1. Copyright Pearson Prentice Hall
Biology
Copyright Pearson Prentice Hall

2. Copyright Pearson Prentice Hall
30-1 The Chordates
Photo Credit: ©Art Wolfe/Stone
Copyright Pearson Prentice Hall

3. Copyright Pearson Prentice Hall
What Is a Chordate?
What characteristics do all chordates share?
Copyright Pearson Prentice Hall

4. Copyright Pearson Prentice Hall
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.
Copyright Pearson Prentice Hall

5. Copyright Pearson Prentice Hall
What Is a Chordate?
Characteristics of Chordates
Notochord
Muscle segments
Hollow nerve cord
All chordates share four characteristics: a dorsal, hollow nerve cord; a notochord; pharyngeal pouches; and a tail that extends beyond the anus. Some chordates possess all these characteristics as adults; others possess them only as embryos.
Tail
Anus
Mouth
Pharyngeal pouches
Copyright Pearson Prentice Hall

6. Copyright Pearson Prentice Hall
What Is a Chordate?
The notochord is a long supporting rod that runs through the body just below the nerve cord.
Notochord
All chordates share four characteristics: a dorsal, hollow nerve cord; a notochord; pharyngeal pouches; and a tail that extends beyond the anus. Some chordates possess all these characteristics as adults; others possess them only as embryos.
Copyright Pearson Prentice Hall

7. Copyright Pearson Prentice Hall
What Is a Chordate?
Pharyngeal pouches are paired structures in the throat (pharynx) region.
All chordates share four characteristics: a dorsal, hollow nerve cord; a notochord; pharyngeal pouches; and a tail that extends beyond the anus. Some chordates possess all these characteristics as adults; others possess them only as embryos.
Pharyngeal pouches
Copyright Pearson Prentice Hall

8. Copyright Pearson Prentice Hall
What Is a Chordate?
The tail can contain bone and muscle and is used for swimming by many aquatic species.
All chordates share four characteristics: a dorsal, hollow nerve cord; a notochord; pharyngeal pouches; and a tail that extends beyond the anus. Some chordates possess all these characteristics as adults; others possess them only as embryos.
Tail
Copyright Pearson Prentice Hall

9. 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.
Copyright Pearson Prentice Hall

10. Most Chordates Are Vertebrates
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.
Copyright Pearson Prentice Hall

11. Most Chordates Are Vertebrates
Phylogeny of Chordates
Mammals
Birds
Reptiles
Amphibians
Bony fishes
Sharks
& their relatives
Jawless fishes
Nonvertebrate chordates
Although nonvertebrate chordates lack a vertebral column, they share a common ancestor with vertebrates.
Invertebrate ancestor
Copyright Pearson Prentice Hall

12. Nonvertebrate Chordates
What are the two groups of nonvertebrate chordates?
Copyright Pearson Prentice Hall

13. Nonvertebrate Chordates
The two groups of nonvertebrate chordates are tunicates and lancelets.
Copyright Pearson Prentice Hall

14. 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.
Copyright Pearson Prentice Hall

15. Nonvertebrate Chordates
Tail
Tunicates
The larval form of filter-feeding tunicates have all of the chordate characteristics.
Hollow nerve cord
Waste- eliminating organ
Notochord
Mouth
Intestine
Pharynx with gill slits
Stomach
Tunicates are one of two groups of nonvertebrate chordates. The tadpole-shaped tunicate larva has all four chordate characteristics. The blue arrows show where water enters and leaves the tunicate’s body.
Heart
Larva
Copyright Pearson Prentice Hall

16. 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
Tunicates are one of two groups of nonvertebrate chordates. Adult tunicates look nothing like the larvae, or even like other adult chordates. Both larvae and adults are filter feeders. The blue arrows show where water enters and leaves the tunicate’s body.
Intestine
Reproductive organs
Heart
Stomach
Adult
Copyright Pearson Prentice Hall

17. Nonvertebrate Chordates
Lancelets
Lancelets are small, fishlike creatures that live on the ocean bottom.
Notochord
Hollow nerve cord
Segmented muscles
Lancelets are small nonvertebrate chordates that often live with their bodies half buried in sand. Because lancelets do not have fins or legs, they can move only by contracting the paired muscles on their bodies.
Mouth
Tail
Pharynx with gill slits
Anus
Intestine
Reproductive organs
Copyright Pearson Prentice Hall

18. 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.
Lancelets are small nonvertebrate chordates that often live with their bodies half buried in sand. Because lancelets do not have fins or legs, they can move only by contracting the paired muscles on their bodies.
Mouth
Pharynx with gill slits
Copyright Pearson Prentice Hall

19. 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.
Copyright Pearson Prentice Hall

20. Copyright Pearson Prentice Hall
30-1
Copyright Pearson Prentice Hall

21. Copyright Pearson Prentice Hall
30-1
A characteristic of most, but not all, chordates is
pharyngeal pouches.
a backbone.
a hollow nerve cord.
a tail that extends beyond the anus.
Copyright Pearson Prentice Hall

22. Copyright Pearson Prentice Hall
30-1
In vertebrates, the developing backbone replaces the
pharyngeal pouches.
hollow nerve cord.
notochord.
siphon and tunic.
Copyright Pearson Prentice Hall

23. Copyright Pearson Prentice Hall
30-1
To which group of vertebrates are tunicates most closely related?
amphibians
fishes
reptiles
mammals
Copyright Pearson Prentice Hall

24. Copyright Pearson Prentice Hall
30-1
An animal that retains a notochord as an adult is a
tunicate.
lancelet.
fish.
reptile.
Copyright Pearson Prentice Hall

25. Copyright Pearson Prentice Hall
30-1
In the lancelet, the pharynx and gill slits are used for
feeding and gas exchange.
reproduction and excretion.
circulation and sensory detection.
movement and digestion.
Copyright Pearson Prentice Hall

26. END OF SECTION