Download Evolutionary Trends in Animals

Name ______________________________ Class___________________Date__________________
Skills Worksheet
Directed Reading
Section: Evolutionary Trends in Animals
In the space provided, write the letter of the description that best matches each
term.
_____ 1. body plan
_____ 2. asymmetrical
_____ 3. radial symmetry
_____ 4. cephalization
_____ 5. bilateral symmetry
a. body parts arranged around a central axis,
like the spokes of a bicycle wheel
b. sensory structures and nerves concentrated at
the body’s anterior
c. a term used to describe an animal’s shape,
symmetry, and internal organization
d. body is irregularly shaped
e. body has a distinct right and left half
Complete each statement by writing the correct term or phrase in the space
provided.
6. The cells of all animals except sponges are organized into structural and
functional units called ______________________.
7. In all animals except sponges, the zygote undergoes cell divisions forming a
hollow ball of cells called a(n) ____________________.
8. The ______________________ is the layer of cells in the blastula that gives
rise to the outer layer of skin, the nervous system, and the sense organs.
9. The ______________________ is the layer of cells in the blastula that gives
rise to the lining of the digestive tract, respiratory system, and many glands.
10. The ______________________ is the layer of cells in the blastula that gives
rise to most of the skeleton, muscles, and circulatory system.
11. In ______________________, the mouth develops from the end of the embryo
near the blastopore.
12. In ______________________, the mouth develops from the end of the embryo
opposite the blastopore.
13. Animals with _____________________ _____________________ may have
one of three basic kinds of internal body plans.
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Biology
5
Introduction to Animals
Name ______________________________ Class___________________Date__________________
Directed Reading continued
14. Animals with no body cavity are called ______________________.
15. Animals that have a body cavity between the mesoderm and the endoderm are
called ______________________.
16. A true coelom is lined with mesoderm and wraps around the
______________________.
Read each question, and write your answer in the space provided.
17. What are the four stages, in order, of embryonic development before
differentiation?
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18. What benefit do animals derive from having a coelom?
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19. What are some advantages of body segmentation?
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20. How did the development of jointed appendages benefit animals?
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Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Holt Biology
6
Introduction to Animals