Download Chapter-24

Animals II–
The Chordates
Chapter 24
Biology Concepts and Applications, Eight Edition, by Starr, Evers, Starr. Brooks/Cole,
Cengage Learning 2011.
24.1 Windows on the Past
Archaeopteryx Fossil
 Size of a large crow, long, bony tail, three
clawed fingers on each forelimb, and a heavy
jaw with short, spiky teeth, and feathers.
 Radiometric dating indicates that the fossil lived
150 million years ago.
 Most widely known transitional fossil in the bird
lineage
Fossils of China
 Sinosauropteryx prima
• Found in 1994 – China
• Flightless bird that used the feathers to stay warm
 Confuciusornis sanctus
• 1st bird with a beak
• Wings had digits with claws at their tips
Evolutionary Biology
 Fossils are physical evidence of changes and
radiometric dating assigns the fossils to places
in time
 Structure, biochemistry, and genetic makeup
provide information about branching
24.2 Chordate Heritage
 Four features define chordates
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A notochord
A dorsal hollow nerve cord
A pharynx with gill slits
A tail extending past the anus
 All features form in embryos
• May or may not persist in adults
Invertebrate Chordates
 Tunicates and lancelets (marine filter-feeders)
• Tunicate  invertebrate chordate that loses its
defining chordate traits during the transition into
adulthood
• Lancelet  invertebrate chordate that has a
fishlike shape and retains the defining chordate
traits into adulthood
Tunicate Body Plans
 Adult and larva
Lancelet Body Plan
Craniates
 Chordates with a braincase of cartilage or bone
• Hagfish (jawless fish): Simplest modern craniate
tentacles
gill slits (twelve pairs)
mucous glands
Fig. 24.5, p.387
Chordate Family Tree
1. Braincase Develops  Craniates
2. Backbone Develops  Vertebrates
- Endoskeleton: internal skeleton made up of
hardened components such as bones
3. Jaw Develops
4. Swim bladder or lungs Develop
5. Bony Appendages Develop
6. Four limbs develop  Tetrapods
7. Amniote eggs develop  Amniotes
- Amniote: vertebrate in which the embryo
develops surrounded by fluid by membranes
inside the egg
Key Concepts:
CHARACTERISTICS OF CHORDATES
 A unique set of four traits characterizes
chordates: a supporting rod (notochord), a
dorsal nerve cord, a pharynx with gill slits in the
wall, and a tail extending past an anus
 Certain invertebrates and all vertebrates belong
to this group
Vertebrate Evolution
 Key innovations laid the foundation for adaptive
radiations of vertebrates
• Vertebral column of cartilaginous or bony
segments
• Jaws evolved in predatory fishes
• Gills evolved in water, then lungs for dry land
• Paired fins were a starting point for other limbs
24.3 The Fishes
Early Body Forms – Lamprey Vertebrate
Hagfish  Jawless fish with a skull case but no backbone
Lamprey  Jawless fish with a backbone of cartilage
Gill-Supporting Structures and the
Evolution of the Jaw
Fig. 24.7, p.388
Fig. 24.7, p.388
Fig. 24.7, p.388
Major Vertebrate Groups
Key Concepts:
TRENDS AMONG VERTEBRATES
 In some vertebrate lineages, a backbone
replaced the notochord as the partner of
muscles used in motion
 Jaws evolved, sparking the evolution of novel
sensory organs and brain expansions
Key Concepts:
TRENDS AMONG VERTEBRATES (cont.)
 On land, lungs replaced gills, and more efficient
blood circulation enhanced gas exchange
 Fleshy fins with skeletal supports evolved into
limbs, now typical of vertebrates on land
Jawed Fishes and Tetrapods
 Jawed fishes
• Cartilaginous fishes (sharks and rays)
• Skeleton of cartilage
• Bony fishes
• Lungs or swim bladder and a skeleton of bone
 Body plans adapted to life in water
• Streamlined shape reduces drag
• Swim bladder (in bony fishes) adjusts buoyancy
Cartilaginous Fishes
Bony Fishes
 The most diverse vertebrates
• Lungfishes
• Lobe-finned fishes (coelacanth)
• Fleshy fins that contain bones
• Ray-finned fishes
• Fins supported by thin rays
derived from skin
Body Plan: Ray-Finned Bony Fishes
24.4 Amphibians – The First Tetrapods
 Late in the Devonian, lobe-finned bony fishes
gave rise to tetrapods (four-legged vertebrates)
Early Lineages
 Coelacanth, lungfish, and Devonian tetrapod
Amphibians
 Amphibians
• Tetrapod with a three-chambered heart and
scaleless skin
• Typically develops in water then lives on land as
a carnivore with lungs
 Frogs, toads, and salamanders
• Carnivorous vertebrates
• First to evolve from aquatic Devonian tetrapods
• Adapted to life on land (lungs, 3-chambered
heart)
• Nearly all return to the water to reproduce
Amphibian Evolution
Vanishing Amphibians
 Many amphibians now face extinction due to
pollution and habitat loss
 Frog deformity due to infection from fluke
Key Concepts:
TRANSITION FROM WATER TO LAND
 Vertebrates first evolved in the seas, where
lineages of cartilaginous and bony fishes persist
 Of all vertebrates, modern bony fishes show the
most diversity
 Mutations in master genes that control body
plans were pivotal in the rise of aquatic
tetrapods and their move onto dry land
24.5 Amniotes
 First vertebrates able to complete their life cycle
on dry land
• Water-conserving skin and kidneys
• Amniote eggs (four membranes)
• Allow amniote embryo to develop away from
water
• Active life-styles
 Reptiles
• Amniote subgroup that includes lizards, snakes,
turtles, crocodilians, and birds
Amniote Eggs
Amniote Family Tree
24.6 Nonbird Reptiles
 Major Groups
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Turtles (shell attached to skeleton)
Lizards (the most diverse reptiles)
Snakes (limbless)
Tuataras (some amphibian-like traits; third eye)
Crocodilians (closest relatives of birds)
24.6 Nonbird Reptiles
 Ectotherm “heated from outside”
• Control its internal temperature by altering its
behavior – sitting on a warm rock
• “cold-blooded” animals
• Fish and amphibians
 Endotherms “heated from within”
• Control its internal temperature by adjusting it
metabolism
• Birds and mammals
Reptile Characteristics
 General characteristics
• Live on land or in water
• Cold-blooded
• Have a cloaca (opening for wastes and
reproduction)
• Eggs are fertilized in the body, usually laid on
land
Turtle
Bony shell attached to their skeleton
When threatened, withdraw into shell
Lived in the sea about 200 million years ago
No Teeth – horny beak over their jaw
Crocodilian
Closest living relative of birds, four chamber heart.
Jaw, snout, and sharp teeth
Can weigh up to 2,200 lbs
hindbrain, midbrain,
forebrain
olfactory lobe
(sense of smell)
spinal vertebral
column
cord
gonad
kidney (control of water,
solute levels in internal
environment)
snout
unmatched rows
of teeth on upper
and lower jaws esophagus lung heart liver stomach
intestine
cloaca
Fig. 24.16, p.396
24.7 Birds – Reptiles with Feathers
 Birds are warm-blooded amniotes
 Only living animals with feathers
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•
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Light weight
Derived from scales
Insulates
Allows for flight
Displays courtship
Adaptations for Flight and Migration
 Feathers, lightweight bones, and highly efficient
respiratory and circulatory systems
Bird Skeleton and Flight Muscles
skull
internal
structure
of bird
limb bones
radius
ulna
pectoral
girdle
humerus
pelvic
girdle
Sternum
(breastbone)
two main flight
muscles attached
to keel of sternum
Stepped Art
Fig. 24.21, p.399
24.8 Mammals
 Animals with hair or fur
 Females that nourish young with milk from
mammary glands
 a single lower jawbone and four kinds of teeth
incisors
molars
premolars
canines
Fig. 24.22, p.400
Modern Mammals
 Three major lineages
• Egg-laying mammals (monotremes)
• Pouched mammals (marsupials)
• Placental mammals (eutherians), the most
diverse and widespread mammals
Three Major Lineages
Placental Mammals
placenta
uterus
embryo
Fig. 24.25, p.401
Key Concepts:
THE AMNIOTES
 As a group, the amniotes—known informally as
the reptiles, birds, and mammals—are
vertebrate lineages that radiated into nearly all
habitats on land
24.9 Primates
 Include prosimians (lemurs and tarsiers),
anthropoids (such as monkeys and apes), and
hominids (humans and extinct humanlike forms)
Primates
Primate Evolution
 Key trends
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Better daytime vision
Upright walking (bipedalism)
More refined hand movements
Smaller teeth
Bigger brains
Social complexity (extended parental care;
culture evolved in some lineages)
• Grasping hands with nails
The Foramen Magnum
 Four-legged walkers versus upright walkers
Origins and Early Divergences
 Early primates were shrewlike
Tree Shrew
24.10 Emergence of Early Humans
 Hominoids and hominids originated in Africa
Australopiths: Upright Walking
Early Humans
 Humans (Homo) arose 2 million years ago
• H. habilis was an early toolmaking species
• H. erectus dispersed into Europe and Asia
24.11 Emergence of Modern Humans
 Extinct Neandertals and modern humans are
close relatives with distinct gene pools
 Modern H. sapiens evolved 195,000 years ago
Multiregional Model
 H. erectus populations in many regions slowly
evolve into H. sapiens
Replacement Model (African Emergence)
 Modern humans evolved from H. erectus in
Africa, then dispersed and replaced H. erectus
populations, driving them to extinction
Multiregional model
Replacement model
Fig. 24.34, p.406
African Emergence
 Most data support the
African emergence
model
• Regional variations
among human
groups evolved very
recently
• Influenced by longterm shifts in climate
Dispersal of Homo sapiens
 Based on fossils and studies of genetic markers
Key Concepts: EARLY HUMANS
AND THEIR ANCESTORS
 Primates that were ancestral to the human
lineage became physically and behaviorally
adapted to changes in global climate and
available resources
 Behavioral and cultural flexibility helped humans
disperse from Africa throughout the world
Animation: Amniote egg
Animation: Avian bone and muscle
structure
Animation: Bony fish body plan
Animation: Cartilaginous fishes
Animation: Crocodile body plan
Animation: Evolution of jaws
Animation: Evolution of limb bones
Animation: Feather development
Animation: Fossils of australopiths
Animation: Homo skulls
Animation: Jawless fishes
Animation: Lancelet body plan
Animation: Mammalian radiations
Animation: Primate skeletons
Animation: Structure of the placenta
Animation: Tortoise shell and skeleton
Animation: Tunicate body plan
Animation: Vertebrate evolution