Teresa Audesirk • Gerald Audesirk • Bruce E. Byers
Biology: Life on Earth
Eighth Edition
Lecture for Chapter 24
Animal Diversity II:
Vertebrates
Copyright © 2008 Pearson Prentice Hall, Inc.
Chapter 24 Outline
• 24.1 What Are the Key Features of Chordates?
p. 470
• 24.2 What Are the Major Groups of
Vertebrates? p. 472
Section 24.1 Outline
• 24.1 What Are the Key Features of
Chordates?
– Invertebrate Chordates Lack a Backbone
– Vertebrates Have a Backbone
Key Features of Chordates
• All chordates possess four features at some
stage of their lives:
• Notochord
– Stiff flexible rod extending the length of the body
• Dorsal, hollow nerve cord
– Expands anteriorly to form brain
• Pharyngeal gill slits
– May form respiratory organs or may appear as
grooves
• Post-anal tail
– Extends past the anus
Are Humans Chordates?
• Humans are members of the Phylum
Chordata
FIGURE 24-1
An evolutionary tree of
the chordates
Are Humans Chordates?
• Only one chordate characteristic, the
nerve cord, is present in adult humans;
however, human embryos exhibit all four
– Tail will disappear completely
– Notochord is replaced by the backbone
– Gill slits (grooves) contribute to the formation
of the lower jaw
FIGURE 24-2 Chordate features in the human embryo
This 5-week-old human embryo is about 1 centimeter long and clearly shows a
tail and external gill slits (more properly called grooves, since they do not
penetrate the body wall). Although the tail will disappear completely, the gill
grooves contribute to the formation of the lower jaw.
Vertebrate Chordates
• Have a backbone (vertebral column)
composed of bone or cartilage
(resembles bone, but is more flexible)
– Supports body
– Provides attachment sites for muscles
– Protects nerve cord and brain
Vertebrate Adaptations
• Several adaptations have allowed
vertebrates to successfully invade most
habitats
– Endoskeleton that can grow and repair itself
– Paired appendages (fins, legs, wings)
– Increased size and complexity of the brain
and sensory structures
Section 24.2 Outline
• 24.2 What Are the Major Groups of
Vertebrates?
– Some Vertebrates Lack Jaws
– Jawed Fishes Rule Earth’s Waters
– Amphibians Live a Double Life
– Reptiles and Birds Are Adapted for Life on
Land
– Mammals Provide Milk to Their Offspring
Major Vertebrate Groups
• Present-day vertebrates include jawless
fishes, cartilaginous fishes, bony fishes,
amphibians, reptiles, birds, and mammals
Jawless Fishes
• Jawless
• Have eel-shaped bodies and smooth
unscaled skin
• Include the hagfishes (class Myxini) and
the lampreys (class Petromyzontiformes)
Hagfishes
• Exclusively marine (live near ocean floor)
• Feed primarily on worms
• Secrete massive quantities of slime as a
defense against predators
• Lack a true backbone (not a true
vertebrate), but have a rudimentary
braincase
• Represent the chordate group that is most
closely related to the vertebrates
FIGURE 24-4a Jawless fishes
(a) Hagfishes live in communal burrows in mud, feeding on
worms.
Lampreys
• Spinal cord protected by cartilaginous
segments
• Live in both fresh and salt waters
– Marine forms must return to fresh water to
spawn
• Some species are parasites of larger fish
– Attach to host with suckerlike mouths
– Rasping teeth on tongue used to suck blood
and body fluids
FIGURE 24-4b Jawless fishes
(b) Some lampreys are parasitic, attaching to fish (such as this
carp) with sucker-like mouths lined with rasping teeth (inset).
Jawed Fishes
• Appeared in the fossil record about 425
million years ago
• Jaws permit fish to exploit a wider range of
food sources than could jawless fish
• Present-day jawed fishes include the
cartilaginous fishes and the bony fishes
Cartilaginous Fishes
•
•
•
•
Class Chondrichthyes
Marine
Cartilaginous skeleton
Body protected by a leathery skin
embedded with tiny scales
Cartilaginous Fishes
• Respire using gills
• Two-chambered heart
• Tend to sink when they stop swimming
because they lack a swim bladder
• Includes sharks, skates, and rays
Sharks
• Many have several rows of razor-sharp
teeth
– Back rows move forward as front teeth are
lost
FIGURE 24-5a
Cartilaginous fishes
(a) A sand tiger shark
displaying several rows
of teeth. As outer teeth
are lost, they are
replaced by the new
ones behind them.
Both sharks and rays
lack a swim bladder
and tend to sink toward
the bottom when they
stop swimming.
Skates and Rays
• Some have a spine near the base of the
tail
– Capable of inflicting dangerous wounds
• Others produce an electrical shock that
can stun prey
• Swim by undulating lateral extensions of
the body
FIGURE 24-5b Cartilaginous fishes
(b) The tropical blue-spotted stingray swims by graceful
undulations of lateral extensions of the body.
Bony Fishes
• Bony fish are found in nearly every watery
habitat, both freshwater and marine
• Include
– Ray-finned fishes
– Lobe-finned fishes
Ray-Finned Fishes
• Class Actinopterygii
• Most diverse and abundant group of
vertebrates
• Live in marine and freshwater habitats
• Bony skeleton
• Skin covered with interlocking scales
FIGURE 24-6a The diversity of ray-finned fishes
Ray-finned fishes have colonized nearly every aquatic habitat. (a) This female
deep-sea anglerfish attracts prey with a living lure that projects just above her
mouth. The fish is ghostly white; at the 6000-foot depth where anglers live, no
light penetrates and thus colors are unnecessary. Male deep-sea anglerfish are
extremely small and remain attached to the female as permanent parasites,
always available to fertilize her eggs. Two parasitic males can be seen attached
to this female.
FIGURE 24-6b The diversity of ray-finned fishes
(b) This tropical green moray eel lives in rocky crevices. A small
fish (a banded cleaner goby) on its lower jaw eats parasites that
cling to the moray's skin.
FIGURE 24-6c
The diversity of ray-finned
fishes
(c) The tropical seahorse
may anchor itself with its
prehensile tail (adapted for
grasping) while feeding on
small crustaceans.
Ray-Finned Fishes
• Two-chambered heart
• Gills for respiration
• Most have a swim bladder that allows
them to float effortlessly at any level
• Important food source for humans
Lobe-Finned Fishes
• Two lineages have been evolving
separately for hundreds of millions of
years
– Coelacanths (Actinista)
– Lungfish (Dipnoi), the closest living relatives
of tetrapods
Lobe-Finned Fishes
• Fleshy fins that contain rod-shaped bones
surrounded by a thick layer of muscle
• Lungfish are found in freshwater habitats
• Have both gills and lungs
• Tend to live in stagnant waters low in
oxygen
• Lungs allow them to supplement their
supply of oxygen by breathing air directly
FIGURE 24-7a Lungfish are lobe-finned fish
Among the fishes, (a) lungfish are the group most closely
related to land-dwelling vertebrates.
Lobe-Finned Fishes
• Some species can survive even if the
water dries up
– Burrow into mud
– Seal themselves in a mucous-lined chamber
and breathe through lungs as metabolic rate
slows
– Resume underwater life when rains return
and pool refills
FIGURE 24-7b Lungfish are lobe-finned fish
(b) Lungfish may wait out dry periods sealed in burrows
in the mud.
Lobe-Finned Fishes
• Some early groups had modified fleshy
fins that could be used to drag themselves
from a drying puddle to a deeper pool
• Gave rise to the first vertebrates to invade
land: the amphibians
Amphibians Live a Double Life
• Include frogs, toads, and salamanders
• “Double life” of amphibians
– Begin life adapted to aquatic environment
(e.g. tadpoles have gills)
– Mature into semi-terrestrial adult with lungs
FIGURE 24-8a "Amphibian" means "double life”
The double life of amphibians is illustrated by the bullfrog's
transition from (a) a completely aquatic larval tadpole to (b) an
adult leading a semi-terrestrial life.
FIGURE 24-8c "Amphibian" means "double life”
(c) The red salamander is restricted to moist habitats in the
eastern United States. Salamanders hatch in a form that closely
resembles the adult
Amphibians
• Three-chambered heart
• Most adults respire through lungs and moist
skin
• Most have four limbs
• Reproduce sexually; external fertilization
• Most are confined to damp terrestrial habitats
(skin must be kept moist; use of external
fertilization; eggs and larvae develop in
water)
Reptiles and Birds
•
•
•
•
•
Adapted for life on land
Respire through lungs exclusively
Skin is less permeable
Fertilization is internal
Shelled amniotic egg (encapsulates
embryo in a liquid filled membrane, the
amnion)
FIGURE 24-10 The amniote egg
An anole lizard struggles free of its egg. The amniotic egg
encapsulates the developing embryo in a fluid-filled membrane
(the amnion), ensuring that development occurs in a watery
environment, even if the egg is far from water.
Reptiles
• Evolved from an amphibian ancestor
about 250 million years ago
• Tough, scaly skin (protects body and
resists water loss)
• Modified three-chambered heart (better
separation of oxygenated and
deoxygenated blood)
• Include the dinosaurs (extinct), lizards,
snakes, turtles, alligators, and crocodiles
FIGURE 24-9a The
diversity of reptiles
(a) This milk snake has
a color pattern very
similar to that of the
poisonous coral snake,
which potential
predators avoid. This
mimicry helps the
harmless milk snake
elude predation.
FIGURE 24-9b The diversity of reptiles
(b) The outward appearance of the American alligator, found in
swampy areas of the South, is almost identical to that of 150million-year-old fossil alligators.
FIGURE 24-9c The diversity of reptiles
(c) The tortoises of the Galapagos Islands, Ecuador, may live to
be more than 100 years old.
Birds
• Appeared in the fossil record about 150
million years ago
• Considered by modern systematists to be
‘feathered reptiles’
– The earliest known bird, Archaeopteryx
FIGURE 24-12 Archaeopteryx, the earliest-known bird
Archaeopteryx is preserved in 150-million-year-old limestone.
Feathers, a feature unique to birds, are clearly visible; but the
reptilian ancestry of birds is also apparent: like a modern reptile (but
unlike a modern bird), Archaeopteryx had teeth, a tail, and claws.
Birds
• Distinctive group of “reptiles” adapted for
flight
– Feathers (provide lift and control as well as
insulation)
– Hollow bones (reduce weight of skeleton)
– Females have a single ovary
– Shelled egg (frees female from carrying
developing offspring)
Birds
• Maintain a constant body temperature
(warm-blooded)
• High metabolic rate
– Increases demand for energy
• Must eat frequently
– Requires efficient oxygenation of tissues
• Heart has four chambers (prevents mixing
of oxygenated and deoxygenated blood)
• Respiratory system with air sacs that
provide a continuous supply of oxygen
FIGURE 24-11a The diversity of birds
(a) The delicate hummingbird beats its wings about 60 times per
second and weighs about 0.15 ounce (4 grams).
FIGURE 24-11b The
diversity of birds
(b) This young frigate
bird, a fish-eater from the
Galapagos Islands, has
nearly outgrown its nest.
FIGURE 24-11c The diversity of birds
(c) The ostrich, the largest of all birds, weighs more than 300
pounds (136 kilograms); its eggs weigh more than 3 pounds
(1500 grams).
Mammals
• Appeared in the fossil record about 250
million years ago
• Did not diversify and dominate terrestrial
habitats until the dinosaurs became extinct
(65 million years ago)
FIGURE 24-15a The diversity of placental mammals
(a) A humpback whale gives its offspring a boost.
FIGURE 24-15b The diversity of placental mammals
(b) A bat, the only type of mammal capable of true flight,
navigates at night by using a kind of sonar. Large ears help the
animal detect echoes as its high-pitched cries bounce off
nearby objects.
FIGURE 24-15d The diversity
of placental mammals
(d) The male orangutan can
weigh up to 75 kilograms
(165 pounds). These gentle,
intelligent apes occupy
swamp forests in limited
areas of the tropics but are
endangered by hunting and
habitat destruction
Mammals
•
•
•
•
•
Warm-blooded with high metabolic rates
Four-chambered heart
Most have hair that protects and insulates
Most have legs designed for running
Have sweat, scent, and sebaceous (oilproducing) glands
• Females have mammary glands that
produce milk to nourish young
FIGURE 24-15c
The diversity of placental
mammals
(c) Mammals are named
after the mammary
glands with which
females nurse their
young, as illustrated by
this mother cheetah.
Mammals
• Brain is highly developed
– Increases survival in a changing environment
– Allows for the alteration of behavior based on
experience
• Extended parental care after birth
– Allows some mammals to learn extensively
under parental guidance
• Subdivided into three groups
1) Monotremes
2) Marsupials
3) Placental mammals
1) Monotremes
• Include the platypus and spiny anteater
– Lay leathery eggs
– Newly hatched young nourished by milk
FIGURE 24-13a Monotremes
(a) Monotremes, such as this platypus, lay leathery eggs
resembling those of reptiles. Platypuses live in burrows that they
dig on the banks of rivers, lakes, or streams.
FIGURE 24-13b Monotremes
(b) The short limbs and heavy claws of spiny anteaters (also
known as echidnas) help them unearth insects and earthworms to
eat. The stiff spines that cover a spiny anteater's body are
modified hair
2) Marsupials
• Include the opossums, koalas, kangaroos,
wallabies, wombats, and the Tasmania
devil
FIGURE 24-14b&c Marsupials
(b) The wombat is a burrowing marsupial whose pouch opens
toward the rear of its body to prevent dirt and debris from entering
the pouch during tunnel digging. One of the wombat's predators
is (c) the Tasmanian devil, the largest carnivorous marsupial.
2) Marsupials
• Embryos begin development in the uterus
of the female
• Young are born at a very immature stage
and must crawl to and grasp a nipple to
complete development
• Post-birth development, in most, is
completed in a protective pouch
FIGURE 24-14a Marsupials
(a) Marsupials, such as the
wallaby, give birth to
extremely immature young
who immediately grasp a
nipple and develop within
the mother's protective
pouch (inset).
3) Placental Mammals
• Include most mammals
• Highly diverse class includes: bat, mole,
impala, whale, seal, monkey, and cheetah
• Rodents most numerous mammals (40%)
• Young retained in uterus for entire
embryonic development
• Uterus contains a placenta that functions
in gas, nutrient, and waste exchange
between circulatory systems of mother
and embryo