
(frogs, salamanders)
Amniotes
Reptilia
(turtles, snakes,
crocodiles, birds)
Dipnoi
(lungfishes)
Actinopterygii
(ray-finned fishes)
Tetrapods
Actinistia
(coelacanths)
Cephalaspidomorphi
(lampreys)
Chondrichthyes
(sharks, rays, chimaeras)
Cephalochordata
(lancelets)
Myxini
(hagfishes)
–  Subphylum Urochordata
Urochordata
(tunicates)
Echinodermata
(sister group to chordates)
Osteichthyans
–  Subphylum Cephalochordata
Milk
Amniotic egg
•  Subphylum Craniata includes
Legs
–  the invertebrate hagfish, and
Lobed fins
Lungs or lung derivatives
Jaws, mineralized skeleton
–  the Vertebrata
Vertebral column
Head
Brain
Notochord
Figure 34.2
Ancestral deuterostome
Derived Characters of Chordates
Derived Characters of Chordates
•  All chordates share a set of derived characters
•  Two of these characters are shared with
members of Phylum Hemichordata: the ‘halfchordates’ (acorn worms)
–  Although some of these traits persist only
during embryonic development
–  Pharyngeal slits
Dorsal,
hollow
nerve cord
Muscle
segments
–  Dorsal, hollow nerve cord
Brain
Notochord
•  True synapomorphies of P. Chordata are the
–  Notochord
Mouth
Anus
Figure 34.3
Muscular,
post-anal tail
Pharyngeal
slits or clefts
–  Post-anal tail
Notochord: Chordate Synapomorphy
Muscular, Post-Anal Tail: Chordate Synapomorphy
•  The notochord
•  Chordates have a tail extending posterior to
the anus
–  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
–  Although in many species it is lost during
embryonic development
•  The chordate tail contains skeletal elements
and muscles
–  It provides much of the propelling force in
many aquatic species
2
Dorsal, Hollow Nerve Cord: also in Hemichordata
Pharyngeal Slits/Clefts: Shared with Hemichordata
•  The nerve cord of a chordate embryo
•  In most chordates, grooves in the pharynx,
‘pharyngeal clefts’
–  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
•  A dorsal, hollow nerve cord is also found in the
Hemichordata
–  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
PHYLUM
HEMICHORDATA
P. Chordata, Subphylum Urochordata: Tunicates
P. CHORDATA
•  Tunicates, subphylum Urochordata
SUBP. CRANIATA
VERTEBRATA
SUBP. UROCHORDATA
& CEPHALOCHORDATA
GNATHOSTOMATA
Jaws, etc.
–  Belong to the deepest-branching lineage of
chordates
–  Are marine suspension feeders commonly
called sea squirts
10. Median fins
7. Neural crest
3. Notochord
4. Post-anal tail
1. 
2. 
Chordata: Urochordata
Chordata: Urochordata
•  Tunicates most
resemble
chordates during
their larval stage:
•  As an adult
Notochord
–  A tunicate draws in water through an incurrent
siphon, filtering food particles
Dorsal, hollow
nerve cord
Tail
–  often only a few
minutes
Incurrent
siphon
to mouth
Excurrent
siphon
Excurrent
siphon
Muscle
segments
Excurrent
siphon
Incurrent
siphon
Atrium
Intestine
Pharynx
with
numerous
slits
Stomach
Atrium
Tunic
Pharynx with slits
Figure 34.4c
(c) A tunicate larva is a free-swimming but
nonfeeding “tadpole” in which all four
chief characters of chordates are evident.
Figure 34.4a, b
(a) An adult tunicate, or
sea squirt, is a sessile
animal (photo is
approximately life-sized).
Anus
Intestine
Esophagus
Stomach
(b) In the adult, prominent
pharyngeal slits function
in suspension feeding,
but other chordate
characters are not obvious.
3
P. Chordata, Subphylum Cephalochordata
Early Chordate Evolution
•  Lancelets are marine suspension feeders that
retain the characteristics of the chordate body plan
as adults & are named for their bladelike shape
Tentacle
–  Probably does not reflect that of the ancestral
chordate
2 cm
–  Earlier hypotheses suggested derived
chordates evolved through
Mouth
Pharyngeal slits
Atrium
Notochord
•  The current life history of tunicates
–  Paedomorphosis of a tunicate’s tadpole larvae
Digestive tract
Atriopore
Dorsal, hollow
nerve cord
Segmental
muscles
Anus
Tail
Figure 34.5
•  Gene expression in lancelets
–  Holds clues to the evolution of the vertebrate form
BF1
Otx
Hox3
•  Craniates are chordates that have a head with
skeletal support/protection
•  The origin of a head
–  Opened up a completely new way of feeding
for chordates: active predation
Nerve cord of lancelet
embryo
BF1
•  Craniates share some common characteristics
Hox3
Otx
–  A skull, brain, eyes, and other sensory organs
Brain of vertebrate embryo
(shown straightened)
Midbrain
Figure 34.6
Hindbrain
Forebrain
Derived Characters of Craniates
•  One feature unique to craniates
•  Neural crest cells
–  Is the neural crest, a collection of cells that
appears near the dorsal margins of the closing
neural tube in an embryo
Dorsal edges
of neural plate
Neural
crest
Ectoderm
–  Give rise to a variety of structures, including
some of the bones and cartilage of the skull
Neural
tube
Ectoderm
Notochord
(a) The neural crest consists of
bilateral bands of cells near
the margins of the embryonic
folds that form the neural tube.
Figure 34.7a, b
Migrating neural
crest cells
(b) Neural crest cells migrate to
distant sites in the embryo.
(c) The cells give rise to some
of the anatomical structures
unique to vertebrates, including
some of the bones and cartilage
of the skull.
Figure 34.7c
4
The Origin of Craniates
•  Craniates evolved
during the Cambrian
explosion ~ 530 mya
•  Paleontologists have found fossils of even
more advanced chordates in other Cambrian
rocks, e.g. Haikouichthys
5 mm
•  The most primitive
fossils are those of the
3-cm-long Haikouella
(a) Haikouella. Discovered in 1999 in
southern China, Haikouella had eyes
and a brain but lacked a skull, a
derived trait of craniates.
Figure 34.8a
Figure 34.8b
(b) Haikouichthys. Haikouichthys had a
skull and thus is considered a true craniate.
Chordata: Craniata: Myxini - Hagfishes
Class Myxini: Hagfishes
•  Class Myxini, Hagfishes, or Slime Hags:
•  Class Myxini, Hagfishes, or Slime Hags:
–  The least derived craniate lineage alive today
–  Are jawless marine craniates
Slime glands
–  They have a cartilaginous skull and axial rod of
cartilage derived from the notochord
–  Lack vertebrae or any vertebral elements
–  Can produce copious amounts of mucus to
protect themselves and their food
Figure 34.9
PHYLUM
HEMICHORDATA
Chordata: Craniata: Vertebrata
P. CHORDATA
SUBP. UROCHORDATA
& CEPHALOCHORDATA
SUBP. CRANIATA
VERTEBRATA
GNATHOSTOMATA
Jaws, etc.
10. Median fins
7. Neural crest
3. Notochord
4. Post-anal tail
1. 
2. 
•  Vertebrates are craniates
•  Three Vertebrate Synapomorphies:
–  Vertebrae enclosing a spinal cord
•  A backbone, or at least vertebral elements
–  An elaborate skull
–  Median fins with finrays (aquatic forms)
•  A lineage of craniates evolved into vertebrates
during the Cambrian period
5
Vertebrata: Petromyzontida/Cephalaspidomorphi
Vertebrata: Petromyzontida/Cephalaspidomorphi
•  Lampreys: Class Cephalaspidomorphi /
Petromyzondtida
•  Lampreys are jawless vertebrates
–  Represent the oldest living lineage of
vertebrates
–  Inhabit various marine and freshwater habitats
–  Juveniles resemble cephalochordates
–  Have cartilaginous segments surrounding
the notochord and arching partly over the
nerve cord
•  Lampreys are jawless vertebrates
–  Inhabiting various marine and freshwater
habitats
Figure 34.10
Origins of Bone and Teeth
Fossils of Early Vertebrates
•  Mineralization
•  Conodonts were the first vertebrates
–  Appears to have originated with vertebrate
mouthparts
–  With mineralized skeletal elements in their
mouth and pharynx
•  The vertebrate endoskeleton
–  Became fully mineralized much later
Dorsal view
of head
Figure 34.11
Dental
elements
Chordata: Craniata: Vertebrata: Gnathostomata
•  Armored, jawless vertebrates called
ostracoderms
–  Had defensive plates of bone on their skin
•  Gnathostomes are vertebrates that have jaws
•  Today, jawless vertebrates (previously placed
in Class Agnatha - paraphyletic)
–  Are far outnumbered by those with jaws
•  Jawless vertebrates were previously placed in
Class Agnatha - but,
Pteraspis
–  The lack of jaws is pleisiomorphic, and
–  The Agnatha are paraphyletic
Pharyngolepis
Figure 34.12
6
Vertebrata: lineages
Derived Characters of Gnathostomes
VERTEBRATA
GNATHOSTOMATA
OSTEICHTHYES
Cephalaspidomorphi
ACTINOPTERYGII
SARCOPTERYGII
CHONDRICHTHYES
TETRAPODA
13. Four walking limbs
14. Ears adapted for
airborne sounds
9. Claspers
10. Placoid scales
•  Gnathostomes jaws
Gill slits
–  Evolved from
skeletal supports
of the pharyngeal
slits
Cranium
Mouth
Skeletal rods
11. Lungs or derivatives
12. Bony operculum
4. Jaws
5. Paired fins
6. Lateral line
7. Mineralized parts (e.g. teeth)
2. Median fins
Figure 34.13
Fossil Gnathostomes
•  Other derived characters of the Gnathostomata
include
–  Enhanced sensory systems, including the
lateral line system
•  The earliest gnathostomes in the fossil record
–  Are an extinct lineage of armored vertebrates
called placoderms
–  An extensively mineralized endoskeleton
–  Paired appendages
•  Pectoral and Pelvic fins (in aquatic forms)
–  Further development of organs/organ systems
–  A second duplication of Hox genes
(a) Coccosteus, a placoderm
Figure 34.14a
•  Another group of jawed vertebrates called
acanthodians
VERTEBRATA
GNATHOSTOMATA
OSTEICHTHYES
Cephalaspidomorphi
ACTINOPTERYGII
SARCOPTERYGII
CHONDRICHTHYES
TETRAPODA
–  Radiated during the Devonian period
airborne sounds
–  Were closely related to the ancestors of
osteichthyans
9. Claspers
10. Placoid scales
(b) Climatius, an acanthodian
Figure 34.14b
12. Bony operculum
4. Jaws
5. Paired fins
6. Lateral line
2. Median fins
7
Chondrichthyans (Sharks, Rays, and Their Relatives)
Chondrichthyans (Sharks, Rays, and Their Relatives)
•  Class Chondrichthyes: Synapomorphies
•  Class Chondrichthyes contains about 750 spp.
in two subclasses:
–  Claspers to aid in Internal Fertilization
–  Subclass Elasmobranchii: sharks, skates &
rays
–  Placoid scales or dermal denticles
•  Chondrichthyans have a skeleton that is
composed primarily of cartilage
–  Subclass Holocephali: ratfish and chimaeras
–  The cartilaginous skeleton evolved secondarily
from an ancestral mineralized skeleton
•  Many Chondrichthyan characters are typical of
ancestral gnathostomes:
–  Heterocercal tail, large size (one meter),
spiracles, spiral valve intestine, etc.
Class Chondrichthyes: Subclass Elasmobranchii
C. Chondrichthyes: Elasmobranchii
•  Subclass Elasmobranchii is the most diverse
group of chondrichthyans (700+ spp)
•  Most sharks are carnivorous, with
–  Includes the sharks and rays
–  streamlined bodies for swift swimming, but
more dense than water
–  acute senses for detecting prey
(a) Blacktip reef shark (Carcharhinus melanopterus).
Fast swimmers with acute senses, sharks have
paired pectoral and pelvic fins.
Pectoral fins
Pelvic fins
–  teeth to manipulate prey
(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
Figure 34.15a, b their gaping mouth.
•  Most Elasmobranchs are skates & rays
–  evolved for life on the bottom
–  often with crushing, plate-like teeth
The largest sharks & rays are planktivores
that feed low on the food chain
–  Whale shark (largest fish)
–  Manta rays
8
C. Chondrichthyes: Holocephali
C. Chondrichthyes
•  Subclass Holocephali
•  All Chondrichthyans have internal fertilization
with claspers
–  Is composed of a few dozen species of
ratfishes or chimaeras
•  Internal fertilization is associated with live birth
–  50% of chondrichthyans lay eggs: Ovipary
–  Most other chondrichthyan mothers retain eggs
in their reproductive tract until hatching:
Ovovivipary
–  A few species (e.g. hammerheads) provide
nutrients to the developing embryo via a
vascular connection: true Vivipary
(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.
Figure 34.15c
PHYLUM
HEMICHORDATA
VERTEBRATA
P. CHORDATA
SUBP. CRANIATA
VERTEBRATA
SUBP. UROCHORDATA
& CEPHALOCHORDATA
GNATHOSTOMATA
GNATHOSTOMATA
OSTEICHTHYES
Cephalaspidomorphi
ACTINOPTERYGII
SARCOPTERYGII
CHONDRICHTHYES
TETRAPODA
Jaws, etc.
airborne sounds
10. Median fins
7. Neural crest
3. Notochord
4. Post-anal tail
1. 
2. 
9. Claspers
10. Placoid scales
12. Bony operculum
4. Jaws
5. Paired fins
6. Lateral line
2. Median fins
Osteichthyes: Ray-Finned & Lobed-Finned Fishes
Osteichthyes
•  (Class?) Osteichthyes: bony fishes
•  Nearly all living osteichthyans
•  The vast majority of vertebrates are jawed,
bony fishes, including their
–  Tetrapod descendants
•  Primary synapomorphy: the lung or swim
bladder
•  A bony operculum is also synapomorphy of the
Osteichthyes
–  Have a bony endoskeleton
•  Aquatic osteichthyans
–  Are the vertebrates we informally call fishes
(some definitions)
–  Control their buoyancy with an air sac known
as a swim bladder
9
Osteichthyes: Origin of the Lung
Osteichthyes: Neutrally buoyant
•  The ancestor of bony fish evolved a lung
•  Most aquatic osteichthyans
–  An outpocketing of the gut that holds air for the
purpose of gas exchange
•  The lung likely evolved in a freshwater fish
living in warm, stagnant water: low in oxygen
–  Surface layers of ponds relatively high in O2
–  Fishes breathing water at the surface may also
take in air bubbles
–  Retaining these bubbles in a vascularized
chamber increases available oxygen!
–  Have lost a connection between the air and
their ‘lung’
–  Instead, the lung evolved into a hydrostatic
organ to control their buoyancy:
–  An air sac known as a swim bladder
•  Swim bladders allow bony fishes to achieve
neutral buoyancy: they no longer need to
spend energy to swim off the bottom
•  The swim bladder allowed for changes in fin
shape: e.g. homocercal caudal fin (tail)
•  Most modern bony fishes evolved additional
changes in fin shape, position and locomotion
Dorsal fin
Adipose fin
(characteristic of
trout)
Swim bladder
Spinal cord
Nostril
Cut edge of
operculum
Caudal
fin
–  Pelvic fins move forward (anterior)
Brain
Gills
Heart
Gonad
Stomach
Anal fin
Urinary
Anus bladder
Liver
Kidney
Figure 34.16
–  Pectoral fins move upward (dorsal)
Lateral
line
Pelvic fin
Intestine
Osteichthyes: Bony operculum
•  Fishes breathe by drawing water over four or
five pairs of gills
–  Located in chambers covered by a protective
bony flap called the operculum
Adipose fin
Dorsal fin
Nostril
Spinal cord
Brain
Swim bladder
Cut edge of
operculum Gills
Heart
Figure 34.16
Gonad
Urinary
Anus bladder
Liver
Kidney
(characteristic of
trout)
Stomach Pelvic fin
Osteichthyes: Bony operculum
•  The bony operculum improves respiration
–  and allows for greater suction feeding
Shark
Bony fish
Caudal
fin
Anal fin
Lateral
line
Intestine
10
Osteichthyes: C. Actinopterygii Ray-Finned Fishes
Osteichthyes: C. Actinopterygii: Ray-Finned Fishes
•  Class Actinopterygii, the ray-finned fishes: the
familiar aquatic osteichthyans
•  Class Actinopterygii, the ray-finned fishes
includes nearly all the modern bony fishes
•  The fins are supported by long, flexible rays
(a) Yellowfin tuna (Thunnus
albacares), a fast-swimming,
schooling fish that is an important
commercial fish worldwide
–  Modified for maneuvering, defense, and other
functions
(b) Clownfish (Amphiprion
ocellaris), a mutualistic
symbiont of sea anemones
Figure 34.17a–d
(c) Sea horse (Hippocampus
ramulosus), unusual in
the animal kingdom in that
the male carries the young
during their embryonic
development
•  Most ray-finned fishes can use their pectoral
fins to swim forward, stop, hover, and even
swim backward
(d) Fine-spotted moray eel
(Gymnothorax dovii), a
predator that ambushes
prey from crevices in its
coral reef habitat
Class Actinopterygii: Ray-Finned Fishes
Class Actinopterygii: Ray-Finned Fishes
•  Ray-Finned fishes are the most diverse group
of chordates: 24,000 species (half the verts)
•  Flexible jaws & bony operculum provide suction
feeding & diverse specializations/niches
•  Additional specializations include:
–  Reduction in parts and size: 10 cm average
–  Reduced Parental Investment with increased
reproductive output (to 100’s/day)
–  Extreme sexual plasticity
–  Flexible jaws for feeding, digging, etc.
Osteichthyes: Class Sarcopterygii: Lobe-Fins
Osteichthyes, Sarcopterygii, Subclass(?) Tetrapoda
•  The lobe-fins, Class Sarcopterygii
•  Tetrapods are lunged gnathostomes with
supporting limbs and feet
–  Have muscular pectoral fins
–  Include coelacanths, lungfishes, and tetrapods
•  One of the most significant events in vertebrate
history
–  Was when the fins of some lobe-fins evolved
into the limbs and feet of tetrapods
Figure 34.18
11
Derived Characters of Tetrapods
The Origin of Tetrapods
•  Tetrapod adaptations (synapomorphies)
•  In one lineage of lobe-fins
–  Four limbs with rod-shaped bones, supporting
bones and feet with digits
–  Ears for detecting airborne sounds
–  The fins became progressively more limb-like
while the rest of the body retained adaptations
for aquatic life
Bones
supporting
gills
Figure 34.19
Osteichthyes, Sarcopterygii, Tetrapoda
•  Extraordinary
fossil
discoveries
over the past
20 years have
allowed
paleontologists
to reconstruct
the origin of
tetrapods
Tetrapod
limb
skeleton
Why leave the pond?
Millions of years ago
420
415
Silurian
400
385
Devonian
370
355
340
325
310
295
Carboniferous
280
265
Permian
Paleozoic
To
present
Ray-finned fishes
Coelacanths
Lungfishes
Eusthenopteron
Panderichthys
Elginerpeton
Metaxygnathus
Acanthostega
lchthyostega
Hynerpeton
Greerpeton
Amphibians
Amniotes
Figure 34.20
Origins of the Tetrapoda
Why leave the pond? II
•  Why leave the pond? Two main hypotheses
have been suggested
HI. Fish needed to leave the water because
shallow ponds were drying up
Evidence rejects HI.
Experiments in mixed aquaria/terraria found:
–  Fish retreat to the bottom of the pond when
water levels drop
12
Origins of the Tetrapoda
Tetrapoda: Amphibians
•  Why leave the pond?
•  Class Amphibia: two-lives
HII. Opportunity! Fish periodically ventured onto
land to exploit new niches (avoid predators?)
favoring terrestrial adaptations
–  Evidence supports HII:
–  Is represented by about 4,800 species of
organisms
•  Most amphibians have ‘two lives’
•  Many fishes today feed out of water
–  a larval aquatic stage followed by
metamorphosis into a terrestrial adult
•  Experiments find fish willing to leave water
for food, especially in damp conditions
–  and moist skin that complements the lungs in
gas exchange
Class Amphibia
Class Amphibia
•  Order Urodela
•  Order Anura
–  Includes salamanders, which have tails
(a) Order Urodela. Urodeles
(salamanders) retain their tail as adults.
Figure 34.21a
–  Includes frogs and toads, which lack tails
(b) Order Anura. Anurans, such as
this poison arrow frog, lack a tail as adults.
Figure 34.21b
Class Amphibia
Class Amphibia
•  Order Apoda
•  Amphibian means “two lives”
–  Includes caecilians, which are legless and
resemble worms
–  A reference to the metamorphosis of an
aquatic larva into a terrestrial adult
(c) Order Apoda. Apodans, or caecilians,
are legless, mainly burrowing amphibians.
(b) The tadpole is
an aquatic
herbivore with
a fishlike tail and
internal gills.
Figure 34.21c
(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
Figure 34.22a–c would desiccate in air.
(c) During metamorphosis, the
gills and tail are resorbed, and
walking legs develop.
13
Class Amphibia
Tetrapoda: Amniota
•  The future of Amphibians is bleak
•  Amniotes are fully adapted for terrestrial life
–  120 species lost since 1980
–  2000 species currently threatened
–  The double life and moist skin of amphibians
make them susceptible to environmental stress
e.g. UV radiation, pollution, habitat loss, etc.
–  Chytridomycosis (from chytrid fungus) may be
‘the straw that breaks the camel’s back’
•  Amniotes are tetrapods that have an
–  Amniotic egg
•  Amniotes are a group of tetrapods
–  Whose living members are the reptiles,
including birds and the extinct dinosaurs
–  and the mammals
–  Loss of amphibians will change ecosystems
Derived Characters of Amniotes
The Amniotic Egg
•  Amniotes are named for the major derived
character of the clade, the amniotic egg
•  Four extraembryonic membranes & functions
Extraembryonic membranes
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.
Allantois. The allantois is a disposal
sac for certain metabolic wastes produced by the embryo. The membrane
of the allantois also functions with
the chorion as a respiratory organ.
–  Which contains specialized membranes and a
shell that protect the 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”).
Amnion. The amnion protects
the embryo in a fluid-filled
cavity that cushions against
mechanical shock.
–  Internal fertilization, with live-bearing in some
•  Amniotes have other terrestrial adaptations:
Embryo
Amniotic cavity
with amniotic fluid
–  Relatively impermeable skin (keratin)
Yolk (nutrients)
–  Ability to use the rib cage to ventilate the lungs
Albumen
Shell
Figure 34.24
–  Appeared in the Carboniferous period
tes
als
ma
mm
ua
Ma
Sq
os
au
rs
tara
Ich
thy
Tu
a
ds
sio
sa
urs
Bir
Ple
Sa
u
din risch
os ian
tha aurs
n b oth
ird er
s
Cro
Pte
co
d
ilia
ns
les
rare
pti
Pa
ros
au
rs
Orn
it
din hisc
os hia
n
au
rs
The Amniotes
•  Early amniotes
les
Early Amniotes
Tu
rt
–  Included large herbivores and predators
Saurischians
•  Early amniotes gave rise to two groups:
Dinosaurs
–  Diapsids (refer to two holes in their skulls),
includes the modern Reptilia (including birds)
Lepidosaurs
Archosaurs
–  Synapsids (one hole in their skulls), includes
the modern Mammalia
Diapsids
Synapsids
Reptiles
Ancestral
amniote
Figure 34.23
14
Reptilia
•  The reptile clade includes
•  Reptiles
–  Chelonia: turtles
–  Have keratin scales that create a waterproof
barrier
–  Lepidosauria: lizards and snake, tuatara
–  Lay shelled eggs on land (some live-bearing)
–  Archosaurs: include the extinct dinosaurs &
•  Crocodilia: alligators, crocodiles, etc.
•  Aves: birds, derived from dinosaurs
Figure 34.25
The Origin and Evolutionary Radiation of Reptiles
•  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
•  The oldest reptilian fossils
–  Date to about 300 million years ago
•  The first major group of reptiles to emerge
–  Were the parareptiles, which were mostly
large, stocky herbivores
•  The diapsids diversified next, into two main
lineages
–  The lepidosaurs and the archosaurs
Reptilia: Archosauria
Reptilia: Archosauria
•  The Archosaurs include the extinct dinosaurs
•  Traditionally, dinosaurs were considered slow,
sluggish creatures
•  Dinosaurs
–  Diversified into a vast range of shapes and
sizes
–  Included the long-necked giants and
–  The theropods, which include Tyrannosaurus
rex, related bipedal carnivores, and their only
living descendants -
–  But fossil discoveries and research have led to
the conclusion that dinosaurs were agile and
fast moving
•  Paleontologists have also discovered signs of
parental care among dinosaurs
•  Birds, ‘Class’ Aves
Figure 34.26
15
Reptilia: Chelonia
•  Turtles
–  Are the most distinctive group of reptiles alive
today
•  All turtles have a boxlike shell
–  Made of upper and lower shields that are fused
to the vertebrae, clavicles, and ribs
–  Diverged early from other reptiles
•  Some turtles have adapted to deserts
–  others live entirely in ponds, rivers or oceans
Figure 34.27d (d) Eastern box turtle (Terrapene carolina carolina)
Reptilia: Lepidosauria
Reptilia: Lepidosauria: Squamata
•  One surviving lineage of lepidosaurs
•  The other major living lineage of lepidosaurs
–  Is represented by two species of lizard-like
reptiles called tuatara
–  Are the squamates, the lizards and snakes
•  Lizards
–  Are the most numerous and diverse reptiles,
apart from birds
Figure 34.27a
(a) Tuatara (Sphenodon punctatus)
Figure 34.27b (b) Australian thorny devil
lizard (Moloch horridus)
Squamata
Reptilia: Archosauria: Crocodylia
•  Snakes are legless lepidosaurs
•  Crocodylians: Alligators, crocodiles, caymans
–  That evolved from lizards
(c) Wagler’s pit viper (Tropidolaemus wagleri), a snake
Figure 34.27c
–  Belong to an archosaur lineage that dates back
to the late Triassic
Figure 34.27e (e) American alligator (Alligator mississipiensis)
16
Class Aves: Birds
Class Aves: Birds
•  Birds are the modern descendants of
dinosaurs: 8,600 species
•  Feathers are keratin derivatives
•  Birds evolved many adaptations to flight:
•  Increasing numbers of non-flying dinosaurs
show evidence of rudimentary feathers
–  Keeled sternum for flight muscles
–  Probably provided a thermoregulatory benefit
–  Reductions: loss of teeth, one ovary
–  May have become elaborated for
–  Increased metabolism: endothermy, fourchambered heart
•  Sexual displays
•  To trap food
–  Feathers, however, are NOT a synapomorphy
of the birds; ancestral dinosaur origin
•  Eventually aid in gliding
Derived Characters of Birds
•  A bird’s most obvious adaptations for flight
–  Are its wings and feathers (modified for flight)
•  By 150 million years ago
–  Feathered theropods had evolved into birds
•  Archaeopteryx
–  Remains the oldest bird known
Finger 1
Wing claw
Toothed beak
(b) Bone structure
Palm
(a) wing
Finger 2
Forearm
Wrist
Finger 3
Shaft
Vane
Shaft
Figure 34.28a–c
Barb
Barbule
Airfoil wing with
contour feathers
Hook
(c) Feather structure
Demands of Flight Select for a common Body Plan
Figure 34.29
Long tail with
many vertebrae
Variation in Bird Foot Structure
(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.
Perching bird
(such as a
cardinal)
Grasping bird
(such as a
woodpecker)
Raptor
(such as a
bald eagle)
Swimming bird
(such as a duck)
Figure 34.31
17
Tetrapoda: Amniota: Class Mammalia
Derived Characters of Mammals
•  Mammals are amniotes that have hair and
produce milk in mammary glands
•  Mammary glands, which produce milk
•  Mammals, class Mammalia
–  Are represented by more than 5,000 species
–  Are a distinctively mammalian character
•  Hair/fur (keratin) is also unique to mammals
•  Mammals evolved greater metabolism
–  Endothermy, four-chambered heart, diaphragm
•  Mammals have large brains for learning
–  Associated with a long time protected by
mother
Early Evolution of Mammals
Mammal Synapomorphy: Malleus, Incus & Stapes
•  Mammals evolved from synapsids
•  The jaw was remodeled during the evolution of
mammals from nonmammalian synapsids
–  In the late Triassic period (early Mesozoic)
•  Living lineages of mammals originated in the
Jurassic (middle Mesozoic)
–  And two of the bones that formerly made of the
jaw joint were incorporated into the mammalian
middle ear
Jaw joint
•  Mammals underwent significant adaptive
radiation in the Cenozoic
Key
Jaw joint
Dentary
Angular
Squamosal
Articular
Quadrate
Dimetrodon
Morganucodon
(a) The lower jaw of Dimetrodon is composed of several fused bones; two small bones, the quadrate
and articular, form part of the jaw joint. In Morganucodon, the lower jaw is reduced to a single bone,
the dentary, and the location of the jaw joint has shifted.
–  after the Cretaceous extinction of dinosaurs
(end of the Mesozoic)
Middle ear Stapes
Eardrum
Inner ear
Middle ear
Inner ear
Stapes
Eardrum
Sound
Sound
Incus (evolved
from quadrate)
Malleus (evolved
from articular)
Figure 34.32a, b
Morganucodon
Dimetrodon
(b) During the evolutionary remodeling of the mammalian skull, the quadrate and articular bones became incorporated
into the middle ear as two of the three bones that transmit sound from the eardrum to the inner ear. The steps in
this evolutionary remodeling are evident in a succession of fossils.
Class Mammalia
Monotremes
•  Mammals include three groups:
•  Monotremes: 5 species
–  Monotremes: lay eggs, no nipples
–  egg-laying mammals: echidnas & platypus
–  Live bearers (viviparous) with nipples
•  Marsupials: with a pouch-like marsupium
•  Eutherians: placentals
Figure 34.33
18
Marsupials
•  Marsupials: opossums, kangaroos, koalas, etc.
–  are born very early in development
–  complete embryonic development nursing
within a maternal pouch called a marsupium
(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 Australia,
convergent
evolution
Marsupial mammals
Eutherian mammals
Plantigale
Deer mouse
Mole
Marsupial mole
–  Has resulted in
a diversity of
marsupials that
resemble
eutherians in
other parts of
the world
Sugar glider
Flying squirrel
Wombat
Woodchuck
Wolverine
Tasmanian devil
Patagonian cavy
Kangaroo
Figure 34.34a
Figure 34.35
Eutherians (Placental Mammals)
Class Mammalia: Phylogeny
•  Compared to marsupials
–  Eutherians have a longer period of pregnancy
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.
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.
•  Young eutherians
Proboscidea Sirenia
Tubulidentata
Hyracoidea
Afrosoricida (golden
moles and tenrecs)
Macroscelidea
(elephant shrews)
–  Complete their embryonic development within
a uterus, joined to the mother by the placenta
Monotremata
Marsupialia
Monotremes
Marsupials
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.
Ancestral mammal
Monotremes
(5 species)
Class Mammalia: Phylogeny
Monotremata
Major Orders of Eutherians
MAIN
CHARACTERISTICS
ORDERS
AND EXAMPLES
Marsupials
(324 species)
ANCESTRAL
MAMMAL
Carnivora
Cetartiodactyla
Perissodactyla
Chiroptera
Eulipotyphla
Pholidota
(pangolins)
Eutherians
Figure 34.36
Rodentia
Lagomorpha
Primates
Dermoptera
(flying lemurs)
Scandentia
(tree shrews)
Xenarthra
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.
Lay eggs; no
nipples; young
suck milk from
fur of mother
Monotremata
Platypuses,
echidnas
Marsupialia
ORDERS
AND EXAMPLES
Echidna
Proboscidea
Elephants
Koala
Long, muscular
trunk; thick,
loose skin; upper
incisors elongated
as tusks
Tubulidentata
Aardvark
African elephant
Eutherians
(5,010 species)
Proboscidea
Sirenia
Tubulidentata
Hyracoidea
Afrosoricida (golden
moles and tenrecs)
Macroscelidea (elephant
shrews)
Hyracoidea
Hyraxes
Rock hyrax
Reduced teeth or
no teeth; herbivorous
(sloths) or carnivorous
(anteaters,
armadillos)
Rodentia
Squirrels,
beavers, rats,
porcupines,
mice
Tamandua
Lagomorpha
Rabbits,
hares, picas
Chisel-like incisors;
hind legs longer than
forelegs and adapted
for running and
jumping
Carnivora
Dogs, wolves,
bears, cats,
weasels, otters,
seals, walruses
Rodentia
Lagomorpha
Primates
Dermoptera (flying lemurs)
Scandentia (tree shrews)
Sharp, pointed canine
teeth and molars for
shearing; carnivorous
Perissodactyla
Horses,
zebras, tapirs,
rhinoceroses
Cetaceans
Whales,
dolphins,
porpoises
Hooves with an
even number
of toes on each
foot; herbivorous
Pacific whitesided porpoise
Hooves with an
odd number of toes
on each foot;
herbivorous
Indian rhinoceros
Chiroptera
Bats
Frog-eating bat
Bighorn sheep
Figure 34.36
Opposable thumbs;
forward-facing eyes;
well-developed
cerebral cortex;
omnivorous
Golden lion
tamarin
Coyote
Cetartiodactyla
Artiodactyls
Sheep, pigs
cattle, deer,
giraffes
Chisel-like, continuously
growing incisors worn
down by gnawing;
herbivorous
Red squirrel
Primates
Lemurs,
monkeys,
apes,
humans
Jackrabbit
Short legs; stumpy tail;
herbivorous; complex,
multichambered
stomach
Manatee
Xenarthra
Sloths,
anteaters,
armadillos
Xenarthra
Carnivora
Cetartiodactyla
Perissodactyla
Chiroptera
Eulipotyphla
Pholidota (pangolins)
Teeth consisting of
many thin tubes
cemented together;
eats ants and termites
Aardvark
Aquatic; finlike
forelimbs and
no hind limbs;
herbivorous
Sirenia
Manatees,
dugongs
MAIN
CHARACTERISTICS
Embryo completes
development in
pouch on mother
Marsupialia
Kangaroos,
opossums,
koalas
Aquatic; streamlined
body; paddle-like
forelimbs and no
hind limbs; thick
layer of insulating
blubber; carnivorous
Eulipotyphla
“Core insectivores”: some
moles, some
shrews
Adapted for flight; broad
skinfold that extends
from elongated fingers
to body and legs;
carnivorous or
herbivorous
Diet consists mainly
of insects and other
small invertebrates
Star-nosed
mole
19
Primates
Derived Characters of Primates
•  The mammalian order Primates include
•  Most primates
–  Lemurs, tarsiers, monkeys, and apes
•  Humans are members of the ape group
–  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
Living Primates
Anthropoids
•  Anthropoids
arose ~ 45 mya
Humans
Gorillas
Chimpanzees
Gibbons
Orangutans
Tarsiers
Old World monkeys
10
New World monkeys
0
Lemurs, lorises, and pottos
–  The lemurs of
Madagascar (photo) and
the lorises and pottos of
tropical Africa and
southern Asia
•  Fossils indicate
that tarsiers are
more closely
related to
anthropoids
•  There are three groups of
living primates:
20
30
–  The tarsiers of SE Asia
40
–  The anthropoids:
monkeys, apes and
humans
50
Figure 34.37
•  The first monkeys
–  Evolved in the Old World (Africa and Asia)
•  Monkeys first appeared in the New World
(South America) during the Oligocene
Figure 34.38
60
Ancestral primate
•  New World and Old World monkeys
–  Underwent separate adaptive radiations during
their many millions of years of separation
–  According to the fossil record
–  Arrived from Africa via rafting (?)
(a) New World monkeys, such as spider
(b) Old World monkeys lack a prehensile tail, and their nostrils
monkeys (shown here), squirrel monkeys, and
open downward. This group includes macaques (shown here),
capuchins, have a prehensile tail and nostrils
mandrills, baboons, and rhesus monkeys.
that open to the sides.
Figure 34.39a, b
20
•  The other group of anthropoids, the hominoids
–  Consists of primates informally called apes
•  Hominoids diverged from other Old World
monkeys about 20–25 million years ago
•  Humans are bipedal hominoids with a large
brain
(a) Gibbons, such as this Muller's gibbon, are
found only in southeastern Asia. Their very
long arms and fingers are adaptations for
brachiation.
•  Homo sapiens is about 160,000 years old
(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.
–  Which is very young considering that life has
existed on Earth for at least 3.5 billion years
–  Evolved in Africa
Figure 34.40a–e
(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.
Derived Characters of Hominids
The Earliest Humans
•  A number of characters distinguish humans
from other hominoids
•  The study of human origins
–  Upright posture and bipedal locomotion
–  Larger brains
–  Language capabilities
–  Is known as paleoanthropology
•  Paleoanthropologists have discovered fossils
of approximately 20 species of extinct
hominoids
–  That are more closely related to humans than
to chimpanzees
–  Symbolic thought
–  The manufacture and use of complex tools
–  Shortened jaw
–  These species and living humans make up the
Hominids
Hominids
Paranthropus
robustus
0
Paranthropus
boisei
0.5
1.0
2.5
3.0
3.5
5.0
Australopithecus
garhi
Homo
Homo
rudolfensis habilis
Australopithecus
afarensis
5.5
6.0
6.5
Figure 34.41
7.0
Homo
erectus
Australopithecus
anamensis
Ardipithecus
ramidus
•  Hominids originated in Africa
–  Approximately 6–7 million years ago
•  Early hominids
Kenyanthropus
platyops
4.0
4.5
?
Australopithecus
africanus
1.5
2.0
Homo
Homo
neanderthalensis sapiens
Homo
ergaster
–  Had a small brain, but probably walked upright,
exhibiting mosaic evolution
•  Note: some recent fossils suggest an
increase in brain size may have occurred
earlier than current predictions
Orrorin tugenensis
Sahelanthropus
tchadensis
21
Australopiths
•  Two common misconceptions of early hominids
include
–  Thinking of them as chimpanzees
•  Australopiths are a paraphyletic assemblage of
hominids
–  That lived between 4 and 2 million years ago
–  Imagining human evolution as a ladder leading
directly to Homo sapiens
Bipedalism & Tool Use
•  Some species walked fully erect
–  And had human-like hands and teeth
•  Hominids began to walk long distances on two
legs
–  About 1.9 million years ago
•  The oldest evidence of tool use—cut marks on
animal bones
(a) Lucy, a 3.24-million-year-old skeleton,
represents the hominid species
Australopithecus afarensis.
(b) The Laetoli footprints, more than
3.5 million years old, confirm that
upright posture evolved quite early
in hominid history.
–  Is 2.5 million years old
(c) An artist’s reconstruction of what
A. afarensis may have looked like.
Figure 34.42a–c
Early Homo
•  The earliest fossils that paleoanthropologists
place in our genus Homo
–  Are those of the species Homo habilis, ranging
in age from about 2.4 to 1.6 million years
•  Homo ergaster lived 1.9-1.6 million years ago
–  Was the first fully bipedal, large-brained
hominid
•  Stone tools have been found with H. habilis
–  Giving this species its name, which means
“handy man”
Figure 34.43
22
Neanderthals
•  Homo erectus
•  Neanderthals, Homo neanderthalensis
–  Originated in Africa 1.8 million years ago
–  Was the first hominid to leave Africa
–  Lived in Europe and the Near East from
200,000 to 30,000 years ago
–  Were large, thick-browed hominids
–  Became extinct a few thousand years after the
arrival of Homo sapiens in Europe
–  New genetic evidence suggests significant
interbreeding did NOT occur between these
species
Homo sapiens
•  Homo sapiens evolved in Africa
•  The rapid expansion of our species
–  Fossils at least 160,000 years old in Africa
–  Oldest fossil outside of Africa 50,000 years old
–  May have been preceded by changes to the
brain that made symbolic thought and other
cognitive innovations possible
Figure 34.45
Figure 34.44
Taxon A
Taxon B
Taxon C
Cephalaspidomorphi
Taxon D
CHONDRICHTHYES
Taxon E
Taxon F
airborne sounds
9. Claspers
10. Placoid scales
Synapomorphies 11 & 12
Synapomorphies 4-8
2. Median fins
23

Vertebrates

Transcription

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