Download Chapter 25: Vertebrate Diversity

Chapter 25: Vertebrate Diversity
25.1: Vertebrate Origins
• 25.1: Vertebrate Origins
• Words to Know: Chordate, Notochord,
Endoskeleton
Phylum Chordata
• 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.
• Most chordate groups lose some or all of these characteristics in
adulthood, but they are present in the embryo.
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 and hollow bones.
Mammals – animals with fur, mammary glands, and
three middle ear bones. Includes humans, elephants,
kangaroos etc…
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.
Jawless Fish: 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 toothlike 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.
25.2: Fish Diversity
• 25.2: Fish Diversity
• 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.
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.
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.
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 swimmers
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.
25.3: A Closer Look at Bony
Fish
• 25.3: A Closer Look at 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 rayfin.
• 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.
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.
25.4: Amphibians
• 25.4: Amphibians
• Words to Know: Tetrapod, Amphibian, Tadpole
• 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.
Amphibians
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.
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.
25.5: Vertebrates on Land
• Words to Know: Amniote, Keratin,
Amniotic Egg, Placenta
• An Amniote is a vertebrate
that has a thin, tough,
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.
Amniotes
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.