Name______Class______Date______
CHAPTER 32 ACTIVE READING WORKSHEETS
INTRODUCTION TO ANIMALS
Section 32-1: The Nature of Animals
Read the passage below, which covers topics from your textbook. Answer the questions that follow.
The term symmetry refers to a body arrangement in which parts that lie on opposite sides of an axis are identical. The simplest animals, sponges, display no symmetry. Moreover, although sponges are multicellular, their cells are not organized into tissues. Animal bodies range from those that lack true tissues and an organized body shape, such as that of the sponge, to those that have very organized tissues and a consistent body shape, as is found in most other animal phyla.
Some animals have a top side and a bottom side, but no front, back, right, or left end. These animals are said to display radial symmetry. In radial symmetry, similar parts branch out in all directions from a central line. Cnidarians, such as sea anemones, jellyfish, and hydra, are radially symmetrical.
Most animals have a dorsal (back) and ventral (abdomen) side, an anterior (head) and posterior (tail) end, and a right and left side. Such animals have two similar halves on either side of a central plane and are said to display bilateral symmetry. Bilaterally symmetrical animals tend to exhibit cephalization. Cephalization is the concentration of sensory and brain structures in the anterior end of the animal; a cephalized animal has a head. As a cephalized animal swims, burrows, walks, or flies through its environment, the head precedes the rest of the body, sensing danger, prey, or a potential mate.
Read each question and write your answer in the space provided.
SKILL:Recognizing Text Structure
1.A writer will use different types of text structure to present organized ideas or events. The ability to understand how ideas are organized will help you understand a text. What type of text structure did the author use in the above passage?
______
2.How does the body structure of a sponge differ from that of a jellyfish?
______
______
3.What are the similarities and differences between radial symmetry and bilateral symmetry?
______
______
______
______
______
4.Classify each of the drawings below as showing bilateral symmetry, no symmetry, or radial symmetry. Write your answers on the lines provided.
Circle the letter of the phrase that best completes the statement.
5.An animal that exhibits cephalization
a.has a head.
b.usually is bilaterally symmetrical.
c.lacks a brain.
d.Both (a) and (b)
Original content Copyright © by Holt, Rinehart and Winston. Additions and changes to the original content are the responsibility of the instructor.
Modern Biology1The Nature of Animals