Biology
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30-1 The Chordates
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30-1 The Chordates
What Is a Chordate?
What characteristics do all chordates
share?
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30-1 The Chordates
What Is a Chordate?
What Is a Chordate?
Members of the phylum Chordata are called
chordates.
A chordate is an animal that has, for at
least some stage of its life, a dorsal,
hollow nerve cord; a notochord;
pharyngeal pouches; and a tail that
extends beyond the anus.
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30-1 The Chordates
What Is a Chordate?
Characteristics of Chordates
Muscle segments
Tail
Anus
Notochord
Hollow nerve cord
Mouth
Pharyngeal pouches
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30-1 The Chordates
What Is a Chordate?
The notochord is a long supporting rod that runs
through the body just below the nerve cord.
Notochord
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30-1 The Chordates
What Is a Chordate?
Pharyngeal pouches are paired structures in the
throat (pharynx) region.
Pharyngeal pouches
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30-1 The Chordates
What Is a Chordate?
The tail can contain bone and muscle and is used for
swimming by many aquatic species.
Tail
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30-1 The Chordates
What Is a Chordate?
Most Chordates Are Vertebrates
About 96 percent of all chordate species are
vertebrates.
Most vertebrates have a vertebral column, or
backbone.
In vertebrates, the dorsal, hollow nerve cord is
called the spinal cord.
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30-1 The Chordates
What Is a Chordate?
As a vertebrate embryo develops, the front end of the
spinal cord grows into a brain.
The backbone is made of individual segments called
vertebrae.
In addition to support, vertebrae enclose and protect
the spinal cord.
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30-1 The Chordates
What Is a Chordate?
Phylogeny of Chordates
Sharks
& their
Jawless
relatives
fishes
Nonvertebrate
chordates
Bony
fishes
Reptiles Birds
Amphibians
Mammals
Invertebrate ancestor
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30-1 The Chordates
Nonvertebrate Chordates
What are the two groups of nonvertebrate
chordates?
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30-1 The Chordates
Nonvertebrate Chordates
Nonvertebrate Chordates
The two groups of nonvertebrate
chordates are tunicates and lancelets.
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30-1 The Chordates
Nonvertebrate Chordates
Similarities in anatomy and embryological
development indicate that vertebrates and
nonvertebrate chordates evolved from a common
ancestor.
Both tunicates and lancelets are soft-bodied marine
organisms.
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30-1 The Chordates
Nonvertebrate Chordates
Tunicates
Tail
The larval form of
filter-feeding
tunicates have all of
the chordate
Mouth
characteristics.
Pharynx
with gill
slits
Hollow
nerve cord
Wasteeliminating
organ
Notochord
Intestine
Stomach
Heart
Larva
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30-1 The Chordates
Nonvertebrate Chordates
Adult filter-feeding tunicates have neither a notochord
nor a tail.
Siphon to mouth
Pharynx with gill slits
Siphon from anus
Anus
Tunic
Intestine
Reproductive organs
Heart
Stomach
Adult
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30-1 The Chordates
Tunicates
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30-1 The Chordates
Nonvertebrate Chordates
Lancelets
Lancelets are small, fishlike creatures that live on
the ocean bottom.
Notochord
Hollow nerve cord
Segmented muscles
Mouth
Tail
Anus
Pharynx with gill slits
Intestine
Reproductive organs
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30-1 The Chordates
Nonvertebrate Chordates
An adult lancelet has a definite head region that
contains a mouth.
As water passes through the pharynx, a sticky mucus
catches food particles.
The lancelet swallows the mucus into the digestive
tract.
Mouth
Pharynx with gill slits
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30-1 The Chordates
Nonvertebrate Chordates
Lancelets use the pharynx for gas exchange.
Lancelets are thin enough to exchange gases
through their body surface.
Lancelets have a closed circulatory system and do
not have a true heart.
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30-1 The Chordates
Lancelet
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30-1
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A characteristic of most, but not all, chordates is
a. pharyngeal pouches.
b. a backbone.
c. a hollow nerve cord.
d. a tail that extends beyond the anus.
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30-1
In vertebrates, the developing backbone
replaces the
a. pharyngeal pouches.
b. hollow nerve cord.
c. notochord.
d. siphon and tunic.
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30-1
To which group of vertebrates are tunicates most
closely related?
a. amphibians
b. fishes
c. reptiles
d. mammals
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An animal that retains a notochord as an
adult is a
a. tunicate.
b. lancelet.
c. fish.
d. reptile.
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In the lancelet, the pharynx and gill slits are
used for
a. feeding and gas exchange.
b. reproduction and excretion.
c. circulation and sensory detection.
d. movement and digestion.
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