Biology: Life on Earth Plus Mastering Biology with Pearson eText -- Access Card Package (11th Edition)
Biology: Life on Earth Plus Mastering Biology with Pearson eText -- Access Card Package (11th Edition)
11th Edition
ISBN: 9780134153742
Author: Gerald Audesirk, Teresa Audesirk, Bruce E. Byers
Publisher: PEARSON
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Chapter 24, Problem 1MC

Which of the following groups contains radially symmetrical organisms?

  1. arthropods

  2. cnidarians

  3. mollusks

  4. roundworms

Expert Solution & Answer
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Summary Introduction

Introduction:

Body symmetry was not evident in the earlier eukaryotes. It is noted down when tissues were developed in the animals. There are various types of body symmetry. In radial body symmetry, any plane going through the central axis divides the organism into equal halves. In bilateral symmetry, animals can be divided into almost mirror-image halves only among one particular plane through central axis.

Answer to Problem 1MC

Correct answer:

Radially symmetrical organisms are found in cnidarians group among the given groups.

Explanation of Solution

Explanation for the correct answer:

Option (b) is given that radially symmetrical organisms are found in cnidarians. The body plan of cnidarians is unique as any plane passing through their central axis divides these animals into equal halves. This property makes cnidarians different from the organisms evolved before them. Hence, option (b) is a correct answer.

Explanation for incorrect answers:

Option (a) is given that radially symmetrical organisms are found in arthropods. Arthropods are bilaterally symmetrical organisms as there is only one plane that passes through the central axis that can divide them into mirror-image halves. So, it is an incorrect option.

Option (c) is given that radially symmetrical organisms are found in molluscs. Molluscs are bilaterally symmetrical organisms as there is only one plane that passes through the central axis that can divide them into mirror-image halves. So, it is an incorrect option.

Option (d) is given that roundworm possesses radial symmetry. Roundworms are bilaterally symmetrical organisms as there is only one plane that passes through the central axis that can divide them into mirror-image halves. So, it is an incorrect option.

Hence, options (a), (c), and (d) are incorrect.

Conclusion

Therefore, it can be concluded that from the given groups, radially symmetrical organisms are found in cnidarians.

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Students have asked these similar questions
Which of the following is not a characteristic of all animals?  Answers: They are multicellular eukaryotes. They ingest and digest food. They are mobile at some point in their life. They reproduce sexually. They have a coelom. Please explain which one is correct.
Animals that have true tissues, bilateral symmetry, segmented bodies, and are protostomes are known as:     Arthropods     Cnidarians     Sponges     Chordates
Which of the following phyla or classes displays the greatest number of species: options:   Mollusca   Nematoda   Annelida   Insecta
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