Interest Grabber
Section 33-1
Covering the Chordates
Though all chordates share certain characteristics, they are extremely
diverse. With a partner, identify the characteristic body covering for each of
the six major groups of animals listed below. Then, explain how that
covering is useful for that group of animals.
1. Nonvertebrate chordates
2. Fishes
3. Amphibians
4. Reptiles
5. Birds
6. Mammals
Section Outline
Section 33-1
33–1
Chordate Evolution
A. Chordate Origins
B. The Chordate Family Tree
C. Evolutionary Trends in Vertebrates
1. Adaptive Radiations
2. Convergent Evolution
D. Chordate Diversity
Concept Map
Section 33-1
Chordates
have the following
key features
Notochord
which is
A flexible
supporting
structure
Dorsal hollow
nerve cord
Muscular
tail
Pharyngeal
pouches
Figure 33–2 A Cladogram of
Chordates
Section 33-1
Nonvertebrate chordates
Jawless fishes
Cartilaginous fishes
Bony fishes
Amphibians
Reptiles
Birds
Mammals
Figure 33–4 Diversity of Chordates
Section 33-1
Nonvertebrate chordates
(4%)
Mammals
(8%)
Birds
(18%)
Reptiles
(14%)
Amphibians
(9%)
Fishes
(47%)
Interest Grabber
Section 33-2
How Hot Is Too Hot?
As you know, your body, for the most part, maintains a constant
temperature. Enzymes in your body function most efficiently at a
temperature that is very close to your body temperature.
1. What is the body’s normal temperature?
2. What happens to your body’s temperature when you have a viral or
bacterial infection? What purpose might this serve?
3. What do you think would happen if your body temperature radically
increased or decreased from its normal level? Explain why.
Section Outline
Section 33-2
33–2
Controlling Body Temperature
A. Body Temperature and Homeostasis
1. Ectothermy
2. Endothermy
B. Comparing Ectotherms and Endotherms
C. Evolution of Temperature Control
Temperature Control in Chordates
Body Temperature (°C)
Section 33-2
Environmental Temperature (°C)
Interest Grabber
Section 33-3
How Do They Do That?
As you have read, the problems faced by a land-dwelling chordate are
very different from those faced by a water-dwelling chordate. Thus, the
characteristics of these chordates are also quite different.
Choose two chordates—one that lives in the water and one that lives on
land. Construct a compare/contrast table that shows the similarities and
differences in feeding, respiration, movement, and circulation between
these two chordates.
Section Outline
Section 33-3
33–3
Form and Function in Chordates
A. Feeding
B. Respiration
1. Gills
2. Lungs
C. Circulation
1. Single- and Double-Loop Circulation
2. Heart Chambers
D. Excretion
E. Response
F. Movement
G. Reproduction
Compare/Contrast Table
Section 33-3
Comparing Functions of Chordates
Function
Nonvertebrate
Chordates
Fishes
Amphibians
(adult)
Reptiles
Birds
Respiration
Gills and
diffusion
Gills/air sacs
Simple lungs
and skin
Lungs
Lungs (tubes Lungs
and air sacs; (alveoli)
one-way flow)
Circulation
No true
chambers
Single loop; 2 Double loop;
chambers
3 chambers
Double loop;
3 chambers
Double loop;
4 chambers
Double loop;
4 chambers
Excretion
Gills and
gill slits
Kidney and
gills
Kidney
Kidney
Kidney
Response
Simple; mass Cephalization; Cephalization; Cephalization; Cephalization; Cephalization;
of nerve cells small
small
small
large
large
cerebrum
cerebrum
cerebrum
cerebrum
cerebrum
Kidney and
gills
Mammals
Compare/Contrast Table continued
Section 33-3
Comparing Functions of Chordates
Fishes
Amphibians
Amphibians
(adult)
(adult)
Reptiles
Birds
Mammals
Muscles on
either side of
backbone
Limbs stick
out sideways;
muscles and
ligaments
Limbs point
directly
toward
ground;
muscles and
ligaments
Upper limbs
are wings; 2
feet; muscles
and ligaments
2 or 4 legs;
walk with legs
straight under
them;
muscles and
ligaments
Reproduction External
fertilization
External
fertilization
External
fertilization
Internal
fertilization;
shelled egg
Internal
fertilization;
shelled egg
Internal
fertilization
and
development
Temperature Ectothermic
Control
Ectothermic
Ectothermic
Ectothermic
Endothermic
Endothermic
Function
Movement
Nonvertebrate
Chordates
Muscles,
no bones
Figure 33–8 The Digestive Systems
of Vertebrates
Section 33-3
Esophagus
Stomach
Intestine
Liver
Gallbladder
Pancreas
Cloaca
Crop
Gizzard
Cecum
Rectum
Shark
Salamander
Lizard
Pigeon
Cow
Figure 33–10 Vertebrate Lungs
Section 33-3
Nostrils, mouth, and throat
Trachea
Lung
Air sac
Salamander
Lizard
Primate
Pigeon
Figure 33–11 The Circulatory Systems
of Vertebrates
Section 33-3
Single-Loop
Circulatory System
FISHES
Double-Loop Circulatory System
MOST REPTILES
CROCODILIANS, BIRDS,
AND MAMMALS
Figure 33–11 The Circulatory Systems
of Vertebrates
Section 33-3
Single-Loop
Circulatory System
FISHES
Double-Loop Circulatory System
MOST REPTILES
CROCODILIANS, BIRDS,
AND MAMMALS