Notes to Instructors
Chapter 34 Vertebrates
What is the focus of this activity?
As noted in Activity 32.1/33.1, when studying biodiversity, many students try to
What is this activity designed to do?
Activity 34.1 What can we learn about the evolution of the chordates by examining
modern chordates?
This activity is designed to help students understand the relationships that exist among
Answers
Activity 34.1 What can we learn about the evolution of the
chordates by examining modern chordates?
Fill in the chart on the next two pages to organize the major characteristics of key groups
of chordates.
234 Notes to Instructors
Characteristics of phylum chordata
Subphylum
Urochordata
Subphylum
Cephalochordata Subphylum Vertabrata
Characteristics Agnatha Chondrichthyes Osteichthyes Amphibia Mammalia Reptilia Aves
Examples of
organisms
Sea squirts Amphioxus Lamprey and
hagfish
Sharks, rays,
skates
Bony
fish—for
example
bass, trout,
tuna
Frogs,
salamanders
Mice,
rabbits,
humans
Lizards,
snakes,
turtles
Birds
Characteristics of phylum chordata
Subphylum
Urochordata
Subphylum
Cephalochordata Subphylum Vertabrata
Characteristics Urochordata Cephalo-
chordata Agnatha Chondrichth
yes Osteichthyes Amphibia Mammalia Reptilia Aves
Paired limbs?
Structure? Limb
None None None or
a single
pair (some
fossil
species)
Two pairs
of lateral
fins
(pectoral
and pelvic)
Two pairs of
lateral fins
(pectoral
and pelvic)
Tetrapods; four
limbs, each
with one upper
and two lower
limb bones and
five phalanges
(pentadactyl
limb structure).
Tetrapods; four
limbs, each
with one upper
and two lower
limb bones and
five phalanges.
Limbs are
positioned
Tetrapods; four
limbs, each
with one upper
and two lower
limb bones and
five phalanges.
Limbs are
positioned
Tetrapods;
four limbs,
each with one
upper and two
lower limb
bones and five
phalanges.
Hind limbs are
Characteristics of phylum chordata
Subphylum
Urochordata
Subphylum
Cephalo-
chordata Subphylum Vertabrata
Characteristics Agnatha Chondrichthyes Osteichthyes Amphibia Mammalia Reptilia Aves
Circulatory system?
Closed
circulatory
Closed
circulatory
Closed
circulatory
Closed
circulatory
Closed
circulatory
Closed
circulatory
Closed
circulatory
Using the information in the table, answer the questions.
1. a. According to Campbell Biology, 9th edition, what three characteristics are
common to all chordates?
All chordates have a notochord, pharyngeal gill slits, and a dorsal hollow nerve
chord at some stage in their life cycle.
b. Why don’t we find all three of these chordate characteristics in our own bodies?
The notochord and pharyngeal gill slits are present in the developing embryo.
2. The chart organizes the chordates based on grade or shared body plan features. If
you compare the characteristics of one group with the next, what key differences
separate the groups from each other?
To answer this question, you need to compare the characteristics in a given
3. What unique combination of characteristics defines each group as separate from the
others?
If you read down each column, you can determine the characteristics of each
4. a. Looking across each of the rows in the chart, what major trends do you see in the
evolution of the different organs and organ systems?
This chart is set up to allow you to visualize how the various systems changed in
b. Does this analysis provide evidence for or against the statement: “Evolution adds
onto or modifies what already exists?” Explain.
As is apparent in this chart, modifications are built upon what already exists. For
238 Activity 34.1
5. a. What major changes in structure and function are seen in terrestrial groups as
compared with aquatic groups?
One of the major changes is in reproduction. Evolution of the amniotic egg freed
b. Can these changes be related to differences in natural selection on land versus in
an aquatic environment? Explain.
Early forms of gills probably evolved in an aquatic system and allowed fish to
Activity 34.1 239