Name ______________________________ Class ___________________ Date __________________
Skills Worksheet
Active Reading
Section: Chordate Evolution
Read the passage below. Then answer the questions that follow.
A major group of deuterostomes are the chordates. Chordates
have a very different kind of skeleton, one that is completely
internal, called an endoskeleton. During the development of the
chordate embryo, a stiff rod called the notochord develops along
the back of the embryo. The evolution of an internal skeleton was
an important step that led to the evolution of vertebrates. The
endoskeleton, to which muscles attach, made it possible for
animals to grow large and move quickly.
Chordates also share three other characteristics. They have a
single, hollow, dorsal nerve cord with nerves attached to it that
travel to different parts of the body. Chordates also have a series of
pharyngeal pouches in the throat at some stage of development.
These give rise to structures in the head and neck, including gills
in fish and the inner ear in humans. Another chordate
characteristic is a postanal tail, which is a tail that extends beyond
the anus. All chordates have all four of these characteristics at
some time in their life, even if it is only briefly as embryos, as in
humans.
SKILL: READING EFFECTIVELY
Read each question, and write your answer in the space provided.
1. The prefix endo- means “inside or within.” Using the meaning of this prefix,
define the word endoskeleton.
_______________________________________________________________
_______________________________________________________________
2. What capabilities were made possible for animals due to the evolution of an
internal skeleton?
_______________________________________________________________
_______________________________________________________________
3. Where do pharyngeal pouches develop in chordates?
_______________________________________________________________
4. Where does the notochord develop in chordates?
_______________________________________________________________
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Biology
15
Introduction to Animals
Name ______________________________ Class ___________________ Date __________________
Active Reading continued
In the space provided, write the letter of the term or phrase that best completes
each statement or best answers each question.
_____ 5. The evolution of an internal skeleton was an important step that led to
the evolution of
a. vertebrates.
b. deuterostomes.
c. invertebrates.
d. amoebas.
_____ 6. A member of the phylum Chordata is a
a. protostome.
b. deuterostome.
c. jawless fish.
d. arthropod.
_____ 7. An endoskeleton is a(n)
a. notochord.
b. nerve cord.
c. external skeleton.
d. internal skeleton.
_____ 8. The development of which characteristic made it possible for animals
to grow large and move quickly?
a. dorsal nerve cord
b. notochord
c. endoskeleton
d. exoskeleton
_____ 9. Pharyngeal pouches in fish give rise to which structures?
a. fins
b. gills
c. scales
d. teeth
_____ 10. Humans have postanal tails
a. all of their lives.
b. briefly at birth.
c. only as embryos.
d. until puberty.
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Biology
16
Introduction to Animals