Chapter 25: Vertebrate Diversity
25.1: Vertebrate Origins
• 25.1: Vertebrate Origins
• Objectives: Identify and give examples of
the three groups of organisms in the phylum
Chordata.
• Describe the characteristics and origins of
vertebrates.
• Warm Up: In what obvious way is a snake
different from a worm?
• Words to Know: Chordate, Notochord,
Endoskeleton
Phylum Chordata
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The phylum Chordata is made of three groups: Urochordata,
Cephalochordata, and Vertebrates
Both Urochordates and Cephalochordates are invertebrates.
Urochordates are Tunicates like sea squirts.
Cephalochordates are Lancelets that spend most of their lives buried in the
sand.
Vertebrates are large, active animals that have a well-developed brain
encased in a hard skull.
ALL Chordates share the same four features at some stage in development:
– Notochord – a flexible skeletal support rod embedded in the animal’s back.
– Hollow Nerve Cord – runs along the animal’s back.
– Pharyngeal Slits – slits through the body wall in the pharynx, where water can
enter the mouth
and leave the animal through these slits without passing
through the entire digestive system.
– Tail – extends beyond the anal opening and contain muscles for movement.
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Most chordate groups lose some or all of these characteristic in adulthood,
but they are present in the embryo.
How are humans similar to sea squirts? How are they different?
Phylum Chordata
Vertebrate Common Features
• Endoskeletons
• An Endoskeleton is an internal
skeleton built of bone or
cartilage.
• Vertebrate endoskeletons can be
divided into distinct parts.
– Braincase – protects the brain.
– Vertebrae – a series of short,
stiff vertebrae are separated by
joints and protect the spinal
cord.
– Bones – support and protect the
body’s soft tissues and provide
points for muscle attachment.
– Gill Arches – found in fish and
some amphibians; help support
the gills.
• Vertebrate endoskeletons can
slowly change size and shape.
Vertebrate Common Features
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Vertebrate Classes
There are currently 7 classes of vertebrates:
Agnatha – jawless fish including lampreys.
Chondrichthyes – cartilaginous fish that include sharks, rays, and
chimeras.
Osteichthyes – bony fish that include ray-finned fish, trout, and
goldfish.
Amphibia – first vertebrates adapted to land and include frogs,
toads, salamanders, and caecilians.
Reptilia – can retain moisture and live exclusively on land. Include
snakes, lizards, crocodiles, alligators and turtles.
Aves – Birds, animals with feathers.
Mammals – animals with fur, mammary glands, and three middle ear
bones. Includes humans, elephants, kangaroos etc…
How does growth differ between an animals with an endoskeleton
and an animal with an exoskeleton?
Vertebrate Classes
Origins of Vertebrates
• Much of what we
know comes from
fossil evidence found
in the Burgess Shale
locates in the
Canadian Rocky
Mountains in the early
1900’s.
• Many are dated
around the Cambrian
explosion.
Closest Relatives
• Tunicates may
actually be the closest
relatives of
vertebrates.
• Scientists have found
that tunicates have
cells that resemble
the neural crest that is
also found in
vertebrates.
Early Vertebrates
• The first recognizable
vertebrates were fish.
• The oldest fish fossils
date back 530 million
years.
• Early fish were small,
jawless bottomfeeders.
Lampreys
• There are more than 35
species of Lampreys.
• They are highly specialized
fish parasites.
• Physical Characteristics
include:
– Long and slender body plans
with NO paired fins.
– Mouths surrounded by large
suckers.
– Tongues covered by tooth-like
projections.
• The accidental introduction of
sea lampreys into the Great
Lakes in the early 1900’s had a
devastating effect on the
fishing industry.
Hagfish
• A jawless eel-like
animal with a partials
skull but NO
vertebrae.
• It uses a notochord
for support.
• How have scientists’
views on the origins
of vertebrates
changed?
25.2: Fish Diversity
• 25.2: Fish Diversity
• Objectives: Identify the characteristics of the
two classes of jawed fishes.
• Describe the evolution and advantage of
jaws.
• Warm Up: If you dive into a cold lake without
scuba gear or a wetsuit, and you remain
underwater and motionless for a few
moments, what problems will you have?
• Words to Know: Gill, Countercurrent Flow,
Lateral Line, Operculum
Fish
• Fish use specialized organs called gills to take in
the oxygen dissolved in water.
• Gills are large sheets of thin frilly tissue filled
with capillaries that take in dissolved oxygen
from the water and release carbon dioxide.
• Fish circulatory systems pump blood in a single
circulatory loop through a heart with two main
chambers.
Countercurrent Flow
• Countercurrent Flow is the opposite movement
of water against the flow of blood in the fish’s
gills.
• Countercurrent flow maximizes the amount of
oxygen the fish can pull from the water by
diffusion.
Swimming and Maneuvering
• Most fish swim by
contracting large
segmented muscles on
either side of their
vertebral column from the
head to the tail.
• Fins help keep fish
stable.
• What is the connection
between countercurrent
flow and a fish’s
movement in the water?
Jaws
• Jaws evolved from gill arches.
• Gill arches are structures
made of bone or cartilage that
function as a support for fish’s
fills.
• Jaws developed from gill
arches near the mouth, which
fused to the cranium.
• Jaws gave vertebrates a huge
advantage as predators and
quickly pushed them to the top
of the food chain.
• What advantages are provided
to an animal that has jaws,
compared with an animal that
does not have jaws?
Two Groups of Jawed Fish
• Jawed fish diversified very
quickly after their first
appearance about 440 million
years ago.
• Four groups appeared at this
time:
– Acanthodians – were fish
covered with spines and
became extinct 250 million
years ago.
– Placoderms – were heavily
armored with huge bony
plates and became extinct 350
million years ago.
– Cartilaginous Fish – Skeletons
are made of cartilage and
include sharks, rays and
chimera.
– Bony Fish – Include all other
living fish
Cartilagenous Fish (Chondrichthyes)
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Have skeletons made of cartilage.
Their cartilage contains calcium deposits
that make it stiffer than the squishy stuff
around human joints.
Chimeras are a small group of deep-sea
fish with plate-like grinding teeth that feed
on crustaceans.
There are more than 300 species of
shards and nearly 400 species of rays
and skates.
All are predators.
Cartilaginous fish have internal
fertilization and many give birth to live
young.
They are also powerful simmers with
good eyesight and an excellent sense of
smell.
All fish have a Lateral Line system, which
is a series of shallow canals on the sides
of the fish made up of cells that are
sensitive to small changes in water
movement.
This give fish a sense of “distant touch”
letting them sense movement in the
water far away.
Bony Fish (Osteichthyes)
• All other living fish have
skeletons made of bone.
• There are more than
20,000 species of bony
fish living in almost all
aquatic environments.
• The gills of all bony fish
are in a chamber covered
by a protective plate
called the operculum.
– This helps fish move water
over their gills.
• What is the difference
between cartilaginous
and bony fish?
25.3: A Closer Look at Bony Fish
• 25.3: A Closer Look at Bony Fish
• Objectives: Differentiate between the fins of
ray-finned fish and lobe-finned fish.
• Describe the diversity of body plans of bony
fish.
• Explain the origin and function of a fish’s
swim bladder.
• Warm Up: Write common names of fish.
Which of those are bony fish?
• Words to Know: Ray-fin, Swim Bladder,
Lobe-fin
Ray-finned Fish
• All ray-finned fish,
such as goldfish and
tuna, have fins
supported by a fan
shaped array of
bones called a ray-fin.
• Ray-finned fish can
quickly change a fin’s
shape, making it
easier for the fish to
maneuver in the
water.
Diversity of Body Plans
• Long torpedo-shaped fish,
such as barracuda are ambush
predators.
• Fish that are flattened from
side to side, like butterfly fish,
are great at maneuvering
through corals.
• Fish that feed on the surface of
the water have flattened heads
and mouths that point up.
• Flatfish are flat-shaped and lie
on the sea floor waiting for
their prey to swim by.
• Some slow-swimming fish use
camouflage to hide from
predators or prey.
Staying Afloat
• Most ray-finned fish have lungs modified into a
buoyancy organ called a Swim Bladder.
• The Swim Bladder, helps a fish float higher or
lower in the water, by increasing and decreasing
oxygen levels.
• What is a swim bladder and how does it work?
Lobe-Finned Fish
• The lob-finned fish
include the ancestors of
all terrestrial vertebrates.
• Most species are extinct.
• Lobe-fins are paired
pectoral and pelvic fins
that are round in shape.
• These fins are arranged
around a branching
series of bony struts, like
the limbs of a land
vertebrate.
Coelacanths
• Are distinctive-looking fish with thick,
fleshy fins and a tail with three lobes.
• They breathe with gills.
Lungfish
• Live in streams and
swamps in Australia,
South America, and
Africa.
• They can breathe with
either gills or lungs.
• How are lobe-fins
related to vertebrae
evolution?
25.4: Amphibians
• 25.4: Amphibians
• Objectives: Describe the adaptations of amphibians
that help them live on land.
• Summarize the reproduction and development of
amphibians.
• Distinguish among the three groups of modern
amphibians.
• Warm Up: Of the following animals, which are
amphibians: frog, turtle, snake, alligator, toad,
salamander, iguana?
• Words to Know: Tetrapod, Amphibian, Tadpole
Amphibians
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One of the oldest known fossils of a
four-limbed vertebrate was found in
360 million-year-old rocks from
Greenland.
All of the vertebrates that live on
land, as well as their descendants
that have returned to aquatic
environments, are Tetrapods.
A Tetrapod is a vertebrate that has
four limbs.
Amphibians are animals that can live
BOTH on land and in water.
Amphibian literally means “life on
both sides”.
Depending on the species,
amphibians breathe through their
skin or with the use of gills or lungs.
Amphibians have a threechambered heart.
What adaptations helped
amphibians move from water to live
on land?
Amphibian Reproduction
• Amphibians need a source
of water to reproduce.
• Amphibians have several
ways to stop eggs from
drying out that include:
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Laying eggs directly in water,
Laying eggs on moist ground.
Wrapping eggs in leaves.
Brooding eggs in pockets on
the female’s back.
• Some frogs start off as
Tadpoles – aquatic larvae
that have gills and a broadfinned tail.
Amphibian Metamorphosis
• To grow into terrestrial adults,
tadpoles must undergo
metamorphosis.
– Eggs hatch to release tadpoles.
– As the tadpole matures, the gills
are reabsorbed and lungs
develop.
– The circulatory system is
reorganized to send blood to the
lungs.
– The tail fin is reabsorbed.
– The body grows limbs and
completely reorganizes its
skeleton, muscles, and parts of
the nervous
system.
• Many Amphibians do NOT
undergo metamorphosis and
develop directly into their
terrestrial forms.
• Describe the stages of
amphibian metamorphosis.
Three Groups of Amphibians
• Salamanders
• There are more than
300 species of
salamanders.
• They have a long
body, four walking
limbs, and a tail.
• They walk with a sidet-side movement.
• They are carnivores.
Three Groups of Amphibians
• Frogs and Toads
• There are over 3000
species of frogs.
• Toads are a family of
frogs that have
rougher and bumpier
skin and are poor
jumpers.
• Frogs and toads can
make toxins that
protect them from
predators.
Three Groups of Amphibians
• Caecilians
• Are legless, burrowing
amphibians that live in the
tropics.
• There are 160 species
ranging in length from
about 10 cm to 1.5 meters.
• Have banded bodies that
make them look like
earthworms.
• How are caecilians
different from other
amphibians?
25.5: Vertebrates on Land
• Objectives: Describe two important
characteristics of amniotes that help
them retain water.
• Explain the evolutionary importance of
the amniotic egg.
• Warm Up: Why is the amniotic egg so
significant to life on land?
• Words to Know: Amniote, Keratin,
Amniotic Egg, Placenta
Amniotes
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An Amniote is a vertebrate that has a
thin, though, membranous sac that
encloses the embryo or fetus.
Amniotes first appeared as small
lizard-like creature in the late
Carboniferous period.
All Amniotes share a set of
characteristics that prevent water loss.
Skin cells are waterproof with Keratin –
a protein that binds to lipids inside the
cell forming a hydrophobic layer that
keep water inside the animal from
reaching the skin.
Kidneys and large intestines are bigger
in amniotes than in amphibians,
because they can reabsorb water.
What makes your skin cells
waterproof? Why is this important?
Reproduction Without Water
• The Amniotic Egg is an almost
completely waterproof container
that keeps the embryo from
drying out as it develops.
• Once the amniotic egg evolved,
vertebrates no longer had to go
back to water for reproduction.
• Most Mammal embryos develop
inside of the mother’s
reproductive tract.
• The Placenta is a membranous
organ that develops in female
mammals during pregnancy.
• It carries nutrients from mother
to embryo.
• How is an amniotic egg
protected from water loss?